Main Session
Sep
29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement
Presenter(s)
Katherine Amarell, MD, BS - Cleveland Clinic Foundation, Cleveland, OH
K. Amarell1, Z. Zhang2, L. Lu2, H. Arain2, S. Dyer3, J. Schulte1, S. Vay1, Q. Zeedrich1, E. J. Murray4, P. Pendyala2, K. L. Stephans2, R. D. Tendulkar5, S. Moningi4, and P. Xia2; 1Cleveland Clinic Foundation, Cleveland, OH, 2Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH, 3Physics Department, Cleveland Clinic Foundation, Cleveland, OH, 4Cleveland Clinic, Cleveland, OH, 5Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH
Purpose/Objective(s):
The RAD-SG trial utilizes a library adaptive planning protocol for radiation delivery platforms that lack real-time replanning capability. We evaluated early outcomes to assess whether the adaptive approach maintains bladder target coverage and improves bowel dosimetry compared with a standard non-adaptive strategy.Materials/Methods:
Seven patients enrolled on RAD-SG completed 64 Gy in 32 fractions using the trial’s adaptive protocol. Simulation was performed with an empty bladder. After one week of treatment, daily CBCT images were reviewed to identify small, medium and large bladder volumes, from which two additional plans were generated as a plan library. For each fraction, therapists selected one of three plans (small, medium, or large bladder) based on visual concordance on CBCT. Bladder and bowel bag structures were retrospectively contoured on each CBCT, and delivered dosimetry was calculated per fraction and compared with the original base plan applied uniformly across fractions. Average per-fraction values were multiplied by 32 to estimate cumulative dose. The dose coverage of D95% and D90% to the bladder, D0.03cc, D5cc, and D10cc to the bowel bag were analyzed using the Wilcoxon signed-rank test.Results:
Among 224 fractions, D95% and D90% of bladder was comparable between the base and delivered plans. Average (standard deviation) daily bladder volume receiving the full prescription dose was 94.2% (9.7) for the base plan and 94.5% (9.3) for the adaptive approach. Average D95% and D90% were 60.6 (9.0) Gy and 62.7 (6.9) Gy for the base plan, and 61.0 (9.1) Gy and 62.8 (7.0) Gy for the adaptive approach, respectively. No statistically significant differences in bladder dosimetry were observed at either the patient level (n=7) or fraction level (n=224) (p>0.05 for all metrics). Bowel dosimetry was evaluated per fraction and cumulatively. For the base versus adaptive approaches, estimated cumulative metrics were: D0.03cc 67.2 (2.5) Gy vs 67.0 (1.6) Gy (p<0.0001), D5cc 62.7 (7.2) Gy vs 62.3 (6.8) Gy (p<0.0001), and D10cc 59.5 (9.4) Gy vs 59.0 (9.2) Gy (p=0.003). Fraction-level analysis (n=224) showed a statistically significant improvement in all bowel metrics with the adaptive approach. 92 of 224 fractions utilized an adaptive plan over the base plan. In patients for whom the base plan resulted in significant bowel dosing (>10 cc receiving full prescription), use of the adaptive plan reduced this volume by 44.7% (SD 22.0%, p<0.0001).Conclusion:
For treatment platforms without daily adaptive replanning capability, a three-plan bladder-volume adaptive strategy provides bladder target coverage comparable to a standard non-adaptive approach while improving bowel dosimetry at the fraction level, though patient-level comparisons were not statistically significant likely due to sample size. This workflow represents a practical alternative for centers without access to true adaptive technology.