Excess Weight Before 50 Shortens Life with Breast Cancer After 50
Study finds women diagnosed with breast cancer after age 50 who had obesity when they were younger did not live as long as women who didn’t.
The Challenge
Carrying excess body weight is an established risk factor for several types of cancer and accounts for at least 4% of the global cancer burden. Two of the most common cancers related to body weight are breast cancer and colorectal cancer.
The number of people with overweight and obesity continues to increase—for adults, teens, and children. Plus, younger generations are spending a greater part of their lives with these conditions than any generation before. These body weight trends may explain an increasing number of cancer cases in successively younger generations in high-income countries, including the United States.
Research has shown that the link between excess body weight and the development of cancer is “dose-dependent.” That means the more someone is over their recommended BMI or weight range the higher their risk is for developing weight-related cancers. Scientists may refer to the amount of excess body weight (the dose) as “intensity” or “magnitude.” There’s also evidence that how long someone has excess weight conditions—the “duration”—the higher their risk is for developing weight-related cancers.
It's less well known how having overweight or obesity affects survival after a diagnosis of cancer.
The Research
To evaluate the link between excess weight throughout adulthood and survival in postmenopausal women with breast or colorectal cancer a group of researchers studied a very large set of pooled data—from 5 international cohort studies, including almost 600,000 participants from 11 countries, and 3 continents. One of the cohorts studied was the ACS Cancer Prevention Study II (CPS-II). The researchers included Mia Gaudet, PhD, former ACS strategic director of breast and gynecologic cancer research and current senior scientist at the National Cancer Institute.
Body weight plays an important role in the development, treatment, and survival of breast cancer. While this study helps us better understand the role body weight before a diagnosis has on survival after a diagnosis of breast cancer, it is difficult to disentangle the multifactorial role of body weight.”
The team reviewed data for about 23,000 women who were diagnosed with breast or colon cancer after age 50. Their goal was to look at repeated BMI measurements to establish “lifetime overweight.” Specifically, they evaluated whether the women had excess body weight for less or more than 15 years in total.
They found that women who had an average BMI that was equal to or higher than the “overweight” minimum BMI of 25 kg/m2 for at least 15 years during early and mid-adulthood (age 20 through 50) had a shortened lifespan after a diagnosis of breast cancer. Compared with women without excess weight in their younger years, women with excess weight had a 15% shorter survival after a diagnosis of breast cancer. (For example, for every 10 years a woman with “normal” BMIs lived after a postmenopausal diagnosis of breast cancer, women with “overweight” or “obese” BMIs would live an average of 8.5 years. 10 X 15% =1.5 and 10-1.5=8.5)
Why It Matters
This study provides new evidence from a large-scale study about the effect of excess weight in women before a diagnosis of breast cancer and their survival after it. It highlights the negative effect excess weight and time spent with excess weight before the age of 50 on the risk of dying among women diagnosed with breast cancer after age 50.
The authors conclude that their results “emphasize the importance of public health policies aimed at preventing excess weight in early life.”
