Evaluating the influence of 6 MV and 15 MV photon beams on prostate intensity-modulated radiation therapy plans

Objective We aimed to determine the ef ects of low- and high-energy intensity-modulated radiation therapy （IMRT） photon beams on the target volume planning and on the critical organs in the case of prostate can-cer. Methods Thirty plans were generated by using either 6 MV or 15 MV beams separately, and a combination of both 6 and 15 MV beams. Al plans were generated by using suitable planning objectives and dose con-straints, which were identical across the plans, except the beam energy. The plans were analyzed in terms of their target coverage, conformity, and homogeneity, regardless of the beam energy. Results The mean percentage values of V70 Gy for the rectal wal for the plans with 6 MV, 15 MV, and mixed-energy beams were 16.9%, 17.8%, and 16.4%, respectively, while the mean percentage values of V40 Gy were 53.6%, 52.3%, and 50.4%. The mean dose values to the femoral heads for the 6 MV, 15 MV, and mixed-en-ergy plans were 30.1 Gy, 25.5 Gy, and 25.4 Gy, respectively. The mean integral dose for the 6 MV plans was 10% larger than those for the 15 MV and mixed-energy plans.Conclusion These preliminary results suggest that mixed-energy IMRT plans may be advantageous with respect to the dosimetric characteristics of low- and high-energy beams. Although the reduction of dose to the organs at risk may not be clinical y relevant, in this study, IMRT plans using mixed-energy beams exhibited better OAR sparing and overal higher plan quality for deep-seated tumors.

Dosimetric Comparative Analysis of Volumetric Modulated Arc Therapy and Intensity-Modulated Radiation Therapy in Cervical Cancer

Objective:To carry out dosimetric comparison between volumetric modulated arc therapy(VMAT)and intensity-modulated radiation therapy(IMRT)in cervical cancer.Methods:50 postoperative cervical cancer patients were included in this study.The patients were admitted for treatment from January 2021 to January 2022.VMAT and IMRT plans were designed for each patient to analyze the dose distribution in the target area of the two treatment techniques.Results:Comparing the monitor unit for single treatment(638.21±116.21 MU)and time of single treatment(143.21±23.14 s)in the observation group and the monitor unit for single treatment(932.14±74.11 MU)and time of single treatment(223.14±17.26 s)in the control group,there was significant difference(P<0.05);there was also significant difference(P<0.05)between the normal tissue(bladder and rectum)of the observation group and that(bladder and rectum)of the control group.Conclusion:VMAT is more effective in cervical cancer,and it has a certain protective effect on normal tissues in patients and can reduce the radiation dose.

Hypofractionated and intensity-modulated radiotherapy combined with systemic therapy in metastatic hepatocellular carcinoma:A case report

BACKGROUND Liver cancer treatment is characterized by multidisciplinary participation and coexistence of multiple treatment methods.Hypofractionated and intensity-modulated radiotherapy is a new precise radiotherapy technique applied to the treatment of systemic malignant tumors.There is a lack of understanding of hypofractionated and intensity-modulated radiotherapy combined with systemic therapy in metastatic hepatocellular carcinoma(HCC).CASE SUMMARY We report a case of metastatic HCC treated with hypofractionated and intensity-modulated radiotherapy combined with systemic therapy.A 41-year-old man was diagnosed with metastatic HCC(T3N1M1 stage IVB).Because it was found to be in the late stage of cancer and had already metastasized,it was impossible to undergo surgical treatment.In addition to aggressive comprehensive treatment for the primary lesion,local treatment for metastatic cancer can improve the patient's survival potential.Hypofractionated and intensity-modulated radiotherapy can provide a larger single treatment dose within a shorter overall treatment time,and improve the local control rate of the tumor.Follow-up examination demonstrated that the tumor and metastatic lesions had shrunk after therapy.The treatment has showed good efficacy.The patient survived for 18 months without disease progression and stable disease persisted for>38 months.CONCLUSION Targeted therapy and immunotherapy followed by hypofractionated and intensity-modulated radiotherapy are also effective for advanced metastatic HCC.

