PURPOSE

To examine local control, disease-free survival (DFS), and toxicity in elderly (≥ 65 years) breast cancer patients treated with hypofractionated radiotherapy (hypo-RT) with or without a boost to the tumor bed.

PATIENTS AND METHODS

The study was conducted on 752 patients treated from April 2009 to February 2017. Patients received 42.4 Gy in 16 daily fractions (2.65 Gy per fraction). A boost was only administered in cases of grade 3 primary tumor and close or positive margins. Acute and late toxicity was prospectively assessed during and after hypo-RT, based on the Radiation Therapy Oncology Group scale. DFS and local recurrence-free survival were estimated by the Kaplan-Meier method for cumulative probability. Log-rank tests were used to identify differences by subtype. Cox proportional hazard models were used to investigate the impact of various factors on the risk of disease progression.

RESULTS

Among the 752 patients treated, 41 (5.5%) experienced disease progression, including 7 (17.1%) exclusively local recurrences; 1 (2.4%) local and nodal recurrence; 1 (2.4%) local and nodal recurrence plus metastasis; 7 (17.1%) nodal recurrences plus metastases; and 25 (61%) exclusively distant metastases. The 5-year DFS, local recurrence-free survival, breast cancer-specific survival, and overall survival rates were 91.8% (95% confidence interval [CI], 88.6-94.2), 98.0% (95% CI, 96.1-99.1), 98.2% (95% CI, 96.5-99.1), and 87.5% (95% CI, 83.8-90.5), respectively. On univariate analysis, the administration of a boost, disease grade (grades 1 and 2 vs. 3), and molecular subtype (triple negative or human epidermal growth factor receptor 2 [HER2] positive, or luminal B vs. luminal A) significantly affected disease progression (P < .01). These findings were confirmed by multivariate analysis.

CONCLUSION

Hypo-RT is effective and well tolerated in the elderly population, and the routine use of a boost for patients over 65 years is not justified. Further studies on the boost issue are strongly advocated.