Association between weight change and breast cancer prognosis.

Purpose: Results of the associations between weight change after breast cancer diagnosis and prognosis were inconsistent. The modification effects of menopausal status and endocrine therapy on the associations remain poorly understood.

Methods: A total of 2016 breast cancer patients were recruited between October 2008 and January 2018 and followed up until December 31, 2019 in Guangzhou. Multivariate Cox models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (95% CIs) for progression-free survival (PFS) in association with weight change after diagnosis.

Results: Weight loss at 2 years (HR = 1.34, 95% CI 0.87-2.06) or more than 2 years (HR = 1.95, 95% CI 1.22-3.10) after diagnosis increased risk of breast cancer progression. The adverse effect of weight loss was significantly more pronounced in post-menopausal than pre-menopausal women, particularly for weight loss at 2 years after diagnosis, with the HRs and 95% CIs of 2.41 (1.25-4.63) and 0.90 (0.49-1.64), respectively. Weight gain tended to reduce the risk of disease progression among patients with endocrine therapy but not for those with non-endocrine therapy; the significant interaction between weight gain at 2 years after diagnosis and endocrine therapy was observed (P = 0.042).

Conclusion: Our finding suggested that weight loss was detrimental to breast cancer prognosis, particularly for post-menopausal women, while weight gain may be a potential beneficial indicator for the patients with endocrine therapy but not for those with non-endocrine therapy.