Histologic tumor type as a determinant of survival in hormone receptor-positive, HER2-negative, pT1-3 invasive ductal and lobular breast cancer

Abstract Purpose The aim of the study was to compare the difference in survival between invasive ductal (IDC) and lobular carcinoma (ILC). Methods Data of patients (n = 1843) with a hormone receptor-positive, HER2-negative, pT1-3 IDC or ILC cancer without distant metastasis, treated at the Ghent University Hospital over the time period 2001–2015, were analyzed. Results ILC represented 13.9% of the tumors, had a higher percentage of pT3 and pN3 stages than IDC, lymphovascular space invasion (LVSI) was less present and Ki-67 was mostly low. 73.9% of ILCs were grade 2, whereas IDC had more grade 1 and grade 3 tumors. Kaplan–Meier curves and log-rank testing showed a significant worse DFS for ILC with pN ≥ 1 than for their IDC counterpart. In a multivariable Cox regression analysis the histologic tumor type, ductal or lobular, was a determinant of DFS over 120 months (IDC as reference; hazard ratio for ILC 1.77, 95% CI 1.08–2.90) just as the ER Allred score (hazard ratio 0.84, 95% CI 0.78–0.91), LVSI (hazard ratio 1.75, 95% CI 1.12–2.74) and pN3 (hazard ratio 2.29, 95% CI 1.03–5.09). Determinants of OS over ten years were age (hazard ratio 1.05, 95% CI 1.02–1.07), LVSI (hazard ratio 3.62, 95% CI 1.92–6.82) and the ER Allred score (hazard ratio 0.80, 95% CI 0.73–0.89). Conclusion The histologic tumor type, ductal or lobular, determines DFS in hormone receptor-positive, HER2-negative, pT1-3 breast cancer besides the ER Allred score, LVSI and pN3.