Elsevier

Radiotherapy and Oncology

Volume 145, April 2020, Pages 229-237
Radiotherapy and Oncology

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

https://doi.org/10.1016/j.radonc.2020.01.022Get rights and content

Highlights

  • •

    PMRT is associated with improved survival in patients with pT3N0 breast cancer.

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    PMRT benefit is limited to pT3N0 patients who do not receive adjuvant chemotherapy.

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    PMRT does not improve survival for cT3N0 disease after neoadjuvant chemotherapy.

  • •

    PMRT may benefit patients with cT3N0 disease who respond poorly to chemotherapy.

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.

Section snippets

Data source

This study is a retrospective review of patient outcomes collected from the NCDB, which is a joint program of the Commission on Cancer (CoC) of the American College of Surgeons and the American Cancer Society. The NCDB collects information from hospital registry data in more than 1500 CoC-accredited facilities and tracks patients with malignant neoplastic diseases, their treatments, and outcomes. Data in the NCDB represent more than 70 percent of newly diagnosed cancer cases in the U.S. and

Results

We identified 2,445,870 patients with breast cancer diagnosed between 2006 and 2014. After applying the inclusion and exclusion criteria, we identified 4285 pT3N0 patients who did not receive NAC, of whom 1819 were treated with PMRT and 2466 with MTX. We identified 1858 cT3N0 patients who received NAC, of whom 1138 were treated with PMRT and 720 with MTX (Fig. 1). Pre-match characteristics are listed in supplementary Tables 1 and 2. Most notably, patients who received PMRT in the pT3N0 cohort

Discussion

Our results showed improved OS with PMRT in patients with pT3N0 breast cancer, especially those who did not receive AC. For cT3N0 patients who received NAC, there was no improvement in OS with PMRT. Exploratory subgroup analyses showed a potential survival advantage for PMRT in patients with significant residual disease after NAC. This is the first NCDB analysis to account for all available patient, treatment, and tumor related variables, including HER2 receptor status and LVI. Additionally, to

Conflicts of interest

None.

Funding

The authors received no financial support for this research.

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    Authors contributed equally.

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