Evaluation of 3D-CRT and VMAT Radiotherapy Plans for Left Breast Cancer with Regional Lymph Nodes Irradiation

Introduction: Radiation therapy after breast surgery is an integral part of the treatment of early breast cancer. The goal of radiation therapy is to achieve the best possible coverage of the planning target volume (PTV), while reducing the dose to organs at risk (OARs) which are normal tissues whose sensitivity to irradiation could cause damage that can lead to modification of the treatment plan. In the last decade, radiation oncologist started to use the Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) for irradiating the breast, in order to achieve better dose distribution and target dose to the PTV and OAR. The aim of this study is to compare 2 external radiotherapy techniques (VMAT vs 3D) for patients with node-positive left breast cancer. Patients and Methods: We randomly selected 10 cases of postoperative radiotherapy for breast cancer in our hospital. The patients are all female, the average age was 45.4 years old, and the primary lesions are left breast. The ANOVA test was used to compare the mean difference between subgroups, and the p value Results: Dose volume histogram (DVH) was used to analyze each evaluation dose of clinical target volume (CTV) and organs at risk (OARs). Compared to 3DCRT plans, VMAT provided more uniform coverage to the breast and regional lymph nodes. The max point dose for tVMAT was lower on average (106.4% for VMAT versus 109% for 3DCRT). OAR sparing was improved with tVMAT, with a lower average V17Gy for the left lung (27.91% for VMAT versus 30.04% for 3DCRT, p and lower for V28Gy (13.75% for VMAT versus 22.34% for 3DCRT, p = 0.01). We also found a lower V35Gy for the heart on VMAT plan (p = 0.02). On the contrary, dose of contralateral breast was lower in 3DCRT than VMAT (0.59 Gy vs 3.65 Gy, p = 0.00). Conclusion: The both types of plans can meet the clinical dosimetry demands of postoperative radiotherapy for left breast cancer. The VMAT plan has a better conformity, but 3CDRT can provide a lower dose to the contralateral organs (breast and lung) to avoid the risk of secondary cancers.

Intensity-modulated radiation therapy with concurrent chemotherapy for locally advanced cervical and upper thoracic esophageal cancer

AIM： To evaluate the dosimetry, efficacy and toxicity of intensity-modulated radiation therapy （IMRT） and concurrent chemotherapy for patients with locally advanced cervical and upper thoracic esophageal cancer. METHODS： A retrospective study was performed on 7 patients who were definitively treated with IMRT and concurrent chemotherapy. Patients who did not receive IMRT radiation and concurrent chemotherapy were not included in this analysis. IMRT plans were evaluated to assess the tumor coverage and normal tissue avoidance. Treatment response was evaluated and toxicities were assessed. RESULTS： Five- to nine-beam IMRT were used to deliver a total dose of 59.4-66 Gy （median： 64.8 Gy） to the primary tumor with 6-MV photons. The minimum dose received by the planning tumor volume （PTV） of the gross tumor volume boost was 91.2%-98.2% of the prescription dose （standard deviation [SD]： 3.7%-5.7%）. The minimum dose received by the PTV Of the clinical tumor volume was 93.8%-104.8% （SD： 4.3%-11.1%） of the prescribed dose. With a median follow-up of 15 rno （range： 3-21 too）, all 6 evaluable patients achieved complete response. Of them, 2 developed local recurrences and 2 had distant metastases, 3 survived with no evidence of disease. After treatment, 2 patients developed esophageal stricture requiring frequent dilation and 1 patient developed tracheal-esophageal fistula. CONCLUSION： Concurrent IMRT and chemotherapy resulted in an excellent early response in patients with locally advanced cervical and upper thoracic esophageal cancer. However, local and distant recurrence and toxicity remain to be a problem. Innovative approaches are needed to improve the outcome.

