medwireNews: Primary breast cancer patients with rare pre-existing ESR1 mutations are significantly more likely to experience endocrine therapy failure in the adjuvant setting than other individuals, suggests research presented at the 2020 AACR Virtual Annual Meeting I.
Somatic ESR1 mutations were identified in 0.9% of 3217 primary breast tumors recorded in the SCAN-B Study, reported Malin Dahlgren, from Lund University in Sweden.
Over 9 years of follow-up from diagnosis, overall survival was significantly shorter in endocrine-treated patients positive for an ESR1 mutation than those carrying the wild-type gene, and this was confirmed in multivariable analysis, with adjusted hazard ratios of 2.1–2.6 after individually adjusting for age, tumor size, stage, grade, or nodal status.
And after 8 years of follow-up, the relapse-free survival interval was significantly shorter for the ESR1 mutation-positive patients compared with controls, with individually adjusted hazard ratio of 3.6–4.5.
“If replicated, we suggest that it could be clinically relevant to screen for resistance mutations in [estrogen receptor]-positive disease to aid the clinicians in deciding on the best course of treatment,” Dahlgren remarked.
“For example, other evidence suggests that degraders, such as fulvestrant, have greater efficacy against ESR1 mutations than the modulators or aromatase inhibitors.”
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