Drainage Patterns After Mastectomy May Signal Lasting Seroma Risk

Adults undergoing modified radical mastectomy with axillary lymph node dissection sometimes develop a persistent seroma, a collection of fluid that can prolong drainage and slow recovery.

The single-center study included 306 adults with unilateral invasive breast cancer who underwent modified radical mastectomy with level I–II axillary lymph node dissection between 2021 and 2024. The researchers used latent class mixed-effects models to identify trajectories of daily combined drainage volume during the first seven postoperative days.

Three distinct trajectories emerged. A rapid-decline group included 123 patients, a moderate-decline group included 127 patients, and a persistently high-output group included 56 patients.

Persistent seroma on postoperative day 30 occurred in 7.3 percent of the rapid-decline group, 19.7 percent of the moderate-decline group, and 57.1 percent of the persistently high-output group, a difference the authors reported as statistically significant with P < 0.001.

To account for other factors, the researchers used Firth penalized-likelihood logistic regression, adjusting for age, body mass index, diabetes mellitus, neoadjuvant systemic therapy, resected specimen weight, operative time, and the number of dissected lymph nodes. Relative to the rapid-decline trajectory, the adjusted odds ratio for persistent seroma was 2.58 (95 percent confidence interval, 1.10–6.07) for the moderate-decline trajectory and 11.44 (95 percent confidence interval, 3.92–33.37) for the persistently high-output trajectory.

The association for the persistently high-output trajectory remained strong across sensitivity analyses that addressed uncertainty in class assignment, the outcome definition, retention of the original drain, pathologic T category, and the operating surgeon. The association for the moderate-decline trajectory was less stable across these analyses.

The study also compared trajectory classification with simpler drainage measures in exploratory complete-case models. The trajectory model and a model based on postoperative day 7 drainage showed similar discrimination. Adding trajectory class provided little incremental information beyond day 7 drainage, but it improved model fit and discrimination beyond 7-day cumulative drainage and beyond the relative decline from postoperative day 1 to day 7.

The authors concluded that persistently high output was consistently associated with persistent seroma on postoperative day 30, but they cautioned that trajectory classification should remain a research-oriented postoperative risk-stratification variable. They noted that the incremental clinical value of trajectory classification over the simpler day 7 drainage measurement remains uncertain and requires prospective validation.

According to the study’s conclusions, clinical application would require multicenter external validation, assessment of class-assignment reproducibility, calibration, clinically meaningful thresholds, and evaluation of clinical utility. As a single-center retrospective analysis, the findings describe associations observed in one institution’s patient population and do not establish that trajectory classification improves patient outcomes.

Subject of Research: Drainage volume decline trajectories after modified radical mastectomy and their association with persistent seroma.

Article Title: Association of drainage volume decline trajectories during the first 7 postoperative days with persistent seroma on postoperative day 30 after modified radical mastectomy for breast cancer

Article References: Bian, Q., Wu, X., & Cui, M. (2026). Association of Drainage Volume Decline Trajectories During the First 7 Postoperative Days With Persistent Seroma on Postoperative Day 30 After Modified Radical Mastectomy for Breast Cancer. Frontiers in Oncology, 16, 1981532. https://doi.org/10.3389/fonc.2026.1981532

Image Credits: AI Generated

DOI: 10.3389/fonc.2026.1981532

Keywords: breast cancer, modified radical mastectomy, axillary lymph node dissection, persistent seroma, drainage trajectory, postoperative drainage, risk stratification, retrospective study, surgical outcomes, seroma, Association, drainage