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Weight Gain After Breast Cancer Diagnosis Ups Mortality Risk


 

Weight gain following a diagnosis of breast cancer significantly increases a woman's risk not only of breast cancer mortality but also of all-cause mortality over a 6-year follow-up period, results of a large study suggest.

“We found that a weight gain of 5 kg [11 pounds] increased the risk of death due to breast cancer and other causes by 14%,” study investigator Hazel B. Nichols, an epidemiology doctoral student at Johns Hopkins University in Baltimore, reported at a press briefing. The briefing was held in conjunction with the annual international conference of the American Association for Cancer Research.

The findings suggest that efforts to prevent postdiagnosis weight gain could improve breast cancer survival.

Ms. Nichols and her colleagues analyzed data from a cohort of 4,021 women, who had previously participated in consecutive population-based, case-control studies of incident breast cancer in Wisconsin, Massachusetts, and New Hampshire. In the initial studies, women aged 20–70 years with a definitive diagnosis of invasive breast cancer between 1988 and 2001 were identified through state registries. Women were included in the studies once they had completed a structured telephone interview with information on height and weight, reproductive and menstrual factors, lifestyle characteristics, family and personal history of breast cancer, and demographics.

During 1998–2001, all surviving women from the original case-control studies were mailed a follow-up questionnaire, which addressed postdiagnosis weight, weight gain, physical activity, diet, medication history, alternative therapies, and quality of life. Vital status was obtained by linkage with the National Death Index through 2005. The researchers identified 121 breast cancer deaths and 428 non-breast cancer deaths after an average follow-up of 6 years (see graphic).

The researchers controlled for age, state of enrollment, time from breast cancer diagnosis to completion of the follow-up questionnaire, family history of breast cancer, menopausal status, and stage of disease. Women with metastatic disease at diagnosis were excluded from the analysis to avoid the influence of disease on postdiagnosis body weight.

Obesity, regardless of weight before diagnosis, also increased a woman's risk of breast cancer and all-cause death. Women with a body mass index greater than 30 kg/m

Ms. Nichols cautioned that the women may have had other medical conditions that could have confounded the results, but the researchers did not have access to this information. The researchers plan to look next at the effect of postdiagnosis weight loss.

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