Predicting Outcomes of Breast-Conserving Surgery in Patients with Breast Cancer Using the Modified 5-Item Frailty Index: A Retrospective Cohort Study.

Background: Breast cancer is the most common malignancy among women worldwide, with breast-conserving surgery (BCS) being a key treatment. The modified 5-item frailty index (mFI-5), a well-validated tool for assessing frailty, has shown predictive utility in other surgical contexts but remains under-explored in BCS.

Methods: Using the American College of Surgeons National Surgical Quality Improvement Program database (2008-2021), we identified adult female patients with breast cancer who underwent BCS. Frailty was assessed using the mFI-5 and scored from 0 to 5, with higher scores indicating greater frailty. Multivariable logistic regression was employed to evaluate associations between mFI-5 scores and postoperative outcomes.

Results: A total of 96,586 patients were included. Higher mFI-5 scores were significantly associated with older age, higher body mass index (BMI), and increased ASA scores. Multivariate analysis showed greater frailty was linked to higher risks of any (mFI = 1: OR 1.06; mFI = 2: OR 1.26; mFI ≥ 3: OR 2.45), surgical (mFI = 1: OR 1.18; mFI = 2: OR 1.65; mFI ≥ 3: OR 3.17), and medical complications (mFI = 1: OR 1.72; mFI = 2: OR 2.56; mFI ≥ 3: OR 6.05). Similarly, frail patients had significantly higher odds of mortality (mFI = 1: OR 2.27; mFI = 2: OR 4.3; mFI ≥ 3: OR 11.05) and unplanned readmission (mFI = 1: OR 1.38; mFI = 2: OR 2.25; mFI ≥ 3: OR 6.05). Reoperation risk decreased with higher mFI-5 scores (mFI = 1: OR 0.92; mFI = 2: OR 0.73; mFI ≥ 3: OR 0.92).

Conclusions: The mFI-5 is strongly associated with postoperative outcomes after BCS and serves as a valuable tool for risk stratification. Our findings reinforce its role as a critical preoperative index to identify high-risk patients and guide surgical planning.