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

The PROSPECT trial investigates the feasibility of avoiding chemoradiation in selected patients with locally advanced rectal cancer. We identified patients who met PROSPECT trial eligibility criteria and found favorable outcomes for eligible compared to ineligible patients. Our findings support the PROSPECT study design, as it selects a patient population in whom omission of radiotherapy should be actively investigated. 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.