Rethinking the Role of Radiation Therapy in the Management of Epithelial Ovarian Cancer

Radiation has been relegated to a palliative role in the management of epithelial ovarian cancer (EOC). Contemporary radiation techniques, including intensity modulated radiation therapy (IMRT), stereotactic body radiation therapy (SBRT), and image-guided radiation therapy, enable conformal treatment that controls local disease with minimal morbidity. Recent studies from multiple institutions support the role of radiation in the ablative treatment of oligometastatic disease and control of locally recurrent and metastatic disease. Effective local treatment with radiation complements the role of systemic therapy in the management of EOC; reduces symptoms and disease burden, and may contribute to a prolonged drug free interval.

Cost-effectiveness of short course radiation therapy versus long-course chemoradiation for locally advanced rectal adenocarcinoma.

749 Background: Long-course chemoradiation (LCRT; 50.4 Gy in 28 fractions with concurrent chemotherapy) followed by surgery and adjuvant chemotherapy is the standard of care in the United States for locally advanced rectal cancer. However, many countries follow a protocol of short course radiation therapy (SCRT; 25 Gy in 5 fractions). The purpose of this study was to analyze the cost-effectiveness of SCRT versus LCRT. Methods: We developed a cost-effectiveness model simulating 10-year outcomes for 65-year-old patients treated with either SCRT or LCRT. For the base case analysis, we assumed 3D-conformal radiation treatment. We used probabilities, utilities and costs based on the literature and Medicare Fee schedules to determine the incremental cost-effectiveness ratio (ICER) of SCRT versus LCRT. We defined cost effectiveness at an ICER of $100,000/quality-adjusted life-year (QALY) or less. We assumed that SCRT would not result in tumor downstaging adequate enough to change rates of sphincter preservation, while LCRT resulted in higher rates of low anterior resection (LAR). To model preference-sensitive care, we conducted a two-way sensitivity analysis in which we simultaneously varied the utilities of the no evidence of disease states with LAR (NED-LAR) and abdominoperineal resection (APR; NED-APR). To model current practice, we repeated the analysis assuming 3D-conformal treatment for LCRT but intensity modulated radiation therapy (IMRT) for SCRT. Results: With an ICER of $351,731/QALY, SCRT was cost-effective as compared to LCRT. SCRT remained the cost-effective strategy with 3D-conformal treatment for LCRT but IMRT for SCRT (ICER of $314,022/QALY). On one-way sensitivity analysis, LCRT became the cost-effective approach when the utility of NED-APR was below 0.61. Two-way sensitivity analysis revealed that the cost-effective approach for a given patient depended on the utilities for the NED-LAR and NED-APR states. Conclusions: SCRT was the cost-effective strategy as compared to LCRT. However, the cost effectiveness of SCRT versus LCRT was sensitive to the utilities of NED-LAR and NED-APR, highlighting the importance of patient preference-sensitive care.

Study of impacts of different evaluation criteria on gamma pass rates in VMAT QA using MatriXX and EPID

Aim: This study evaluates the impacts of using different evaluation criteria on gamma pass rates in two commercially available QA methods employed for the verification of VMAT plans using different hypothetical planning target volumes (PTVs) and anatomical regions. Introduction: Volumetric modulated arc therapy (VMAT) is a widely accepted technique to deliver highly conformal treatment in a very efficient manner. As their level of complexity is high in comparison to intensity-modulated radiotherapy (IMRT), the implementation of stringent quality assurance (QA) before treatment delivery is of paramount importance. Material and Methods: Two sets of VMAT plans were generated using Eclipse planning systems, one with five different complex hypothetical three-dimensional PTVs and one including three anatomical regions. The verification of these plans was performed using a MatriXX ionization chamber array embedded inside a MultiCube phantom and a Varian EPID dosimetric system attached to a Clinac iX. The plans were evaluated based on the 3%/3 mm, 2%/2 mm, and 1%/1 mm global gamma criteria and with three low-dose threshold values (0%, 10%, and 20%). Results: The gamma pass rates were above 95% in all VMAT plans, when the 3%/3mm gamma criterion was used and no threshold was applied. In both systems, the pass rates decreased as the criteria become stricter. Higher pass rates were observed when no threshold was applied and they tended to decrease for 10% and 20% thresholds. Conclusion: The results confirm the suitability of the equipments used and the validity of the plans. The study also confirmed that the threshold settings greatly affect the gamma pass rates, especially for lower gamma criteria.

Incidental Dose to Pelvic Nodal Regions in Prostate-Only Radiotherapy

Objectives: Pelvic lymph nodal regions receive an incidental dose from conformal treatment of the prostate. This study was conducted to investigate the doses received by the different pelvic nodal regions with varying techniques used for prostate radiotherapy. Methods and Materials: Twenty patients of high-risk node-negative prostate cancer treated with intensity-modulated radiotherapy to the prostate alone were studied. Replanning was done for intensity-modulated radiotherapy, 3-dimensional conformal treatment, and 2-dimensional conventional radiotherapy with additional delineation of the pelvic nodal regions, namely, common iliac (upper and lower), presacral, internal iliac, obturator, and external iliac. Dose–volume parameters such as Dmean, D100%, D66%, D33%, V40, and V50 to each of the nodal regions were estimated for all patients. Results: The obturator nodes received the highest dose among all nodal regions. The mean dose received by obturator nodal region was 44, 29, and 22 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The mean dose was significantly higher when compared between 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment ( P < .001), 2-dimensional conventional radiotherapy and intensity-modulated radiotherapy ( P < .001), and 3-dimensional conformal treatment and intensity-modulated radiotherapy ( P < .001). The D33% of the obturator region was 64, 39, and 37 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The dose received by all other pelvic nodal regions was low and not clinically relevant. Conclusion: The incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques as used in the trials studying elective pelvic nodal irradiation. However, with intensity-modulated radiotherapy, this dose is lower, making elective pelvic irradiation more relevant. Advances in Knowledge: This study highlights that incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques.

Use Dose Bricks Concept to Implement Nasopharyngeal Carcinoma Treatment Planning

Purpose. A “dose bricks” concept has been used to implement nasopharyngeal carcinoma treatment plan; this method specializes particularly in the case with bell shape nasopharyngeal carcinoma case.Materials and Methods. Five noncoplanar fields were used to accomplish the dose bricks technique treatment plan. These five fields include (a) right superior anterior oblique (RSAO), (b) left superior anterior oblique (LSAO), (c) right anterior oblique (RAO), (d) left anterior oblique (LAO), and (e) superior inferior vertex (SIV). Nondivergence collimator central axis planes were used to create different abutting field edge while normal organs were blocked by multileaf collimators in this technique.Results. The resulting 92% isodose curves encompassed the CTV, while maximum dose was about 115%. Approximately 50% volume of parotid glands obtained 10–15% of total dose and 50% volume of brain obtained less than 20% of total dose. Spinal cord receives only 5% from the scatter dose.Conclusions. Compared with IMRT, the expenditure of planning time and costing, “dose bricks” may after all be accepted as an optional implementation in nasopharyngeal carcinoma conformal treatment plan; furthermore, this method also fits the need of other nonhead and neck lesions if organ sparing and noncoplanar technique can be executed.