Long‐term follow‐up of a prospective policy of margin‐directed radiation dose escalation in breast‐conserving therapy

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Abstract
BACKGROUND: A prospectively applied treatment policy for breast‐conserving therapy used margin assessment as the exclusive guide to the intensity of radiation therapy directed at the tumor bed.METHODS: From 1982 to 1994, 498 women with 509 Stage I/II breast carcinomas with a median follow‐up of 121 months were treated. Final margin status (FMS) categories were defined as greater than 5 mm, greater than 2–5 mm, greater than 0–2 mm, and positive. For margins less than or equal to 2 mm or indeterminate, reexcisions were performed if feasible. All patients received whole breast irradiation to 50.0–50.4 Gy. Final tumor bed boosts as a function of FMS were as follows: no residual on reexcision, no boost performed; FMS greater than 5 mm, boost of 10 Gy; FMS greater than 2–5 mm, boost of 14 Gy; FMS greater than 0–2 mm or positive, boost of 20 Gy. Cases were analyzed for local failure with respect to histology, age, tumor size, excision volume, reexcision, and total dose.RESULTS: FMS was positive, greater than 0–2 mm, greater than 2–5 mm, and greater than 5 mm, and no residual tumor on reexcision in 21%, 20%, 17%, 14%, and 28% of cases, respectively. At 12 years, Kaplan–Meier local failure rates were 17% for FMS positive, 9% for FMS greater than 0–2 mm, 5% for FMS greater than 2–5 mm, 0% for FMS greater than 5 mm, and 6% for specimens without evidence of residuum on reexcision (P = 0.009). Patients 45 years old and younger had a 12‐year local failure rate of 15% whereas patients older than 45 years had a 12‐year local failure rate of 6% (P = 0.01). On multivariate analysis, young age (P = 0.03) predicted increased local failure rate, whereas margins that were less than or equal to 2 mm or positive predicted late (> 5 years) but not early (≤ 5 years) recurrence (P = 0.003).CONCLUSIONS: Graded tumor bed dose escalation in response to FMS results in very low rates of local failure over the first 5 years for all FMS categories. However, tumors with close/positive margins have significantly increased local failure rates after 5 years of follow‐up even with increased radiation boost dose. In addition, graded tumor bed dose escalation does not fully overcome the adverse influence of young age. Cancer 2003;97:30–9. © 2003 American Cancer Society.DOI 10.1002/cncr.10981

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