The outcome and the frequency of pathological complete response after neoadjuvant radiotherapy in curative resections for advanced rectal cancer: a population-based study

Aim Pathological complete response (ypCR) after neoadjuvant treatment for rectal cancer is associated with favourable survival and a low rate of local recurrence. The aim of the study was to assess the incidence of ypCR among patients with advanced rectal cancer treated with neoadjuvant chemoradiotherapy and curative resection and to explore factors associated with survival. Method From 2000 to 2009, 1384 patients enrolled in the national population-based colorectal cancer registry of Norway with advanced T3 and T4 rectal cancer with N0-2, M0 received neoadjuvant long-course (chemo) radiation. The duration of follow-up was a median of 5 years. Results ypCR was achieved in 147 (10.6%) patients. The estimated 5-year overall survival rate was 87% (confidence interval +/- 5.4) among ypCR and 67% among non-ypCR (confidence interval +/- 2.7) (P < 0.0001). Distant metastasis developed in 12 (8%) of 147 and 328 (26.5%) of 1237 patients respectively (P < 0.001). In a Cox proportional hazards ratio model the effect of ypCR on survival was adjusted for age [hazard ratio (HR) 1.056, P = 0.0001], metachronous metastasis (HR 4.7, P = 0.0001), local recurrence (HR 4.3, P = 0.0001) and surgical procedure (HR 1.48, P = 0.0001). The independent effect of ypCR (HR 0.65, P = 0.041) on survival almost disappeared compared with the univariate analysis. Conclusion The rate of ypCR in advanced rectal cancer was about 10%. This phenomenon seems to occur in tumours with a low risk of metastasizing. The contribution of neoadjuvant therapy to ypCR on survival was small or absent.