Cross-Border Referral for Early Breast Cancer: An Analysis of Radiation Fractionation Patterns

摘要

Introduction: Due to increasing waiting times for adjuvant radiation in the province of Ontario, patients from one Canadian (CN) centre were referred to two centres in the United States (US). This provided the opportunity to compare radiation practices. Materials and methods: A retrospective review was performed of radiation prescribed to patients following breast-conserving surgery for invasive breast cancer. Patients with positive margins, 3 4 positive lymph nodes, recurrent disease or large tumors (5 cm) were excluded. A random sample of similar patients treated at the CN centre during the same time period was reviewed for comparison. Results: A total of 120 referred and 217 non-referred patients were eligible for comparison. The analysis included 98 pairs of patients (n=196), fully matched on age, nodal status, T stage, grade and ER status. Mean patient age was 60.7 years. The median total dose and number of fractions differed between centres: 6040 (US) vs. 4250 (CN) cGy in 32 vs. 16 fractions respectively (both p0.001). Boost was more often used in US (97%) than in CN (4%, p0.001). Variation in prescribing patterns was seen. In the US, seven different schedules for whole breast irradiation were used, whereas at the CN centre, two schedules were prescribed. Predicted radiobiological effects of these schedules were calculated to be similar. Conclusions: Differences in fractionation patterns were observed between and within the US and CN centres. Such variability is likely to impact on patient convenience and resource utilization. While patient selection, referring surgeon and changing policies may account for some of the observed differences, further research is necessary to understand the causes better.