Patient perspectives of value of delayed disease progression on imaging (imaging PFS). A treatment trade-off experiment.

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. PFS is a composite endpoint 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) participated in a discrete choice experiment, with a structured treatment 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 treatment options resulting in the same OS duration. A sliding scale was used for duration of delay in imaging progression to determine each patient's willingness to trade longer time for a given level of toxicity.

Results: 20 (11 M, 9 F) patients participated. 85 % (n = 17) of patients chose treatment with less toxicity and shorter duration even if associated with a shorter time to worsening imaging. 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: Most patients with metastatic cancer currently being treated with palliative chemotherapy considered delayed imaging progression in the absence of OS gain to be of low value.

Policy Statement: PFS should not be assumed to have intrinsic value to patients in the absence of surrogacy for OS or QOL when making drug treatment and policy decisions.