A phase I/II trial of intraoperative breast radiotherapy in an Asian population: 10-year results with critical evaluation

Abstract

Although phase III trials have been published comparing whole breast irradiation (WBI) with accelerated partial breast irradiation (APBI) using intraoperative radiotherapy (IORT), long-term follow-up results are lacking. We report the 10-year follow-up results of a prospective phase I/II clinical trial of IORT. The inclusion criteria were as follows: (i) tumor size <2.5 cm, (ii) desire for breast-conserving surgery, (iii) age >50 years, (iv) negative margins after resection and (v) sentinel lymph node-negative disease. A single dose of IORT (19-21 Gy) was delivered to the tumor bed in the operation room just after wide local excision of the primary breast cancer using a 6-12 MeV electron beam. Local recurrence was defined as recurrence or new disease within the treated breast and was evaluated annually using mammography and ultrasonography. A total of 32 patients were eligible for evaluation. The median patient age was 65 years and the median follow-up time was 10 years. Two patients experienced local recurrence just under the nipple, out of the irradiated field, after 8 years of follow-up. Three patients had contralateral breast cancer and one patient experienced bone metastasis after 10 years of follow-up. No patient experienced in-field recurrence nor breast cancer death. Eight patients had hypertrophic scarring at the last follow-up. There were no lung or heart adverse effects. This is the first report of 10-year follow-up results of IORT as APBI. The findings suggest that breast cancer with extended intraductal components should be treated with great caution.

Keywords: APBI; IORT; breast cancer; local control; long follow-up.

© The Author(s) 2020. Published by Oxford University Press on behalf of The Japanese Radiation Research Society and Japanese Society for Radiation Oncology.

Figures

Fig. 1.

Local control rate.

Fig. 2.

Dynamic contrast-enhanced MRI and pathological images of the primary tumor of patient #2 in Table 2 who had recurrence after 8 years follow-up. Axial view of delayed-phase (~5 min after gadolinium injection) T1-weighted image (left) shows linear enhancement toward nipple. She was diagnosed to have invasive cT1c tumor with extensive intraductal components. However, the resected specimen had intraductal components only (right).

Fig. 3.

Dynamic contrast-enhanced MRI images of patients #1 and #2 (Table 2) at first presentation and MRI or CT image at recurrence. (A) Sagittal view of delayed-phase (~5 min after gadolinium injection) T1-weighted image (T1WI) of primary tumor at first presentation. Patient #1: a small enhanced nodule (↑) is captured in the nipple direction which indicates the EIC of the primary tumor (*). Patient #2: a 1.2 cm enhanced tumor is captured. In this view, the EIC is not completely clear, but as shown in Fig. 2, the axial view is suspected of having EIC. (B) Delayed-phase T1WI (achieved in the prone position) of patient #1 at recurrence and contrast enhanced CT image (achieved in the supine position) of patient #2 at recurrence. Enhanced tumor just under the nipple is captured in both patients.