PURPOSE: To determine whether autoimmune hypothyroidism (AIHT) influences breast cancer (BRCA) incidence or all-cause survival. METHODS: Administrative data were used to identify elderly women living in Ontario, Canada with and without AIHT based on prescriptions for levothyroxine (LT4) (N = 178,186). Women were followed from April 1, 1994-March 31, 2003 for BRCA outcomes. RESULTS: The incidence of BRCA was similar in LT4 users and a propensity-matched cohort of non-users (adjusted HR = 0.99; 95% CI: 0.92-1.07). All-cause mortality was significantly lower in LT4 users compared to non-users (HR 0.95; 95% CI: 0.93-0.97, P < 0.001), as was all-cause mortality following BRCA diagnosis (HR 0.87; 95% CI: 0.77-0.98, P = 0.02). CONCLUSIONS: LT4 use, as a surrogate for AIHT, is not a risk factor for BRCA in elderly women. The small survival advantage noted among LT4 users who developed BRCA likely represents a 'healthy user' effect. Further study is needed to investigate whether autoimmunity in general is related to BRCA development or related outcomes.
PURPOSE: To determine whether autoimmune hypothyroidism (AIHT) influences breast cancer (BRCA) incidence or all-cause survival. METHODS: Administrative data were used to identify elderly women living in Ontario, Canada with and without AIHT based on prescriptions for levothyroxine (LT4) (N = 178,186). Women were followed from April 1, 1994-March 31, 2003 for BRCA outcomes. RESULTS: The incidence of BRCA was similar in LT4 users and a propensity-matched cohort of non-users (adjusted HR = 0.99; 95% CI: 0.92-1.07). All-cause mortality was significantly lower in LT4 users compared to non-users (HR 0.95; 95% CI: 0.93-0.97, P < 0.001), as was all-cause mortality following BRCA diagnosis (HR 0.87; 95% CI: 0.77-0.98, P = 0.02). CONCLUSIONS:LT4 use, as a surrogate for AIHT, is not a risk factor for BRCA in elderly women. The small survival advantage noted among LT4 users who developed BRCA likely represents a 'healthy user' effect. Further study is needed to investigate whether autoimmunity in general is related to BRCA development or related outcomes.
Authors: Anne Mette Falstie-Jensen; Anders Kjærsgaard; Ebbe Laugaard Lorenzen; Jeanette Dupont Jensen; Kristin Valborg Reinertsen; Olaf M Dekkers; Marianne Ewertz; Deirdre P Cronin-Fenton Journal: Breast Cancer Res Date: 2019-03-22 Impact factor: 6.466
Authors: Lauren McVicker; Christopher R Cardwell; Stuart A McIntosh; Úna C McMenamin Journal: Breast Cancer Res Treat Date: 2022-07-31 Impact factor: 4.624