Chronologically changing patterns in the survival of korean patients with breast cancer and related clinical factors: a nationwide registry-based study

Purpose: Advances in breast cancer treatment have contributed to marked improvements in patient outcomes over the past three decades. This study aims to chronologically evaluate the survival of patients with breast cancer and investigate the observed changes over time. Methods: Statistics from the Korean National Cancer Registry, based on all 60,571 patients with invasive breast cancer during the 21 year period, were analyzed. We divided the study interval into four periods (P1: 1988–1992, P2: 1993–1997, P3: 1998–2002, P4: 2003–2008). Results: The patients treated during P4 showed significantly better 5-year overall survival (OS) than did those treated during P1 (5Y OS; P1 = 79.0 vs. P4 = 92.2, p < 0.001). In the multivariate analyses, younger age, mastectomy, high stage, high tumor grade, lymphovascular invasion, and hormone receptor negativity were poor prognostic factors. The multivariate analysis demonstrated that diagnosis periods significantly and independently associated with OS in the overall group of patients. In our analysis of age-period-interaction models, the hazard ratio (HR) for death for patients who were under 35 years of age, compared to those who were older, tended to decrease over time (HR of age < 35 vs. 35 ~ 50; P1 = 0.739, p = 0.007; P2 = 0.744, p < 0.001; P3 = 0.886, p = 0.041; P4 = 0.983, p = 0.813). The survival rate of patients who underwent breast conserving surgery (BCS) has recently gotten better than that of mastectomy (HR of mastectomy vs. BCS; P1 = 0.957, p = 0.790; P2 = 0.542, p < 0.001; P3 = 0.543, p < 0.001; P4 = 0.425, p < 0.001). Conclusions: The clinical factors related to the changes in breast cancer survival have improved and increased patient OS over the past 20 years in Korea. In addition, we provided new insights into the effects of age and surgery methods on prognosis in each period.