Feasibility Study Shows Multicenter, Observational Case-Control Study Is Practicable to Determine Risk of Secondary Breast Cancer in Females With Differentiated Thyroid Carcinoma Given Radioiodine Therapy in Their Childhood or Adolescence; Findings Also Suggest Possible Fertility Impairment in Such Patients.

Objective: This single-center, observational case-control feasibility study sought to test key elements of a protocol for an eventual long-term international observational case-control study of a larger patient cohort, to evaluate the risk of breast cancer as a second primary malignancy in females with differentiated thyroid cancer (DTC) given radioiodine therapy (RAI) during childhood or adolescence. Patients: Females developing DTC after the Chernobyl accident in Belarus and ≤19 years old at the time of thyroid surgery were enrolled: patients given RAI (n = 111) and controls of similar age not given RAI (n = 90). Results: One case of breast cancer was newly diagnosed among the RAI patients, but none in controls. Patients given RAI significantly less frequently needed 2nd surgeries than did controls (23%, 26/111 vs. 39%, 35/90, P < 0.05); the main indication for such procedures usually is suspicion of local recurrence. RAI patients appeared to have had more frequent reproductive difficulties than did controls: 78% (87/111) of the former vs. 93% (84/90) of the latter had a history of pregnancy (P < 0.01), and the mean number of pregnancies was 1.5 ± 1.2 in RAI patients vs. 1.9±1.1 in controls (P < 0.05). Most notably, infertility was observed in 23% (26/111) of RAI patients vs. 4% (4/90) of controls (P < 0.01). In conclusion, a international observational case-control study on breast cancer after DTC in patients given RAI vs. not given RAI appears to be feasible. Additional research and everyday clinical attention should be devoted to reproductive function after RAI in young females.

Recombinant human thyrotropin to help confirm lack of evidence of radiation-induced differentiated thyroid cancer in young women seeking pregnancy.

BACKGROUND: Women with a history of differentiated thyroid carcinoma who are contemplating pregnancy may wish reassurance regarding apparent remission. However, the thyroid hormone withdrawal needed to obtain serum thyroglobulin testing (Tg) results in weeks-long biochemical and clinical hypothyroidism, which could increase miscarriage and fetal death rates if pregnancy occurred during withdrawal of thyroxine or soon thereafter. Recombinant human thyrotropin (rhTSH) elevates thyrotropin exogenously, allowing uninterrupted thyroid hormone therapy and avoids hypothyroidism. MATERIAL AND METHODS: Thirty female radiation-induced papillary thyroid carcinoma survivors who had undergone total- or near-total thyroidectomy and who were now seeking pregnancy (mean age 23.9 ± 1.8 years), and who were considered cancer-free by local standards, underwent rhTSH-aided Tg testing to help confirm remission. At the time of rhTSH testing, mean follow-up after primary surgical treatment was 11.1 ± 3.9 years, and all patients had negative neck ultrasonography, undetectable unstimulated serum Tg (< 0.2 ng/mL) and no interfering anti-Tg antibodies. However, based on T3, N1 or M1 status, 28/30 (93.3%) patients had high recurrence risk. RESULTS: rhTSH produced no serum Tg increase in 27/30 women (90.0%). Serum Tg increases to 0.4-0.9 ng/ml were observed in 3 women, but careful neck ultrasonography found no lymphadenopathy. Reassured about their remission, 14/30 women (46%) have become pregnant and delivered healthy children in the 3 years since rhTSH-aided testing. CONCLUSIONS: rhTSH-aided Tg testing is useful in confirming absence of tumor in female patients with a history of radiation-induced thyroid cancer who are seeking pregnancy, but who also have a high risk of thyroid cancer recurrence.