The relation between pathological complete response and clinical outcome in patients with rectal cancer

Preoperative chemoradiotherapy (CRT) is the standard treatment modality in locally advanced rectal cancer. The primary aim was to correlate pathological complete response (pCR) with patient outcome, and the secondary objective was to identify predictive factors of pCR.

Patients with clinical stage II/III rectal cancer who received preoperative CRT between 2002 and 2010 were retrospectively studied.The median radiotherapy dose was 54 Gy (range, 45 to 64 Gy), and all patients received concurrent infusional 5-fluorouracil-based chemotherapy.

Median follow-up time was 48.3 months (range, 24 to 96 months) and 51 months (range, 44 to 110 months) for no-pCR and pCR groups, respectively. Eighteen patients (18.6%) had pCR. The 5-year overall survival was 95% for patients with pCR and 74.8% in patients without pCR (p=0.009). The 5-year local relapse free survival was 87.5% and 95% for the no-pCR and pCR groups, respectively (p=0.09). The 5-year distant relapse free survival was 93% in pCR group and 79.8% in no-pCR group (p=0.02). The 5-year distant free survival was 94% and 66% in patients with and without pCR, respectively (p=0.017). The clinical T4 (p=0.043) and pretreatment carcinoembryonic antigen level (CEA) >5ng/mL (p=0.012) were significantly associated with a lower pCR rate. In the multivariate logistic regression analysis, pretreatment CEA level >5ng/mL (p=0.008) was the only independent factor associated with a lower pCR rate.

Patients with pCR after preoperative CRT had a significantly improved outcome. Furthermore, the pretreatment CEA level was independently associated with pCR.