Stereotactic Body Radiation Therapy (SBRT)-Induced 68 Ga-PSMA PET Bone Flare.

A 65-year-old man with oligometastatic prostate cancer underwent radical prostatectomy and stereotactic body radiation therapy (SBRT) to a right pubic bone metastasis. Four weeks after SBRT, PSMA PET showed increased extent and intensity of uptake at the treated site, despite a 92% PSA decline (8.5 to 0.7 ng/mL) and no new lesions. Later imaging confirmed resolution of uptake, consistent with bone flare, but revealed multiple new osseous metastases and rising PSA (2.8 ng/mL), indicating progression. To our knowledge, this is the first reported case of SBRT-induced bone flare, highlighting the need for cautious interpretation of early posttreatment PSMA PET.