Hua Ren¹, Jing Jin¹, Yuan Tang¹, Ning Li²

¹Radiation Oncology,Cancer Hospital, CAMS, ²Radiation Onocology, CancerHospital, CAMS

Objective:Preoperative concurrent chemoradiotherapy(chemoRT) has been established as the standard of care for patients with cT3-4rectal cancer. As an alternative strategy, we launched a randomized phase IIstudy to evaluate efficacy and toxicities of the modality of regularpreoperative intensity-modulated chemoRT with a simultaneous integrated boost (SIB)or regular preoperative intensity-modulated chemoRT (regular). Method: cT3-4rectal cancer patients were randomly assigned to receive either preoperativeIMRT (50 Gy in 25 fractions of 2 Gy) plus capecitabine (825 mg/m²twice daily) with a SIB to the rectal tumor up to a total dose of 56 Gy (boost-arm)or preoperative IMRT (50 Gy in 25 fractions of 2 Gy) plus capecitabine (825 mg/m²twice daily) (regular-arm). Surgery was performed 6-8 weeks after completion ofpreoperative treatment. Pathologic complete response rate (ypCR) was theprimary endpoint, planned sample size was52patientsin each arm. Acute sideeffects were scored using the National Cancer Institute Common TerminologyCriteria for Adverse Events version 3.0. Result: 99 patients wererandomly assigned to the boost-arm (n=52) or regular-arm (n=47), 79 patientsfinished preoperative concurrent chemoradiation, per protocol rate were 96.16%(SIB) vs. 95.74% (regular). Acute grade 3 toxicity occurred in 2.4% of thepatients in the boost-arm compared to 5.3% in the regular-arm (P=0.606).No acute grade 4 or 5 toxicities were observed. Acute hematology toxicity (≥grade2) occurred in 12.2% of the patients in the boost-arm compared to 26.3% in theregular-arm (P=0.353). Acute GI toxicity (≥grade 2) occurred in 19.5% ofthe patients in the boost-arm compared to 28.9% in the regular-arm (P=0.369).To date, 76 patients undergone R0 resection in the boost-arm (n=41) andregular-arm (n=35); ypCR was 12.2% in the boost-arm compared to 17.1% in theregular-arm (P=0.527). Conclusion: limited acute grade 3toxicity were found in both arms. No significant difference in the ypCR rate.This phase 2 trial is still recruiting patients, mature data are awaited laterthis year.

Key Words: rectal cancer  properative chemoradiation  SIB IMRT