Temporal trends in breast cancer treatment patterns and survival: A comprehensive analysis of the SEER database from 1990 to 2017

Breast cancer remains one of the most common malignancies in women globally and continues to represent a significant public health challenge. The last 30 years have seen significant improvements in understanding, detection, and treatment of breast cancer, resulting in major modifications to clinical management approaches. This study analyzed 5,859 breast cancer patients from the Surveillance, Epidemiology, and End Results (SEER) database from 1990 to 2017. To assess changes over this 27-year period, westratified the timeframe into five separate segments (1990- 1995, 1996-2000, 2001-2005, 2006-2010, and 2011-2017), evaluating tumor characteristics, lymph node evaluation practices, demographic factors, treatment approaches, and clinical outcomes. Cox proportional hazards regression models with increasing levels of adjustment were developed to analyze temporal trends in breast cancer mortality risk. While tumor size remained relatively consistent throughout the study period, significant changes were observed in lymph node assessment practices, with the average number of regional nodes examined decreasing from 30.44 in 1990-1995 to 16.07 in 2011-2017 (P<0.001). Patient demographics showed notable shifts, including increased racial diversity and changes in age distribution. Treatment approaches evolved with surgery remaining the predominant intervention (96.70% overall), minimal changes in radiation therapy utilization (60.45% overall), and a substantial increase in chemotherapy use from 81.69% to 91.20% (P<0.001). Cox regression analysis revealed progressively improving survival over time, with the fully adjusted hazard ratio declining to 0.63 (95% CI: 0.56-0.70) for 2011-2017 compared to 1990- 1995 (P<0.001). Breast cancer management has undergone substantial transformation over the past three decades, with evidence of improving long-term outcomes despite complexities in interpreting temporal trends.