Second primary tumors in patients with thyroid cancer: data of the Italian Thyroid Cancer Observatory

  • BACKGROUND: Epidemiological studies have shown an increase in incidence of second cancer after, as well as before, thyroid carcinoma. The relationship has been attributed to environmental risk factor, genetic susceptibility, a treatment effect, surveillance bias or prolonged survival.

    METHODS: We analyzed data prospectively collected in The Italian Thyroid Cancer Observatory database over a 6-year period (from January 2013 to January 2019). Patients with thyroid cancer, diagnosed with a secondary primary tumor (other than thyroid cancer) were evaluated.

    RESULTS: A total of 6317 patients were considered: 501 patients (7.9%) had at least two primary malignancies (459 patients had double primary malignancies, 42 patients, 0.7% had more than two primary malignancies; 341 [68%] females). The median age of diagnosis was 50 years for the second primary tumor and 57 years for thyroid cancer. Considering the second primary malignancy, 462 (85%) were solid and 84 (15%) were hematological. Among solid neoplasms, breast cancer was the most represented (31.6%), followed by melanoma (14.2%), colorectal (8.4%), kidney (5.6%), prostate (5.4%), other skin cancer (5.4%), lung cancer (3.4%), neuroendocrine tumor (2.8%), and others (23.2%). Among hematologic malignancies, lymphomas were 57%, leukemias 32%, multiple myelomas 2%, and others 9%.

    DISCUSSION & CONCLUSION: Breast cancer is the most common tumor diagnosed in patients with thyroid cancer. The age of diagnosis of thyroid cancer seems not to be influenced by the presence of another malignancy. In contrast to other studies, the time between the two tumors is longer than one year, thus patients develop metachronous second primary tumor. 


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