Increased use of adjuvant regional radiotherapy for node-positive breast cancer in British Columbia.

This study was to determine if the use of regional radiotherapy (RT) changed in British Columbia after publication of new randomized trial data in 1997. Women with pathologic T1-3N1, nonmetastatic breast cancer treated with a mastectomy or breast-conserving surgery (BCS) were included. The use of regional RT was compared in two cohorts: cohort 1, July 1, 1995-June 30, 1997 (n = 834); and cohort 2, July 1, 1998-June 30, 2000 (n = 1072). All p-values were two-sided. Adjuvant systemic therapy was given to 96% and 95% of women in cohorts 1 and 2, respectively. Forty-five percent of cohort 1 and 48% of cohort 2 had BCS. Regional RT was received by 44% of cohort 1 and 66% of cohort 2 (p < 0.001). Eighty-eight percent and 90% of women with four or more positive nodes in cohorts 1 and 2 received regional RT, respectively. For women in cohorts 1 and 2 with one to three positive nodes, regional RT use increased from 32% to 54% after mastectomy, and from 23% to 59% after BCS, respectively (p < 0.001 for both). Publication of randomized trials and a coordinated guideline implementation process in British Columbia was associated with a significant increase in the use of regional RT in women with one to three positive nodes.