Rationalization and regionalization of treatment for ductal carcinoma in situ of the breast.

PURPOSE: In ductal carcinoma in situ (DCIS) of the breast, conservative surgery plus radiotherapy (CS+RT) decreases risk of recurrence compared with CS alone. Although nearly one third of patients are reported as treated with CS alone, it is unclear whether this potentially "undertreated" group represents high- or low-risk patients. We evaluated national patterns of DCIS treatment from 1996 to 2001 by patient risk profile. METHODS AND MATERIALS: In a retrospective cohort of DCIS patients from the Surveillance, Epidemiology, and End Results data, patients were risk stratified on the basis of age at diagnosis, tumor grade, tumor size, and comedo histology. Treatment included CS alone, CS+RT, or mastectomy. Patients were followed for the development of ipsilateral invasive or in situ event.
RESULTS: Of 14,202 patients, 19% were low-risk, 46% moderate-risk, and 35% high-risk. A total of 28% received CS alone, 40% CS+RT, and 31% mastectomy. Overall, only 17% of high-risk patients but 44% of low-risk patients received CS alone (p < 0.001). In multivariable analysis, older age, smaller tumor size, and treatment in San Francisco/Los Angeles predicted treatment with CS alone (p < 0.01). Yet despite the tendency to receive CS alone, patients in San Francisco/Los Angeles did not experience an increased risk of ipsilateral event (hazard ratio = 0.79; 95% confidence interval, 0.55-1.12).
CONCLUSION: Patient risk profiles rationally affect treatment choice in DCIS patients, and the vast majority of high-risk patients do not receive CS alone. Additional follow up is needed to determine whether geographic variation in care influences long-term outcomes.