ADJUVANT CHEMOTHERAPY IN LOCALLY ADVANCED RECTAL CANCER: DECIDING ON THE OPTIMAL STRATEGY

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).

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.

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.

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.

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.