# Anti-Obesity Medications and the Risk of Obesity-Related Cancers in Older Women: A Propensity Score Matching Analysis of 2007–2015 SEER-Medicare Data

## TL;DR

Using anti-obesity medications like phentermine may lower cancer risk in older women, especially for breast and endometrial cancers.

## Contribution

This study is the first to show that AOM use, particularly phentermine, is linked to reduced risk of obesity-related cancers in older women.

## Key findings

- AOM use was associated with a 22% lower risk of obesity-related cancers in older women.
- Phentermine specifically reduced the risk of breast and endometrial cancers.
- No significant association was found between liraglutide and cancer risk.

## Abstract

Obesity rates in the U.S. have reached alarming levels (42% of adults). Severe obesity (BMI ≥ 40 kg/m2) affects 9.2% of the population, more prevalent in women. This increases the risk of obesity-related cancers (ORCs), including breast (BrCa), colorectal (CRC), endometrial (ECa), and ovarian (OCa) cancers in women. Anti-obesity medications (AOMs) are becoming more commonly used to help with weight loss. This study explored whether using AOM is associated with a reduce risk of ORCs in older women. We found that AOM use, including phentermine, was associated with a reduced risk of ORCs, advanced-stage ORCs, BrCa, CRC, and advanced-stage CRC in older women. Notably, phentermine use was specifically associated with a reduced risk of BrCa and ECa. These findings could support clinical trials to evaluate phentermine as a potential preventive strategy for BrCa and ECa in high-risk older women, including those with obesity, genetic factors, and hormone replacement therapy use.

Background/Objectives: The increasing prevalence of obesity has led to a growing interest in anti-obesity medications (AOMs). While these medications have shown promise in aiding weight loss, their potential impact on reducing obesity-related cancers (ORCs) incidence remains poorly understood, particularly among women over 65 years of age. This study examined the association between the use of AOMs and the risk of ORCs in this population. Methods: A retrospective cohort study was conducted using 2007–2015 SEER-Medicare data, including 10,830 women aged ≥65 years in a 1:2 propensity-score matching design. The primary exposure was AOM use, with additional analyses focused specifically on phentermine and liraglutide exposure. Conditional multivariable Cox proportional hazards models were conducted. Results: We found an inverse association between the use of AOMs and the risk of ORCs (aHR: 0.78; 95% CI: 0.73–0.84; p < 0.001). Similar findings were observed in cancer-specific sites analysis, advanced-stage ORCs (aHR: 0.76; 95% CI: 0.65–0.89; p < 0.001), breast (aHR: 0.84; 95% CI: 0.77–0.91; p < 0.001), colorectal (aHR: 0.82; 95% CI: 0.71–0.96; p = 0.010), and advanced-stage colorectal cancers (aHR: 0.71; 95% CI: 0.54–0.91; p < 0.001). In secondary analyses, phentermine was inversely associated with the risk of ORCs, breast, and endometrial cancers, but no associations with liraglutide were observed. Conclusions: The use of AOMs, including phentermine, was inversely associated with ORCs and some cancer-specific sites in a cohort of older women. Further prospective studies are warranted to validate these findings among women of different age groups and to identify the underlying biological mechanisms.