Stereotactic body radiotherapy in pancreatic adenocarcinoma

Background:Stereotactic body radiotherapy(SBRT)in pancreatic cancer allows high delivery of radiation doses on tumors without affecting surrounding tissue.This review aimed at the SBRT application in the treatment of pancreatic cancer.Data sources:We retrieved articles published in MEDLINE/PubMed from January 2017 to December 2022.Keywords used in the search included:“pancreatic adenocarcinoma”OR“pancreatic cancer”AND“stereotactic ablative radiotherapy(SABR)”OR“stereotactic body radiotherapy(SBRT)”OR“chemoradiotherapy(CRT)”.English language articles with information on technical characteristics,doses and fractionation,indications,recurrence patterns,local control and toxicities of SBRT in pancreatic tumors were included.All articles were assessed for validity and relevant content.Results:Optimal doses and fractionation have not yet been defined.However,SBRT could be the standard treatment in patients with pancreatic adenocarcinoma in addition to CRT.Furthermore,the combination of SBRT with chemotherapy may have additive or synergic effect on pancreatic adenocarcinoma.Conclusions:SBRT is an effective modality for patients with pancreatic cancer,supported by clinical practice guidelines as it has demonstrated good tolerance and good disease control.SBRT opens a possibility of improving outcomes for these patients,both in neoadjuvant treatment and with radical intent.

Stereotactic body radiotherapy combined with sintilimab in patients with recurrent or oligometastatic hepatocellular carcinoma: A phase Ⅱ clinical trial

BACKGROUND Stereotactic body radiotherapy(SBRT)and programmed cell death 1 inhibitors have shown potential in treating hepatocellular carcinoma(HCC)in retrospective studies.AIM To evaluate the efficacy of combining SBRT with sintilimab for patients with recurrent or oligometastatic HCC.METHODS This trial involved patients with recurrent or oligometastatic HCC intravenously treated with SBRT plus sintilimab every 3 wk for 12 mo or until disease progression.The primary endpoint was progression-free survival(PFS).RESULTS Twenty-five patients were enrolled from August 14,2019,to August 23,2021.The median treatment duration was 10.2(range,0.7-14.6)months.SBRT was delivered at a median dose of 54(range,48-60)Gy in 6(range,6-10)fractions.The median follow-up time was 21.9(range,10.3-39.7)mo,and 32 targeted lesions among 25 patients were evaluated for treatment response according to the Response Evaluation Criteria in Solid Tumors version 1.1.The median PFS was 19.7 mo[95%confidence interval(CI):16.9-NA],with PFS rates of 68%(95%CI:52-89)and 45.3%(95%CI:28-73.4)at 12 and 24 mo,respectively.The median overall survival(OS)was not reached,with OS rates of 91.5%(95%CI:80.8-100.0)and 83.2%(95%CI:66.5-100.0)at 12 and 24 mo,respectively.The 1-and 2-year local control rate were 100%and 90.9%(95%CI:75.4%-100.0%),respectively.The confirmed objective response rate and disease control rate was 96%,and 96%,respectively.Most adverse events were graded as 1 or 2,and grade 3 adverse events were observed in three patients.CONCLUSION SBRT plus sintilimab is an effective,well-tolerated treatment regimen for patients with recurrent or oligometastatic HCC.

Uninvolved liver dose prediction in stereotactic body radiation therapy for liver cancer based on the neural network method

BACKGROUND The quality of a radiotherapy plan often depends on the knowledge and expertise of the plan designers.AIM To predict the uninvolved liver dose in stereotactic body radiotherapy(SBRT)for liver cancer using a neural network-based method.METHODS A total of 114 SBRT plans for liver cancer were used to test the neural network method.Sub-organs of the uninvolved liver were automatically generated.Correlations between the volume of each sub-organ,uninvolved liver dose,and neural network prediction model were established using MATLAB.Of the cases,70%were selected as the training set,15%as the validation set,and 15%as the test set.The regression R-value and mean square error(MSE)were used to evaluate the model.RESULTS The volume of the uninvolved liver was related to the volume of the corresponding sub-organs.For all sets of Rvalues of the prediction model,except for D_(n0)which was 0.7513,all R-values of D_(n10)-D_(n100)and D_(nmean)were>0.8.The MSE of the prediction model was also low.CONCLUSION We developed a neural network-based method to predict the uninvolved liver dose in SBRT for liver cancer.It is simple and easy to use and warrants further promotion and application.

