Prognostic impact of radiation therapy in tubular carcinoma of the breast

Abstract

Purpose: Tubular carcinoma (TC) is an invasive breast cancer with favorable prognosis. While pathology-specific guidelines exist for TC regarding adjuvant chemotherapy and endocrine therapy, no recommendations exist regarding locoregional treatment based on tumor histology. Prognostic impact of radiotherapy for patients with TC remains unclear.

Materials and methods: The National Cancer Database was queried (2004-2015) for patients with pN0M0 TC who underwent lumpectomy. Chi-square testing compared categorized variables between those who did and did not receive radiotherapy. Kaplan-Meier analysis evaluated overall survival (OS). Cox proportional hazard analysis identified variables prognostic for OS. Patients were divided into age cohorts ≤60 years and >60 years. Propensity score matching (PSM) was utilized to create similar cohorts.

Results: 9705 patients met selection criteria; 6182 (75.1%) received radiotherapy while 2045 (24.9%) did not. After PSM, radiotherapy (HR 0.582; 95% CI 0.494-0.686) and endocrine therapy (HR 0.737; 95% CI 0.623-0.872) were favorable prognostic factors on multivariate Cox regression analysis while age > 60 years (HR 5.131; 95% CI 3.753-7.016), Black race (HR 1.445; 95% CI 1.016-2.055), and Charlson-Deyo comorbidity score > 0 (HR 1.708; 95% CI 1.403-2.079) were unfavorable prognostic factors. After PSM, 5-year OS was 91.7% for those who received radiotherapy and 84.5% for those who did not; 10-year OS was 76.1% and 64.1%, respectively (p < 0.001).

Conclusion: This is the largest study to date on TC and the prognostic impact of adjuvant radiotherapy. Postoperative radiotherapy is a favorable prognostic factor for OS in patients with pN0M0 TC, suggesting adjuvant radiotherapy should remain standard of care in these patients.

Keywords: Adenocarcinoma; Breast neoplasms; Radiation oncology; Radiotherapy.