Metabolic flare phenomenon mimicking disease progression on 18Flouride- Fluorodeoxyglucose PET/CT scan in breast cancer treated with paclitaxel-based chemotherapy.

Abstract

¹⁸F-fluorodeoxyglucose Positron emission tomography (¹⁸F-FDG PET/CT ) is now being used as a single modality for metastatic workup and response evaluation in breast cancer. An increase in metabolic activity indicates disease progression; however, metabolic flare should be kept in mind. Metabolic flare is a well-documented phenomenon reported in metastatic breast and prostate cancer. Despite a favorable response to therapy, there is a paradoxical increase in radiopharmaceutical uptake. The flare phenomenon with various chemotherapeutic and hormonal agents is well acknowledged in bone scintigraphy. However, very few cases have been documented on PET/CT. Increased uptake may be noted after treatment is instituted. The increased osteoblastic activity is associated with the healing response of bone tumors. We report a case of treated breast cancer. She presented with metastatic recurrence after four years of initial management. The patient was started on paclitaxel chemotherapy. Serial ¹⁸F- FDG PET/CT demonstrated metabolic flare and complete metabolic response.