Earlier Recurrence Detection Using Routine FDG PET-CT Scans in Surveillance of Stage IIB to IIID Melanoma: A National Cohort Study of 1480 Patients

BACKGROUND

The effect of routine imaging in melanoma surveillance is unknown. In 2016, Denmark was the first country in the world to implement routine imaging with positron emission tomography-computed tomography with fluorodeoxyglucose (FDG PET-CT) in a nationwide, population-based surveillance program. This study aimed to determine the impact of surveillance with routine FDG PET-CT on hazard, cumulative incidence, and absolute risk of overall, locoregional, and distant recurrence detection in patients with stage IIB to IIID cutaneous melanoma.

METHODS

This retrospective, population-based, nationwide cohort study used prospectively collected data from five national health registries to compare hazard, cumulative incidence, and absolute risk of recurrence in patients with cutaneous melanoma diagnosed in 2008-2010 (cohort 1, followed with clinical examinations) and patients with cutaneous melanoma diagnosed in 2016-2017 (cohort 2, followed with clinical examinations and routine FDG PET-CT at 6, 12, 24, and 36 months).

RESULTS

The study included 1480 patients with stage IIB to IIID cutaneous melanoma. Cumulative incidences of overall and distant recurrence were higher in cohort 2, with a peak difference at three years (32.3 % vs 27.5 % and 25.8 % vs. 18.5 %, respectively). The hazard of recurrence was higher in cohort 2 during the first two years, with hazard rates for overall and distant recurrence of 1.16 (95 % confidence interval [CI], 0.93-1.44) and 1.51 (95 % CI, 1.16-1.96), respectively. The patterns persisted in absolute risk estimates.

CONCLUSIONS

Patients with stage IIB to IIID melanoma followed with routine FDG PET-CT had a 51 % increased hazard of distant recurrence detection within the first two years of surveillance. Future studies must determine whether this earlier recurrence detection translates into improved survival.

Practical Considerations When Interpreting FDG PET/CT Imaging for Staging and Treatment Response Assessment in Melanoma Patients

While FDG PET/CT bears a high sensitivity and specificity for the staging of stage III and IV melanoma as well as for the purpose of melanoma recurrence detection, overall results tend to vary from one part of the body to another as well as for melanoma from cutaneous or choroidal origin. In this paper, organ or site-related differences in sensitivity and specificity in melanoma patients, both from cutaneous and choroidal origin, as well as their impact on clinical decision making are discussed. Furthermore, with the advent of immunotherapy for the treatment of malignant melanoma, post-treatment related potential false positive findings have emerged, the knowledge of which is essential for accurate treatment response assessment. These post-treatment related potential false positive findings are summarized in this paper so as to help the nuclear medicine physician in avoiding erroneous interpretation of acquired FDG PET/CT images in melanoma patients receiving immuntherapy.

Routine PET-CT scans provide early and accurate recurrence detection in asymptomatic stage IIB-III melanoma patients

INTRODUCTION

The use of routine imaging with 18F-FDG PET-CT (PET-CT) in melanoma surveillance is debated and evidence of its diagnostic value and yield in asymptomatic patients is limited. Denmark introduced nationwide routine surveillance with PET-CT in high-risk patients in 2016. The aim of this study was to examine the sensitivity, specificity, negative and positive predictive values, numbers-needed-to-scan and clinical impact of routine PET-CT in the surveillance of asymptomatic stage IIB-III melanoma patients.

MATERIALS AND METHODS

Data was retrieved from the population-based Danish Melanoma Database and patient records. All patients diagnosed with stage IIB-III melanoma at two University Hospitals in 2016 and 2017 were included. Patients underwent surveillance with clinical examinations and PET-CT scans at 6, 12, 24 and 36 months.

RESULTS

In 138 patients, 243 routine PET-CTs were performed within a median follow-up time of 17.7 months. Routine PET-CT detected recurrence at least once in 25 patients (18.1%), including distant recurrence in 19 patients (13.8%). Stage IIB patients had the lowest recurrence rate (11.1%). Numbers-needed-to-scan to detect one distant recurrence was 12.8 patients and median time-to-recurrence was 6.8 months. Sensitivity was 100%, specificity was 94.7% and negative and positive predictive values were 100% and 74.4%, respectively. False positive findings prompted 22 additional investigations (of which ten invasive) in 17 patients (12.3%).

CONCLUSION

Routine PET-CT has a high sensitivity and specificity when used in high-risk melanoma surveillance. Time-to-recurrence and stage-specific recurrence rates indicate high gain of early routine imaging at six months especially for stage IIC and III patients.

Primary malignant melanoma of the stomach: a rare entity

A 54-year-old man presented with easy fatiguability, dyspnoea on exertion and dyspeptic symptoms. On evaluation, he was found to have an ulcero-proliferative growth in the gastric fundus, the biopsy of which was malignant melanoma of the stomach. Further evaluation with 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) scan showed operable disease with no focus of disease elsewhere. He was diagnosed as primary gastric melanoma and underwent radical total gastrectomy with adequate margins. His postoperative period was uneventful. Further adjuvant therapy was refused by the patient. At 6-month follow-up, an 18F-FDG PET-CT scan was done, which showed no evidence of disease. On follow-up at 1-year, he was alive and asymptomatic.