P64. Survival after attempt at cytoreductive surgery for colorectal cancer with high peritoneal disease burden: A secondary analysis of the Intraperitoneal Chemotherapy After Cytoreductive Surgery (ICARuS) randomized trial

Cytoreductive surgery (CRS) is favored for patients with colorectal cancer and peritoneal metastases (CRCPM) when complete CRS can be achieved. However, the oncologic impact of CRS in patients with high disease burden (Peritoneal Cancer Index [PCI] ≥15) remains poorly defined. This study evaluates the outcomes of CRCPM patients enrolled in a prospective trial with strict inclusion criteria, a subset of whom underwent complete CRS.


Methods:

The Intraperitoneal Chemotherapy After Cytoreductive Surgery for Peritoneal Metastasis (ICARuS) randomized clinical trial enrolled CRCPM patients deemed eligible for CRS and intraperitoneal chemotherapy (IPC). Upon surgical exploration, patients who achieved a Completeness of Cytoreduction (CC) 0/1 CRS were randomized to one of two IPC arms (floxuridine or mitomycin C), whereas those who could not achieve CC 0/1 exited the trial. The clinicopathologic characteristics and oncologic outcomes of all patients explored were analyzed.


Results:

Ninety-five patients were enrolled and surgically explored (median age 54 years, 47% female). CC0/1 CRS was achieved for 74 patients (CC0: 73; CC1: 1), whereas 21 patients did not have disease amenable to complete CRS. CRS was not achieved due to extraperitoneal disease (retroperitoneal lymphadenopathy) in 4 cases, and due to involvement of critical abdominal structures in 17 cases (all with PCI ≥ 15). In the entire cohort, CC0/1 CRS was associated with better survival (median overall survival [OS] 41 mo vs 9 mo, p< 0.0001). In the subset of patients with PCI ≥ 15 and no extraperitoneal disease, baseline demographics and clinical variables were comparable between the CRS group (N=23) and the No-CRS group (N=17), except that right-sided primary tumors were more common in the CRS group (p=0.04). Six patients in the No-CRS group did not receive systemic therapy after exploration due to rapid progression and decline. CRS for patients with PCI≥15 was associated with improved OS (Figure 1A), but this difference was primarily driven by the rapid decline of No-CRS patients who were not able to return to chemotherapy after exploration (Figure 1B).


Conclusions:

CRCPM with PCI ≥15 confers a poor prognosis. Complete CRS in this population may be associated with a modest improvement in survival, but this has to be considered in the context of chemotherapy interruption risk for patients explored but ultimately unable to achieve complete CRS.