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21-09-2022 | ESMO 2022 | Conference coverage | News

Extended anastrozole benefits dependent on tumor characteristics

Author: Laura Cowen

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medwireNews: Extending adjuvant aromatase inhibition to beyond 5 years of sequential therapy should not be recommended to all postmenopausal women with hormone receptor-positive early breast cancer, but some subgroups may benefit, research suggests.

Speaking at the ESMO Congress 2022 in Paris, France, Vivianne Tjan-Heijnen, from Maastricht University Medical Centre in the Netherlands, said the long-term follow-up of the phase 3 DATA trial revealed that “[h]ormone receptor status is a predictive factor for extended endocrine therapy and should be considered in the decision for extending aromatase inhibition.”

She added: “Prognostic factors like nodal status and tumor status may further help to identify patients who will experience the highest absolute benefit from extending aromatase inhibition.”

The study included 1912 patients with hormone receptor-positive breast cancer who were disease-free after 2–3 years of adjuvant tamoxifen. They were randomly assigned to receive anastrozole 1 mg/day for either 3 or 6 years.

Of these, 1660 were disease-free at 3.0 years after randomization and were subsequently followed up for a median of 10.1 years.

Tjan-Heijnen reported that the 10-year adapted disease-free survival (DFS) rate – defined as DFS from 3 years after randomization – was 69.1% in the 827 participants who received anastrozole for 6 years and 66.0% in the 833 who took the drug for 3 years. The difference between the two arms was not statistically significant.

However, there was a significant treatment effect among the 76% of participants who expressed both estrogen and progesterone receptors. In this group, adapted DFS was 70.8% with 6 years of anastrozole and 64.4% with 3 years of treatment, corresponding to a significant hazard ratio (HR) of 0.77 in favor of extended treatment.

By comparison, there was no such effect among the participants who were only positive for one type of hormone receptor.

Just over half (51%) of participants were node-positive and positive for both hormone receptors. These individuals had 10-year adapted DFS rates of 68.7% and 60.7% with 6 years and 3 years of anastrozole, respectively, and a corresponding significant HR of 0.74 in favor of longer treatment.

For the 26% of study participants who were dual hormone receptor-positive, node-positive, and had a tumor diameter of 2 cm or larger, the adapted 10-year DFS rate was 70.0% with 6 years of anastrozole versus 56.4% with 3 years. The associated HR of 0.64 was statistically significant and again favored extended treatment.

Tjan-Heijnen also reported that the 10-year adapted overall survival rates were 80.9% in the 6-year treatment arm versus 79.2% in the 3-year treatment arm, with no significant difference between the two either in the whole cohort or among the subgroups.

“We cannot recommend extending aromatase inhibition beyond 5 years of sequential therapy in all postmenopausal women with hormone receptor-positive breast cancer,” the presenter concluded but added that “it may however be considered in subgroups of patients.”

However, session discussant Lucia Del Mastro, from the University of Genova in Italy, said that even though the findings for the overall cohort were not significant, they were in line with those of the GIM4 and NSABP B-42 trials, which both concluded in favor of extended endocrine therapy. She suggested that the lack of statistical difference in this case may be a result of a higher proportion of patients receiving prior chemotherapy than in the other studies.

Del Mastro noted that identifying patients who should receive extended therapy is crucial, and added that the Breast Cancer Index and CTS5 score could be useful to predict relapse beyond 5 years, particularly in node-negative breast cancer and in patients with 1–3 positive nodes.

She concluded: “In my opinion, the high risk associated with four or more involved lymph nodes [means that] all these patients should receive extended adjuvant endocrine therapy.”

medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2022 Springer Healthcare Ltd, part of the Springer Nature Group

ESMO Congress 2022; Paris, France: 9–13 September

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