Impact of boost irradiation with surgically placed radiopaque clips on local control in breast-conserving therapy.

BACKGROUND: The purpose of this study was to determine whether boost irradiation relying on radiopaque clips placed surgically around the resected margin of breast cancer contributes to increasing the local control rate in patients with close or positive margins in breast-conserving therapy (BCT).

METHODS: Among 837 patients with breast cancer who underwent BCT between November 1987 and December 1998, 181 patients with close or positive surgical margins received boost irradiation following conventional tangential whole breast irradiation. Since 1994, four radiopaque clips were surgically placed around the resected margin of the breast cancer in 155 patients treated with wide excision. The four clips were clearly and accurately identified with a CT-simulator (CT-S). The boost irradiation field was automatically determined with a safety margin of 3 cm according to one-to-one correspondence of radiopaque clips to pathologically close or positive surgical margins. In the remaining 26 patients treated before 1994, the boost irradiation field was determined according to the skin tattoo of the primary tumor.

RESULTS: The median follow-up period of the 155 patients receiving the radiopaque clips was 42 months (range: 19 to 78), and that of the 26 patients without the clips was 87 months. Local recurrence was observed in two of the 155 patients who underwent boost irradiation using the radiopaque clips 39 and 54 months after the surgery, while 4 of the 26 patients developed local recurrence 14, 23, 51, and 76 months after BCT. In three of the four patients without the clips developing local recurrences, local recurrences were observed at the margin of the boost irradiation field. The 5-year local recurrence-free survival rate of patients who received boost irradiation with the radiopaque clips was 97%, and that of patients without the clips was 88%. The difference of local recurrence-free survival rates between the patients with and without the clips was significant (p<0.05).

CONCLUSION: Surgically placed radiopaque clips appear to be useful for determining adequate boost field in the BCT using the CT-S and help increase the local control rate.