Pseudoprogressions in Oncolytic Therapy: Alerts and Regulations Needed

Pseudoprogression (PsP) refers to either visually observed or imaging-detected tumor enlargement followed by regression after cancer therapies. Characterized by robust localized immune infiltration, PsP is most commonly seen in immunotherapies, with an occurrence rate of around 10%. However, there was limited discussion of oncolytic therapy-related PsP. We argue that PsP is a commonly encountered phenomenon in oncolytic virotherapy, warranting increased attention during assessments in clinical applications and trials. In a phase 1/2 study, PsP occurred in 45% of patients who received AdAPT-001 local injections. Tumor enlargement was typically observed within the initial month, whereas tumor regression or stabilization at three months indicates PsP. Patients with PsP had superior daily functioning and prolonged survival compared to those with genuine progressions. Delayed PsP, detected within a 10-month timeframe, was also noted with oncolytic treatments