Therapeutic Effects of Stereotactic Radiotherapy on 389 Cases of Brain Glioma

Objective： To investigate the treatment effectiveness and side effects of stereotactic radiotherapy for brain glioma. Methods： From Jun. 1995 to Dec. 1998, 389 cases of brain gliomas were treated by stereotactic radiotherapy, among which 151 cases were treated by stereotactic radiosurgery （SRS） and the other 238 cases, by fractionated stereotactic radiotherapy （FSRT）. In the SRS group, the marginal tumor dose was 20 to 30 Gy （median, 2.6 Gy）. One to 6 isocenters （median, 2.48） and 5 to 21 irradiation arcs （median, 8.45） were applied. In the FSRT group, the per-fraction marginal tumor dose was 8 to 12 Gy with 1 to 6 isocenters （median, 2.53）, 6 to 20 irradiation arcs （median, 8.25） and 2-5 fractions delivered everyday or every other day. Results： Three months after treatment, the complete and partial response rates were 13.9% and 45.7% in SRS group respectively. The stable disease rate was 17.2%. The total effective rate was 76.8%. In FSRT group, the complete and partial remission rates were 19.7% and 47.9% respectively. The stable disease rate was 20.6%. The total effective rate was 88.2%. The total effective rate of FSRT group was higher than that in SRS group （X^2=9.874, P=0.020）. The 1-year, 3-year and 5-year survival rate of all patients was 54.3%, 29.3%, 16.5% respectively. The 1-year, 3-year and 5-year survival rate in SRS group and FSRT group was 52.3% vs 26.5%, 11.9% vs 55.5%, and 31.1 vs 19.3% respectively. There was no significant difference between the two groups （X^2=2.16, P=0.1417）. The brain edema caused by the main radiation was more severe in the SRS group than in FSRT group （X^2=4.916, P=0.027）. Conclusion： It is effective for brain glioma to be treated by stereotactic radiotherapy. Compared with SRS, the FSRT has the advantage of good effect and less side response.

Stereotactic conformal radiotherapy of hepatic metastases:clinical analysis of 8 cases

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Hepatocellular carcinoma with child Pugh-A Cirrhosis treated with stereotactic body radiotherapy

AIM To evaluate the control, survival, and hepatic function for Child Pugh(CP)-A patients after Stereotactic body radiotherapy(SBRT) in hepatocellular carcinoma(HCC).METHODS From 2009 to 2016, 40 patients with Barcelona Liver Clinic(BCLC) stages 0-B HCC and CP-A cirrhosis completed liver SBRT. The mean prescription dose was 45 Gy(40 to 50 Gy in 4-5 fractions). Local relapse, defined as recurrence within the planning target volume was assessed with intravenous multiphase contrast computed tomography or magnetic resonance imaging every 4-6 mo after completion of SBRT. Progression of cirrhosis was evaluated by CP and Model for End Stage Liver Disease scores every 3-4 mo. Toxicities were graded per the Common Terminology Criteria for Adverse Events(v4.03). Median follow-up was 24 mo.RESULTS Forty-nine HCC lesions among 40 patients were analyzed in this IRB approved retrospective study. Median tumor diameter was 3.5 cm(1.5-8.9 cm). Six patients with tumors ≥ 5 cm completed planned selected transarterial chemoembolization(TACE) in combination with SBRT. Eight patients underwent orthotropic live transplant(OLT) with SBRT as a bridging treatment(median time to transplant was 12 mo, range 5 to 23 mo). The Pathologic complete response(PCR) rate in this group was 62.5%. The 2-year in-field local control was 98%(1 failure). Intrahepatic control was 82% and 62% at 1 and 2 years, respectively. Overall survival(OS) was 92% and 60% at 1 and 2 years, with a median survival of 41 mo per Kaplan Meier analysis. At 1 and 2 years, 71% and 61% of patients retained CPA status. Of the patients with intrahepatic failures, 58% developed progressive cirrhosis, compared to 27% with controlled disease(P = 0.06). Survival specific to hepatic failure was 92%, 81%, and 69% at 12, 18, and 24 mo. There was no grade 3 or higher toxicity. On univariate analysis, gross tumor volume(GTV) < 23 cc was associated with freedom from CP progression(P = 0.05), hepatic failure-specific survival(P = 0.02), and trended with OS(P = 0.10).CONCLUSION SBRT is safe and effective in HCC with early cirrhosis and may extend waiting time for transplant in patients who may not otherwise be immediate candidates.

