ABSTRACT Background:

Neoadjuvant therapy, followed by surgery, reduces the risk of local relapse in rectal cancer, but approximately 30% will relapse with distant metastases, highlighting the importance of adjuvant chemotherapy (aCT).

Objective:

The objective of the study was to study two regimens of adjuvant treatment in patients with locally advanced rectal cancer and analyze their efficacy and toxicity.

Methods:

Between January 2009 and December 2016, 193 patients with Stage II-III rectal cancer who had received neoadjuvant therapy were included by consecutive non-probability sampling. The decision to administer aCT, as well as the specific regimen, was at the discretion of the medical oncologist. Disease-free survival (DFS) and overall survival (OS) were calculated.

Results:

The mean DFS was 84.85 (95% confidence interval [CI]: 79-90) months in 164 patients receiving aCT, compared to 57.71 (95% CI: 40-74) months in 29 who did not receive aCT (p < 0.001). Then, mean OS was 92.7 (95% CI: 88-97) months and 66.18 (95% CI 51-81) months, respectively (p < 0.001). DFS was 83.6 (95% CI: 76-91) months in 74 patients receiving adjuvant 5-fluorouracil (5-FU), and 82.9 (95% CI: 75-90) months in 90 receiving 5-FU plus oxaliplatin (p = 0.49). OS was 87 (95% CI: 80-94) versus 93.65 (95% CI: 88-99) months, respectively (p = 0.76). The multivariate analysis identified aCT hazard ratio (HR) 0.30 (95% CI: 0.1-0.46), perineural invasion HR 3.36 (95% CI: 1.7-6.5), and pathological complete response HR 0.10 (95% CI; 0.01-0.75) as independent markers of DFS.

Conclusions:

In our study, aCT was associated with longer DFS and OS. 5-FU plus oxaliplatin showed greater toxicity with no added benefit in DFS or OS.