Risk of second primary cancer following differentiated thyroid cancer

Abstract

Concerns remain over the risk of cancer following differentiated thyroid carcinoma and its causes. Iodine-131 ((131)I) and external irradiation are known to have potential carcinogenic effects. Thyroid carcinoma is a polygenic disease which may be associated with other malignancies. We investigated the incidence of second cancer and its aetiology in a cohort of 875 patients (146 men, 729 women) with differentiated thyroid carcinoma originating from Basse-Normandie, France. Cancer incidence was compared with that of the general population of the Département du Calvados matched for age, gender and period. The cumulative proportion of second cancer was estimated using the life-table method. Factors that correlated with the risk of second cancer were studied using the Cox model. After a median follow-up of 8 years, 58 second cancers had been observed. Compared with general population incidence rates, there was an overall increased risk of second cancer in women [standardised incidence ratio (SIR)=1.52; P<0.01], but not in men (SIR=1.27; P>0.20). Increased risk related to cancers of the genitourinary tract (SIR=3.31; P<0.001), and particularly to cancer of the kidney (SIR=7.02; P<0.01). Multivariate analysis showed that age above 40 years (P<0.01) and a history of previous primary cancer (P<0.001) correlated with risk. In contrast, neither cervical irradiation nor cumulative activity of (131)I was related to the risk. These data confirm that women with differentiated thyroid carcinoma are at risk of developing a second cancer of the genitourinary tract and kidney. Only age and medical history of primary cancer before thyroid carcinoma are risk factors for second cancer. Common environmental or genetic factors as well as long-term carcinogenic effects of primary cancer therapy should be considered.

Multiple Primary Tumors in Differentiated Thyroid Carcinoma and Relationship to Thyroid Cancer Outcome

“…In our series, despite the low radioiodine dose, colon carcinoma was developed 9 years after in only one patient with DTC. The other second primary neoplasms were fibrosarcoma, malign fibrous histiocytoma, malign melanoma, renal cell carcinoma, multiple myeloma, breast, colon carcinoma and chronic myelocytic leukemia in agreement with the previous results in the literature [17,18,20]. The most dramatic case in this series (pt no: 11) had a previous history of external radiotherapy due to fibrosarcoma of supraclavicular region at the age of 31.…”

“…Previous studies reported an increased risk of second cancers of the genitourinary tract [18][19][20], endocrine glands, nervous system [19], digestive tract, bone and soft tissue [17], salivary gland [17,20] and adrenal gland [20] in patients treated radioiodine for DTC. In the current study, second primary tumors were developed in 9 patients 2-9 years after thyroid carcinoma.…”

The incidence of second primary tumors in thyroid cancer patients is increased, but not related to treatment of thyroid cancer

“…Their data did not support the hypothesis that a significant proportion of double primary cancers are due to hereditary factors. In the present study, we found a standardized incidence ratio of 1.52 (95% CI: 0.46-3.18) for breast cancer comparable with the data published by Berthe et al (4). Moreover, an increased overall incidence (the SIR increases up to 3.95 (95% CI: 2.06-6.45)) for breast cancer in thyroid cancer patients was observed, when taking also the tumors preceding DTC into account.…”

Implications of mediastinal uptake of 131I with regard to surgery in patients with differentiated thyroid carcinoma

“…14,15 Furthermore, in several reported instances, posttreatment WBS has revealed mediastinal 131 I activity that, on subsequent surgical exploration, was found to be attributable to physiologic enlargement of the thymus. 5,16 -20 Without appropriate guidelines, it is difficult to obtain a consensus regarding diagnostic and therapeutic strategies for patients with mediastinal uptake of 131 I.…”