Treatment of metastatic liver tumors using stereotactic ablative radiotherapy

The prognosis of patients with metastatic liver disease remains dismal with a median survival of only 6-12 mo. As 80%-90% of patients are not candidates for surgical therapy, there is a need for effective non-surgical therapies that would improve outcomes in these patients. The body of evidence related to the use of stereotactic ablative radiotherapy(SABR) in metastatic liver disease has substantially grown and evolved over the past decade. This review summarizes the current evidence supporting liver SABR with particular attention given to patient selection, target delineation, organ at risk dose volume constraints, response evaluation imaging and the various SABR techniques for delivering ablative radiotherapy to the liver. Even though it is unclear what dose-fractionation scheme, delivery system, concomitant therapy or patient selection strategy yields the optimum liver SABR outcomes, clear and growing evidence is available that SABR is a safe and effective therapy for the treatment of oligometastatic liver disease.

Stereotactic body radiotherapy for isolated paraaortic lymph node recurrence from colorectal cancer

AIM： To evaluate the efficacy and complications of stereotactic body radiotherapy in localized paraaortic lymph node recurrence from colorectal cancer. METHODS： From 2003 to 2009, 7 patients with paraaortic lymph node recurrence （1-3 lesions） from colorectal cancer were treated with stereotactic body radiotherapy. Total gross tumor volumes ranged from 4 to 40 mL. The doses were escalated from 36 Gy/patient to 51 Gy/patient and were delivered in 3 fractions. RESULTS： One and 3 year overall survival rates were 100% and 71.4%, respectively, and median survival was 37 mo. Grade IV intestinal obstruction was reported in 1 of 7 patients. This patient received 48 Gy in 3 fractions with a maximum point dose to the intestine of 53 Gy and V45Gy = 3.6 mL. However, 6 patients received an intestinal maximum point dose of 〈 51 Gy and V45Gy of 〈 1 mL, and did not develop any severe complications. CONCLUSION： This pilot study suggests selected paraaortic lymph node recurrence （1-3 closed lesions） that failed to respond to chemotherapy can be potentially salvaged by stereotactic body radiotherapy.

Initial experience with stereotactic body radiotherapy for intrahepatic hepatocellular carcinoma recurrence after liver transplantation

BACKGROUND Graft hepatocellular carcinoma(HCC)recurrence after liver transplant is more frequently encountered.Graft hepatectomy is technically challenging and is associated with high morbidity.Stereotactic body radiation therapy(SBRT)has been shown to be safe and effective for the treatment of primary HCC.However,its role in HCC recurrence in a liver graft remains unclear.AIM To evaluate the safety and efficacy of SBRT for the treatment of graft HCC recurrence after liver transplantation.METHODS A retrospective study was conducted.From 2012 to 2018,6 patients with intrahepatic HCC recurrence after liver transplant were treated with SBRT at Queen Mary Hospital,the University of Hong Kong.The primary outcome was time to overall disease progression and secondary outcomes were time to local progression and best local response,as assessed with the Modified response Evaluation Criteria for Solid Tumours criteria.Patients were monitored for treatment related toxicities and graft dysfunction.RESULTS A total of 9 treatment courses were given for 13 tumours.The median tumour size was 2.3 cm(range 0.7-3.6 cm).Two(22%)patients had inferior vena cava tumour thrombus.The best local treatment response was:5(55%)complete response,1(11%)partial response and 3(33%)stable disease.After a median follow up duration of 15.5 mo,no local progression or mortality was yet observed.The median time to overall disease progression was 6.5 mo.There were 6 regional progression in the liver graft(67%)and 2 distant progression in the lung(22%).There was no grade 3 or above toxicity and there was no graft dysfunction after SBRT.CONCLUSION SBRT appears to be safe in this context.Regional progression is the mode of failure.

