PET-CT upstaging of unilateral operable breast cancer and its correlation with molecular subtypes

CONTEXT: Prognosis and survival rates for breast cancer vary greatly depending on the cancer stage of the patient. Instead of a step-by-step approach using multiple investigations, we can get all the information about the metastatic load of the disease in PET-CT imaging by one single investigation. There is also a correlation between prognosis, FDG uptake, and molecular subtype of breast cancer (Luminal A, Luminal B, Human epidermal growth factor receptor 2 (HER2) positive and Triple-negative). Pre-treatment baseline PET-CT scan was done in 156 unilateral early and operable breast cancer patients from November 2017 to April 2019 in our prospective observational study. AIMS: To evaluate the utility of PET-CT in staging and upstaging of early and operable breast cancer by detection of unsuspected lymph nodes and distant organ metastases. To determine the prognostic association between SUVmax of the primary breast lesion in the upstaged cases and the molecular subtypes. RESULTS: Thus, PET-CT can serve as one-stop imaging in unilateral operable early breast cancer patients for upstaging and prognostication based on the correlation of SUVmax with molecular subtypes of breast lesions in patients who will surely benefit from whole-body imaging. Out of 156 patients, approximately 27 patients were upstaged after pre-treatment PET CT. Six patients were upstaged to stage IIIC and 21 patients were upstaged to IV. Regional nodes like internal mammary and supraclavicular nodes were detected in 7 patients and 5 patients, respectively, out of 156 patients. Non-regional distant nodes and organ metastases were detected in 11 and 18 patients out of 156 patients. Most common molecular subtype detected in the upstaged cases in our study was Luminal A (13 patients) followed by Triple negative (6), Luminal B (3) and HER2-neu-positive subtypes (1). CONCLUSIONS: FDG PET-CT is a substantial modality to provide information on regional, non regional lymph nodes and distant metastases in early operable breast cancer. It helps in evaluating the whole body metastatic burden in a single sitting, therefore, reducing the need for multiple investigations. SUVmax association of the index lesion with molecular subtype in the FDG PET scanning can serve as a prognostication factor in operable early breast cancer patients.