Role of 18F-FDG PET/CT in triple-negative breast cancer – A retrospective observational study from a tertiary care center in India.

Introduction: Breast cancer is the most common cancer in females. Based on the expression of receptors breast cancers can be classified as luminal A, luminal B, HER2neu amplified, and basal (triple-negative) type. Of all these types, the triple-negative type has a poor prognosis. So, early diagnosis and treatment are necessary to reduce the progression and mortality of the disease. ¹⁸F-FDG PET/CT plays a major role in the diagnosis and management of breast cancer. The aim of our study is to analyze the metastatic pattern in ¹⁸F-FDG PET/CT of triple-negative breast cancer patients.

Methods: We systematically analyzed ¹⁸F-FDG PET/CT scans of patients with breast cancer who underwent ¹⁸F-FDG PETCT in our department from January 2017 to September 2021. Patients who didn’t have histopathology reports and who were either immunopositive for estrogen, progesterone, and HER2neu receptor were excluded. We found 138 patients satisfying inclusion criteria. Based on age, the patients were divided into two groups – group A (<45 years) and group B (≥45 years). The scans were reviewed by two experienced nuclear medicine physicians to look for sites of disease. We also compared the chances of different metastases in both groups.

Results: A total of 138 patients satisfying inclusion and exclusion criteria were included. Of the 138 patients, 54(39.1%) patients had right-sided, 74(53.6%) patients had left-sided disease and 10(7.2%) patients had bilateral breast disease. 47(34.1%) patients underwent modified radical mastectomy and 91(65.9%) patients had no surgery at the time of ¹⁸F-FDG PETCT. Lymph nodal metastases were present in 115(83.3%) patients and 58(42%) patients had distant metastases. Out of 58 patients with distant metastases, 22(15.9%) had liver metastases, 31(22.5%) had skeletal metastases, 33(23.9%) had lung metastases, 5(3.6%) patients had adrenal metastases and 2(1.4%) patients had brain metastases. Group A had 64(46.4%) patients and 74(53.6%) were in group B. In group A, distant metastases were present in 31 patients with 53(82.8%) lymph nodes, 20(31.3%) lung, 20(31.3%) skeletal, 12(18.8%) liver, 2 (3%) adrenal and 1(1.5%) brain metastases patients. In group B distant metastases were present in 27(36.5%) patients with 62(83.8%) lymph node,13(17.6%) lung, 10(13.5%) liver, 11(14.9%) skeletal, 3(4%) adrenal and 1(1.3%) brain metastases patients. We found that patients in group A had significantly more chances of getting skeletal(P=0.021) and lung(P=0.048) metastases than group B patients. The chances of liver and lymph node metastases were similar in both groups.

Conclusions: ¹⁸F-FDG PET/CT is a useful tool in assessing triple-negative breast cancer patients and helps in the early detection of distant metastases which plays an important role in reducing progression and mortality.