Substantial increase in the use of adjuvant systemic treatment for early stage breast cancer reflects changes in guidelines in the period 1990-2006 in the southeastern Netherlands.

Patients diagnosed with early stage breast cancer in 1990-2006 were selected from the registry of the Comprehensive Cancer Centre South (n=8261). The probability of receiving therapy was determined per characteristic for the periods 1990-1997, 1998-2001 and 2002-2006, separately.

The impact of patient and tumour characteristics on treatment choice varied over time, reflecting major changes in the Dutch treatment guidelines. Patients older than 70 years received almost no chemotherapy.

The use of any adjuvant systemic treatment increased from 37% in 1990-1997 to 51% in 1998-2001 and 53% in 2002-2006 (p for trend < 0.0001). In the period 1990-1997, lymph node status (positive vs. negative: probability ratio (PR=25.8; 95% CI, 16.5-40.4) and age ( 60 vs. 35 years: PR=0.01; 95% CI, 0.00-0.02) were the main determinants of the likelihood of receiving chemotherapy. From 1998 onwards, age remained the most important factor in decreasing the likelihood of receiving chemotherapy. During 1990-1997 the use of hormonal therapy was mainly determined by positive lymph node status (PR=35; 95% CI, 25-49) and age ( 70 vs. 35 years: PR=9.3; 95% CI, 4.4-20), whereas positive hormone receptor status mainly affected hormonal therapy use (PR=17; 95% CI, 10-28) in the period 2002-2006. Marked differences were observed between hospitals in the adoption of adjuvant systemic treatment for node-negative patients.

This study evaluated trends in adjuvant systemic treatment among breast cancer patients and analyzed the factors on which treatment choice was based.