# Risk of severe infections in patients with triple-negative breast cancer treated with atezolizumab plus nab-paclitaxel: a real-world, postmarketing database study in Japan

## TL;DR

This study examines whether adding atezolizumab to nab-paclitaxel increases the risk of severe infections in Japanese patients with triple-negative breast cancer.

## Contribution

The study provides real-world evidence on the risk of severe infections in TNBC patients treated with atezolizumab plus nab-paclitaxel in Japan.

## Key findings

- The incidence rate ratio of severe infections was 3.29 in the primary analysis but not statistically significant.
- In the sensitivity analysis using a revised definition, the incidence rate ratio was 1.05, indicating no significant increase.
- The results suggest no significant increase in severe infection risk in real-world clinical practice.

## Abstract

An increased risk of infection has been suggested for patients with triple-negative breast cancer (TNBC) treated with atezolizumab plus nab-paclitaxel based on the IMpassion130 trial.

This Japanese postmarketing study aimed to compare the incidence of severe infections in patients with TNBC treated with atezolizumab plus nab-paclitaxel versus nab-paclitaxel alone. Anonymized patient records regarding medical claims and laboratory tests were extracted from the Japanese Medical Data Vision database. Patients with a drug index date of November 27, 2019,–May 31, 2022, were included in the analysis. Based on the published literature, severe infections were declared when a patient had a confirmed diagnosis of infection, a hospitalization record, infection as the primary reason for hospitalization, and a record of immunological infection tests. In the sensitivity analysis, the definition of severe infections was modified as a combination of confirmed infection diagnosis and intravenous antibacterial drug prescription records.

Overall, 321 and 319 patients were included in the exposure (atezolizumab plus nab-paclitaxel) and control (nab-paclitaxel alone) groups, respectively. After adjusting for standardized mortality/morbidity ratio weighting, the baseline characteristics were balanced between the groups. The incidence rate ratio (exposure/control) of severe infections was estimated at 3.29 (95% confidence interval [CI]: 0.93–13.53) originally and 1.05 (95% CI: 0.56–1.84) in the sensitivity analysis. Additional analyses supported the appropriateness of the revised definition of severe infections.

Overall, our results did not indicate a significant increase in the risk of severe infections with atezolizumab plus nab-paclitaxel in daily clinical practice. Further research is required.

The online version contains supplementary material available at 10.1007/s10147-025-02904-0.