# Obesity and Tolerance to Neoadjuvant Chemotherapy in Breast Cancer: A Retrospective Cohort Study

## TL;DR

This study finds that obesity is common in high-risk early breast cancer patients and is linked to higher chemotherapy toxicity and treatment discontinuation.

## Contribution

The study identifies obesity as an independent risk factor for increased toxicity and treatment discontinuation during neoadjuvant chemotherapy in breast cancer patients.

## Key findings

- Obese patients had higher odds of global toxicity and treatment discontinuation during chemotherapy.
- Peripheral neuropathy was more frequent and severe in obese patients compared to non-obese patients.
- Obesity was associated with a 2.3 times higher risk of treatment discontinuation after adjusting for other factors.

## Abstract

Obesity is becoming increasingly common and may influence chemotherapy tolerance and survival outcomes. However, its effect on tolerance to neoadjuvant chemotherapy in real-world practice is not fully understood. This study assessed the prevalence of overweight and obesity among patients with high-risk early breast cancer receiving chemotherapy before surgery and whether obesity is associated with a higher risk of treatment-related side effects. We also explored whether obesity is associated with treatment response and survival outcomes. By better understanding the relationship between obesity and treatment tolerance, these findings may help clinicians identify patients at greater risk of complications and tailor supportive care, as well as treatment planning.

Background: Obesity is increasingly prevalent and has been associated with poorer outcomes and higher toxicity in breast cancer treatment. Its impact on tolerance to neoadjuvant chemotherapy (NAC) remains understudied. Objectives: This study aimed to determine the prevalence of overweight and obesity among patients with high-risk early-stage breast cancer (BC) treated with NAC. It evaluated the association between obesity and clinically significant chemotherapy-related toxicities. Pathological complete response (pCR), progression-free survival (PFS), and overall survival (OS) were explored. Methods: This is a retrospective cohort study on stage I–III BC assigned for NAC between January 2020 and December 2022. Patients were categorized by body mass index. Patients with obesity were compared with an age-matched non-obese cohort (1:1). The toxicities evaluated were hospitalization, dose reduction, treatment delay, or treatment discontinuation. Multivariable logistic regression models were performed, adjusting for age, comorbidity burden, and carboplatin use. Results: Of 487 eligible patients, 31.2% were overweight and 27.7% were obese. Peripheral neuropathy was more frequent and severe in obese patients (63.7% vs. 36.3%, p < 0.001). In multivariable analysis, obesity was independently associated with increased odds of global toxicity (OR = 1.83; 95% CI: 1.08–3.15; p = 0.027) and treatment discontinuation (OR = 2.30; 95% CI: 1.18–4.59; p = 0.016). Conclusions: Obesity is highly prevalent among high-risk early BC patients. It is independently associated with increased treatment-related toxicity, particularly discontinuation. These findings highlight the need for closer toxicity monitoring in patients with obesity. Reliance on BMI alone may be insufficient, underscoring the potential value of incorporating body composition assessment into clinical practice.