Repeated inductive heating using a sintered MgFe2O4 needle for minimally invasive local control in breast cancer therapy.

Purpose: This study investigated the efficacy of repeated thermotherapy for breast cancer utilising a novel sintered MgFe(2)O(4) needle and alternating current (AC) magnetic field in xenograft animal models mimicking human breast cancer.

Materials And Methods: A sintered MgFe(2)O(4) needle and an apparatus to apply an AC magnetic field were prepared for this study. Animals bearing BT-474 tumours (mean (+/-standard deviation) volume, 471 +/- 153 mm(3)) were divided into four groups. A sintered MgFe(2)O(4) needle (length, 5 mm) was placed in the centre of each tumour. An AC magnetic field (amplitude, 4 kA/m; 2 kW; 540 kHz) was applied for 10 min once, twice or three times for the first, second and third groups, respectively, and was not applied for the control group. Temperature during treatment and tumour volume 8 weeks after first treatment were assessed.

Results: Maximum tumour temperature tended to increase in repeated-application groups: group 1, 59.2 +/- 4 degrees C; group 2, 58.9 +/- 3.3 degrees C and 61.2 +/- 8.9 degrees C for the first and second applications; and group 3, 60.4 +/- 4.6 degrees C, 62.1 +/- 7.8 degrees C and 71.1 +/- 6.1 degrees C for the first, second and third applications. Tumour volumes in control, groups 1, 2 and 3 at 8 weeks after treatment were 3633 +/- 2478 mm(3), 3240 +/- 1031 mm(3), 1252 +/- 1289 mm(3) and 0 mm(3), respectively. Tumours were significantly smaller in group 3 than in the control and group 1 at 8 weeks.

Conclusions: The efficacy of repeated inductive heating utilising a sintered MgFe(2)O(4) needle was demonstrated. Thermotherapy using the present method may offer an effective non-surgical treatment for human breast cancer.