SPOTLIGHT Study Results: Novel PSMA PET Radiopharmaceutical Offers Low Bladder Activity

The phase 3, multicenter, single-arm SPOTLIGHT study investigated the safety and efficacy of ¹⁸F-rhPSMA-7.3, a novel prostate specific membrane antigen-targeting positron emission tomography (PSMA PET) radiopharmaceutical, in patients with prostate cancer with recurrence after primary treatment with radiation therapy.

Results of the SPOTLIGHT trial were presented at the American Urological Association 2023 Annual Meeting. Researchers found ¹⁸F-rhPSMA-7.3 to have a high affinity and potential for low bladder activity.

A total of 389 patients received an evaluable ¹⁸F-rhPSMA-7.3 scan. Of those, 76 patients were included in a subgroup to determine the impact of ¹⁸F-rhPSMA-7.3 in patients who had received primary treatment with radiation therapy only. Patients underwent PET 50 to 70 minutes after intravenous administration of 296 MBq ¹⁸F-rhPSMA-7.3. Scans were evaluated by 3 blinded central readers, with data reported for the individual readers and for the majority read (agreement for =2 readers). Detection rates, including region level analyses, were stratified by the prior treatment.

A total of 75 (99%) of the 76 patients had a positive ¹⁸F-rhPSMA-7.3 scan, and 32 (42%) patients had positive findings that were confined to the prostate with no further extraprostatic detection. In contrast, ¹⁸F-rhPSMA-7.3-avid pelvic nodes were detected in 25% of patients, with distant lesions detected in 43%.

High ¹⁸F-rhPSMA-7.3 detection rates were observed in the SPOTLIGHT study in patients with intact prostates experiencing prostate cancer recurrence after radiation therapy. While 42% of patients experienced prostate-only recurrence, the finding of ¹⁸F-rhPSMA-7.3-avid lesions in distant extrapelvic sites calls for additional research, especially if salvage therapy to the intact prostate is being considered for patients.