Investigation of demographic and etiological characteristics of cases with differentiated thyroid cancer and breast cancer together

Cancer is a significant global public health issue and ranks among the leading causes of mortality. Breast cancer is the most common malignancy in women, and its prognosis can vary depending on early diagnosis and multidisciplinary treatment approaches. Differentiated thyroid cancer is the most prevalent endocrine malignancy, generally associated with a favorable prognosis, although some patients carry a risk of metastasis and recurrence. The co-occurrence of breast cancer and thyroid cancer has become an increasingly prominent research topic in recent years. Studies in the literature suggest that individuals diagnosed with breast cancer have an increased risk of developing thyroid cancer, which may be related to hormonal, genetic, and environmental factors. This retrospective study examines the sociodemographic characteristics of patients diagnosed with breast cancer and differentiated thyroid cancer, evaluating the potential risk factors and reasons for their coexistence. The findings of this study indicate that estrogen receptor positivity may be a significant factor in the development of differentiated thyroid cancer. Additionally, obesity and physical inactivity have been identified as risk factors for both malignancies. Furthermore, genetic predisposition and a family history of cancer have been found to increase the likelihood of developing both diseases. It has been proposed that chemotherapy agents used in breast cancer treatment may contribute to the development of a second primary malignancy by inducing mutations in thyroid cells. In our study, the incidence of differentiated thyroid cancer was found to be higher among individuals with a history of chemotherapy. Radioactive iodine (RAI) therapy was also associated with an increased risk of breast cancer, whereas no statistically significant relationship was found between radiotherapy and differentiated thyroid cancer. These findings suggest that breast and thyroid cancer may be linked through shared etiological mechanisms, emphasizing the need for further research involving larger patient populations. This study aims to contribute new insights into the potential relationship between these two malignancies and their common risk factors, ultimately aiding in early diagnosis, monitoring, and preventive healthcare services. Keywords: Differentiated thyroid cancer, Papillary carcinoma, Follicular carcinoma Breast cancer, Risk factor