Imaging progression-free survival: How much does it matter to patients?

Abstract

99 Background: Progression-free survival (PFS) is often used as a clinical trials outcome for evaluating new therapies for solid tumors. While PFS is a validated surrogate for overall survival (OS) or quality of life (QOL) in some settings, it is increasingly used in contexts where surrogacy is not established. The end point is a composite of survival, symptomatic progression, and imaging-only progression. The intrinsic value of asymptomatic (imaging-only) progression from the patient perspective is not known. Methods: Patients with advanced metastatic cancer (lung, colorectal, or ovarian) who had completed at least 3 months of chemotherapy and were attending a routine ambulatory clinic were recruited and participated in a structured discrete choice trade-off exercise. The interview guide and visual aids were developed by a multidisciplinary team including patient representatives. Participants were provided with a hypothetical clinical scenario and associated treatment options. Treatment options presented had the same OS time but longer time to imaging progression and were associated with various levels of toxicity and treatment time. A sliding scale was used for duration of imaging-only PFS to determine each patient’s willingness to trade longer time for a given level of toxicity. Results: 20 (11M, 9F) patients participated in interviews (Nov 2017 - Jun 2018). Given the scenario 85% (n = 17) of patients chose treatment with less toxicity and treatment duration even if associated with a shorter imaging-only PFS. Two patients chose a trade-off for a more toxic treatment with an increase in imaging PFS by 18 months and 24 months respectively. One patient chose to always opt for most aggressive treatment irrespective of PFS benefit and toxicity. Conclusions: Patients with metastatic cancer currently being treated with palliative chemotherapy overwhelmingly considered imaging-only PFS to be of low value when it was associated with increased toxicity but not with longer OS. In situations where surrogacy for OS and QOL has not been established, endpoints that de-emphasise the importance of imaging are required.