Daily Dose: Obesity Linked to Higher Risk for Breast Cancer Recurrence

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Last week, we reported on findings from a study published in JAMA Network Open that examined the association between body mass index (BMI) and breast cancer recurrence.

The study

Researchers tapped the clinical database of the Danish Breast Cancer Group, which covers all women in Denmark and includes information on breast cancer diagnosed since 1977. They identified all postmenopausal women with a primary diagnosis of stage I-III HR+ breast cancer from January 1, 1998, until December 31, 2016. Inclusion required receiving endocrine therapy with aromatase inhibitors (AIs) and information on BMI.

The end point was breast cancer recurrence, defined as the time from 6 months after the date of breast cancer surgery until the earliest occurrence of any breast cancer recurrence recorded.

Investigators used “healthy” weight as the reference category for calculation of associations. BMI was recorded at the time of surgery or at the first appointment for administration of adjuvant treatment following surgery.

The final cohort comprised 13 230 postmenopausal women with primary, early-stage, HR+ breast cancer. The participants had a median age of 64.4 years at diagnosis. Distribution of BMI at the time of diagnosis was:

• 6.5% severe obesity (BMI ≥35.0 kg/m2)

• 14.4% obesity (30-34.9 kg/m2)

• 32.5% overweight (25-29.9 kg/m2)

• 44.4% normal weight (18.5-24.9 kg/m2)

• 2.2% underweight (<18.5 kg/m2)

At the median follow up of 6.2 years, there were 1587 cases of recurrence.

Findings

Investigators reported in a multivariable analysis that the risk of breast cancer recurrence was 18% among participants with obesity and nearly double that, 32%, among those with severe obesity.

Among participants classified as overweight at baseline, the team observed a trend toward an increased risk of recurrence, but the association did not reach statistical significance. The risk of breast cancer recurrence among participants who were underweight or had a healthy BMI was similar.

Authors' comment

"In this study, obesity was associated with an increased risk of breast cancer recurrence among postmenopausal patients with HR+ early-stage breast cancer treated with aromatase inhibitors. Physicians should be aware of the significance of obesity on breast cancer outcomes to secure optimal treatment benefit in all patients."

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