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Radiotherapy did not increase thyroid cancer risk among women with breast cancer: A nationwide population‐based cohort study
Author(s) -
Sun LiMin,
Lin ChengLi,
Liang JiAn,
Huang WenSheng,
Kao ChiaHung
Publication year - 2015
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.29667
Subject(s) - medicine , breast cancer , cancer , radiation therapy , thyroid cancer , cohort study , cohort , oncology , thyroid , population , gynecology , obstetrics , environmental health
The aim of this study was to evaluate whether an increased risk of thyroid cancer exists among women with breast cancer in Taiwan, particularly among those receiving RT. We used data from the National Health Insurance system of Taiwan for the investigation. The breast cancer cohort contained 55,318 women (including 28,187 who received RT and 27,131 who received no RT), each of whom was randomly frequency matched according to age and index year with three women without breast cancer from the general population. Cox's proportion hazards regression analysis was conducted to estimate the effects of breast cancer with or without RT treatment on subsequent thyroid cancer risk. We found that women with breast cancer exhibited a significantly higher risk of subsequent thyroid cancer (adjusted hazard ratio [aHR] = 1.98, 95% confidence interval [CI] = 1.60–2.44). The two groups (with or without RT) in the breast cancer cohort exhibited significantly increased risks. However, in the breast cancer cohort, the risk of thyroid cancer among women who received RT was not significantly higher than that of women who received no RT (aHR = 1.28, 95% CI = 0.90–1.83). Stratified analysis according to age revealed that only younger women with breast cancer (20–54 y) had a significantly higher risk of developing thyroid cancer. This study determined that Taiwanese women with breast cancer had a higher risk of developing thyroid cancer; however, RT seems to not play a crucial role in this possible relationship.