The Neo-PLANET phase II trial of neoadjuvant camrelizumab plus concurrent chemoradiotherapy in locally advanced adenocarcinoma of stomach or gastroesophageal junction.

The synergistic effect of neoadjuvant immunotherapy and chemoradiotherapy in gastric adenocarcinoma is unclear. This phase II trial (NCT03631615) investigated this neoadjuvant combination in locally advanced adenocarcinoma of stomach or gastroesophageal junction. Thirty-six patients received capecitabine 850 mg/m² twice daily and simultaneous radiotherapy for 5 weeks, sandwiched by a 21-day cycle of oxaliplatin 130 mg/m² (day 1) plus capecitabine 1000 mg/m² twice daily (days 1-14), respectively, followed by surgery. Camrelizumab 200 mg (day 1) was given for 5 cycles since initiating chemotherapy. Primary endpoint was pathological complete response (pCR, ypT0) rate. Secondary endpoints included total pCR (tpCR, ypT0N0) rate, major pathological response (MPR, < 10% residual tumor cells) rate, margin-free (R0) resection rate, downstaging, progression-free survival (PFS), overall survival (OS), and safety. The pCR rate was 33.3% (95% CI, 18.6-51.0), meeting pre-specified endpoint. TpCR, MPR, and R0 resection rates were 33.3%, 44.4%, and 91.7%, respectively. Twenty-eight (77.8%) patients reached ypN0. Two-year PFS and OS rates were 66.9% and 76.1%, respectively. The most common grade 3-4 adverse event was decreased lymphocyte count (27 [75.0%]). Neoadjuvant camrelizumab plus concurrent chemoradiotherapy exhibits promising pathological response in patients with locally advanced gastric adenocarcinoma, with an acceptable safety profile.