Radiation De-Escalation in Older Women with Early-Stage ER+/HER2- Invasive Breast Cancer.

BACKGROUND

National recommendations since 2004 have allowed for omission of post-lumpectomy radiotherapy for patients ≥70 years old with early-stage estrogen receptor positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer. Rates of omission in the era of abbreviated radiotherapy regimens are unknown. This study aimed (1) to determine contemporary trends in post-lumpectomy radiotherapy omission, (2) to determine trends in use of partial-breast (PB), ultra-hypofractionated (UHF), moderately hypofractionated (MHF), and conventionally fractionated (CF) radiotherapy regimens, and (3) to identify targetable factors to de-escalate radiotherapy in patients eligible for omission.

METHODS

A retrospective cohort analysis was performed using the National Cancer Database. The study identified patients ≥70 years old with pT1, cN0 pNX-0, cM0 ER+/HER2- breast cancer who underwent lumpectomy from 2012 to 2021. Radiotherapy treatment strategies based on number of fractions received were evaluated and compared using multivariable analysis.

RESULTS

The study included 121,160 patients: 51.0 % with no radiotherapy, 8.4 % with PB, 4.1 % with UHF, 30.2 % with MHF, and 6.3 % with CF radiotherapy. Radiotherapy omission decreased from 53.7 % to 46.8 % between 2012 and 2021. Whereas MHF radiotherapy doubled from 16.4 % to 32.9 %, CF radiotherapy decreased from 17.1 % to 2.0 %. A minority of patients received PB or UHF radiotherapy, although the rate of UHF increased from 4.6 % to 7.7 % between 2020 and 2021. Treatment at academic/research or Integrated Network Cancer Program facilities and higher-volume hospitals was associated with increased likelihood of treatment with abbreviated radiotherapy regimens.

CONCLUSIONS

Despite efforts to promote treatment de-escalation, rates for omission of post-lumpectomy radiotherapy have decreased over time. To avoid overtreatment, patients who are eligible for omission but opt to receive radiotherapy should be considered for PB or UHF radiotherapy regimens.