Nomogram Predicting Long-Term Survival After TME Surgery for Locally Advanced Rectal Cancer Based on 1798 Patients Treated in a Single Institution Between 2000 and 2010

Abstract

Materials/Methods: cT3-4 rectal cancer patients were randomly assigned to receive either preoperative IG-IMRT (46 Gy in 23 fractions of 2 Gy) with a SIB to the rectal tumor up to a total dose of 55.2 Gy (boost-arm) or preoperative IG-IMRT (46 Gy in 23 fractions of 2 Gy) plus capecitabine (825 mg/m2 twice daily) (chemo-arm). Surgery was performed 6-8 weeks after completion of preoperative treatment. Metabolic tumor activity reduction, assessed by comparing the maximal standardized uptake value (SUVmax) on sequential 18-fluorodeoxyglucose positron emission tomography (FDG-PET), was the primary endpoint. Acute side effects were scored using the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Results: To date, 114 patients were randomly assigned to the boost-arm (n Z 55) or chemo-arm (n Z 59). Acute grade 3 toxicity occurred in 4% of the patients in the boost-arm compared to 7% in the chemo-arm (p Z 0.38). No acute grade 4 toxicities were observed. There was a trend for a lower rate of acute grade 2 enteritis in the boost-arm (25% vs 36% in the chemo-arm; p Z 0.16). The R0 resection rate was 98% for patients in the boostand chemo-arm. Pathologic complete response rate (ypCR, Dworak grade 4) was 16% in the boost-arm compared to 21% in the chemo-arm (p Z 0.33). Dworak regression grade 3-4 was 48% and 40% in the boost-arm and chemo-arm, respectively (p Z 0.27). The mean fractional change in SUVmax at 5 weeks after completion of preoperative RT as compared to baseline was 53.5% 19.4% and 50.7% 25.7% for patients in the boost-arm and chemo-arm, respectively (p Z 0.28). Conclusions: The implementation of preoperative IG-IMRT resulted in limited acute grade 3 toxicity in both arms. In terms of downstaging, impressive rates of major histomorphologic regression (Dworak grade 3-4) were recorded in both treatment arms, with no significant difference in the ypCR rate. We observed no differences in metabolic response. Mature data from this ongoing trial are awaited later this year. Author Disclosure: B. Engels: None. A. De Paoli: None. G. Cattari: None. F. Munoz: None. S. Vagge: None. D. Norkus: None. P. Gabriele: None. G. Tabaro: None. H. Versmessen: None. M. De Ridder: None.