The following is a summary of “Impact of BMI in Patients With Early Hormone Receptor–Positive Breast Cancer Receiving Endocrine Therapy With or Without Palbociclib in the PALLAS Trial,” published in the November 2023 issue of Oncology by Pfeiler, et al.

For a study, researchers sought to explore the influence of Body Mass Index (BMI) on the side-effect profile, treatment adherence, and efficacy of palbociclib, a CDK4/6 inhibitor integral to breast cancer therapy. Unlike cytotoxic chemotherapy, CDK4/6 inhibitors are administered at a fixed dose, irrespective of BMI or weight. The preplanned analysis delved into the global, randomized PALLAS trial to unravel the relationship between BMI and the aforementioned parameters.

The PALLAS trial participants were stratified based on World Health Organization (WHO) BMI categories at baseline. The study employed both univariable and multivariable logistic regression to assess neutropenia rates. Time to early discontinuation of palbociclib was scrutinized using Fine and Gray competing risk models. Unstratified Cox models were applied to scrutinize the correlation between BMI category and the duration until invasive disease-free survival (iDFS). The analysis incorporated the derivation of 95% CIs for robust statistical interpretation.

In the comprehensive analysis encompassing 5,698 patients, baseline BMI distribution revealed 68 (1.2%) underweight, 2,082 (36.5%) normal weight, 1,818 (31.9%) overweight, and 1,730 (30.4%) obese individuals. Within the palbociclib arm, a notable correlation emerged between higher BMI and a significant reduction in neutropenia rates (unadjusted odds ratio for 1-unit change, 0.93; 95% CI, 0.91 to 0.94; adjusted for age, race-ethnicity, region, chemotherapy use, and Eastern Cooperative Oncology Group at baseline, 0.93; 95% CI, 0.92 to 0.95). This association translated into a considerable decrease in the treatment discontinuation rate with an elevated BMI (adjusted hazard ratio [HR] for 10-unit change, 0.75; 95% CI, 0.67 to 0.83). However, despite these findings, the addition of palbociclib to endocrine therapy (ET) did not yield a significant improvement in invasive disease-free survival (iDFS) within any BMI category during the early 31-month follow-up period. The hazard ratios for iDFS were 0.84 (95% CI, 0.63 to 1.12) for normal weight, 1.10 (95% CI, 0.82 to 1.49) for overweight, and 0.95 (95% CI, 0.69 to 1.30) for obese individuals.

The preplanned examination of the PALLAS trial established a substantial influence of Body Mass Index (BMI) on various facets, including side effects, dose reductions, early discontinuation of treatment, and relative dose intensity. Notably, higher BMI was associated with a significant reduction in neutropenia rates and a lower likelihood of treatment discontinuation. The assessment of invasive disease-free survival (iDFS) did not reveal a significant improvement with the addition of palbociclib to endocrine therapy (ET) across different BMI categories during the initial 31 months of follow-up.

Source: ascopubs.org/doi/full/10.1200/JCO.23.00126