Stereotactic radiotherapy for prostate cancer:A review and future directions

Prostate cancer affects over 200000 men annually in the United States alone.The role of conventionally fractionated external beam radiation therapy (RT) is well established as a treatment option for eligible prostate cancer patients; however,the use of stereotactic body radiotherapy (SBRT) in this setting is less well defined.Within the past decade,there have been a number of studies investigating the feasibility of SBRT as a potential treatment option for prostate cancer patients.SBRT has been well studied in other disease sites,and the shortened treatment course would allow for greater convenience for patients.There may also be implications for toxicity as well as disease control.In this review we present a number of prospective and retrospective trials of SBRT in the treatment of prostate cancer.We focus on factors such as biochemical progression-free survival,prostate specific antigen (PSA) response,and toxicity in order to compare SBRT to established treatment modalities.We also discuss future steps that the clinical community can take to further explore this new treatment approach.We conclude that initial studies examining the use of SBRT in the treatment of prostate cancer have demonstrated impressive rates of biochemical recurrencefree survival and PSA response,while maintaining a relatively favorable acute toxicity profile,though long-term follow-up is needed.

Stereotactic body radiotherapy using Cyber Knife for locally advanced unresectable and metastatic pancreatic cancer

AIM: To evaluate the efficacy and toxicity of stereotactic body radiotherapy using Cyber Knife for locally advanced unresectable and metastatic pancreatic cancer.METHODS: From June 2010 to May 2014,25 patients with locally advanced unresectable and metastatic pancreatic cancer underwent stereotactic body radiotherapy.Nine patients presented with unresectable locally advanced disease and 16 had metastatic disease.Primary end-points of this study were overall survival,relief of abdominal pain,and toxicity.RESULTS: Fourteen patients were treated with a total dose of 30-36 Gy in three fractions and the remainder with 40-48 Gy in four fractions.Median follow-up was 11 mo(range: 2-25 mo).The median survival duration calculated from the time of stereotactic body radiotherapy for the entire group,the locally advanced group,and the metastatic group was 9.0 mo,13.5 mo,and 8.5 mo,respectively.Overall survival was 37% and 18% at one and two years,respectively.Abdominal pain relief was achieved within 2 wk of completing radiotherapy in the patients who received successful palliation(13 of 20 patients had significant pain).Five patients(20%) had grade 1 nausea,and one(4%) had grade 2 nausea.No acute grade 3+ toxicity was seen.CONCLUSION: Stereotactic body radiotherapy using the Cyber Knife system is a promising,noninvasive,palliative treatment with acceptable toxicity for locally advanced unresectable and metastatic pancreatic cancer.

Partial and Full Arc Volumetric Modulated Arc Therapy in Lung Cancer Stereotactic Body Radiotherapy with Different Definitions of Internal Target Volume Based on 4D CT

