Short course pembrolizumab in complete responders with advanced non-small cell lung cancer.

Abstract

e20537 Background: Pembrolizumab has been available in Singapore since October 2014 for clinical use. All clinical trial protocols of Pembrolizumab in patients with advanced non-small cell lung cancer (NSCLC) require a 2 year period of treatment in responders, even in complete responders. It is not known if shorter treatment durations in complete responders can afford reasonable progression free interval (PFS). Such abbreviated treatment in complete responders would result in significant cost savings and lesser side effects. Methods: A single physician practising at a single private medical oncology center in Singapore collated consecutive cases of advanced NSCLC seen by him and treated with Pembrolizumab from October 2014 till December 2016. All were smokers except for 2 patients. All patients were biopsy and imaging proven to have advanced NSCLC. 46 patients were treated with Pembrolizumab 2mg/kg body weight 3 weekly and observed with sequential imaging every 3-6 months with the first assessment scan after Cycle 4. All complete responders by imaging stopped treatment after 4 cycles of Pembrolizumab by mutual consent. PD-L1 IHC testing by DAKO 22C3 was not done on any of the patients’ tumours as the test has only been available in Singapore since December 2016. Results: Cut-off date for analysis of data was 1 Feb 2017. 4 out of 46 patients (9%) achieved a complete metabolic response on FDG PET by irRC and/or CT scans by RECIST 1.1. All 4 patients with complete response (CR) (except Patient #3) were smokers. All 4 patients remain in CR with ECOG Performance Status (PS) 0 without any further treatment. Conclusions: Real world clinical usage of Pembrolizumab in advanced NSCLC can afford long PFS in complete responders in spite of abbreviated treatment of 4 cycles. Clinical trials should be designed to address this issue due to its impact on health care costs. [Table: see text]