TY - JOUR

T1 - Influence of the anti-oestrogens tamoxifen and letrozole on thyroid function in women with early and advanced breast cancer

T2 - A systematic review

AU - Marina, Djordje

AU - Rasmussen, Åse Krogh

AU - Buch-Larsen, Kristian

AU - Gillberg, Linn

AU - Andersson, Michael

AU - Schwarz, Peter

N1 - Publisher Copyright: © 2022 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

PY - 2023

Y1 - 2023

N2 - Introduction: Breast cancer (BC) is a common type of cancer in women. Advances in therapy options have resulted in higher overall survival rates but side effects of cancer treatment are increasingly in the spotlight. The beneficial effects of anti-oestrogen therapy with tamoxifen and letrozole in the prevention of BC recurrence are well documented. While the most common side-effects of this therapy are well-defined, less is known about its effects on thyroid function. In women treated for early BC, an average of 1–5 kg weight gain has been observed after treatment with chemotherapy/anti-oestrogens. We aim to evaluate the current knowledge on the side effects of tamoxifen and letrozole treatments on thyroid function, followed by its potential influence on the observed weight gain. Methods: We searched PubMed and found 16 publications on thyroid function and tamoxifen treatment in pre- and post-menopausal women with early- and advanced BC, whereas five publications on letrozole treatment in post-menopausal women with advanced BC. Results: According to the current literature, there is an overall tendency towards a mild and transient thyroid dysfunction, that is, subclinical hypothyroidism in tamoxifen-treated patients. Only one publication reported further significant changes in thyroid hormones beyond one year of tamoxifen treatment. No significant changes in thyroid function have been observed among letrozole-treated patients. Conclusion: Tamoxifen-treated patients can develop mild and transient thyroid dysfunction within the first 12 months, yet further significant changes in thyroid function beyond one year of tamoxifen treatment have been reported in a single study. There is no evidence of thyroid dysfunction in letrozole-treated patients. Current literature does not focus on subclinical hypothyroidism as a possible cause of weight gain in patients with BC. Subgrouping of BC patients and studies with a longer observation of thyroid hormones and weight changes during and after anti-oestrogen treatment are needed to further elucidate how anti-oestrogens affect thyroid function.

AB - Introduction: Breast cancer (BC) is a common type of cancer in women. Advances in therapy options have resulted in higher overall survival rates but side effects of cancer treatment are increasingly in the spotlight. The beneficial effects of anti-oestrogen therapy with tamoxifen and letrozole in the prevention of BC recurrence are well documented. While the most common side-effects of this therapy are well-defined, less is known about its effects on thyroid function. In women treated for early BC, an average of 1–5 kg weight gain has been observed after treatment with chemotherapy/anti-oestrogens. We aim to evaluate the current knowledge on the side effects of tamoxifen and letrozole treatments on thyroid function, followed by its potential influence on the observed weight gain. Methods: We searched PubMed and found 16 publications on thyroid function and tamoxifen treatment in pre- and post-menopausal women with early- and advanced BC, whereas five publications on letrozole treatment in post-menopausal women with advanced BC. Results: According to the current literature, there is an overall tendency towards a mild and transient thyroid dysfunction, that is, subclinical hypothyroidism in tamoxifen-treated patients. Only one publication reported further significant changes in thyroid hormones beyond one year of tamoxifen treatment. No significant changes in thyroid function have been observed among letrozole-treated patients. Conclusion: Tamoxifen-treated patients can develop mild and transient thyroid dysfunction within the first 12 months, yet further significant changes in thyroid function beyond one year of tamoxifen treatment have been reported in a single study. There is no evidence of thyroid dysfunction in letrozole-treated patients. Current literature does not focus on subclinical hypothyroidism as a possible cause of weight gain in patients with BC. Subgrouping of BC patients and studies with a longer observation of thyroid hormones and weight changes during and after anti-oestrogen treatment are needed to further elucidate how anti-oestrogens affect thyroid function.

KW - breast cancer

KW - letrozole

KW - subclinical hypothyroidism

KW - tamoxifen

KW - thyroid hormones

KW - weight gain

U2 - 10.1002/cam4.4949

DO - 10.1002/cam4.4949

M3 - Review

C2 - 35748065

AN - SCOPUS:85132589534

VL - 12

SP - 967

EP - 982

JO - Cancer Medicine

JF - Cancer Medicine

SN - 2045-7634

IS - 2

ER -