Purpose: To investigate the feasibility of partial arc volumetric modulated arc therapy (VMAT) in lung cancer stereotactic body radiotherapy (SBRT), as well the volumetric and dosimetric effects of different internal target volume (ITV) definitions with 4D CT. Methods: Fourteen patients with primary and metastatic lung cancer underwent SBRT were enrolled. Full and partial arc VMAT plans were generated with four different ITVs: ITVall, ITVMIP, ITVAIP and ITV2phases, representing ITVs generated from all 10 respiratory phases, maximum intensity projection (MIP), average intensity projection (AIP), and 2 extreme respiratory phases. Volumetric and dosimetric differences, as well as MU and delivery time were investigated. Results: Partial arc VMAT irradiated more dose at 2 cm away from planning target volume (PTV) (P = 0.002), however, it achieved better protection on mean lung dose , lung V5, spinal cord, heart and esophagus compared with full arc VMAT. The average MU and delivery time of partial arc VMAT were 240 and 1.6 min less than those of full arc VMAT. There were no significant differences on target coverage and organ at risks (OARs) sparing among four ITVs. The average percent volume differences of ITVMIP, ITVAIP and ITV2phases to ITVall were 8.6%, 13.4%, and 25.2%, respectively. Conclusions: Although partial arc VMAT delivered more dose 2 cm out of PTV, it decreases the dose to lung, spinal cord, and esophagus, as well decreased the total MU and delivery time compared with full arc VMAT without sacrificing target coverage. Partial arc VMAT was feasible and more efficient for lung SBRT.

Stereotactic radiotherapy and the potential role of magnetic resonance-guided adaptive techniques for pancreatic cancer

BACKGROUND Pancreatic cancer is a malignancy with one of the poorest prognoses amongst all cancers.Patients with unresectable tumours either receive palliative care or undergo various chemoradiotherapy regimens.Conventional techniques are often associated with acute gastrointestinal toxicities,as adjacent critical structures such as the duodenum ultimately limits delivered doses.Stereotactic body radiotherapy(SBRT)is an advanced radiation technique that delivers highly ablative radiation split into several fractions,with a steep dose fall-off outside target volumes.AIM To discuss the latest data on SBRT and whether there is a role for magnetic resonance-guided techniques in multimodal management of locally advanced,unresectable pancreatic cancer.METHODS We conducted a search on multiple large databases to collate the latest records on radiotherapy techniques used to treat pancreatic cancer.Out of 1229 total records retrieved from our search,36 studies were included in this review.RESULTS Studies indicate that SBRT is associated with improved clinical efficacy and toxicity profiles compared to conventional radiotherapy techniques.Further dose escalation to the tumour with SBRT is limited by the poor soft-tissue visualisation of computed tomography imaging during radiation planning and treatment delivery.Magnetic resonance-guided techniques have been introduced to improve imaging quality,enabling treatment plan adaptation and re-optimisation before delivering each fraction.CONCLUSION Therefore,SBRT may lead to improved survival outcomes and safer toxicity profiles compared to conventional techniques,and the addition of magnetic resonance-guided techniques potentially allows dose escalation and conversion of unresectable tumours to operable cases.

Challenges and opportunities of using stereotactic body radiotherapy with anti-angiogenesis agents in tumor therapy

Microvessels promote proliferation of tumor cells by delivering oxygen and nutrients, but rapid growth of tumors results in unmet demands for oxygen and nutrients, thereby creating a hypoxia microenvironment. Under hypoxic conditions, vascular endothelial cells（ECs） initiate the formation of immature and abnormal microvasculature. This results in leakage and tortuosity that facilitates tumor cell invasion, metastasis and resistance to cytotoxic treatment.Radiotherapy（RT） is a vital tumor treatment modality. Currently, more than 60% of patients with malignant tumors receive RT at certain points during their treatment. Hypoxia induced by abnormal microvessels can hamper the cytotoxic effect of ionizing radiation, particularly, stereotactic body radiotherapy（SBRT）. Anti-angiogenesis（AA） agents are known to reduce and renormalize microvessels in tumors, and hence alleviate hypoxia. The combination of AA agents with SBRT may have a synergistic role in inhibiting the growth of tumors. On the contrary, large doses of irradiation may affect tumor microvessels itself. In this review, we aim to clarify the relationship between SBRT and microvessel formation in tumors. In addition, we provide a retrospective analysis of the combination therapy involving SBRT and AA agents in preclinical and clinical practice to define its role in antitumor treatment.

