Travel distance to radiation therapy and receipt of radiotherapy following breast-conserving surgery.

Breast-conserving surgery (BCS) followed by radiation therapy is an efficacious alternative treatment to mastectomy for women with early-stage breast cancer(1,2). However, 15%–30% of the women treated with BCS for early-stage disease fail to undergo postoperative breast irradiation, despite the known increased risk of ipsilateral recurrence associated with the omission of radiotherapy (3–8). Older age has been identified as a major determinant of not receiving radiotherapy after BCS (4,6,7,9). Other factors that could account for failure to receive radiation therapy, particularly among younger women, remain to be identified. Travel distance to a radiationtreatment facility may influence the receipt of postoperative breast irradiation. Radiotherapy that follows BCS typically involves daily treatments (weekends excluded), for a period of 5–6 consecutive weeks. The necessity of long-distance travel may increase the inconvenience or cost of radiotherapy to a point where it simply is not feasible to receive treatment. A study of breast cancer treatment conducted in the midto late-1980s in the Seattle–Puget Sound area found that living in a county without a radiationtreatment facility was associated with a 50% lower likelihood of receiving radiotherapy after BCS(4). A similar contemporaneous study in New Mexico (3) found no relationship between radiotherapy and travel distance, but the analysis was limited to manual identification of geographic clustering of BCS patients not receiving radiotherapy. In this study, we used a geographic information system (GIS) to measure actual patient travel distances to radiationtreatment facilities to more precisely examine the relationship between travel distance and receipt of radiotherapy after BCS. For our analysis, all cases of localized breast cancer diagnosed in 1994 and 1995 in female residents of New Mexico were selected from the New Mexico Tumor Registry (NMTR) database. The NMTR, a member of the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program, 1 collects information on all cases of cancer in New Mexico residents by use of the methods previously described(3,8). Native-American women were excluded from the analysis because the NMTR does not record their addresses at diagnosis. Stage of cancer at diagnosis was coded according to the SEER Summary Staging Guide (10), which defines localized cancer as an invasive cancer confined to the organ of origin. For classification of patients by treatment received, we considered all therapy that occurred in the first 4 months of cancer-directed therapy, the standard SEER definition for the first course of therapy. Surgery was classified as either mastectomy or BCS. BCS included lumpectomy or excisional biopsy, quadrantectomy, wedge resection, partial mastectomy, and subcutaneous mastectomy. For the BCS case subjects, we considered that adjuvant radiotherapy was received if the NMTR record documented radiotherapy during the first course of therapy. The address at diagnosis was obtained for each case subject from the NMTR database and geocoded by use of ArcView 3.0a software (Environmental Systems Research Institute, Redlands, CA). Approximately 70% of the case subjects were geocoded to a unique street address. The remaining 30% of the subjects, most of whom had either post office boxes or rural routes as their addresses, were geocoded to the centroids of their ZIP codes. Twelve radiation-treatment facilities were operational in New Mexico or in nearby areas in 1995. Four facilities were located in Albuquerque, NM; two in Las Cruces, NM; one each in Santa Fe, NM, Roswell, NM, Farmington, NM, and Carlsbad, NM; and one each in El Paso, TX, and Durango, CO. Each treatment facility was geocoded to a unique street address. We assumed that each patient was treated at the nearest facility and used the GIS to calculate the shortest travel distance to it. A total of 1122 women diagnosed with localized breast cancer were included in the analysis. Of these, 533 (48%) were treated with BCS, and 409 (77%) received radiation therapy following BCS (Table 1). Age was a strong and statistically significant predictor of post-BCS radiotherapy (two-sided P for trend <.0001). Among women less than 60 years of age, 83% received follow-up breast irradiation compared with 79% of those aged 60–69 years and 63% of those 70 years and older. After adjusting for the effects of race/ethnicity and travel distance, patients 70 years and older were roughly three times less likely to receive radiotherapy after BCS compared with patients younger than 60 years. Race/ethnicity was not predictive for receipt of radiotherapy following BCS. After adjustment for age, the likelihood of receiving radiotherapy following BCS decreased significantly with increasing travel distance to the nearest