Focused microwave thermotherapy for preoperative treatment of invasive breast cancer: a review of clinical studies.

BACKGROUND: Preoperative focused microwave thermotherapy (FMT) is a promising method for targeted treatment of breast cancer cells. Results of four multi-institutional clinical studies of preoperative FMT for treating invasive carcinomas in the intact breast are reviewed. METHODS: Externally applied wide-field adaptive phased-array FMT has been investigated both as a preoperative heat-alone ablation treatment and as a combination treatment with preoperative anthracycline-based chemotherapy for breast tumors ranging in ultrasound-measured size from 0.8 to 7.8 cm. RESULTS: In phase I, eight of ten (80%) patients receiving a single low dose of FMT prior to receiving mastectomy had a partial tumor response quantified by either ultrasound measurements of tumor volume reduction or by pathologic cell kill. In phase II, the FMT thermal dose was increased to establish a threshold dose to induce 100% pathologic tumor cell kill for invasive carcinomas prior to breast-conserving surgery (BCS). In a randomized study for patients with early-stage invasive breast cancer, of those patients receiving preoperative FMT at ablative temperatures, 0 of 34 (0%) patients had positive tumor margins, whereas positive margins occurred in 4 of 41 (9.8%) of patients receiving BCS alone (P = 0.13). In a randomized study for patients with large tumors, based on ultrasound measurements the median tumor volume reduction was 88.4% (n = 14) for patients receiving FMT and neoadjuvant chemotherapy, compared with 58.8% (n = 10) reduction in the neoadjuvant chemotherapy-alone arm (P = 0.048). CONCLUSIONS: Wide-field adaptive phased-array FMT can be safely administered in a preoperative setting, and data from randomized studies suggest both a reduction in positive tumor margins as a heat-alone treatment for early-stage breast cancer and a reduction in tumor volume when used in combination with anthracycline-based chemotherapy for patients with large breast cancer tumors. Larger randomized studies are required to verify these conclusions.

Focused microwave phased array thermotherapy for ablation of early-stage breast cancer: results of thermal dose escalation.

BACKGROUND: Tumor ablation as a means of treating breast cancer is being investigated. Microwave energy is promising because it can preferentially heat high-water-content breast carcinomas, compared to adipose and glandular tissues. METHODS: This is a prospective, multicenter, nonrandomized dose-escalation study of microwave treatment. Thermal dose was measured as (1) thermal equivalent minutes (cumulative equivalent minutes; CEM) of treatment relative to a temperature of 43 degrees C and (2) peak tumor temperature. Microwaves were guided by an antenna-temperature sensor placed percutaneously into the tumor. Outcomes measured were pathologic response (tumor necrosis) side effects. RESULTS: Twenty-five patients (mean age, 57 years) were enrolled. The mean tumor diameter was 1.8 cm. Tumoricidal temperatures (>43 degrees C) were reached in 23 patients (92%). Tumor size was unchanged after thermotherapy (P = not significant). Pathologic necrosis was achieved in 17 (68%) patients. Complete necrosis of the invasive component was achieved in two patients. One hundred forty CEM is predictive of a 50% tumor response, and 210 CEM is predictive of a 100% tumor response (P =.003). Univariate linear regression predicts that peak tumor temperatures of 47.4 degrees C and 49.7 degrees C cause a 50% tumor response and a 100% tumor response, respectively. CONCLUSIONS: Thermotherapy causes tumor necrosis and can be performed safely with minimal morbidity. The degree of tumor necrosis is a function of the thermal dose. Future studies will evaluate the impact of high doses of thermotherapy on margin status and complete tumor ablation.

Focused microwave phased array thermotherapy for primary breast cancer.

BACKGROUND: A pilot safety study of focused microwave phased array thermotherapy in the treatment of primary breast carcinomas was conducted. METHODS: Ten patients with breast carcinomas beneath the skin surface that ranged in maximal clinical size from 1 to 8 cm (mean, 4.3 cm) were treated with the breast compressed in the prone position. We planned to deliver a tumor thermal dose equivalent to 60 minutes at 43 degrees C. Breast imaging and pathology data were used to assess efficacy. RESULTS: For the 10 patients, the mean tumor equivalent thermal dose was 51.7 minutes, the mean peak tumor temperature was 44.9 degrees C, and the mean treatment time was 34.7 minutes. Ultrasound imaging demonstrated a significant reduction in tumor size (mean, 41%) 5 to 18 days after thermotherapy in 6 (60%) of 10 patients. A significant tumor response on the basis of reduction in tumor size or significant tumor cell kill occurred in 8 (80%) of 10 patients. CONCLUSIONS: With sufficient skin cooling, delivery of focused microwave phased array thermotherapy is safe in treating breast carcinomas when used alone, and some potential efficacy was demonstrated at the tumor thermal doses administered. Increased tumor thermal dose efficacy studies in larger patient populations for improved breast conservation should be investigated.