by Elisabeth
Solmunde, Anne Mette Falstie-Jensen, Ebbe L. Lorenzen, Marianne Ewertz, Kristin
V. Reinertsen, Olaf M. Dekkers, Deirdre P. Cronin-Fenton
The Breast: Published: February 18, 2023
Objective
Breast cancer and
breast cancer-directed radiation therapy (RT) may increase the risk of late
effects, such as hypothyroidism. We conducted a systematic review and
meta-analysis to investigate the association between breast cancer, RT, and
risk of hypothyroidism in breast cancer survivors.
Methods
Through February
2022, we searched PubMed, EMBASE, and references of relevant articles, to
identify papers on breast cancer and breast cancer-directed RT and subsequent
risk of hypothyroidism. Articles were screened by title and abstract and
reviewed for eligibility. We used a pre-formed data extraction sheet and
identified key design elements that could potentially introduce bias. The main
outcome was the confounder-adjusted relative risk (RR) of hypothyroidism in
breast cancer survivors versus women without breast cancer, and in breast
cancer survivors according to the receipt of RT to the supraclavicular lymph
nodes. We used a random-effects model to calculate pooled RRs and associated
95% confidence intervals (95% CI).
Results
From 951 papers
screened by title and abstract, 34 full-text papers were reviewed for
eligibility. We included 20 studies published between 1985 and 2021–19 were
cohort studies. Compared with women without breast cancer, the pooled RR of hypothyroidism
in breast cancer survivors was 1.48 (95% CI: 1.17, 1.87), with highest risk
associated with RT to the supraclavicular region (RR = 1.69, 95% CI:
1.16, 2.46). The most important limitations of the studies were small sample
size yielding estimates with low precision, and lack of data on potential
confounders.
Conclusion
Breast cancer and
radiation therapy to the supraclavicular lymph nodes is associated with an
increased risk of hypothyroidism.
