1998-1999 patterns of care study process survey of national practice patterns using breast-conserving surgery and radiotherapy in the management of stage I-II breast cancer.

PURPOSE: The Patterns of Care Study survey process evaluation has been an effective means of assessing the evaluation and treatment practices used by radiation oncologists in the United States for Stage I-II breast cancer. The current 1998-1999 report updates the previous 1989 and 1993-1994 analyses and reflects the recent changes in surgery and systemic therapy observed nationally in the management of early-stage disease. METHODS AND MATERIALS: A weighted sample size of 71,877 patient records of women treated with breast-conserving surgery and radiotherapy (RT) was obtained from a stratified two-stage sampling of 353 patient records. These cases were centrally reviewed from academic and private radiation oncology practices across the United States. The data collected included patient characteristics, clinical and pathologic factors, and surgical and RT details. The results were compared with those of previous Patterns of Care Study survey reports.
RESULTS: Of the patients in the current survey, 97% had undergone mammography before biopsy. A review of the primary tumor pathologic findings indicated improved quantification of an intraductal component from 7.0% in 1993-1994 to 20.4% in 1998-1999 (p = 0.01). The tumor characteristics were better defined, with estrogen and progesterone receptor measurement performed in 91.4% and 91.3% in the 1998-1999 survey vs. 83.7% and 80.3% in the 1989 survey, respectively (p = 0.03 and p = 0.002, respectively). Axillary dissection was performed in 82.2% in the present survey compared with 93.6% in the 1993-1994 survey (p = 0.0004); sentinel node biopsy was performed in 20.1% of the present cases. The use of CT for planning was increased in the current survey, with 22.9% cases CT planned vs. 9% in 1993-1994 (p = 0.10). In the present survey, 100% had received whole breast RT. When a supraclavicular field was added, the dose was prescribed to a specified depth in 67.5% of cases, most commonly 3 cm. When an axillary field was added, the dose was generally prescribed to the mid-plane. Chemotherapy and tamoxifen was used in 36% and 55.8% of patients, respectively, in the 1998-1999 survey, representing a statistically significant increase compared with the 1993-1994 survey, despite comparable pathologic tumor size and nodal involvement.
CONCLUSION: The present results demonstrate a high level of compliance of the sampled radiation oncology practices with current breast conservation standards and continued improvement in many categories compared with prior patterns of care study surveys. The estimates in the current survey after whole breast RT will serve as a benchmark against newer trends in breast cancer RT, such as partial breast RT.