Clinical outcomes of pembrolizumab plus chemotherapy for postoperative recurrent esophageal squamous cell carcinoma

Summary Background Immunotherapy combined with chemotherapy has been the first-line treatment for metastatic or unresectable locally advanced esophageal cancer. However, postoperative recurrences have not been sufficiently investigated. We investigated the clinical outcomes of pembrolizumab plus cisplatin plus 5-fluorouracil (CF) therapy for postoperative recurrent esophageal squamous cell carcinoma. Methods We retrospectively analyzed 100 consecutive patients with postoperative recurrence and compared their treatment response and survival outcomes in response to pembrolizumab plus CF therapy and conventional CF therapy. Results Pembrolizumab plus CF therapy had higher response and objective response rates (41% vs. 27%, 77% vs. 57%, respectively) and prolonged progression-free survival (median 6.5 vs. 4.9 months, P = 0.011) and overall survival (not reached [NR] vs. 14.0 months, P = 0.087) compared to CF therapy. Early tumor shrinkage (ETS) ≧20% had a longer duration of response with pembrolizumab plus CF therapy compared with conventional CF therapy (NR vs. 10.2 months, P = 0.007). Conversely, the additional benefit of pembrolizumab in CF therapy was limited when ETS was <20% (4.0 vs. 3.4 months, P = 0.814). CF therapy was associated with worse survival outcomes for recurrences within 6 months post-surgery compared to those after 6 months. Pembrolizumab plus CF therapy provided comparable survival outcomes regardless of the timing of recurrence; however, it was less effective in combined positive score < 10 within the first 6 months. Conclusion First-line pembrolizumab plus chemotherapy for postoperative recurrent esophageal cancer improved clinical outcomes compared to conventional CF therapy and can be expected to be one of the treatment options even in early postoperative recurrence.