Post-mastectomy radiotherapy is associated with improved overall survival in T3N0 patients who do not receive chemotherapy

Muayad F Almahariq; Thomas J Quinn; Zaid A Siddiqui; Andrew B Thompson; Maha S Jawad; Peter Y Chen; Gregory S Gustafson; Joshua T Dilworth

doi:10.1016/j.radonc.2020.01.022

Post-mastectomy radiotherapy is associated with improved overall survival in T3N0 patients who do not receive chemotherapy

Radiother Oncol. 2020 Apr:145:229-237. doi: 10.1016/j.radonc.2020.01.022. Epub 2020 Feb 14.

Authors

Muayad F Almahariq¹, Thomas J Quinn¹, Zaid A Siddiqui¹, Andrew B Thompson¹, Maha S Jawad¹, Peter Y Chen¹, Gregory S Gustafson¹, Joshua T Dilworth²

Affiliations

¹ Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, United States.
² Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, United States. Electronic address: joshua.dilworth@beaumont.edu.

PMID: 32065903
DOI: 10.1016/j.radonc.2020.01.022

Abstract

Background and purpose: There is limited retrospective evidence addressing the utility of post-mastectomy radiotherapy (PMRT) in patients with T3N0 breast cancer. We performed a retrospective analysis of the National Cancer Database (NCDB) comparing overall survival (OS) in T3N0 patients treated with mastectomy alone (MTX) or with PMRT.

Materials and methods: We performed a matched-cohort analysis of NCDB breast cancer patients with pT3N0 disease who did not receive NAC, or cT3N0 patients who received NAC treated between 2006 and 2014. Patients were matched for all available baseline characteristics using propensity scores with inverse probability of treatment weighting (IPTW) with stabilized weights.

Results: We identified 13,901 eligible patients. In the pT3N0 cohort, median follow-up was 47 months for the MTX group and 50 months for the PMRT group. In the cT3N0 cohort, median follow-up was 44 months for the MTX group and 46 months for the PMRT group. OS was higher in pT3N0 patients treated with PMRT compared to MTX: 7-year OS of 74% vs. 65% (P < 0.001). Doubly robust multivariable analysis showed an association between PMRT and improved OS (HR 0.78, 95% CI 0.68-0.89, P < 0.001). There was no benefit to PMRT in patients who received adjuvant chemotherapy (AC). In the NAC cohort, PMRT did not change OS, with 7-year OS of 78% with MTX and 79% with PMRT. There was a trend of improved OS with PMRT in patients with residual disease in the breast and lymph nodes (HR 0.70, 95% CI 0.46-1.07).

Conclusion: PMRT improves OS in patients with pT3N0 disease, but the benefit appears limited to those who do not receive AC. PMRT does not improve OS in patients with cT3N0 disease who receive NAC, but there might be a benefit in patients with a poor response to chemotherapy. However, longer follow-up may be needed to make a definitive conclusion about the benefit of PMRT in patients who receive chemotherapy.

Keywords: Adjuvant chemotherapy; Breast cancer; Neoadjuvant chemotherapy; Post-mastectomy radiotherapy; T3N0.

MeSH terms

Breast Neoplasms* / drug therapy
Breast Neoplasms* / radiotherapy
Chemotherapy, Adjuvant
Humans
Mastectomy*
Neoplasm Staging
Radiotherapy, Adjuvant
Retrospective Studies