Obesity Links to Earlier Mortality for Breast Cancer Survivors
A new study involving the emerging research on lifestyle’s role in breast cancer survivorship suggests that obesity – both before and after a breast cancer diagnosis – is associated with earlier death from cancer or other causes, compared to women at a healthy weight.
The paper, published in the Annals of Oncology, adds to a complex and relatively new area of research: what survivors can do to lengthen life and stay healthy.
In a major report on breast cancer survivorship due this Fall, World Cancer Research Fund International’s Continuous Update Project (CUP) expert panel will consider this latest paper as it works to shape official recommendations for cancer survivors. The American Institute for Cancer Research (AICR) is the US member of World Cancer Research Fund International.
The paper found that increased body size is related to survival after a diagnosis of breast cancer…"The findings are not proof, however, that weight loss in overweight or obese women could lengthen life."
The CUP’s international panel of experts will analyze the data compiled in today’s article and judge the strength of the evidence linking weight, diet and physical activity to improved health of breast cancer survivors.
The Annals of Oncology paper was written by a team of scientists involved in the CUP, including Anne McTiernan, MD, PhD, Director of the Prevention Center at the Fred Hutchinson Cancer Research Center. The paper found that “increased body size is significantly related to survival after a diagnosis of breast cancer, although there is also evidence that women who are underweight may also have increased risk,” said Dr. McTiernan.
“The findings are not proof, however, that weight loss in overweight or obese women could lengthen life. To say that, we would need evidence from a clinical trial, the gold standard for treatment in cancer patients and survivors.”
The new paper analyzed the 82 studies that had investigated survival in women with breast cancer and BMI, a measure of body fatness. The studies included approximately 213,000 breast cancer survivors. During the studies, 41,477 of the women died, with slightly over half dying from breast cancer.
The analysis found that women who are obese and develop breast cancer are 41 percent more likely to die earlier than women who are in the normal weight range before diagnosis. Mortality from breast cancer was 35 percent higher for obese women. The increased risk of earlier death was seen for both pre- and post-menopausal cancers. Being overweight also linked to a modest increased risk of an earlier death.
Women who were obese 12 months after diagnosis also had an increased risk of death compared to those at a normal weight.
As the authors of today’s paper conclude, these findings are limited by the challenges and limitations of the individual studies. For example, most studies did not adjust for other conditions [comorbidities] and assess intentional weight loss. Another possible limitation the article notes: obese women commonly under-dose their chemotherapy, which may contribute to their increased mortality.
Randomized clinical trials are needed to test interventions for weight loss and maintenance in the survival of women with breast cancer, says McTiernan, referring to a rigorous method of study considered among the highest levels of proof.
For now, says McTiernan: “I would suggest that [most survivors] try not to gain weight through their treatments, and try to be as physically active as they can tolerate. Increased physical activity has been shown to improve quality of life and fatigue in survivors, which are very important for women going through a cancer diagnosis and treatment, and beyond.
“And women should follow as healthy a diet as possible… eat more vegetables and fruits, and lower amounts of high-calorie deserts and sweets. There’s no guarantee these eating styles will improve survival, but they might help women keep their weight stable.”
Source: Doris S. M. Chan et al. "Body mass index and survival in women with breast cancer—systematic literature review and meta-analysis of 82 follow-up studies." Ann Oncol (2014). First published online: April 27, 2014.