Comparative Study between Field-in-Field and IMRT Techniques in Prostate Cancer Radiotherapy: A Treatment Planning Study

Introduction: Field-in-Field (FIF) and Intensity Modulated Radiation Therapy (IMRT) are two advanced radiation therapy planning techniques. Both of them are being used to achieve the same two related aims which are, to expose the targeted tumor to the full radiation dose and to spare the nearby normal tissues (or organs) from being exposed to high amounts of radiation more than its tolerance dose limits. FIF is a forward planning while IMRT is an inverse planning and FIF is a forward IMRT. Aim: The purpose of this study was to compare between Field-in-Field and IMRT techniques in prostate cancer radiotherapy. Method: A treatment planning system supporting both inverse and forward planning facilities is used. Ten prostate cancer patients were planned with both FIF and IMRT planning techniques. Doses received by the Planning Target Volume (PTV) and Organs at Risk (OARs) were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that the IMRT planning technique achieved better dose coverage to the PTV than the FIF planning technique but, except RT and LT Femoral Heads, FIF achieved a better protection to the Rectum and the Bladder (OARs) than IMRT. Conclusions: The results showed that the inverse planning based IMRT technique is better and recommended in the prostate cancer radiotherapy than the FIF technique.

Adjuvant Pelvic Radiotherapy vs.Sequential Chemoradiotherapy for High-Risk StageⅠ-ⅡEndometrial Carcinoma

Objective To explore if the addition of adjuvant chemotherapy with paclitaxel and carboplatin to radiotherapy confers an advantage for overall survival(OAS),and progression free survival(PFS);to assess the incidence of relapses over standard pelvic radiotherapy; and to evaluate the related toxicity in high-risk stageⅠ-Ⅱendometrial carcinoma Methods Medical records were reviewed to identify high-risk stageⅠ-Ⅱendometrial carcinoma cases treated in the Clinical Oncology and Nuclear Medicine department between 2002 and 2008 with adjuvant radiotherapy alone(armⅠ)(57 patients) or with sequential carboplatin(AUC5-6) and paclitaxel(135-175 mg/m^2) with radiotherapy(armⅡ)(51 patients).Radiotherapy was performed through the four-field box technique at doses of 45-50 Gy(1.8 Gy/day×5 days/week). Results The toxicity was manageable and predominantly hematologic with a grade 3 neutropenia and thrombocytopenia in 9.8% and 6% of the patients in armⅠand armⅡ,respectively,without febrile neutropenia.All patients experienced hair loss. Chemoradiotherapy arm was associated with a lower incidence rate of relapse(9.8% vs.22.7% ).After a median follow-up period of 48 months,the 5-year OAS and PFS rates for chemoradiotherapy-treated patients were significantly more favorable than those who did not receive chemotherapy(P=0.02 and 0.03,respectively).In armⅠ,the OAS and PFS rates were 73.7% and 66.7% compared with those in armⅡ,whose rates were 90.2% and 84.3% . Conclusions Adjuvant chemoradiation with paclitaxel and carboplatin improved the survival rates and decreased the recurrence rates in patients with high-risk stageⅠ-Ⅱendometrial carcinoma.Chemotherapy was associated with an acceptable rate of toxicity. However,a prospective study with a larger number of patients is needed to define a standard adjuvant treatment for high-risk stageⅠ-Ⅱendometrial carcinoma.

Effect of Non-Delineated Normal Volumes in IMRT Treatment for Left Breast Cancer: A Treatment Planning Study

Introduction: Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints. So, if there was any structure along the treatment beam path not delineated, it would not be taken into account during that calculation process. During IMRT routine practical work, it is noticed that there are some non-delineated normal tissue volumes that received un-aimed dose. Aim: The purpose of this study was to study the effect of unusually delineated normal volumes in IMRT treatment for left sided breast cancer. Method: Ten left sided breast cancer patients were planned with IMRT inverse planning system. The unusually delineated normal volumes were delineated and taken into account in IMRT dose constraints as an Organ at Risk. Doses received by that volume were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that doses received by the unusually delineated volume when they were delineated and taken into account in IMRT dose constraints were significantly higher than when they were not. Conclusions: The results showed that for IMRT planning technique used for treating left-sided breast cancer, all of the normal tissues/structures that are closed to the treatment targets must be delineated and taken into account in the IMRT planning dose constraints.

Dose Validation of Physical Wedged Asymmetric Fields in Artiste Linear Accelerator

Aim: The purpose of this study was to make a comparison between measured and calculated physical wedge dose distributions using the superposition algorithm. Settings and Design: The accurate determination of absorbed dose is important radiotherapy because of the relatively steep sigmoidal dose response curves for both tumor control and normal-tissue damage. Materials and Methods: High-energy photons (6 and 10 MV) from Artiste Treatment System Linear Accelerator Machine, available at Alexandria Ayadi Al-Mostakbal Oncology Center, were used. Results and Discussion: The results showed that the difference between measured and calculated wedged isodose curves depends on field size, beam energy, and the angle of the used wedge. Conclusion: The results showed that the presence of a wedge alters the primary and scattered components generated by a linear accelerator and causes beam hardening in 6 and 10 MV. The beam hardening increased as the wedge angle increased.