Surgery after neoadjuvant chemotherapy for synchronous and exclusive peritoneal metastasis from colorectal cancer: a...

Colorectal cancer (CRC) with synchronous and exclusive peritoneal carcinomatosis (PC) is rare and associated with poor prognosis. The role and type of neoadjuvant chemotherapy (NAC) before cytoreductive surgery (CRS) remains controversial. We aimed to characterize this population and evaluate outcomes and prognostic factors after surgery following NAC.

We conducted a retrospective study of CRC patients with isolated synchronous PC (2016-2021) who received NAC followed by surgical reassessment. The primary endpoint was overall survival (OS). Prognostic factors included the peritoneal cancer index (PCI) and Peritoneal Regression Grading Score (PRGS).

Eighty-one patients were included (median follow-up 80.7 months). NAC regimens were FOLFOX (70%), FOLFIRI (12%), or FOLFIRINOX (17%); 54% also received targeted therapy. CRS was performed in 54 patients (65%), with complete cytoreduction (R0) achieved in 94%. Twenty-seven patients (33%) did not undergo CRS after NAC. 5-year OS was 29.5% and median OS was 37.9 months in the global population. Median OS in patients who had a CRS with HIPEC, a CRS without HIPEC and who did not have a CRS were 54,9 months [37.0-NA], 37,1 months [28.0-48.9] and 20.9 months [16.2-39.9] respectively. Targeted therapy or type of NAC were not associated with improved OS. PRGS showed clinical relevance with a median OS 54.9 months (PRGS 1-2) vs 34.5 months (PRGS 3-4) (HR = 2.23 [0.94-5.25], p = 0.067). In multivariable analysis, PCI by increments of 5 was associated with worse OS (HR = 1.27 [1.03-1.58], p = 0.026) while HIPEC was associated with improved OS (HR = 0.48 [0.24-0.96], p = 0.039). PRGS showed clinical relevance with a median OS 54.9 months (PRGS 1-2) vs 34.5 months (PRGS 3-4) (HR = 2.23 [0.94-5.25], p = 0.067).

In CRC patients with isolated PC, complete CRS is a key survival factor. HIPEC seems to lead to an improvement in overall survival among our patients, and its benefits remain a subject of debate. Further trials are needed to define optimal regimens and personalize strategies.