Dosimetric Impact of Tumor Position and Lung Density Variations in Lung Stereotactic Body Radiotherapy

Purpose of this study was to evaluate the variation of the dose to gross tumor volume (GTV) related to tumor position and lung density for lung stereotactic body radiotherapy (SBRT) using a virtual phantom. The density of the equivalent lung surrounding the GTV (10 mm diameter) was defined as 0.10, 0.15, 0.25, 0.35, and 0.45 g/cm3. A planning target volume (PTV) was generated by adding a uniform 8 mm margin to the internal target volume (ITV). We defined that the 99% of the GTV should be covered by 100% of the prescribed dose using Monte Carlo (MC) calculation. The GTV structure was replicated from ITV to the PTV periphery at 1 mm intervals. Planned dose to the GTV was defined as the predicted dose in the replicated GTV structure. Simulated dose to the GTV was defined as the calculated dose in the replicated GTV structure taking into account the tumor position error. D99 of the planned dose to the GTV at the 8 mm shift position was 78.1%, 81.6%, 87.3%, 91.4% and 94.4% at equivalent lung densities of 0.10, 0.15, 0.25, 0.35, and 0.45 g/cm3, respectively. D99 of the simulated dose to the GTV at the 8 mm shift position was 96.9%, 95.3%, 94.2%, 95.1 % and 96.3% at equivalent lung densities of 0.10, 0.15, 0.25, 0.35, and 0.45 g/cm3, respectively. Planned dose to GTV is strongly dependent on lung density and tumor position errors, while simulated dose to GTV does not show any significant dependence.

Stereotactic body radiotherapy for oligo-recurrence within the nodal area from colorectal cancer

Recurrence of colorectal cancer(CRC)often presents as solitary metastases,oligometastases or oligo-recurrence.Surgical resection became the preferred treatment for patients with CRC lung and hepatic metastases.However,surgical treatment for oligo-recurrence within nodal area is not a widely accepted treatment due to due to their relative rarity and high postoperative morbidity.Stereotactic body radiotherapy(SBRT)is one of the emerging radiation treatment techniques in which a high radiation dose can be delivered to the tumor.High-dose SBRT can ablate the tumor with an efficacy similar to that achieved with surgery,especially for small tumors.However,there have been very few studies on SBRT for oligo-recurrence within nodal area,although several studies have evaluated the role of SBRT in the treatment of liver and lung metastases from CRC.This article reviews the current clinical status of and treatment methods for oligo-recurrence within nodal area from CRC,with particular emphasis on SBRT.

Hepatocellular carcinoma effective stereotactic body radiotherapy using Gold Anchor and the Synchrony system:Two case reports and review of literature

BACKGROUND Radiotherapy for hepatocellular carcinoma(HCC)is considered to have limited efficacy because of treatment intensity considering that the irradiated area includes the liver,which is highly radiosensitive.In this report,we present two cases in which tumor control by surgical resection,radiofrequency ablation,transcatheter arterial chemoembolization(TACE),and lenvatinib administration was difficult,but stereotactic body radiotherapy(SBRT)using the Synchrony system by Radixact?and Gold Anchor?(GA)was effective.CASE SUMMARY A 60-year-old man had a single 10-cm HCC in the right lobe.Viable lesions remained after TACE,and levels of alpha-fetoprotein and protein induced by vitamin K antagonists II(PIVKA-II)decreased and quickly re-elevated.We performed SBRT with GA.Three weeks after implantation,localized radiotherapy(SBRT;40 Gy/5 fractions)was performed using the Synchrony system by Radixact?.Four weeks later,the viable lesion had disappeared,and the PIVKA-II levels decreased.A 77-year-old man had a single 12-cm HCC in the right lobe.The patient experienced recurrence after hepatectomy.Further recurrence occurred after TACE,and we performed SBRT with GA.Because of the proximity of the HCC to the gastrointestinal tract,localized radiotherapy(SBRT;39 Gy/13 fractions)to the HCC was performed 3 wk after implantation using the Synchrony system by Radixact?.Four weeks later,the viable lesion had disappeared on computed tomography,and the PIVKA-Ⅱlevels decreased.CONCLUSION SBRT using the Synchrony system and GA can deliver a large dose accurately and safely,and could have a high therapeutic effect.

