E369: Patterns and Outcomes of Post-Operative Systemic Therapy for Colorectal Peritoneal Metastasis Patients Who Undergo Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy with Complete Cytoreduction

Patients with colorectal peritoneal metastasis (CPM) have traditionally been treated with palliative chemotherapy; however, cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) has become the recommended approach. After undergoing a complete cytoreduction, limited data suggests that adjuvant chemotherapy may not be beneficial for CPM patients and time off chemotherapy may be an added benefit of CRS-HIPEC. This study aimed to characterize time away from post-operative systemic treatment (POST) and outcomes for this cohort at an NCI-designated comprehensive cancer center.

Methods:

CPM patients who underwent CRS-HIPEC with a complete cytoreduction (CC-0) from 2007-2023 were included. Demographic and clinical data, including time from surgery to POST and date of last follow-up or death were recorded. POST was initiated in cases of imaging or biopsy-proven recurrence, or multidisciplinary consensus. Recurrence-free survival and overall survival were defined as time from CRS-HIPEC to initiation of POST or date of last follow-up or death, respectively. Descriptive and time-to-event analyses were performed.

Results:

Overall, 46 patients met inclusion criteria and 25 patients (54.4%) had a proven or suspected recurrence and received POST. The median follow-up time was 22.9 months and the median time to POST was 9.4 months. Presence of lymphovascular invasion was associated with POST (p< 0.05); however, age, peritoneal carcinomatosis index, T stage, N stage, BMI, colon perforation, KRAS, BRAF, MSI, and neoadjuvant systemic treatment (delivered to 80.4% of patients) were not associated with POST. The mortality rate for the cohort was 34.8%. For the POST cohort, the mortality rate was 40% with median OS of 39.5 months. For those not receiving POST, the mortality was 28.6% and the median OS was not reached.

Conclusions: In this cohort of CPM patients who underwent CRS-HIPEC with complete cytoreduction, just over half of all patients had a recurrence leading to POST. These data suggest that despite deferring systemic treatment until suspicion of recurrence, this cohort of patients experienced good overall survival comparable to clinical trial reports and may have a quality-of-life benefit during the time away from chemotherapy. Limitations include the lack of an immediate adjuvant systemic treatment group and relatively short median follow-up time.