Early PD-1 Therapy Discontinuation in Responding Metastatic Cancer Patients

Most clinical trials have investigated PD-(L)1 agents until disease progression or severe side effects, but the optimal duration of the treatment remains to be elucidated. Our institutional guideline has restricted maximal PD-(L)1 therapy length to 6 months, and therefore our cohort provides a unique opportunity to investigate the effects of short PD-1 therapy.

We retrospectively collected all patients who had been treated with PD-1 therapy for metastatic cancer at Oulu University Hospital from 2014 to 2018. Clinical variables, treatment history, and survival were collected.

A total of 59 patients received PD-1 therapy for metastatic disease in lung and genitourinary (renal and bladder) cancers as well as melanoma. Median overall survival was close to what has been seen in clinical trials. Seventeen patients had PD-1 therapy discontinued in response, most of them because of reaching the maximal restricted PD-1 therapy length (n = 12, 70.6%). Patients whose therapy was discontinued in response experienced a long immuno-oncology (IO) therapy-free survival (median 12 months), and only 6 patients had need for therapy re-initiation during the follow-up. We also investigated alternative response evaluation criteria which outperformed conventional RECIST 1.1 in predicting IO therapy-free survival.

The results of the current study suggest that patients whose PD-1 therapy has been discontinued in response can have a long IO therapy-free period without need for a next line of therapy.