A prospective trial of volumetric intensity-modulated arc therapy vs conventional intensity modulated radiation therapy in advanced head and neck cancer

AIM: To prospectively compare volumetric intensitymodulated arc therapy(VMAT) and conventional intensity-modulated radiation therapy(IMRT) in coverage of planning target volumes and avoidance of multiple organs at risk(OARs) in patients undergoing definitive chemoradiotherapy for advanced(stage Ⅲ or Ⅳ)squamous cell cancer of the head and neck. METHODS: Computed tomography scans of 20 patients with advanced tumors of the larynx, naso-, oroand hypopharynx were prospectively planned using IMRT(7 field) and VMAT using two arcs. Calculated doses to planning target volume(PTV) and OAR were compared between IMRT and VMAT plans. Dose-volume histograms(DVH) were utilized to obtain calculated doses to PTV and OAR, including parotids, cochlea,spinal cord, brainstem, anterior tongue, pituitary and brachial plexus. DVH's for all structures were compared between IMRT and VMAT plans. In addition the planswere compared for dose conformity and homogeneity. The final treatment plan was chosen by the treating radiation oncologist. RESULTS: VMAT was chosen as the ultimate plan in 18 of 20 patients(90%) because the plans were thought to be otherwise clinically equivalent. The IMRT plan was chosen in 2 of 20 patients because the VMAT plan produced concentric irradiation of the cord which was not overcome even with an avoidance structure. For all patients, VMAT plans had a lower number of average monitor units on average(MU = 542.85) than IMRT plans(MU = 1612.58)(P < 0.001). Using the conformity index(CI), defined as the 95% isodose volume divided by the PTV, the IMRT plan was more conformal with a lower conformity index(CI = 1.61) than the VMAT plan(CI = 2.00)(P = 0.003). Dose homogeneity, as measured by average standard deviation of dose distribution over the PTV, was not different with VMAT(1.45 Gy) or IMRT(1.73 Gy)(P = 0.069). There were no differences in sparing organs at risk.CONCLUSION: In this prospective study, VMAT plans were chosen over IMRT 90% of the time. Compared to IMRT, VMAT plans used only one third of the MUs, had shorter treatment times, and similar sparing of OAR. Overall, VMAT provided similar dose homogeneity but less conformity in PTV irradiation compared to IMRT. This difference in conformity was not clinically significant.

Comparison of efficacy and safety between late-course and simultaneous integrated dose-increasing intensity-modulated radiation therapy for cervical cancer complicated with pelvic lymph node metastasis

Objective This study aimed to compare and analyze the clinical efficacy and safety of late-course and simultaneous integrated dose-increasing intensity-modulated radiation therapy(IMRT) for cervical cancer complicated with pelvic lymph node metastasis. Methods Sixty patients with cervical cancer complicated with pelvic lymph node metastasis who were admitted to our hospital from January 2013 to January 2015 were enrolled. The patients were randomly divided into the late-course dose-increasing IMRT group and the simultaneous integrated dose-increasing IMRT group, with 30 cases included in each group, respectively. All patients were concurrently treated with cisplatin. After treatment, the clinical outcomes of the two groups were compared. Results The remission rate of symptoms in the simultaneous integrated dose-increasing IMRT group was significantly higher than that in the late-course dose-increasing IMRT group(P < 0.05). The follow-up results showed that the overall survival time, progression-free survival time, and distant metastasis time of patients in the simultaneous integrated dose-increasing IMRT group were significantly longer than those in the late-course dose-increasing IMRT group(P < 0.05). The recurrent rate of lymph nodes in the radiation field in the simultaneous integrated dose-increasing IMRT group was significantly lower(P < 0.05) than in the late-course dose-increasing IMRT group. There was no significant difference in the incidence of cervical and vaginal recurrence and distant metastasis between the two groups(P > 0.05). The radiation doses of Dmax in the small intestine, D1 cc(the minimum dose to the 1 cc receiving the highest dose) in the bladder, and Dmax in the rectum in the simultaneous integrated dose-increasing IMRT group were significantly lower(P < 0.05) than in the late-course dose-increasing IMRT group. There was no significant difference in intestinal D2 cc(the minimum dose to the 2 cc receiving the highest dose) between the two groups(P > 0.05). The incidence of bone marrow suppression in the simultaneous integrated dose-increasing IMRT group was significantly lower(P < 0.05) than in the late-course dose-increasing IMRT group.Conclusion The application of simultaneous integrated dose-increasing IMRT in the treatment of cervical cancer patients complicated with pelvic lymph node metastasis can significantly control tumor progression, improve the long-term survival time, and postpone distant metastasis time with high safety.

