Treatment beyond progression with anti-PD-1/PD-L1 based regimens in advanced solid tumors: a systematic review

Background Treatment beyond progression with immunotherapy may be appropriate in selected patients based on the potential for late responses. The aim of this systematic review was to explore the impact of treatment beyond progression in patients receiving an anti-PD-1/PD-L1 based regimen for an advanced solid tumor. Methods A systematic literature search was performed to identify prospective clinical trials reporting data on overall response rate by immune-related criteria and/or the number of patients treated beyond conventional criteria-defined PD and/or the number of patients achieving a clinical benefit after an initial PD with regimens including an anti-PD-1/PD-L1 agent which received the FDA approval for the treatment of an advanced solid tumor. Results 254 (4.6%) responses after an initial RECIST-defined progressive disease were observed among 5588 patients, based on 35 trials included in our analysis reporting this information. The overall rate of patients receiving treatment beyond progressive disease was 30.2%, based on data on 5334 patients enrolled in 36 trials, and the rate of patients who achieved an unconventional response among those treated beyond progressive disease was 19.7% (based on 25 trials for a total of 853 patients). Conclusion The results of our systematic review support the clinical relevance of unconventional responses to anti-PD-1/PD-L1-based regimens; however, most publications provided only partial information regarding immune-related clinical activity, or did not provide any information at all, highlighting the need of a more comprehensive report of such data in trials investigating immunotherapy for the treatment of patients with advanced tumors.