The diagnostic accuracy and clinical impact of FDG-PET/CT follow-up for patients on adjuvant immunotherapy for high-risk malignant melanoma

• Published in: European journal of nuclear medicine and molecular imaging 2022-06, Vol.49 (7), p.2342-2351
• Main Authors: Andersen, Jesper A. S., Spatzek, Anders D., Vilstrup, Mie H., Grupe, Peter, Hess, Søren, Holdgaard, Paw C., Bastholt, Lars, Gerke, Oke, Hildebrandt, Malene G.
• Format: Article
• Language: English
• Subjects: Biopsy; Cardiology; Cohort analysis; Computed tomography; Diagnostic systems; Fluorodeoxyglucose F18; Follow-Up Studies; Humans; Imaging; Immunotherapy; Medical diagnosis; Medical records; Medicine; Medicine & Public Health; Melanoma; Melanoma - diagnostic imaging; Melanoma - pathology; Melanoma - therapy; Melanoma, Cutaneous Malignant; Metastases; Neoplasm Recurrence, Local - diagnostic imaging; Nuclear Medicine; Oncology; Oncology – General; Original Article; Orthopedics; Patients; Positron emission; Positron emission tomography; Positron Emission Tomography Computed Tomography - methods; Radiology; Radiopharmaceuticals; Retrospective Studies; Risk; Sensitivity; Sensitivity and Specificity; Skin cancer; Skin Neoplasms; Surgery; Tomography
• ISSN: 1619-7070; 1619-7089
• DOI: 10.1007/s00259-022-05704-0

Objective The benefit of FDG-PET/CT in follow-up of patients treated with adjuvant immunotherapy after resection of high-risk malignant melanoma (MM) is debated. This study evaluated the diagnostic accuracy and clinical impact of FDG-PET/CT for diagnosing MM recurrence during the first year after surgery. Methods We retrospectively included 124 patients with resected high-risk MM, who received adjuvant immunotherapy and follow-up FDG-PET/CT. Clinical information and AJCC-8 stage was obtained from patients’ medical records. Recurrence was verified by biopsy/progression on a subsequent scan leading to change of treatment. Non-recurrence was assumed when no metastases were observed until the subsequent follow-up scan. Incidence of recurrence, sensitivity, specificity, positive and negative predictive values (PPV and NPV) were outcome measures. Results Incidence rate of MM recurrence was 0.27 [95% CI 0.17–0.37] per person-year during the first-year. Recurrence was detected in 13 patients (10%) at 3-month FDG-PET/CT, in 10 patients (8.1%) at 6 months, 1 patient (0.8%) at 9 months, 3 patients (2.4%) at 12 months. The overall sensitivity, specificity, PPV, and NPV were 97% [86–99], 82% [78–86], 39% [29–50], and 99% [98–99], respectively. The PPV trended towards higher values as disease stage increased. At the 3-month scan, the majority of actions derived from positive findings were surgery or earlier expedition of the subsequent follow-up scan. Conclusion The high rate of recurrence in patients with high-risk MM treated with adjuvant immunotherapy emphasizes the need for follow-up. The potential harm by a moderately low specificity reflecting a high number of false-positive results must be weighed against the benefit of early detection of recurrence.