Complexity of Response Evaluation During Primary Systemic Therapy of Breast Cancer: Scoring Systems and Beyond-Preliminary Results

BACKGROUND: Precise and standardized response evaluation enables clinicians to tailor primary systemic therapy (PST). PATIENTS AND METHODS: Breast cancer patients underwent (18)F-fluoro-deoxy-glucose positron emission tomography and computerized tomography (FDG-PET/CT) before and after PST. Response was assessed by maximal Standardized Uptake Value (SUVmax); morphological changes and Ki-67 labeling index (LI). In parallel response assessment was performed by European Organization for Research and Treatment of Cancer (EORTC); PET Response Criteria in Solid Tumors (PERCIST); World Health Organization (WHO); Response Evaluation Criteria in Solid Tumors (RECIST); Chevallier and Sataloff classifications, and by a novel Ki-67 score. Accuracy of different scoring systems was evaluated. RESULTS: In the 42 enrolled patients, SUVmax, size, and Ki-67 LI decreased significantly on PST. Significant differences between patients with versus those without pathological complete response were observed for pre-treatment Ki-67 LI and SUVmax and for post-treatment Ki-67 LI, SUVmax and size. Change in Ki-67 LI was the best predictor of pathological complete response. Correlation patterns of the directly measured metabolic, morphological, and proliferation responses differed from those determined by scoring methods. CONCLUSION: During PST, FDG-PET/CT enables for robust assessment of treatment efficacy, but more reliable scoring systems are still needed for more precise response evaluation