18F-FDG PET/CT and Melanoma: Value of Fourth and Subsequent Posttherapy Follow-up Scans for Patient Management

Purpose We aimed to evaluate the added value of performing fourth and subsequent follow-up ¹⁸F-FDG-PET/CT scans to clinical assessment and impact on the patient's management in patients with melanoma. Methods This was a retrospective study of 232 biopsy-proven melanoma patients who underwent ¹⁸F-FDG-PET/CT scans. Of these, 71 patients had 4 or more follow-up ¹⁸F-FDG-PET/CT scans after completion of primary treatment, with a total of 246 fourth or subsequent follow-up PET/CT scans. The added value of each follow-up PET/CT scan to the patient's clinical assessment and treatment management was established. Kaplan-Meier plots with a Mantel-Cox log-rank test were used to establish the patient's overall survival. Results Of the 246 fourth and subsequent follow-up PET/CT scans, 61% (150/246) were negative for malignancy, and 39.0% (96/246) were positive for recurrence/metastases. FDG-PET/CT was helpful in identifying malignancy in 6.5% of the scans performed without prior clinical suspicion, which ruled out malignancy in 28.5% of the scans obtained with prior clinical signs suggestive of recurrence or for secondary therapy assessment. The PET/CT scan resulted in change of the patient's management in approximately 16.7% (41/246) of the scans. Change in management was significantly greater in patients whose scans were done with prior clinical signs suggestive of malignancy, or for therapy assessment than without prior clinical suspicion (29.3% vs 4.1%; P < 0.0001). Statistically significant difference was seen in the overall survival between patients with at least 1 positive and all negative fourth and subsequent follow-up PET/CT scans at patient level (P = 0.001). Conclusions The fourth and subsequent ¹⁸F-FDG-PET/CT scans obtained after completion of primary treatment added value to clinical assessment in patients with melanoma. Patients with clinical signs suggestive of recurrence or metastases or being monitored for treatment response are more likely to benefit from the fourth or subsequent FDG PET/CT than those without prior clinical suspicion.