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SAN ANTONIO -- Endocrine therapy after breast-conserving surgery was associated with worse health-related quality of life (HRQOL) compared with radiotherapy in older women with luminal A-like early breast cancer, interim results from the randomized EUROPA trial showed.

At 24 months, endocrine therapy appeared to have a more negative effect on HRQOL as measured by the global health status (GHS) scale of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire 30-item core module, with a mean change from baseline of -9.79 in the endocrine therapy group versus -3.40 in the radiotherapy group (P=0.045), reported Icro Meattini, MD, of the University of Florence in Italy.

At baseline, the mean GHS score was slightly higher in the endocrine therapy group (75.5 on a 100-point scale, with a higher score indicating better quality of life) versus the radiotherapy group (71.9), but by 24 months it dropped to 67.2 in the endocrine therapy group, while the radiotherapy group remained stable with a score of 70.7, Meattini said during the San Antonio Breast Cancer Symposium.

"In this interim analysis, we have already seen that radiotherapy may offer better health-related quality of life as measured by global health status as compared to endocrine therapy at 24 months," he noted.

Treatment-related adverse events occurred in 85.4% of patients in the endocrine therapy arm compared with 67% of those in the radiotherapy arm, and a higher proportion of patients in the endocrine therapy group did not complete the 24-month HRQOL assessment compared with the radiotherapy group (27% vs 17%).

Results from the EUROPA study were also published in .

"These findings point to important considerations in the management of older patients with breast cancer," Meattini and colleagues wrote in their study. "Although endocrine therapy is often seen as a less invasive option, its higher withdrawal rates and side-effect profile might affect long-term adherence and HRQOL, especially in frail patients. Conversely, short-course radiotherapy could offer a less burdensome alternative, combining similar efficacy with improved tolerability."

"Final results from the EUROPA trial, including long-term recurrence and survival data, will further clarify the roles of radiotherapy and endocrine therapy in this population," they added.

In a , N. Lynn Henry, MD, PhD, of the University of Michigan Medical School in Ann Arbor, suggested that these early findings "show that a subset of patients are likely to stop taking endocrine therapy prematurely and suggest that quality of life might be diminished in this cohort of patients."

"The ipsilateral breast tumor recurrence rates in the two treatment groups, which is the other half of the co-primary endpoints for this clinical trial, will be critical for determining how best to apply these findings to routine clinical practice," Henry wrote. "Importantly, once the findings are mature, this trial is likely to provide useful information for patients and clinicians as they make evidence-based decisions about the trade-offs between different treatment approaches."

The phase III noninferiority is being conducted at 18 academic centers across Italy and Slovenia. The researchers enrolled 926 women ages 70 years and older with histologically confirmed, stage I, luminal A-like breast cancer, who had undergone breast-conserving surgery and had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

Patients were randomly assigned to receive single-modality endocrine therapy or radiotherapy. Endocrine therapy consisted of daily oral aromatase inhibitors or tamoxifen, for a total planned duration of 5-10 years per clinical discretion, while radiotherapy was administered as either whole-breast or partial-breast irradiation, delivered in 5-15 Gy fractions.

This interim analysis included 103 patients in the endocrine therapy group and 104 patients in the radiotherapy group, with a median follow-up of 23.9 months. Patients were predominantly white (99%), and median age was 74 years in the endocrine therapy group and 75 years in the radiotherapy group.

Meattini acknowledged that the study had several limitations, including the fact that it was based on a subset of the total planned cohort and had limited long-term efficacy and safety data.