Editor’s Note: At a recent international oncology symposium, Michael Morris, MD, from Memorial Sloan Kettering Cancer Center (MSKCC), delivered an in-depth academic report on Abstract #18. The presentation focused on the latest data regarding health-related quality of life (HRQoL), pain, and symptomatic skeletal events (SSE) from the Phase 3 PSMAddition study. This trial evaluates the efficacy and safety of 177Lu-PSMA-617 in combination with androgen deprivation therapy (ADT) and an androgen receptor pathway inhibitor (ARPI) for patients with PSMA-positive metastatic hormone-sensitive prostate cancer (mHSPC). Below is a summary of the core findings.01 Study Background and Baseline: Establishing the Foundation for mHSPC Triplet Therapy
PSMAddition is an international, multicenter, randomized Phase 3 clinical trial targeting mHSPC. Enrolled patients were confirmed as PSMA-positive via Gallium-68 PSMA PET scans. Participants were randomized 1:1 to receive either ADT + ARPI (the doublet group) or ADT + ARPI combined with up to 6 cycles (approx. 36 weeks) of 177Lu-PSMA-617 (the triplet group).
The primary endpoint of the study was radiographic progression-free survival (rPFS). Secondary endpoints included overall survival (OS), patient-reported outcomes (PROs, including HRQoL and pain), and time to the first SSE. As previously reported at ESMO, the trial met its primary endpoint with a median follow-up of 23.6 months, showing that the triplet regimen significantly improved rPFS compared to the doublet (HR=0.72). This latest report focuses on how this intensified regimen impacts the patients’ actual quality of life.
02 PRO Assessment Tools and Compliance: Ensuring Data Rigor
To accurately measure the impact of treatment on the patient experience, the study utilized three validated PRO instruments:
- FACT-P: Assessing prostate cancer-specific quality of life (total score).
- EQ-5D-5L: A utility score for general health status.
- BPI-SF: Assessing pain intensity.
A key strength of this data is the high level of patient compliance. Baseline completion rates ranged from 84% to 89%, providing a robust foundation for longitudinal analysis throughout the treatment course.
03 Longitudinal HRQoL Dynamics: From “Time to Worsening” to “Actual Trajectory”
Dr. Morris highlighted a critical shift in statistical interpretation. Standard “Time to Worsening” analyses are “time-to-event” models where patients are censored after their first decline in quality of life. This fails to capture potential recovery or stabilization later in the study. Therefore, this presentation focused on actual longitudinal dynamic data.
Analyzing the data through Week 108 (approx. 25 months), where sample sizes remained robust (triple-digit figures in both arms):
- FACT-P Total Score: During the active treatment phase (when the triplet arm was receiving 177Lu-PSMA-617), the curves showed an initial divergence, with the triplet arm reporting lower scores. However, once the radioligand therapy cycles were completed and patients returned to doublet maintenance, the curves for both arms re-converged. This transient difference was primarily driven by the “Functional Well-being” and “Prostate Cancer-Specific” subscales.
- EQ-5D-5L and BPI-SF: Unlike the FACT-P, the scores for general health utility (EQ-5D-5L) and pain control (BPI-SF) remained remarkably consistent between the two arms throughout the 108-week period, showing no significant divergence.
04 Symptomatic Skeletal Events (SSE): Validating Long-term Skeletal Safety
Skeletal complications are a major concern for patients with advanced prostate cancer. The study assessed “Time to First SSE (with or without death)” as a composite secondary endpoint. Results indicated that the time to first SSE was comparable between the triplet and doublet arms over the follow-up period (median duration approx. 24 months). This demonstrates that adding 177Lu-PSMA-617 to the standard ADT + ARPI regimen does not increase the risk of skeletal-related adverse events.
Conclusion and Outlook
In summary, the longitudinal PRO analysis from the PSMAddition study provides a comprehensive view of the patient experience with radioligand triplet therapy in mHSPC. Dr. Morris concluded that while the 177Lu-PSMA-617 triplet regimen provides a clear survival benefit (rPFS HR=0.72), it does so without compromising long-term general health status (EQ-5D-5L) or pain control (BPI-SF). Although a transient decline in FACT-P scores was observed during the active phase of radioligand therapy, this was reversible, with scores re-converging with the standard-of-care arm shortly after treatment completion. These findings alleviate concerns regarding the cumulative burden of triplet therapy and support the use of 177Lu-PSMA-617 in the earlier mHSPC setting.
