306 - Radiation Quality Control in the PROSPECT Trial

H. J. Mamon¹, Q. Shi², K. S. Smith^3,4, B. Colgrove⁵, J. Quigley⁶, G. Nelson⁵, M. Weiser⁷, M. J. Gollub⁸, L. Saltz⁹, E. Basch¹⁰, A. Dueck¹¹, K. A. Goodman¹², T. J. George¹³, G. Chang¹⁴, J. M. Farma¹⁵, A. Shergill¹⁶, T. Fitzgerald¹⁷, E. OReilly⁹, J. Meyerhardt¹⁸, and D. Schrag⁹; ¹Department of Radiation Oncology, Brigham and Women’s Hospital/Dana-Farber Cancer Institute, Boston, MA, ²Mayo Clinic, Rochester, MN, ³U Mass Chan Medical School, Worcester, MA, ⁴UMass Chan Medical School, worcester, MA, ⁵Mayo, Rochester, MN, ⁶IROC, Lincoln, RI, ⁷Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, ⁸Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, ⁹Memorial Sloan Kettering Cancer Center, New York, NY, ¹⁰University of North Carolina, Chapel Hill, NC, ¹¹Alliance Statistics and Data Center, Mayo Clinic, Scottsdale, AZ, ¹²Department of Radiation Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, ¹³Division of Hematology and Oncology, Department of Medicine, University of Florida, Gainesville, FL, ¹⁴Department of Colon & Rectal Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, ¹⁵Fox Chase Cancer Center, Philadelphia, PA, ¹⁶University of Chicago, Chicago, IL, ¹⁷Image and Radiation Oncology Core-Rhode Island, Lincoln, RI, ¹⁸Dana Farber Cancer Institute, Boston, MA

Purpose/Objective(s): PROSPECT (Clinical Trials.gov NCT01515787) is a prospective randomized trial of neoadjuvant chemoradiation vs. neoadjuvant FOLFOX with selective use of chemoradiation for patients with locally advanced rectal cancer (cT2N+, cT3N-, cT3N+). The primary results demonstrated the non-inferiority of neoadjuvant FOLFOX. Here we report the quality assurance of radiation delivered in the trial. Materials/

Methods: All radiation plans were submitted to the Quality Assurance Review Center (QARC) and reviewed by QARC staff and the first author of this abstract (HM). Patients could be treated with either intensity-modulated radiation therapy (IMRT) or 3D conformal radiation, at the discretion of the treating radiation oncologist. Radiation plans were scored by HM as per-protocol, minor deviation, or major deviation, as defined in the protocol. Patient-reported toxicity and quality of life outcomes were collected.
Results: 1194 patients were randomized from June 2012 through December 2018. This analysis is limited to the 597 patients who were randomized to the control (chemoradiation) group. 543/597 (91%) started chemoradiation, 515/543 (95%) received the planned dose of 5040 cGy. 278/543 (51%) were treated with 3D-conformal radiation and 234/543 (43%) with IMRT. The treatment technique was not available for 31 patients. Although there was no randomization, the IMRT and 3D groups were well-matched by age, gender, and stage of the tumor. 427/512 (83.4%) were treated per protocol, with three major deviations (two treating above the recommended dose, one under-treating the pelvic sidewall) and 82 minor deviations (mostly minor dose deviations and not covering the pre-sacral space in the cone down fields). As only 2% of the patients had a local failure within 5 years, no differences in local recurrence or other survival endpoints were seen for patients based on whether their treatment plans were administered per protocol vs. with minor deviation, or with IMRT vs 3D. The most common Grade 3 and higher patient-reported adverse events (PRO-CTCAE) reported during chemoradiation therapy were diarrhea (20%), fatigue (20%) pain (18%) and constipation (11%). There were no significant differences in toxicity based on treatment with IMRT vs 3D or the presence of minor deviations.
Conclusion: 95% of patients starting chemoradiation on the PROSPECT trial completed the planned dose of radiation with very low rates of recurrence and low rates of patient-reported toxicities. There were only 3 major deviations and 83% of patients were treated per protocol. No differences in efficacy or toxicity were seen between IMRT and 3D conformal radiation.