Neoadjuvant short-course radiotherapy followed by camrelizumab and chemotherapy in locally advanced rectal cancer (UNION): early outcomes of a multicenter randomized phase III trial

Abstract

Neoadjuvant short-course radiotherapy (SCRT) followed by CAPOX and camrelizumab (a PD-1 monoclonal antibody) has shown potential clinical activity for locally advanced rectal cancer (LARC) in a phase II trial. This study aimed to further confirm the efficacy and safety of SCRT followed by CAPOX and camrelizumab compared to long-course chemoradiotherapy (LCRT) followed by CAPOX alone as neoadjuvant treatment for LARC. In this randomized, phase III trial, patients with T3-4/N+ rectal adenocarcinoma were randomly assigned (1:1) to receive SCRT or long-course chemoradiotherapy (LCRT), followed by 2 cycles of camrelizumab and CAPOX or CAPOX alone, respectively. After surgery, each arm underwent either 6 cycles of camrelizumab and CAPOX, followed by up to 17 doses of camrelizumab, or 6 cycles of CAPOX. The primary endpoint was pathological complete response (pCR) rate (ypT0N0) assessed by a blinded independent review committee. Key secondary endpoints tested hierarchically were 3-year event-free survival (EFS) rate and overall survival (OS). Between July 2021 and March 2023, the intention-to-treat population comprised 113 patients in experimental arm and 118 patients in control arm, with surgery performed in 92% and 83.9%, respectively. At data cutoff (July 11, 2023), the pCR rate were 39.8% (95% CI, 30.7 to 49.5) in experimental arm compared to 15.3% (95% CI, 9.3 to 23.0) in control arm (difference, 24.6%; odds ratio, 3.7; 95% CI, 2.0 to 6.9; p < 0.001). In each arm, surgical complication rates were 40.0% and 40.8%, grade ≥ 3 treatment-related adverse events were 29.2% and 27.2%. 3-year EFS rate and OS continue to mature. In LARC patients, neoadjuvant SCRT followed by camrelizumab plus CAPOX demonstrated a significantly higher pCR rate than LCRT followed by CAPOX, with a well-tolerated safety profile. SCRT followed by camrelizumab and chemotherapy can be recommended as a neoadjuvant treatment modality for these patients.