Purpose: To evaluate the prognostic effect of neoadjuvant chemoradiotherapy on the change of programmed death ligand 1 (PD-L1) expression in patients with locally advanced rectal adenocarcinoma, by comparing PD-L1 expression in pretreatment biopsies and PD-L1 expression in pathological specimens after neoadjuvant chemoradiotherapy.
Methods: A total of 25 patients with rectal adenocarcinoma were evaluated. Patients were treated by neoadjuvant chemoradiotherapy (radiotherapy:44Gy normofraxionation; chemotherapy: capecitabine 825 mg/m2 in two daily doses). Surgery was performed 6-8 weeks after the chemoradiotherapy completion. PD-L1 expression was determined in endoscopic biopsies and in resected specimens with immunohistochemistry.
Results: All 25 patients received radiotherapy without interruption, while concomitant chemotherapy was discontinued prematurely in one patient because of hematological toxicity. In 13 patients sphincter-saving surgery were performed, and 12 patients underwent rectum resection. Downstaging was noticed in 17 patients. Stable disease was found in 5 patients, and progression in 3. The median disease free survival (DFS) was not reached. Three-year DFS was 54.3% (95% CI 34.3-74.2). The median overall survival (OS) was 60 months (95% CI 48-60). Three-year OS was 75 % (95% CI 57.7-92.3). No PD-L1 expression was noticed in pretreatment biopsy and in resected tissue after chemoradiotherapy.
Conclusion: No prognostic effect of neoadjuvant chemoradiotherapy on the change of PD-L1 expression was demonstrated in patients with locally advanced rectal adenocarcinoma.