Interstitial laser thermotherapy (ILT) of breast cancer - Methodology and immunological responce

Abstract: Interstitial laser thermotherapy (ILT) is an attractive form of local therapy against cancer because of its anti-tumor immune activity. The aim of this work was to evaluate ILT in breast cancer with respect to technique, changes in tissue immunocompetent cells and effect on prognosis. The method is dependent on accurate assessment of the tumor, and another aim was therefore to evaluate if MRI is better than ultrasound (US) for imaging. Twenty-four patients were treated with ILT, followed by surgical resection about two weeks later. Pre-treatment US estimated the average tumor diameter to be 14 (range 5-35) mm. ILT was performed at 48Cº for 30 minutes under local anesthesia. Three patients were radically treated with ILT and the average tumor necrosis was 33% (0-100). Microscopic examination of the resected specimen showed that the average tumor diameter was 23 (range 7-55) mm. US underestimation of tumor size contributed to the rather poor local efficacy. ILT-induced changes in tissue immunocompetent cells were assessed by comparing findings in pre-treatment core biopsies and post-treatment pathologic specimens (paired comparisons). Changes in regional lymph nodes were assessed by comparison with a control group undergoing surgery only. ILT induced a significant increase of mature dendritic cells, B lymphocytes and macrophages at the tumor border and of cytotoxic T lymphocytes and macrophages within the tumor. In the lymph nodes there was a significant decrease in T regulatory cells. Most of these changes are considered to have a favorable prognostic value. Follow up after ILT was 116 (91-136) months. No patient had local recurrence of disease. Five patients developed distant metastases, and three of them have died. The number of cytotoxic T cells within the tumor was higher in patients with recurrence than in patients without recurrence. Patients with recurrent disease had a lower number of NK cells in tumor-free lymph nodes than patients without recurrence. Possible clinical benefit of ILT should be examined in a larger and less heterogenous patient population. MRI has been used preoperatively in most patients (68%) with breast cancer in Iceland during 2007-2009, in addition to mammography and US. Invasive tumor was measurable on all imaging methods in 267 patients. The study revealed that MRI and US both under- and overestimated size. Routine MRI was not shown to be a better radiological method than US for estimating tumor size in local ablative therapy.