PROSPECT Eligibility and Clinical Outcomes: Results From the Pan-Canadian Rectal Cancer Consortium.

Background: The PROSPECT trial (N1048) is evaluating the selective use of chemoradiation in patients with cT2N1 and cT3N0-1 rectal cancer undergoing sphincter-sparing low anterior resection. We evaluated outcomes of PROSPECT-eligible and -ineligible patients from a multi-institutional database.

Patients And Methods: Data from patients with locally advanced rectal cancer who received chemoradiation and low anterior resection from 2005 to 2014 were retrospectively collected from 5 Canadian centers. Overall survival, disease-free survival (DFS), recurrence-free survival (RFS), and time to local recurrence (LR) were estimated using the Kaplan-Meier method, and a multivariate analysis was performed adjusting for prognostic factors.

Results: A total of 566 (37%) of 1531 patients met the PROSPECT eligibility criteria. Eligible patients were more likely to have better PS (P = .0003) and negative circumferential resection margin (P < .0001). PROSPECT eligibility was associated with improved DFS (hazard ratio [HR], 0.75; 95% confidence interval [CI], 0.61-0.91), overall survival (HR, 0.73; 95% CI, 0.57-0.95), and RFS (HR, 0.68; 95% CI, 0.54-0.86) in univariate analyses. In multivariate analysis, only RFS remained significantly improved for PROSPECT-eligible patients (HR, 0.75; 95% CI, 0.57-1.00, P = .0499). The 3-year DFS and freedom from LR for PROSPECT-eligible patients were 79.1% and 97.4%, respectively, compared to 71.1% and 96.8% for PROSPECT-ineligible patients.

Conclusion: Real-world data corroborate the eligibility criteria used in the PROSPECT study; the criteria identify a subgroup of patients in whom risk of recurrence is lower and in whom selective use of chemoradiation should be actively examined.