Pre-treatment verification of intensity-modulated radiation therapy in paediatric patients: adequate estimation for tolerance limits

Objective: The objective of this work was to establish adequate tolerance limits based on a certain defined institutional indices and generate published data presenting our results to the radiotherapy community. Methods: One hundred paediatric patients were treated using 6-MV X-ray beams produced by Siemens ONCOR Expression linear accelerator. The clinical step-and-shoot intensity-modulated radiation therapy (IMRT) treatment plans were designed using KonRad release 2.2.23. For two treatment sites (abdomen, head and neck), the fluence maps generated by the treatment planning system were all delivered for the quality assurance (QA) which included absolute dose verification for all treatment fields, relative dose verification for each treatment field. Results: The 724 fluence maps were analyzed at three different criteria using the gamma index tool. The 3% dose difference of local prescribed dose /3 mm was considered adequate. The passing rate for all fields of all plans always exceeded 70%. The dose differences between the measured and calculated doses ranged from -2.2% to +4% [mean and standard deviation (s): 1.4 ± 1.5] for the abdominal case, and from -3.3% to +5.6% (1.3 ± 1.6) for head and neck case with total confidence limit 0.046 (4.6%). The 14/100 (14%) of the absolute point dose measurements were out of ±3% from the dose predicted by the treatment planning system. Only two cases were below -3%, while 12 cases over +3%. Conclusion: At 3% dose difference of local prescribed dose /3 mm criteria, a 75% passing a gamma criterion and 3% for absolute point dose can be achieved for abdomen and head and neck treatments site. We considered the tolerance limits based on these indices for IMRT QA adequate.

Local definitive intensity-modulated radiation therapy recommended for patients initially diagnosed with nasopharyngeal carcinoma with distant metastasis after an effective systemic chemotherapy

Objective The aim of the study was to propose a hypothesis that local definitive intensity-modulated radiation therapy(IMRT) should be recommended for initially diagnosed metastatic nasopharyngeal carcinoma(NPC) and demonstrate its feasibility.Methods Recently published papers on local definitive radiotherapy for initially diagnosed metastatic NPC were reviewed to propose a hypothesis.Results Several studies revealed the survival benefits of adding local definitive radiotherapy to the systemic chemotherapy in patients initially diagnosed with metastatic NPC.Conclusion We suggested that local definitive IMRT should be recommended in patients initially diagnosed with NPC with distant metastasis after an effective systemic chemotherapy, which may possibly prolong their survival time and potentially treat the disease.

The Impact of Variation in Bladder Volume on the Doses of Target and Organ-at-Risk in Intensity-Modulated Radiation Therapy for Localized Prostate Cancer

