Objective: To identify locations of recurrence after radical prostatectomy (RP) with prostate-specific antigen (PSA) <2 by Gallium-68 prostate-specific membrane antigen (PSMA)-11 Positron Emission Tomography (PET) imaging, and to determine whether standard nodal radiation fields would cover the location of prostate cancer recurrence.
Materials and methods: We performed a retrospective review of patients with PSMA-PET imaging for biochemical recurrence following RP with PSA ≤2.0 ng/mL and assessed if the recurrent disease was within standard radiation target volumes. We compared patient and clinical variables between men with recurrences covered by standard salvage radiation fields and those with recurrences outside of standard fields.
Results: We identified 125 patients for study inclusion. The median PSA at imaging was 0.40 ng/mL (interquartile range 0.28-0.63). PSMA-avid disease was found in 66 patients (53%). Of these, 25 patients (38%) had PSMA-avid lesions found outside of the pelvis, 33 (50%) had lesions confined to the pelvic lymph nodes and prostate bed, and 8 (12%) men had PSMA-avid recurrence only in the prostate bed. Salvage radiation including standard Intensity Modulated Radiation Therapy (IMRT) pelvic nodal volumes would not cover PSMA-avid nodal disease in 38 men (30%). PSA at the time of imaging was statistically associated with having PSMA-avid disease outside of standard nodal fields (P <.01).
Conclusion: The 68Ga-PSMA-11 PET detects disease in a majority of patients with PSA ≤2.0 following RP. Nearly one-third of men had PSMA-avid disease that would be missed by standard radiation fields. This imaging modality may dramatically impact the design and use of post-RP salvage radiotherapy.
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