medwireNews: The long-term benefit of endocrine therapy in premenopausal women with breast cancer may be influenced by molecular risk, suggest Swedish findings.
When stratified by the MammaPrint 70-gene signature, low-risk patients appeared to derive a greater benefit from tamoxifen, while goserelin seemed more beneficial for those at high risk, reported Annelie Johansson (Karolinska Institute, Stockholm, Sweden) at the ESMO Breast Cancer Virtual Congress 2021.
The discussant – Prudence Francis from the Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia – described the translational study as “innovative,” but she highlighted the “relatively small numbers of patients” in each subgroup stratified by endocrine therapy and molecular risk.
She also noted the short duration of endocrine therapy, prior chemotherapy in some patients, and absence of HER2 therapy, “all of which might influence outcomes,” and concluded that the findings “should be viewed as hypothesis generating.”
For the current analysis, the researchers collated 20-year follow-up data from Swedish national registries for 610 hormone receptor-positive participants of the STO-5 randomized trial of adjuvant endocrine therapy in premenopausal patients. Of these, 465 had molecular risk classification data.
The team found that the 20-year risk for distant recurrence was significantly reduced in the 160 patients who received goserelin, the 142 who received tamoxifen, and the 156 who received both goserelin and tamoxifen, compared with the 152 participants who did not receive endocrine therapy. The respective hazard ratios (HRs) were 0.48, 0.59, and 0.67 after adjusting for prior therapy and patient and tumor characteristics.
Stratification by molecular risk showed that the reduction in distant recurrence risk afforded by goserelin was significant only among high-risk patients, with an HR for recurrence of 0.22 versus no endocrine therapy, while tamoxifen was associated with a significantly reduced risk only among low-risk patients, at an HR of 0.38.
There was no such difference by molecular risk among women who received goserelin plus tamoxifen, said the presenting author.
She added that the benefit of goserelin in the high-risk subgroup remained significant when compared against goserelin plus tamoxifen (HR=0.33) and tamoxifen alone (HR=0.30).
Johansson therefore summarized: “Our findings indicate that the long-term endocrine therapy benefit in premenopausal patients in influenced by molecular risk classification and thus tumor characteristics.”
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