GU Cancers 2021 | STARTAR: ADT + apalutamide + RT + docetaxel for PSA-recurrent prostate cancer following RP

The motivation for the STARTAR trial was to help men who have a PSA recurrence after radical prostatectomy, but because of their high-risk features, have a very high risk of disease progression despite salvage radiation and hormonal therapy. We know certain high-risk features exist for these men, such as a high tumor Gleason score, high PSA, lymph node metastases and tumor staging characteristics like seminal vesicle invasion. We’ve previously published on multi-modality therapies for these patients, such as the multi-modality study with docetaxel and salvage radiation and the STREAM study, which was published last year on enzalutamide and salvage radiation. The STARTAR trial builds on those prior studies in this salvage radiation setting.

STARTAR was designed as an investigator-initiated multi-center study that we conducted within the Department of Defense Prostate Cancer Clinical Trials Consortium, where we investigated the efficacy and safety of apalutamide with standard androgen deprivation therapy for about eight months, which was layered on top of standard salvage radiation to the prostate bed and pelvis, as well as adjuvant docetaxel for up to six cycles. So the ADT apalutamide was given at the same time as the radiation and the docetaxel. After that period of time men had their treatment stopped, this very intensive treatment ended after about eight months, and they are followed now for a primary endpoint of a three-year progression-free survival. So in this poster we’re presenting really the interim analysis to report on the safety, the feasibility, really a trial-in-progress, and the PSA endpoints really with about 14 months of follow-up.

STARTAR was conducted very successfully. We have enrolled 39 patients across several centers that includes Duke University, Cornell, University of Nebraska and Wake Forest Baptist Medical Center. Within this consortium, these patients were enrolled and all patients have now completed their therapy and with a median of 14 months, we’ve had zero relapses. So it’s still very early days, but so far good news, patients have tolerated this well and all these patients who had been at high risk of relapse are currently with a zero PSA and without further relapse, and they’re off therapy.

Many men have experienced testosterone recovery, about 40%, but it’s still very early days. This is a work in progress. The trial was, as expected, no unexpected toxicities. We did have some patients develop some neutropenia from the docetaxel, but no unexpected adverse events. With apalutamide, some men did experience hot flushes, hypertension and a drug rash, but all was manageable and these patients largely have recovered from these experiences and are doing well. We expect in about two years to have the final report. So, overall, it’s been a very positive experience for our patients.

Our goal statistically is to build on an efficacy that we expect without this aggressive approach of about a 50 to 60% success rate at three years. So we’re hoping for a 70 to 80% success rate, meaning durable remissions off therapy.