Stereotactic radiotherapy for intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma(iCCA)is an aggressive malignancy with an increasing incidence worldwide and poor prognosis,despite several advances and continuous efforts to develop effective treatments.Complete surgical resection is the mainstay of treatment and offers a potentially curative option,but is only possible in less than a third of patients,owing to advanced disease.Chemotherapy is a well-established treatment in the adjuvant and palliative setting,however,confers limited benefit.Conventional radiotherapy is challenging due to local toxicity.With recent advances in stereotactic ablative radiotherapy(SABR),it is now possible to focus ablative beams of radiotherapy precisely aimed at tumours to minimise damage to surrounding viscera.This review details the history,technical background and application of SABR to iCCA,with directions for future research suggested.

Stereotactic Radiotherapy Planning Using Modified Dynamic Conformal Arcs under Considering the Possibility for Amended Visual Organ Displacement Resulting from Early Tumor Shrinkage during Treatment for Perioptic Involvement of Myeloma

Treatment planning of radiotherapy for skull base involvement of multiple myeloma presenting with visual impairment should be optimized to alleviate symptoms immediately and sufficiently while minimizing toxicities. Two such patients were treated with fractionated stereotactic radiotherapy by using Dynamic Conformal Arcs (DCA) under image guidance based on bony anatomy alignment. DCA planning was optimized after considering the possibility for amendment of visual organ displacement resulting from early tumor shrinkage during treatment through 1) the use of a target volume with modified geometry as a surrogate for leaf adaptation in order to improve target coverage, and 2) manual adjustment of a subset of leaf positions to reduce the dose gradient immediately inside the target boundary facing the visual organs and to eliminate an undesirable dose hotspot. In both cases, anticipated geometric changes in the target volume associated with improvement of visual organ displacement toward the target centroid were observed before the completion of treatment. Favorable visual functional outcomes as well as local tumor control were achieved during 14 months and 4 months follow-up periods. Notably, inexorable visual loss in one patient was fully reversed within one month after radiotherapy. We described the modification techniques for DCA planning in detail.

Comparison of Stereotactic Body Radiotherapy Delivery Techniques for Early-Stage Lung Cancer Using Lung Toxicity Modeling

Purpose: Lung toxicity is a primary side effect in stereotactic radiotherapy (SBRT) for early-stage non-small cell lung cancer (NSCLC). We aimed to use a set of radiobiological models to evaluate and compare modern IMRT delivery techniques with three-dimensional conformal techniques for SBRT treatment of NSCLC in terms of lung toxicity, and aimed to compare the results from different radiobiologcal models. Methods: Ten early-stage NSCLC patients treated with SBRT were retrospectively selected. Five treatment plans were generated to deliver 50 Gy in five fractions to the planning target volume for each case: a helical tomotherapy (HT) plan, two three-dimensional cofnromal radiotherapy (3D-CRT) plans using 6-MV and 10-MV photon beams respectively, and two volumetric modulated arc therapy (VMAT) plans using one and two arc fields respectively. The lung RDV was calculated with three parallel functional sub-unit (FSU) models and two normal tissue complication probability (NTCP) models. Results: Both the HT and VMAT plans showed significantly higher contralateral mean lung dose and lower ipsilateral mean lung dose compared to the 3D-CRT plans. There was no statistically significant difference in terms of lung toxicities between the IMRT and 3D-CRT techniques using either the FSU models or the NTCP models. Based on both the FSU and the NTCP models, there was strong correlation between lung toxicity and the mean lung dose in SBRT treatment plans. Conclusions: Based on both the NTCP and parallel FSU models, both IMRT and traditional 3D-CRT delivery techniques could achieve comparable lung sparing inn SBRT treatment of early-stage lung cancer. However, the validity of the radiobiological model results should be checked by clinical data.