Ian D. Davis, MBBS, PhD, spoke about the TheraP study which evaluated 177Lu-PSMA-617 vs cabazitaxel in patients with metastatic castration-resistant prostate cancer.
CancerNetwork® spoke with Ian D. Davis, MBBS, PhD, professor of medicine and head of the Eastern Health Clinical School at Monash University and Eastern Health in Melbourne, Australia, at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting, about the phase 2 TheraP study (NCT03392428) which compared 177Lu-PSMA-617 (Pluctivo) vs cabazitaxel (Jevtana) in patients with progressive metastatic castration-resistant prostate cancer (CRPC).1 Data made available at the meeting included the 3-year follow-up for the overall survival analysis.
The ANZUP 1603 cancer trials group also had the opportunity to present updated results of the TheraP study, which was a randomized phase 2 study of 201 patients with metastatic castration-resistant prostate cancer comparing 177Lu-PSMA-617 with cabazitaxel. All patients had prior docetaxel and more than 90% of participants had either abiraterone [Zytiga] or enzalutamide [Xtandi] or both. All participants were deemed suitable for receiving cabazitaxel as the next line of therapy. We published the primary analysis of this in the Lancet last year, showing that 177Lu-PSMA-617 treatment was superior in terms of the primary end point, which was the probability of achieving a PSMA [prostate-specific membrane antigen] response of more than 50%.2 It was also superior to cabazitaxel in terms of safety and patient-reported outcomes.
At ASCO 2022, we presented the updated overall survival results, this was the secondary end point. We showed there is no difference in survival that we could detect between the 2 arms. There are several possible reasons for that. One is that many patients on cabazitaxel crossed over to receive 177Lu-PSMA-617 on progression. About 14 patients withdrew from the cabazitaxel arm before they received treatment and went and received 177Lu-PSMA-617, but they were analyzed as if they had received cabazitaxel. We’re reassured that there is no detriment to survival. When you take the TheraP data together with the [data from the phase 3 VISION trial (NCT03511664) of 177Lu-PSMA-617 vs best supportive care for patients with progressive PSMA-positive metastatic CRPC], we’re confident that this is an active, safe, and relatively well-tolerated treatment, certainly better tolerated than cabazitaxel. We believe that there are positive impacts on survival, even though we’ve not been able to show that difference in our randomized phase 2 underpowered study.