Abstract P6-06-28: Survival gain in patients with de novo metastatic breast cancer in past two decades is largely attributable to treatment
Authors: Bhoo-Pathy N , Verkooijen HM , Tan E-Y , Hui M , Taib NA , Brand JS , Dent R , See M-H , Subramaniam S , Chan PMY , Lee S-C , Hartman M , Yip C-H 
Published: August 2014

Background: In Asia, a substantial proportion of breast cancer patients present with distant metastases at diagnosis. We determined whether metastatic breast cancer survival has improved in a multi-ethnic Asian setting over a span of fifteen years, and disentangled the contribution of various factors on the observed survival trend.

Methods: Patients diagnosed with de novo metastatic breast cancer from three hospitals in Malaysia and Singapore (N = 856) were assigned to three cohorts by year of diagnosis: 1996-2000, 2001-2005 and 2006-2010. Time trends in disease characteristics, treatment, and relative survival rates (RSR) were compared. Adjusted relative excess risks of mortality in recent periods were estimated using a step-wise Poisson regression to assess the contributions of several prognostic factors towards the observed survival pattern.

Results: The proportion of patients presenting with de novo metastatic breast cancer remained fairly stable at 10% in 1996-2000, 7% in 2001-2005, and 9% in 2006 -2010. Recently diagnosed patients were older, and more likely to have multiple metastatic sites involved, and visceral metastases. Surgery of primary tumor became more prevalent over time, and this is also complemented with higher attainments of free surgical margins. Chemotherapy, and endocrine therapy administration also increased with time, with higher use of taxane-based regimens in recent periods. The three-year RSR in the above periods were 20.6% (95%CI: 13.9%-28.2%, median survival = 14 months), 28.8% (95%CI: 23.4%-34.2%, median survival = 18 months), and 33.6% (95%CI: 28.8%-38.5%, median survival = 21 months), respectively. Surgery of the primary tumor explained most of the observed survival gain in the latest period, followed by chemotherapy, and endocrine therapy.

Excess Mortality Risk in Patients with De Novo Metastatic Breast Cancer by Period of Diagnosis Period of diagnosisDeath1996-200012001-20052006-2010Relative excess risk (95%CI)21.000.86(0.68-1.09)0.68(0.54-0.86)7Relative excess risk (95%CI)31.000.82 (0.65-1.05)0.68(0.54-0.87)7Relative excess risk (95%CI)41.000.82 (0.64-1.05)0.66(0.52-0.84)7Relative excess risk (95%CI)51.000.89 (0.69-1.15)0.76(0.59-0.97)7Relative excess risk (95%CI)61.000.89 (0.69-1.16)0.79(0.62-1.01)1 Reference period, 2 Derived using Poisson regression model, matched to background population mortality based on country, year, and age, and adjusted for center, and follow-up time, 3 Similar as model 2, and additionally adjusted for age at diagnosis, and ethnicity, 4 Similar as model 3, and additionally adjusted for T stage at diagnosis, ER status, number of organs with metastatic involvement, and presence of visceral metastasis, 5 Similar as model 4, and additionally adjusted for surgery, and surgical margins, 6 Similar as model 5, and additionally adjusted for radiotherapy, chemotherapy, and endocrine therapy, 7 Statistically significant

Conclusion: The modest survival gain in patients with de novo metastatic breast cancer in Asian settings is largely attributable to improvement in treatment strategies, namely surgery of primary tumor and other treatment modalities.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-28.