Radiation Therapy without Endocrine Therapy for Women Age 70 or Above with Low-Risk Early Breast Cancer: A Microsimulation
A partir d'une microsimulation utilisant les données de trois essais et de deux méta-analyses, cette étude compare l'efficacité, du point de vue de la récidive, et les coûts d'un traitement adjuvant par inhibiteur d'aromatase seul et d'une radiothérapie adjuvante seule chez les patientes âgées de 70 ans ou plus et atteintes d'un cancer du sein HR+ à faible risque de récidive traité par mastectomie partielle
Résumé en anglais
Background : Endocrine therapy without radiation therapy is considered appropriate for women age 70 or above with low-risk hormone-positive breast cancer following partial mastectomy. However, some patients may prefer radiation without endocrine therapy, for which there is minimal modern data. We modeled the comparative efficacy of aromatase inhibition alone without radiation versus radiation alone without endocrine therapy.
Methods : We constructed a patient-level Markov model and compared 5-years of anastrozole to a 15-fraction course of radiation without boost or anastrozole. The relative effectiveness between treatments was based on the NSABP B-21 trial, which was further adjusted such that the endocrine alone arm matched the CALGB 9343 and PRIME II trials. Common or severe side-effects were considered. Eight survival metrics were assessed and validated against clinical trial data. The cost-efficacy of each strategy was considered using the quality-adjusted life year (QALY) and incremental cost-effectiveness ratio (ICER).
Results : The model's predicted outcomes matched those demonstrated by modern trials. Aromatase inhibitors were superior in preventing contralateral cancers, with a small impact on the risk of distant metastatic disease. Radiation was superior in preventing ipsilateral breast-tumor recurrence (IBTR) with a small impact on regional failure. No clinically significant differences were seen in the other four oncologic endpoints. Differences in QALYs were small, but radiation therapy was $3,809 more expensive over the average lifetime. The incremental cost-effectiveness ratio (ICER) suggested anastrozole was cost-effective in 62% of probabilistic simulations. However, the ICER was unstable due to a denominator that approached zero.
Conclusion : Women age 70 or above with low-risk early breast cancer who are reluctant or unable to pursue adjuvant aromatase inhibition can safely pursue adjuvant radiation alone, with limited differences in outcome and a modest increase in costs.
