Metachronous Second Primary Malignancies in Known Breast Cancer Patients on 18F-Fluoro-2-Deoxyglucose Positron Emission Tomography-Computerized Tomography in a Tertiary Care Center.

Introduction: Breast cancer is the most common malignancy among women all over the world, which accounts to 25% of all cancers. In known cases of breast cancer, the risk of developing another denovo malignancy is more when compared to low risk groups, which might be due to common environmental risk factors, treatment induced risk factors, Genetic susceptibility for mutations, presence of cancer syndromes or better detection due to close surveillance.

Objective: To study the profile of Metachronous 2 primary malignancies suspected on 18F-FDG PET CT in known Breast cancer patients. In this Retrospective study from January 2014 to April 2018, all the consecutive patients with known Breast cancer, who were referred to Nuclear Medicine department for 18F- FDG PET CT for follow up evaluation were included. Suspected 2 primary malignancies were correlated with Histopathological examination (HPE).

Results: During the study period, a total of 233 Breast cancer patients (all are females), with a mean age of 54.2+13.4 years were studied. On 18F-FDG PET CT scan, suspicion for 2 primary malignancy was observed in 37 patients. HPE was done in 28/37 patients at the site of suspected lesions. 15/28 were positive for second malignancy, and remaining 13/28 were either a benign pathology or a part of metastatic disease from the primary breast cancer. The sites of 2 primary malignancies included Contralateral breast in 8/15 (53.3%), Ovary in 2/15 (13.3%), Endometrium in 2/15 (13.3%), Lung in 1/15 (6.6%), Stomach in 1/15 (6.6%) and Urinary bladder in 1/15 (6.6%) patients respectively. The incidence of metachronous 2 primaries in breast cancer is 67.3 per 1000 breast cancer patients.

Conclusion: Metachronous second primary cancers in breast cancer patients are not very rare. A high imaging suspicion on 18F-FDG PET CT helps in early detection of 2 primary cancer, thereby facilitating early and appropriate management.