SABCS 2024: The Persistent Association Between Obesity and Breast Cancer Outcomes

In an interview with Pharmacy Times®, Hongchao Pan, MSc PhD, associate professor at the University of Oxford in the United Kingdom, discussed the association of obesity with an increased distant recurrence and breast cancer mortality across all subgroups of early-stage breast cancer. The findings highlight the importance of weight management in breast cancer prevention and treatment. Pan noted that future research should investigate the effectiveness of weight loss interventions in improving outcomes for overweight and obese breast cancer patients.

Pharmacy Times

What are the key findings of this study regarding the association between overweight/obesity and breast cancer prognosis?

Hongchao Pan, MSc PhD

From the analysis of the data from 200,000 women with early-stage breast cancer, we find that there's a very nice association between body mass index and breast cancer distant recurrence and from breast cancer deaths. We also find that this association is not affected much by tumor characteristics or patients’ characteristics. It really doesn't matter whether you are premenopausal or postmenopausal — it doesn't matter whether you got an ER+ disease or ER- disease, that proportional risk stays the same. In addition to that, we also notice that there's a very nice linear association and the absolute difference in the 10-year risk of distant recurrence. It's only moderate to about a 2% risk difference for 12 units change in BMI, or about 1% risk difference by 5 units change in BMI. For most lifestyle intervention, this is very difficult to achieve — BMI reduction of 5 units.

Pharmacy Times

How do these findings contribute to our understanding of the impact of body weight on breast cancer outcomes, particularly in the context of existing treatment strategies?

Pan

Our findings are a little bit surprising. We had expected very strong introductions by ER status and menopausal status on the association of BMI with breast cancer prognosis. Because from the observation of studies in general population, and BMI is proportionally associated with the incidence of breast cancer in only premenopausal women, and it doesn't relate to the incidence of ER- disease, and even reversely associated with the incidence of premenopausal women. Once a woman was breast cancer diagnosed, and then it seems the prognosis is proportionally related to her body mass index. This positive because we know the ER+ cancer cell require estrogen to grow and know Body Mass Index affect circulating estrogen level and in premenopausal women. This all very positive. Our finding will contribute to the understanding of the mechanism behind this new finding. In terms of existing treatment, we also assess the relationship of BMI with breast cancer prognosis by type of treatment. We find the proportional risk stays the same, whether you got chemotherapy or got endocrine therapy only or even women that didn't get any adjuvant chemotherapy at all — it stays the same.

Pharmacy Times

What are the potential clinical implications of these findings for the management of overweight/obese breast cancer patients, including lifestyle interventions and targeted therapies?

Pan

I just mentioned earlier, and we've found the difference in the risk of distant recurrence over 10 years only moderate. With 5 units reduction in BMI, that's only associated with just 1% risk reduction over 10 years, and most of the lifestyle intervention wouldn't be able to just to make women reduce BMI for 5 units, and that's just for women with average height. That just means we lose 13-kilogram weight, and I would think that's beyond what most people could manage and even sustain for 10 years. If lifestyle intervention couldn't reach that target and then assume our observation of BMI with the distant recurrence is causal, so you can properly, use the anti-weight medication, such as GLP-1 agonist might help.

Pharmacy Times

Is there anything you would like to add?

Pan

Our studies mainly focus on the association of BMI with breast cancer prognosis, even when we just find that the risk differences are moderate. But it doesn't mean it doesn't matter for women with any breast cancer, control their body weight. Actually, and our analysis to assess the association of BMI with the non-breast cancer deaths. And then the association of BMI with non-breast cancer is much stronger than associated with the deaths from breast cancer and mainly associated with the cardiovascular deaths. Overweight and obese women to try to lose the weight is very important to just prevent their deaths from other non-growth, cancer deaths.