New research to be presented at this year's European Congress on Obesity (ECO 2025, Malaga, Spain, 11-14 May) and published in The Journal of Internal Medicine shows that, in survivors of breast cancer, having an unhealthy metabolic profile or so called 'metabolic syndrome' increases the risk of breast cancer recurrence by 69%, and subsequent breast cancer mortality by 83%. The study is by Dr Sixten Harborg, Department of Oncology, Aarhus University/Aarhus University Hospital, Aarhus, Denmark. and Department of Nutrition, Harvard T.H. Chan School of Public Health, MA, USA, and colleagues.
Metabolic syndrome was characterised according to the American Heart Association, which includes the presence of three out of five abnormal findings among the risk factors: high blood pressure, high triglycerides (blood fats), low high-density lipoprotein (HDL) or 'good' cholesterol, high fasting glucose (blood sugar), and central or abdominal obesity (a waist circumference of more than 35 inches for women).
Data were obtained from observational studies and randomised controlled trials that used survival statistics and reported survival ratios to investigate how the presence of metabolic syndrome at the time of breast cancer diagnosis is associated with survival. Study data from 42,135 breast cancer survivors were pooled using statistical modelling to assess the relationship between an unhealthy metabolic profile and survival of breast cancer. The pooled estimates revealed that breast cancer survivors who had metabolic syndrome at the time of their breast cancer diagnosis experienced a 69% increased risk of recurrence and an 83% increased risk of breast cancer mortality compared to breast cancer survivors without metabolic syndrome.
Breast cancer survivors with metabolic syndrome were found to be 57% more likely to experience a breast cancer-related event (recurrence, new cancer, or death) during follow-up than breast cancer survivors without metabolic syndrome.
Interestingly, the authors looked into potential differences in the association according to geographical location of the included studies origin continent and found that the association between poorer outcomes among breast cancer survivors with metabolic syndrome was consistent across Europe, North America and Asia.
The authors conclude: "Among breast cancer survivors, metabolic syndrome was associated with poorer breast cancer outcomes. The findings of this study emphasise the importance of metabolic screening for breast cancer survivors. Future research should focus on assessing how control of blood fats, reversing diabetes, and making healthy lifestyle choices could decrease the prevalence of metabolic syndrome in this population and ultimately enhance breast cancer survival."
They add that the precise mechanisms through which metabolic syndrome heightens the risk of breast cancer and its recurrence remain unclear, but are believed to involve chronic inflammation and hormonal imbalances.
They say: "One possible explanation posits that the excessive body fat associated with metabolic syndrome results in increased levels of circulating oestrogen, which may stimulate the growth of breast cancer cells. Additionally, adiposity may induce alterations in the tumour microenvironment that facilitate metastasis, or the spread of cancer. Chronic systemic inflammation, a hallmark of metabolic syndrome, may further contribute to tumour progression by promoting cancer cell survival and impairing immune surveillance. Although our study did not investigate the biological underpinnings of the observed associations, it is likely that multiple interacting mechanisms—primarily driven by obesity-induced molecular changes and chronic inflammation—underlie the link between metabolic syndrome and poor breast cancer outcomes."
