Impact of Staging Ga-PSMA-11 PET Scans on Radiation Treatment Plansin Patients With Prostate Cancer.

OBJECTIVE

To evaluate the impact of staging Ga-PSMA-11 PET imaging on radiotherapy (RT) dose and volumes in patients with prostate cancer.

METHODS

Forty-five patients (89% high or very high risk by NCCN criteria) who underwent Ga-PSMA-11 PET imaging prior to definitive treatment for prostate cancer between December 2015 and December 2016 were included. Locations of Ga-PSMA-11-avid lesions were compared to Radiation Therapy Oncology Group consensus pelvic nodal volumes (clinical target volume [CTV]); coverage of lesions outside the consensus CTV was considered a major change, while dose-escalation to lesions within the consensus CTV was considered a minor change.

RESULTS

All patients had Ga-PSMA-11 PET uptake in the prostate. Twenty-five patients (56%) had N1/M1a disease on Ga-PSMA-11 PET scan, of whom 21 (47%) were previously N0. Six patients (13%) had bone metastases on Ga-PSMA-11 PET scan, of whom 4 had prior negative bone scans. Eight patients (18%) had lymph node metastases outside the consensus CTV. Twelve patients (27%) received a RT boost to nodes within the consensus CTV. Six patients (13%) had limited bone metastases treated with focal RT. Overall PSMA PET imaging resulted in major and/or minor changes to RT plans in 24 patients (53%).

CONCLUSION

Ga-PSMA-11 PET imaging resulted in RT changes in 53% of patients. Prospective investigation is needed to evaluate the clinical benefit of RT changes based on staging Ga-PSMA-11 PET imaging.