Intensity-modulated radiation therapy (IMRT) has become the mainstay of treatment for localized prostate cancer. In IMRT, minimizing differences between the conditions used during planning CT and daily treatment is important to prevent adverse events in normal tissues. In the present study, we evaluated the impact of variation in bladder volume on the doses to various organs. A total of 35 patients underwent definitive radiotherapy at Saitama Medical Center. A Light Speed RT16 (GE Healthcare) was used for planning and to obtain examination CT images. Such images were acquired after 4 - 6 days of planning CT image acquisition. The IMRT plans were optimized using the planning CT data to satisfy the dose constraints set by our in-house protocols for the PTV and the OARs. The dose distributions were then re-calculated using the same IMRT beams, and checked on examination CT images. It was clear that bladder volume affected the doses to certain organs. We focused on the prostate, bladder, rectum, small bowel, and large bowel. Regression coefficients were calculated for variables that correlated strongly with bladder volume (p < 0.05). We found that variation in bladder volume [cm3] predicted deviations in the bladder V70Gy, V50Gy, and V30Gy [%];the maximum dose to the small bowel [cGy];and the maximum dose to the large bowel [cGy]. The regression coefficients were -0.065, -0.125, -0.180, -10.22, and -9.831, respectively. We evaluated the impacts of such variation on organ doses. These may be helpful when checking a patient’s bladder volume before daily IMRT for localized prostate cancer.

Effect of Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy on the cellular malignant biological processes in advanced cervical cancer lesion

Objective:To study the effect of Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy on the cellular malignant biological processes in advanced cervical cancer lesion.Methods: Patients who were diagnosed with advanced cervical cancer in the Second People Hospital of Banan District Chongqing between April 2015 and March 2017 were selected and divided into two groups, group A received Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy, and group B received cisplatin + intensity-modulated radiation therapy. Serum contents of tumor markers, tumor invasion molecules and tumor proliferation molecules of two groups of patients were detected before treatment as well as 2 weeks and 4 weeks after treatment.Results: Serum E-cad, STMN1, Fas and p53 levels of both groups of patients 2 weeks and 4 weeks after treatment were significantly higher than those before treatment while TSGF, TK1, SCC-Ag, CA125, OPN, MMP9, NGAL, CyclinE, CyclinD1 and PCNA levels were significantly lower than those before treatment, and serum E-cad, STMN1, Fas and p53 levels of group A 2 weeks and 4 weeks after treatment were significantly higher than those of group B while TSGF, TK1, SCC-Ag, CA125, OPN, MMP9, NGAL, CyclinE, CyclinD1 and PCNA levels were significantly lower than those of group B.Conclusion: Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy for advanced cervical cancer can induce cancer cell apoptosis and inhibit cancer cell proliferation and invasion.

Feasibility of a Direct-Conversion Method from Magnetic Susceptibility to Relative Electron Density for Radiation Therapy Treatment Planning

Recently, several institutions have been developing magnetic resonance imaging (MRI)-guided radiotherapy treatment systems. In this study, we examine whether it is possible to perform radiation therapy planning (RTP) using a magnetic susceptibility map obtained using MRI. The head of a healthy volunteer was scanned using dual-energy computed tomography (CT) and MRI. A T2-star-weighted 3D gradient echo-based sequence (GRE) with images taken at four different echo times was acquired using the MRI scanner. The CT images were converted to relative electron density (rED) using a predefined ΔCT-rED conversion table. ΔCT was derived using the energy-subtraction method. The rED map was obtained from a single-linear relationship with the ΔCT-rED conversion table, whereas the magnetic susceptibility map was obtained from quantitative susceptibility mapping (QSM) via MRI. Subsequently, to obtain the relationship between the magnetic susceptibility and the rED, the rED map was rigidly aligned to the susceptibility map and resampled at the susceptibility map’s resolution. Finally, the magnetic susceptibility rED conversion table was obtained via voxel-by-voxel mapping between the two maps. No strong relationship between magnetic susceptibility and rED was obtained in the healthy volunteer’s head or in this study. The coefficient correlation between these parameters was 0.0145. Magnetic susceptibility values may be not able to convert to rED using our proposed method in healthy volunteer’s head. In contrast to the magnetic-susceptibility values obtained from the QSM algorithm, which were strongly affected by calcification and iron content, the rED or CT number was not considerably affected by such materials.

