Purpose: Continuous minor steps of improvement in the management of breast cancer have resulted in decreased mortality rates during the last decades. The aim of this study was to compare the clinical outcome of patients with stage I breast cancer diagnosed during two time periods that differed with respect to adjuvant systemic therapy.
Material and methods: The studied population consisted of all women < 60 years of age, who were diagnosed breast cancer stage I between 1986 and 1999 in south-east Sweden, a total of 1 407 cases. The cohort was divided into two groups based on the management programmes of 1986 and 1992, hereafter referred to as Period 1 and Period 2. Before 1992 the only adjuvant systemic therapy recommended was tamoxifen for hormone receptor positive patients aged 50 years or older. During Period 2 the use of adjuvant treatment was extended to younger patients at high risk, identified by a high tumour S-phase fraction, with either hormonal or cytotoxic treatment.
Results: The estimated distant recurrence-free survival rate was significantly higher during Period 2 than during Period 1 (p = 0.008). Subgroup analysis showed that the most evident reduction of distant recurrence risk was among hormone receptor-negative patients (HR = 0.58, 95% CI 0.31-1.09, p = 0.09) and among patients with a high tumour S-phase fraction (HR = 0.53, 0.30-0.93, p = 0.028). The risk reduction between the periods was still statistically significant in multivariate analysis when adjusting for different tumour characteristics and treatment modalities, indicating an influence of other factors not controlled for. One such factor may be the duration of tamoxifen treatment, which likely was more frequently five years during Period 2 than during Period 1.
Conclusions: We conclude that the causes of the increase in distant recurrence free survival for women with breast cancer stage I are complex. The results support though that high-risk subgroups of stage I breast cancer patients did benefit from increased use of systemic therapy as a consequence of an updated management programme.