PSMA-High: EBRT/ PSMA617/ ADT vs. EBRT/ ADT

Men with high-risk localized prostate cancer include those with stage cT3a or Grade Group 4/5 or Prostate Specific Antigen (PSA) \>20 ng/mL, and the proportional rate of high-risk disease has increased to 20% of newly diagnosed patients in the US. These patients are currently recommended treatment with a combination of definitive radiotherapy and long-term androgen deprivation therapy (NCCN category 1) or radical prostatectomy with pelvic lymph node dissection. Radiotherapy most often consists of external-beam radiotherapy (EBRT) in 28 to 45 daily fractions with 1.5 to 3 years of ADT. Multiple phase III studies have shown a benefit in survival with long-term ADT. However, given the toxicities of long-term ADT, including fatigue, mood changes, sexual dysfunction, osteopenia, weight gain, diabetes and cardiovascular disease, many patients are reluctant to complete long-term ADT. This leads to significant demand for investigation of lower-toxicity alternatives to long-term ADT for patients with high-risk localized prostate cancer.

The combination of 177Lu-PSMA-617 with definitive EBRT and 6 months ADT for high-risk prostate cancer has the potential to increase the cumulative absorbed dose to the prostate, involved nodes, and micrometastatic disease, as well as decrease toxicity and improve QoL compared with EBRT and long-term ADT. ADT has been shown to increase radiosensitivity and PSMA expression of prostate cancer; therefore 6 months of ADT was selected to optimize the combination therapy while avoiding toxicities associated with long-term ADT. There are significant unknowns with respect to absorbed dose and toxicities of this potential combination of 177Lu-PSMA-617 and EBRT. In addition, the relative efficacy compared to EBRT plus long-term ADT is unknown. The investigators therefore propose a phase II randomized study of dosimetry, safety, and efficacy of Lu-177-PSMA-617, EBRT, and short-term ADT (6 months) in comparison with EBRT and long-term ADT (24 months).