Long-term outcomes of a phase Ⅱ randomized controlled trial comparing intensity-modulated radiotherapy with or without weekly cisplatin for the treatment of locally recurrent nasopharyngeal carcinoma

Background:Salvage treatment for locally recurrent nasopharyngeal carcinoma(NPC) is complicated and relatively limited.Radiotherapy,combined with effective concomitant chemotherapy,may improve clinical treatment outcomes.We conducted a phase Ⅱ randomized controlled trial to evaluate the efficacy of intensity-modulated radiotherapy with concomitant weekly cisplatin on locally recurrent NPC.Methods:Between April 2002 and January 2008,69 patients diagnosed with non-metastatic locally recurrent NPC were randomly assigned to either concomitant chemoradiotherapy group(n = 34) or radiotherapy alone group(n = 35).All patients received intensity-modulated radiotherapy.The radiotherapy dose for both groups was 60 Gy in 27 fractions for 37 days(range 23-53 days).The concomitant chemotherapy schedule was cisplatin 30 mg/m^2 by intravenous infusion weekly during radiotherapy.Results:The median follow-up period of all patients was 35 months(range 2-112 months).Between concomitant chemoradiotherapy and radiotherapy groups,there was only significant difference in the 3-year and 5-year overall survival(OS) rates(68.7%vs.42.2%,P = 0.016 and 41.8%vs.27.5%,P = 0.049,respectively).Subgroup analysis showed that concomitant chemoradiotherapy significantly improved the 5-year OS rate especially for patients in stage rT3-4(33.0%vs.13.2%,P = 0.009),stages Ⅲ-Ⅳ(34.3%vs.13.2%,P = 0.006),recurrence interval >30 months(49.0%vs.20.6%,P = 0.017),and tumor volume >26 cm^3(37.6%vs.0%,P = 0.006).Conclusion:Compared with radiotherapy alone,concomitant chemoradiotherapy can improve OS of the patients with locally recurrent NPC,especially those with advanced T category(rT3-4) and stage(lll-IV) diseases,recurrence intervals >30 months,and tumor volume >26 cm^3.

Simultaneous modulated accelerated radiation therapy for esophageal cancer:A feasibility study

AIM: To establish the feasibility of simultaneous modulated accelerated radiation therapy (SMART) in esophageal cancer (EC).

CT image fusion in the evaluation of radiation treatment planning for non-small cell lung cancer

Objective: We studied the application of CT image fusion in the evaluation of radiation treatment planning for non-small cell lung cancer (NSCLC). Methods: Eleven patients with NSCLC, who were treated with three-dimensional con-formal radiation therapy, were studied. Each patient underwent twice sequential planning CT scan, i.e., at pre-treatment, and at mid-treatment for field reduction planning. Three treatment plans were established in each patient: treatment plan A was based on the pre-treatment planning CT scans for the first course of treatment, plan B on the mid-treatment planning CT scans for the second course of treatment, and treatment plan F on the fused images for the whole treatment. The irradiation doses received by organs at risk in the whole treatment with treatment A and B plans were estimated by the plus of the parameters in treatment plan A and B, assuming that the parameters involve the different tissues (i.e. V20=AV20+BV20), or the same tissues within an organ (i.e. Dmax=ADmax+BDmax). The assessment parameters in the treatment plan F were calculated on the basis of the DVH of the whole treatment. Then the above assessment results were compared. Results: There were marked differ-ences between the assessment results derived from the plus of assessment parameters in treatment plan A and B, and the ones derived from treatment plan F. Conclusion: When a treatment plan is altered during the course of radiation treatment, image fusion technique should be performed in the establishment of a new one. The estimation of the assessment parameters for the whole treatment with treatment plan A and B by simple plus, is inaccurate.

