Adjuvant hyperthermic intraperitoneal chemotherapy in patients with colon cancer at high risk of peritoneal metastases: individual patient data meta-analysis

Background: About a quarter of patients with locally advanced colon cancer (pT4) develop locoregional recurrence, including peritoneal metastases. The aim of this individual patient data meta-analysis (IPDMA) was to evaluate the efficacy of adjuvant hyperthermic intraperitoneal chemotherapy (HIPEC) with regard to reducing the locoregional recurrence rate in the overall population and high-risk subgroups of patients with locally advanced colon cancer. Methods: A systematic literature search was conducted in July 2024 to identify RCTs on adjuvant HIPEC in addition to routine adjuvant systemic chemotherapy in locally advanced colon carcinoma. An IPDMA was performed, with the locoregional recurrence rate as the primary endpoint and disease-free survival (DFS) and overall survival (OS) as secondary endpoints. Results: The search identified two trials (COLOPEC and HIPECT4). Individual patient data were pooled for 386 patients, of whom 189 patients received adjuvant HIPEC and 197 patients constituted the control group. The median follow-up was 36 (interquartile range 32-60) months. A modified intention-to-treat analysis showed a 36-month locoregional recurrence rate of 16.0% for HIPEC patients and 21.2% for control patients (P = 0.295). Predefined subgroup analyses revealed a significant reduction in locoregional recurrence after HIPEC in patients with right-sided tumours (HR 0.56 (95% c.i. 0.48 to 0.67)) (P < 0.001). No significant differences in survival were found for the overall study population; low event rates in subgroups did not allow for survival analyses. Conclusion: Adjuvant HIPEC significantly reduced the locoregional recurrence rate in right-sided locally advanced colon cancer, but not in the overall study population. Definitive conclusions on DFS and OS require longer follow-up.