Endocrine Abstracts

Aim: Given the aggressive biological features of metastatic prostate cancer, a more aggressive treatment with [177Lu]-PSMA might be appropriate.

Materials and methods: We have treated 15 patients (mean age 69 years) with intended 3 cycles of [177Lu]-PSMA every 4 weeks. All patients have been examined with [68Ga]-PSMA PET/MRI to validate PSMA expression of all metastatic lesions. We monitored haemoglobin (Hb), platelets (Pl), leucocytes and creatinine for assessment of toxicity. The highest toxicity grade until 3 months after the last cycle was assessed. Scintigraphy of the salivary glands before treatment, and after the third cycle has been used to assess salivary toxicity. For treatment response we evaluated PSA values before the first and after the third cycle. For RECIST based response 12/15 patients were examined with [68Ga]-PSMA PET/MRI 4 weeks after the last cycle.

Results: 12/15 patients were treated with all 3 cycles; In 2/15 treatment was stopped after the second cycle due to progressive disease, in 1/15 patient treatment was stopped due to PSA response (−52%) and minimal tumor load. 11/15 patients (73%) had a decreasing PSA (mean −53%), 6/15 (40%) with a decline of more than 50%. According to RECIST 5/12 patients showed PR (42%), 4/12 SD (33%) and 3/12 PD (25%). Treatment was excellent tolerated with no grade 2 toxicity. 1/15 patients showed an increase of Hb toxicity of grade 0 to 1; 2/15 had an increase of Pl toxicity from grade 0 to 1 and 4/15 of leucocytes toxicity, which resolved after 3 months, respectively. We experienced no toxicity regarding creatinine. We did not experience any relevant loss of function neither in scintigraphic monitoring of the salivary glands nor from patient reports.

Conclusion: Aggressive [177Lu]-PSMA treatment was safe and effective and might better reflect the more aggressive nature of castration resistant metastatic prostate cancer.