Introduction: Lutetium-177-PSMA-617 (177Lu-PSMA) is used as the last treatment option in metastatic castrate resistant prostate cancer (mCRPC). We present two cases of mCRPC with bone involvement to see the response of 177Lu-PSMA as an alternative treatment option.
Case presentations: We present two cases, diagnosed as mCRPC with bone involvement, having suboptimal labelling and binding of the tracer and its effect on bone marrow. The two patients had 2-4 cycles of 177Lu-PSMA with progressive disease despite chemotherapy and novel androgen therapy. The response of treatment was determined based on changes in radiological findings, biochemical and post-therapeutic scan. The last post therapy SPECT CT 99mTc-PSMA scans in both patients showed diffuse homogenous tracer distribution in the bone marrow with no suggestion of receptor avid disease. In both patients the PSA level decreased. Side effects seen were pancytopenia and mild increase in creatinine and urea.
Conclusion: The main benefit of 177Lu-PSMA is to offer an alternative therapeutic option for patient with disease progression despite first line of treatment. We advocate a repeat scan is required after every treatment session with 177Lu-PSMA to ensure adequate radioisotope uptake and to assess for therapeutic response. A patient specific dosimetric approach should be applied before therapy to prevent organ toxicity.