A decrease in brown adipose tissue activity is associated with weight gain during chemotherapy in early breast cancer patients

A decrease in thermogenesis is suspected to be implicated in the energy expenditure reduction during breast cancer treatment. This study aimed to investigate the impact of chemotherapy on the metabolic activity of brown adipose tissue (BAT) and the link with weight variation. This was an ancillary analysis of a multicentre trial involving 109 HER2+ breast cancer patients treated with neoadjuvant chemotherapy. A centralised review of 18F-FDG uptake intensity (SUVmax) in specific BAT regions (cervical and supraclavicular) was conducted on two PET-CT scans for each patient (before and after the first course of chemotherapy). Overall, after one course of chemotherapy a significant decrease of 4.4% in 18F-FDG-uptake intensity was observed. It was not correlated to initial BMI, age or season. During chemotherapy, 10.1% (n = 11) of the patients lost weight (− 7.7 kg ± 3.8 kg; ie, − 9.4% ± 3.7%) and 29.4% (n = 32) gained weight (+ 5.1 kg ± 1.7 kg; ie, + 8.5% ± 2.6%). Among these subgroups, only the patients who had gained weight underwent a significant decrease (13.42%) in 18F-FDG uptake intensity (p = 0.042). This study is the first to highlight in a large cohort of patients the negative impact of chemotherapy on brown adipose tissue activity. Weight gain during chemotherapy could thus potentially be explained in part by a decrease in brown adipose tissue activity.