Role of trimodality therapy versus dual-modality in T3N0 rectal cancer patients.

Abstract

597 Background: Adjuvant radiation (R) and chemotherapy (C) is generally recommended for patients (pts) with pT3N0 rectal cancer, although there is no data to support the use of adjuvant chemotherapy. This study examines the whether there is benefit with trimodality therapy vs. dual modality in this population. Methods: The BCCA Colorectal Cancer Outcomes Unit database was used to identify referred pts with pT3N0 rectal carcinoma diagnosed between 2000-2004. The data from this cohort has been previously reported (Johal et al. ASCO Annual Meeting 2007) During this period, “short course” R (25Gy/5, surgery within 10 days) was recommended for resectable cT3 tumors followed by 6 months of C. If not treated pre-operatively (pre-op), guidelines specified post-op “long course” (45Gy/25) R and C. Three treatment groups were identified: Surgery alone (S), S and R (SR), and S, R and C (SRC). Eligible pts had complete surgical resection with or without total mesorectal Excision (TME). Pts treated with “downstaging” pre-op long course R, with S and C only (13 pts) or with R2 resection were excluded. Locoregional Recurrence (LR) and Distant Recurrence (DR) rates determined. Reasons for non-treatment were determined by chart review. Due to the heterogeneity between the groups, a univariate and multivariate analysis was performed. Results: The patient characteristics have been previously reported. 5-yr LR was similar between SR and SRC (3.84 %vs. 6.34% p=0.474). 5-yr DR were 24.81% (SR), and 17.56% (SRC) p=0.0354 and 5 yr OS 68.4% (SR), and 86% (SRC) p=.0002. On multivariate analysis, chemotherapy did impact on OS with a HR of 0.532, p=0.0462. Conclusions: Treatment of pT3N0 rectal cancer was variable in clinical practice despite established guidelines. There was significant heterogeneity with respect to comorbid medical conditions between groups receiving SR and SRC which limits comparability between groups. However, those patients who received tri-modality therapy experienced less distant relapse and an increase in overall survival. No significant financial relationships to disclose.