Association between brown adipose tissue activity and clinical outcomes in melanoma: a retrospective PET/CT analysis

Brown adipose tissue (BAT) activity has been suggested to play a role in cancer progression. Previous studies have shown that BAT activity is higher in patients with cancer, and that BAT volume is a predictor of tumour recurrence and mortality in patients with cancer, but the data on melanoma are limited.

Here, we re-analysed 2-fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography (FDG-PET-CT) images from 135 patients with cutaneous melanoma treated at Turku University Hospital between 2012 and 2021 to assess associations among BAT, melanoma progression, patient survival, and patient weight. We applied a three-stage universal BAT threshold definition using predetermined standardised uptake value thresholds of 0.8, 1.0, and 1.2 g/ml, given the retrospective nature of our study. Of the 135 patients (81 men and 54 women; median age 61 years, interquartile range 54-71), 40 (29.6%), 24 (17.8%), and 19 (14.1%) were BAT-positive at the 0.8, 1.0, and 1.2 g/ml thresholds, respectively.

Our results showed that patients with active melanoma on FDG-PET-CT imaging were more frequently BAT-positive at the 0.8 threshold (P = 0.026) and 1.0 threshold (P = 0.016). We also found a significantly higher BAT volume among patients who survived the observation period (0.8, 1.0, and 1.2 g/ml thresholds; P = 0.018, P = 0.038, and P = 0.571, respectively) and those who did not relapse (0.8, 1.0, and 1.2 g/ml thresholds; P = 0.631, P = 0.012, and P = 0.030, respectively).

No association between BAT positivity and relapse-free survival or overall survival was observed at any threshold. Although higher BAT volumes were observed in subgroups of patients who survived or did not relapse, these findings were not supported by survival analyses and should be considered exploratory.