More than half of patients receiving cancer treatments had a history of obesity, finds study
More than half of people starting systemic cancer treatment in England had a history of obesity, even though only around one in four were living with obesity when treatment began, according to new research.
The real-world study of more than 79,000 patients across 13 cancer types showed that relying on a single body mass index (BMI) measurement at treatment start may greatly underestimate patients’ lifetime exposure to obesity. For pancreatic cancer, obesity at the start of treatment was only 13.7%, but lifetime obesity prevalence was 55.8%, demonstrating that current weight doesn’t provide a complete picture of someone’s health.
A team of scientists led by Professor Simon Lord analysed past BMI data from digital health records of patients who were receiving systemic treatments, meaning any kinds of treatment where drugs travel through the bloodstream, such as chemotherapy.
Funded by World Cancer Research Fund and led by the University of Oxford, the findings, published recently in the journal ESMO Real World Data and Digital Oncology, provide valuable real-world data on obesity prevalence among people living with cancer.
The results highlight the need to consider lifetime obesity exposure in clinical decision-making and precision care. The results also provide important information about the prevalence of obesity in a real-world group of patients. This is crucial for informing healthcare provision since body weight informs treatment, such as chemotherapy dosing.
World Cancer Research Fund’s International Assistant Director of Research and Policy, Dr Helen Croker, said:
“This research highlights the opportunity to consider patients’ history of obesity alongside their current health when thinking about broader clinical decision-making.
“Our previous research highlighted how a lack of accurate pre-diagnosis body weight measures in studies of people living with and beyond cancer presented limitations for interpreting the role of BMI on outcomes. It is wonderful to see research we have funded addressing key questions where we have been missing data.”
Digging into the data
The study found that on average, including historical BMI raised obesity prevalence from 26.4% to 53.5% and that lifetime obesity prevalence exceeded 50% in every one of the 13 cancer types studied.
Analysis showed that obesity prevalence varied across cancer types. Cancers that commonly present with cachexia or reduced dietary intake showed lower obesity rates at first treatment, including pancreatic, gastroesophageal, bowel, and lung cancer, and non-Hodgkin lymphoma. The results revealed higher obesity rates at treatment start for uterine, breast cancer and malignant melanoma.
Further analysis found that patients aged over 75 had lower obesity prevalence at the start of treatment, while those living in more deprived areas had higher levels of obesity.
Impact and implications
Obesity is a risk factor for 13 cancer types, and global projections suggest that over 2 million cancer cases could be attributable to obesity by 2070. However, the precise role obesity plays in cancer outcomes and treatment response remains unclear.
Associate Professor in Experimental Cancer Therapeutics at the University of Oxford, Professor Simon Lord, said:
“This work highlights the limitations of using a single BMI measurement, which fails to accurately reflect past obesity exposure. How obesity affects cancer prognosis is extremely complex, with both current and previous obesity likely to be important. This paper reveals large differences between current and past BMI in patients receiving systemic therapy, highlighting the importance of considering both measures.
“So, this study provides clear rationale for considering both current and past BMI in clinical decision making and outcomes research. Not doing so risks missing an important part of the clinical picture.”
This research is also significant because body weight is often used as a guide for making decisions around treatment, such as chemotherapy dosing, and this is more complex in patients with obesity. But until now, the scale of this need has been unclear due to limited obesity prevalence data in real-world clinical populations.
Senior Research Fellow at the Department of Oncology at the University of Oxford, Dr Victoria Perletta, said:
“This study underlines the importance of using longitudinal BMI measures to accurately classify obesity exposure in cancer patients receiving systemic therapy. Our work could have implications for clinical decision-making, as understanding a patient’s history of obesity may help build a fuller picture of their health than BMI at treatment start alone. Because body weight can inform chemotherapy dosing, this may also be relevant to more personalised care.
“Future research could explore how lifetime BMI versus BMI at treatment start associates with cancer outcomes to resolve unanswered questions.”
Researchers note that the growing use of weight-loss medications such as GLP-1 receptor agonists may further change obesity patterns in cancer patients, making longitudinal tracking even more important in future studies.
“Although the link between obesity and cancer risk is well established, its impact on cancer outcomes remains uncertain and relying only on BMI at treatment start may miss important lifetime exposure that could influence cancer prognosis,” added Dr Croker.
