A Retrospective Analysis of the Safety and Activity of Lutetium-177-Prostate-Specific Membrane Antigen Radionuclide Treatment in Older Patients with Metastatic Castration-Resistant Prostate Cancer.

BACKGROUND: Prostate cancer is a common malignancy of the elderly, and with the aging of the population, the need is growing for therapies suitable for this age group. Lutetium-177-prostate-specific membrane antigen (Lu-PSMA), a radiolabeled small molecule, binds with high affinity to prostate-specific membrane antigen, enabling beta particle therapy targeted to metastatic castration-resistant prostate cancer (mCRPC). In a recent single-arm phase II trial and a subsequent expansion cohort, a prostate-specific antigen (PSA) decline of ≥50% was observed in approximately 60% of patients receiving Lu-PSMA. Taking into account the specific challenges and potential toxicities of Lu-PSMA administration in elderly men, we sought to retrospectively analyze the safety and activity of Lu-PSMA in men aged older than 75 years with mCRPC. PATIENTS AND METHODS: The electronic medical records of 24 patients aged older than 75 years treated with Lu-PSMA "off-trial" were reviewed, and clinical data were extracted. Clinical endpoints were toxicity and activity, defined as a PSA decline ≥50%. Descriptive statistics were performed using Excel. RESULTS: The median age at treatment start was 81.7 years (range 75.1-91.9). The median number of previous treatment lines was four. The number of treatment cycles ranged from one to four; the mean administered radioactivity was 6 GBq per cycle. Treatment was generally tolerable; side effects included fatigue (n = 8, 33%), anemia (n = 7, 29%), thrombocytopenia (n = 5, 21%), and anorexia/nausea (n = 3, 13%). Clinical benefit was observed in 12 of 22 patients (54%); PSA decline above 50% was observed in 11 patients (48%) and was associated with significantly longer overall survival. CONCLUSION: Our results indicate that Lu-PSMA is safe and active in elderly patients with mCRPC. IMPLICATIONS FOR PRACTICE: Lutetium-177-prostate-specific membrane antigen (Lu-PSMA), a radiolabeled small molecule, binds with high affinity to prostate-specific membrane antigen, enabling beta particle therapy targeted to metastatic castration-resistant prostate cancer (mCRPC). The recently published single-arm phase II trial with Lu-PSMA, describing its safety and activity, did not include patients aged older than 75 years. In this study, Lu-PSMA activity was retrospectively analyzed in patients aged older than 75 years and results indicate that treatment was tolerable and similarly active in this age group, with no new emerging safety signals. Despite the small cohort size, this analysis suggests that Lu-PSMA can serve as an advanced palliative treatment line in mCRPC in elderly patients.

Clinical Variables Associated with PSA Response to Lutetium-177-PSMA ([177Lu]-PSMA-617) Radionuclide Treatment in Men with Metastatic Castration-Resistant Prostate Cancer.

Lutetium-177-PSMA ([177Lu]-PSMA-617), a radiolabeled small molecule, binds with high affinity to prostate-specific membrane antigen (PSMA), enabling targeted radiation therapy to metastatic prostate lesions. Our objective was to retrospectively analyze the activity of [177Lu]-PSMA-617 given off-trial to men with metastatic castration resistant prostate cancer (mCRPC) and identify clinical factors associated with PSA response. Electronic medical records of all men treated with [177Lu]-PSMA-617 were reviewed and analyzed. Overall survival was calculated using the Kaplan-Meier method. The association between potential variables and PSA response was analyzed by univariate analysis, using either logistic regression or χ2/Fisher's exact test. Multivariable analysis was carried out using logistic regression on all categorical variables with a P-value of <0.1 on univariate analysis. Variables found to be statistically significant were then used to define a categorical score. A total of 52 patients received at least one cycle of [177Lu]-PSMA-617. Clinical benefit was observed in 28 patients (52%). PSA decline ≥20% and ≥50% was observed in 26 (50%) and 18 patients (35%), respectively. Achievement of any PSA decline at first measurement was significantly associated with survival. There was a negative association between the number of previous chemotherapy lines and PSA decline above 20%. Univariate analysis followed by multivariable analysis showed that older age and higher hemoglobin were significantly associated with a PSA decline >20%. A score combining these two parameters was significantly associated with PSA response. In summary, [177Lu]-PSMA-617 is active in the 'real-life' setting of heavily pretreated men with mCRPC.