Leakage-Penumbra effect in intensity modulated radiation therapy step-and-shoot dose delivery

AIM: To study the leakage-penumbra(LP) effect with a proposed correction method for the step-and-shoot intensity modulated radiation therapy(IMRT).METHODS: Leakage-penumbra dose profiles from 10 randomly selected prostate IMRT plans were studied. The IMRT plans were delivered by a Varian 21 EX linear accelerator equipped with a 120-leaf multileaf collimator(MLC). For each treatment plan created by the Pinnacle3 treatment planning system,a 3-dimensional LP dose distribution generated by 5 coplanar photon beams,starting from 0o with equal separation of 72 o,was investigated. For each photon beam used in the stepand-shoot IMRT plans,the first beam segment was set to have the largest area in the MLC leaf-sequencing,and was equal to the planning target volume(PTV). The overshoot effect(OSE) and the segment positional errors were measured using a solid water phantom with Kodak(TL and X-OMAT V) radiographic films. Film dosimetric analysis and calibration were carried out using a film scanner(Vidar VXR-16). The LP dose profiles were determined by eliminating the OSE and segment positional errors with specific individual irradiations. RESULTS: A non-uniformly distributed leaf LP dose ranging from 3% to 5% of the beam dose was measured in clinical IMRT beams. An overdose at the gap between neighboring segments,represented as dose peaks of up to 10% of the total BP,was measured. The LP effect increased the dose to the PTV and surrounding critical tissues. In addition,the effectdepends on the number of beams and segments for each beam. Segment positional error was less than the maximum tolerance of 1 mm under a dose rate of 600 monitor units per minute in the treatment plans. The OSE varying with the dose rate was observed in all photon beams,and the effect increased from 1 to 1.3 Gy per treatment of the rectal intersection. As the dosimetric impacts from the LP effect and OSE may increase the rectal post-radiation effects,a correction of LP was proposed and demonstrated for the central beam profile for one of the planned beams. CONCLUSION: We concluded that the measured dosimetric impact of the LP dose inaccuracy from photon beam segment in step-and-shoot IMRT can be corrected.

Comparison of Dosiology between Three Dimensional Conformal and Intensity-modulated Radiotherapies (5 and 7 fields) in Gastric Cancer Post-surgery

The purpose of this study was to compare the dose distribution of intensity-modulated ra- diotherapy （IMRT） in 7 and 5 fields as well as 3-D conformal radiotherapy （3D-CRT） plans for gastric cancer using dosimetric analysis. In 15 patients with gastric cancer after D1 resection, dosimetric pa- rameters for IMRT （7 and 5 fields） and 3D-CRT were calculated with a total dose of 45 Gy （1.8 Gy/day） These parameters included the conformal index （CI）, homogeneity index （HI）, maximum dose spot for the planned target volume （PTV）, dose-volume histogram （DVH） and dose distribution in the organs at risk （OAR）, mean dose （Dmean）, maximal dose （Dmax） in the spinal cord, percentage of the normal liver volume receiving more than 30 Gy （V30） and percentage of the normal kidney volume receiving more than 20 Gy （V20）. IMRT （7 and 5 fields） and 3D-CRT achieved the PTV coverage. However, IMRT presented significantly higher CI and HI values and lower maximum dose spot distribution than 3D-CRT （P=0.001）. For dose distribution of OAR, IMRT had a significantly lower Dmean and Dmax in spinal cord than 3D-CRT （P=-0.009）. There was no obvious difference in V30 of liver and V20 of kidney between IMRT and 3D-CRT, but 5-field IMRT showed lower Dmean in the normal liver than other two plans （P=0.001）. IMRT revealed favorable tumor coverage as compared to 3D-CRT and IMRT plans. Specifically, 5-field IMRT plan was superior to 3D-CRT in protecting the spinal cord and liver, but this superiority was not observed in the kidney. Further studies are needed to compare differences among the three approaches.

