Pathological response to neoadjuvant chemotherapy: a new prognosis tool for the curative management of peritoneal colorectal carcinomatosis.

Purpose: The primary objective of this study was to determine the incidence rate of pathological complete responses (pCRs) following neoadjuvant systemic chemotherapy for the treatment of peritoneal carcinomatosis (PC) of colorectal origin. The secondary objective was to evaluate whether pathological response assessments predict survival of patients treated with curative intent by complete cytoreductive surgery (CRS).
Methods: A retrospective review was performed of 115 patients who underwent preoperative irinotecan- or oxaliplatin-based chemotherapy, followed by 124 procedures of complete CRS alone or combined with hyperthermic intraperitoneal chemotherapy (HIPEC). The pathological response was defined as the mean percentage of cancer cells remaining within all specimens. Univariate and multivariate analyses were performed to identify predictors of survival and pathological response outcome.
Results: Twelve procedures (9.7 %) resulted in pCRs, defined as no residual cancer cells in all specimens, 25 (20.2 %) resulted in major responses (1 to 49 % residual cancer cells), and 87 (70.1 %) resulted in minor or no responses (>50 % residual cancer cells). The cumulative 5-year survival rates were 75 and 57 % for patients with pCR and major responses, respectively. Using multivariate analysis, pathological response was the only independent predictor of survival (P = 0.01; major response: hazard ratio [HR] = 4.91; minor response: HR = 13.46). No significant predictor of pathological response was identified.
Conclusions: Pathological complete response can be achieved with preoperative systemic chemotherapy for patients with PC of colorectal origin. The degree of pathological response can be assessed and represented as a new outcome for prognosis following treatment with curative intent.