Temporal trends in the use of adjuvant systemic therapy in breast cancer - a population based study in Sweden 1976-2005

Background. Both adjuvant therapy and mammography screening can decrease breast cancer mortality and there is a need of knowing to what extent those two modalities are used in the population. Screening coverage is well documented but there is a scarcity of population-based data on use of systemic adjuvant treatment. Aim. To describe the introduction, and trends in the use of adjuvant systemic therapy for breast cancer in two of six public health regions in Sweden. Material & methods. Population-based data on use of adjuvant therapy were available from databases with documented high quality and high coverage data for Stockholm (1976-2005) and North Sweden (1980-2003, and 2005). Results. The use of systemic treatment was infrequent before the late 1980s in both regions, but increased during the 1990s. In 2005, the proportion of operable breast cancer patients treated with adjuvant endocrine therapy in the ages 40-59 was around 60 to 80%. The proportion adjuvant chemotherapy was less than 15% for the ages 70-74. For the north region the use of endocrine therapy increased successively over time, with an exception for age group 40-49 were a more rapidly increase occurred in the late 1990s. In Stockholm the increment was higher and more rapidly. There was no clear difference in chemotherapy use between the regions, and the use increased from the mid 1980s in age group 40-49, and in the early 1990s for women aged 50-59. In age group's 60-69 and 70-74 the use was relatively infrequent. Conclusions. Trends in, and levels of the use of adjuvant systemic therapy for breast cancer varied over time in the two study regions, particularly for endocrine therapy. We consider that the differences between the regions mainly reflect different interpretations of new scientific evidence. We stress the importance of a good documentation of all new treatment protocols.