Long-term Therapeutic Outcome and Prognostic Factors of Patients with Nasopharyngeal Carcinoma Receiving Intensity-modulated Radiotherapy: An Analysis of 608 Patients from Low-endemic Regions of China

Objective To evaluate the long-term outcome and prognostic factors of patients with nasopharyngeal carcinoma(NPC)from low-endemic regions of China who received definitive intensity-modulated radiation therapy(IMRT).Methods The clinical data from 608 patients with newly-diagnosed non-metastatic NPC who have received initial treatment at our cancer center from January,2008 to December,2013 were retrospectively reviewed.All patients received definitive IMRT,and 87.7%received platinum-based chemotherapy.Results The median follow-up duration was 51 months(follow-up rate,98.5%;range,10–106 months)for the entire cohort.The 5-year overall survival rate was 79.7%.The 5-year local relapse-free survival rate,regional relapse-free survival rate,distant metastasis-free survival rate and progression-free survival rate were 92.4%,93.3%,79.2%and 74.3%,respectively.A total of 153 patients had experienced treatment failure,with distant metastasis as the primary cause in 77.1%(118/153).Patients with T4 or N3 diseases had a significantly poorer prognosis than other subcategories.Stage T4 and N3 were closely associated with distant metastasis,with the metastatic rate of 29.3%and 45.5%,respectively.Conclusion IMRT provides patients with non-metastatic NPC with satisfactory long-term survival.Both T stage and N stage are important prognostic factors for NPC patients.Patients with T4 or N3 diseases have significantly increased distant metastatic rates and poor survival time.

Intensity-modulated Radiotherapy for Sinonasal Teratocarcinosarcoma

Surgical excision and postoperative radiotherapy are widely accepted therapeutic modalities for sinonasal teratocarcinosarcoma （SNTCS）. Previous studies have shown that intensity-modulated radiation therapy （IMRT） is safe and effective for the treatment of some sinonasal malignancies. We hypothesize that use of IMRT for SNTCS may result in clinical benefits. We report here two cases of SNTCS that were treated by IMRT. One patient was given extensive IMRT involving elective neck irradiation. Follow-up examinations revealed no recurrence and metastasis 3.5 years after IMRT. Another patient simultaneously suffered from multiple systematical diseases and was administered involved-field radiotherapy. He was found to have a marginal recurrence during the follow up and eventually died 8 months after disease diagnosis. It was suggested in this study that appropriate use of IMRT for the treatment of SNTCS may achieve excellent local control.

The Effect of Absorbed Dose to Organs at Risk Following Craniospinal Irradiation Using Different Radiotherapy Techniques

Introduction: In medulloblastoma patients craniospinal irradiation is an important element the treatment. Our study aimed to evaluate the effect of absorbed dose to organs at risk using the hybrid intensity-modulated radiation therapy (IMRT) versus three-dimensional conformal radiotherapy (3DCRT) for craniospinal irradiation (CSI) in average risk medulloblastoma patients. Materials and Methods: In this study, thirteen medulloblastoma patients were included. The prescribed total dose to the planning target volume (PTV) was 23, 40 Gy in 13 fractions. Two radiotherapy techniques, three dimensional conformal radiotherapy (3DCRT) and hybrid intensity modulated radiotherapy (IMRT) were used to treat these patients. The coverage of the Target was evaluated using the D mean, D95%, D2%, D98% and V95%. Other parameters were also compared such as Integral dose (ID), Homogeneity index (HI) and doses to the organs at risk (OARs). Results: There was no significant difference in the mean dose received by the PTV-Brain or the dose received by 95% and 98% of PTV volume using the two techniques. For PTV-Spine, the percentage volume receiving 95% of the total dose increased significantly in the hybrid IMRT technique compared to the conformal technique. So, hybrid IMRT plan achieved the best coverage for PTV spine. Lower dose for OAR was delivered by 3DCRT, except the heart and thyroid, hybrid IMRT achieved better sparing. All plans resulted in the same dose homogeneity index (DHI) for PTV-Brain. For PTV-Spine, hybrid IMRT technique achieved better dose homogeneity compared to 3DCRT technique (1.09 vs. 1.12;p > 0.05). Conclusions: hybrid IMRT technique can be realized on conformal technique because it achieved better dose coverage for the (PTV) and organ at risk (OAR). 3DCRT reduced mean dose to most OARS, except the heart and thyroid. Therefore, the hybrid IMRT technique may be a CSI treatment alternative to 3DCRT.