18F-Fluoride PET Used for Treatment Monitoring of Systemic Cancer Therapy: Results from the National Oncologic PET Registry

In a national prospective registry, we previously studied the impact of F-18-sodium fluoride PET (NaF PET) on the intended management of cancer patients with osseous metastases. The clinical impact of NaF PET for monitoring the response to systemic therapies in such patients is unknown. The objective of this study was to assess the impact of NaF PET results obtained for treatment monitoring of systemic cancer therapy. Methods: Before and after NaF PET, we collected prospective data from referring and interpreting physicians for cancer patients 65 y or older receiving systemic therapy (use of 1 or more categories including hormonal, chemotherapy, bisphosphonates, or immunotherapy). The analysis set consisted of 2,217 patients who underwent 2,839 scans (68% prostate, 17% breast, 6% lung, and 8% other cancers) ordered for treatment monitoring. Two or more categories of systemic therapy were planned in 56% of prostate and 43% of breast cancer patients. Results: The overall rates of prior radionuclide bone imaging were 78%, 76%, and 66% for prostate, breast, and other cancers, respectively. Fifty-seven percent of patients underwent prior NaF PET. Overall change in management associated with NaF PET was 40%. In patients with prior NaF PET scans for comparison, continuing current therapy was planned in 79% when scans showed no change or a decrease or absence of osseous metastasis. Treating physicians planned to switch therapy in 59% of patients after scans showed evidence of new or progressive metastasis. When an additional parameter, estimated prognosis, was worse, switching therapy was even more common (76%). Conclusion: The impact of NaF PET used for treatment monitoring was high in patients with evidence of progressive osseous metastasis. Most such patients had plans to switch to a new cancer-directed therapy.