Background: Breast carcinoma and differentiated thyroid carcinoma(the most common endocrine malignancy) occur predominantly in women. An association between the two tumors has been suggested by some investigators, but the potential impact of treatment of one of these diseases on the development of the other remains unclear. The authors examined the relation between the occurrence of these two tumors.
Methods: There were 41,686 patients with breast carcinoma and 3662 with thyroid carcinoma who registered at The University of Texas M. D. Anderson Cancer Center between March 1944 and April 1997. Women who received both diagnoses since 1976 were identified and incidence rates and relative risks of secondary tumor development were calculated. Surveillance, Epidemiology and End Results (SEER) program data on the age-adjusted incidences of these diseases during the same time period were used for the expected incidences in the same population.
Results: Among 18,931 women with a diagnosis of breast carcinoma since 1976, 11 developed differentiated thyroid carcinoma > or = 2 years after the diagnosis of breast carcinoma. These breast carcinoma patients contributed 129,336 person-years of follow-up; the observed incidence of thyroid carcinoma in this group was not different from that in a similar age group of women in the SEER database. Among 1013 women with a diagnosis of thyroid carcinoma since 1976, 24 developed breast carcinoma > or = 2 years after the diagnosis of thyroid carcinoma. These thyroid carcinoma patients contributed 8380 person-years of follow-up; the observed incidence of breast carcinoma in women ages 40-49 years was significantly higher than the expected incidence for women in the same age group in the SEER database.
Conclusions: Breast carcinoma developing after thyroid carcinoma was diagnosed more frequently than expected in young adult women seen at the study institution since 1976. This potential association and plausible mechanisms of breast carcinoma development after thyroid carcinoma should be evaluated in larger cohorts of patients.