BMI prognostic of adjuvant chemo potency in breast cancer

Body mass index (BMI) has some bearing on the efficacy of different adjuvant chemotherapy schedules in patients with early breast cancer, suggest the results of the GIM2 study, which were presented at the recent SABCS 2023. Additionally, dose-dense (DD) chemotherapy appears to be the better treatment strategy regardless of a patient’s BMI.

“The long-term results of the Italian randomized phase III GIM2 study showed that, in women with node-positive breast cancer, DD chemotherapy significantly improved both disease-free survival (DFS) and overall survival (OS) compared with standard-interval (SI) chemotherapy,” according to presenting author Matteo Lambertini from the University of Genova - San Martino Hospital, Genova, Liguria, Italy.

“Obesity has been identified as an independent poor prognostic factor in patients with breast cancer, with a potential negative impact on the efficacy and toxicity of systemic therapies,” the author added.

Lambertini and colleagues conducted this phase III trial to compare different chemotherapy schedules and regimen in 2,091 node-positive early breast cancer patients. They categorized BMI as underweight (<18.5 kg/m²), lean (18.5 to <25 kg/m²), overweight (25 to <30 kg/m²), or obese (≥30 kg/m²).

The association between BMI and DFS and OS served as the primary endpoint. The authors compared survival estimates using the Kaplan-Meier method and log-rank test. They also employed univariate and multivariable Cox proportional hazard models, adjusting for relevant prognostic factors.

Of the patients, 1,925 (median age 52 years) made it to the final analysis, of whom 632 (31.6 percent) were overweight and 386 (19.3 percent) obese. Overweight and obesity showed a significant interaction with postmenopausal status and greater representation of T2-T4 tumours with N>2 in both patients in the DD and SI groups. [SABCS 2023, abstract PO1-03-02]

After a median follow-up of 15.0 years, patients who were overweight or obese at diagnosis were more likely to experience a DFS event (overweight: hazard ratio [HR], 1.11, 95 percent confidence interval [CI], 0.94‒1.31; obese: HR, 1.37, 95 percent CI, 1.14‒1.65; p=0.003) and OS event (overweight: HR, 1.11, 95 percent CI, 0.89‒1.38; obese: HR, 1.59, 95 percent CI, 1.26‒2.01; p=0.0003) than those with normal BMI.

However, BMI showed no significant association with treatment schedule as regards DFS (p_interaction=0.56) or OS (p_interaction=0.19).

Multivariate analysis in the DD chemotherapy group revealed adjusted HRs of 1.01 (95 percent CI, 0.75‒1.35) for DFS and 1.04 (95 percent CI, 0.72‒1.52) for OS in obese vs normal BMI patients. Likewise, the adjusted HRs were 0.88 (95 percent CI, 0.68‒1.15) for DFS and 0.77 (95 percent CI, 0.54‒1.10) for OS in overweight vs normal BMI patients.

In the SI chemotherapy group, the adjusted HRs were 1.24 (95 percent CI, 0.94‒1.63) for DFS and 1.35 (95 percent CI, 0.96‒1.90) for OS in the obese vs normal BMI arm. Similarly, the adjusted HRs were 1.04 (95 percent CI, 0.82‒1.33) for DFS and 1.01 (95 percent CI, 0.74‒1.40) for OS in the overweight vs normal BMI arm.

“Similar results were observed when considering hormone receptor-positive and negative breast cancer separately,” Lambertini and colleagues said.