PET-derived metabolic–immunonutritional SUVmax–lactate dehydrogenase–albumin–lymphocyte index for survival prediction in human epidermal growth factor receptor 2-positive metastatic breast cancer receiving pertuzumab-based therapy

OBJECTIVE: To evaluate the prognostic value of the PET-derived SUVmax-lactate dehydrogenase-albumin-lymphocyte (SUV-LAL) index in human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer treated with pertuzumab. METHODS: This retrospective single-center study included patients with HER2-positive metastatic breast cancer treated with pertuzumab-containing regimens between January 2018 and October 2025. Baseline clinical, pathological, laboratory, and 18F-fluorodeoxyglucose PET/computed tomography data were retrospectively collected. The SUV-LAL index was calculated as (primary tumor maximum standardized uptake value × lactate dehydrogenase)/(albumin × absolute lymphocyte count). Overall survival (OS) and progression-free survival (PFS) were evaluated using Cox proportional hazards regression analyses. Kaplan-Meier survival analysis, receiver operating characteristic (ROC) analysis, and time-dependent ROC analyses were performed to assess prognostic performance. RESULTS: A total of 80 patients were included, of whom 36 (45.0%) died during follow-up. The SUV-LAL index remained an independent prognostic factor for OS in multivariate analysis [hazard ratio = 1.755, 95% confidence interval (CI) = 1.053-2.927; P = 0.031], together with the number of pertuzumab cycles (hazard ratio = 0.921, 95% CI = 0.872-0.972; P = 0.003). Patients with a high SUV-LAL index had significantly shorter OS and PFS than those with a low SUV-LAL index (log-rank P < 0.001 and P = 0.002, respectively). ROC analysis yielded an area under the curve (AUC) of 0.760. Compared with its individual components, the SUV-LAL index showed the strongest association with OS in univariate Cox regression analysis and achieved the highest 1-year time-dependent AUC (0.735), while maintaining acceptable prognostic performance at 3 years (AUC = 0.705). CONCLUSION: The PET-derived SUV-LAL index independently predicts OS in HER2-positive metastatic breast cancer treated with pertuzumab.