Low BMI Linked to Progression in HR+/HER2– Breast Cancer Treated With CDK4/6i

In In The News by Barbara Jacoby

By: Vicki Moore, PhD

From: cancertherapyadvisor.com

A BMI of below 18.5 was associated with progression compared with a reference BMI range of 18.5 to 25

Low body mass index (BMI) is associated with tumor progression in patients with hormone receptor-positive (HR+)/HER2-negative (HER–) metastatic breast cancer being treated with CDK4/6 inhibitor (CDK4/6i) therapy, according to research presented in a poster at the NCCN Annual Conference 2026.

In addition, central nervous system (CNS) involvement in these patients is associated with higher mortality compared to bone-only metastasis, study researchers reported.

This retrospective analysis of Cleveland Clinic records from 2015 to 2022 included 343 patients who  were being treated in the first-line setting or after prior selective estrogen receptor modulator, aromatase inhibitor, or selective estrogen receptor degrader therapy. Excluded patients had received first-line chemotherapy or had multiple primary malignancies.

The mean patient age at the time of diagnosis of metastatic disease was 62.0 years. Overall, 79.3% of the patients were White and 14.3% were Black. Of the patients, 71.1% experienced disease progression on CDK4/6i. Treatment discontinuation due to toxicity was reported in 10.2% of the patients.

The median progression-free survival (PFS) was 25.0 months, and the estimated 6-month, 12-month, and 24-month PFS rates were 88.0%, 73.7%, and 50.3%, respectively. The mean time to disease progression was 22.6 ± 19.2 months.

In a multivariate analysis of predictors of progression in this population, a BMI of below 18.5 was associated with progression (hazard ratio [HR]; 3.19; 95% CI, 1.33-7.61; P =.0091) compared to a reference BMI range of 18.5 to 25. The BMI categories of 25 to 30 (HR, 0.79; 95% CI, 0.56-1.11; P =.1761) and 30 or higher (HR, 0.8; 95% CI, 0.58-1.10; P =.1686) were not significantly associated with progression.

In a multivariate analysis of risk factors for death, CNS involvement was associated with higher mortality compared to bone-only disease (HR, 1.89; 95% CI, 1.19-2.98; P =.0065). Other metastasis sites that were considered visceral (HR, 0.91; 95% CI, 0.51-1.64; P =.7558) or nonvisceral (HR, 1.14; 95% CI, 0.84-1.56; P =.4057) were not significantly associated with mortality.