Background: Metastatic breast cancer is generally considered an incurable disease. In our study we aimed to detect a time trend of survival over the past 30 years and account for time-varying effects of the prognostic factors.
Patients and methods: A total of 446 patients diagnosed with breast cancer at Saint Vincent de Paul Hospital, Lille, France between 1977 and 2013 who developed metastatic disease after a disease-free interval longer than 3 months and were followed-up for outcome. Data were analyzed using the Cox proportional hazards model and presented as hazard ratios (HRs).
Results: A monotonic time trend of survival was detected: a 2.6% lower risk of death for each increasing year over the past 30 years. Three prognostic factors had time-varying effects; the liver first metastasis (HR during the first 16 months of follow-up: 2.26; 95% confidence interval [CI], 1.65-3.11), the bone first metastasis (HR during the first 24 months of follow-up: 0.56; 95% CI, 0.43-0.74), and the disease-free interval (HR during the first 16 months of follow-up: 0.90; 95% CI, 0.85-0.95). The brain first metastasis, multiple first metastases, the lymph node ratio, and estrogen receptor status had a constant effect over time.
Conclusion: In our study we detected a constant time trend of improvement in prognosis of metastatic breast cancer patients over the past 30 years and identified prognostic factors with time-varying effects.
Keywords: Disease-free interval; Outcome; Prognostic factors of survival; Site of metastasis; Time-varying effects.
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