Comparative analysis for renal stereotactic body radiotherapy using Cyberknife, VMAT and proton therapy based treatment planning.

PURPOSE: We conducted this dosimetric analysis to evaluate the feasibility of a multi-center stereotactic body radiation therapy (SBRT) trial for renal cell carcinoma (RCC) using different SBRT platforms. MATERIALS/METHODS: The computed tomography (CT) simulation images of 10 patients with unilateral RCC previously treated on a Phase 1 trial at Institution 1 were anonymized and shared with Institution 2 after IRB approval. Treatment planning was generated through five different platforms aiming a total dose of 48 Gy in three fractions. These platforms included: Cyberknife and volumetric modulated arc therapy (VMAT) at institution 1, and Cyberknife, VMAT, and pencil beam scanning (PBS) Proton Therapy at institution 2. Dose constraints were based on the Phase 1 approved trial. RESULTS: Compared to Cyberknife, VMAT and PBS plans provided overall an equivalent or superior coverage to the target volume, while limiting dose to the remaining kidney, contralateral kidney, liver, spinal cord, and bowel. CONCLUSION: This dosimetric study supports the feasibility of a multi-center trial for renal SBRT using PBS, VMAT and Cyberknife.

Robust treatment planning in whole pelvis pencil beam scanning proton therapy for prostate cancer.

Whole-pelvis pencil beam scanning (PBS) proton therapy is utilized in both the intact and post-operative settings in patients with prostate cancer. As whole pelvis prostate radiotherapy has traditionally been delivered with standard photon beams, limited evidence and technical descriptions have been reported regarding the use of proton therapy. Here we present two robust three-field treatment planning approaches utilized to maximize target coverage in the presence of anatomic and delivery uncertainties. Both techniques, conventional optimization (CO) and robust optimization (RO), create treatment plans with acceptable target coverage and sparing of organs at risk (OAR). While the RO method is less time intensive and may theoretically allow for superior OAR sparing and improved robustness, the CO method can be implemented by institutions who do not have RO capabilities.

Adjuvant radiation therapy for bladder cancer: a dosimetric comparison of techniques.

Trials of adjuvant radiation after cystectomy are under development. There are no studies comparing radiation techniques to inform trial design. This study assesses the effect on bowel and rectal dose of 3 different modalities treating 2 proposed alternative clinical target volumes (CTVs). Contours of the bowel, rectum, CTV-pelvic sidewall (common/internal/external iliac and obturator nodes), and CTV-comprehensive (CTV-pelvic sidewall plus cystectomy bed and presacral regions) were drawn on simulation images of 7 post-cystectomy patients. We optimized 3-dimensional conformal radiation (3-D), intensity-modulated radiation (IMRT), and single-field uniform dose (SFUD) scanning proton plans for each CTV. Mixed models regression was used to compare plans for bowel and rectal volumes exposed to 35% (V35%), 65% (V65%), and 95% (V95%) of the prescribed dose. For any given treatment modality, treating the larger CTV-comprehensive volume compared with treating only the CTV-pelvic sidewall nodes significantly increased rectal dose (V35% rectum, V65% rectum, and V95% rectum; p < 0.001 for all comparisons), but it did not produce significant differences in bowel dose (V95% bowel, V65% bowel, or V35% bowel). The 3-D plans, compared with both the IMRT and the SFUD plans, had a significantly greater V65% bowel and V95% bowel for each proposed CTV (p < 0.001 for all comparisons). The effect of treatment modality on rectal dosimetry differed by CTV, but it generally favored the IMRT and the SFUD plans over the 3-D plans. Comparison of the IMRT plan vs the SFUD plan yielded mixed results with no consistent advantage for the SFUD plan over the IMRT plan. Targeting a CTV that spares the cystectomy bed and presacral region may marginally improve rectal toxicity but would not be expected to improve the bowel toxicity associated with any given modality of adjuvant radiation. Using the IMRT or the SFUD plans instead of the 3-D conformal plan may improve both bowel and rectal toxicity.