Abstract PO2-18-07: Ultrasound – guided Interstitial Laser therapy for Stage I Breast Cancer: a phase 2 trial
Authors: Matsumoto Danielle , Bromberg Silvio , Corpa Marcus , Garcia Rodrigo , Mariotti Guilherme , Rudner Monica , Waitzberg Angela , Nazário Afonso , Facina Gil 
Published: May 2024

Abstract
Background: Screening programs are changing the scope of breast cancer, with a growing number of patients diagnosed at a nearly stage. The current standard treatment (breast conservation and radiation therapy) offers an excellent prognosis for these patients. Besides tumor removal, other techniques can be used to destroy a mass in place. A range of minimally invasive techniques holds promise on local breast tumor ablation (i.e. thermotherapy, cryotherapy, and irreversible electroporation). Previous studies with Interstitial laser thermotherapy (ILT) for breast cancer report mean ablation rates between 33% to 87%. Most common cited causes for failure are equivocal tumor size estimation, inadequate technique and the learning curve. Objective: Improve the ILT technique and achieve better ablation rates through the evaluated procedure. Methods: A prospective study with 15 patients with Stage I invasive breast cancer, presented as a unique lesion as inclusion criteria was conducted. MRI and US were used to estimate the primary tumor volume and rule out multicentric/multifocal disease. ILT ablation was performed using an Echolaser unit (Elesta) through percutaneous laser optical fibers with a US-guided insertion in the lesion center. All procedures were performed under local anesthesia and sedation. The post procedure image reevaluation included an immediate US after the ablation and a new MRI about 3 hours after the procedure. The definitive proposed surgical treatment was carried out 8-13 days after the ILT ablation. Results: Eighteen patients were included in the study, of whom 14 (with 15 lesions) completed the protocol. The mean tumor size measured by MRI was 13.7 (4-20) mm.
The mean treatment time was 10.1 minutes and all patients went home the same day, reporting only mild (78%) or moderate (22%) pain, controlled with analgesics.
The mean ablation index, evaluated by H&E and CK8/18, was 61,5% (0 -93%) and when only tumors under 15 mm were considered the mean ablation index was 75% (30%-93%).
The MRI performed after ablation procedure showed a large area of edema around the clip in all cases. The sensitivity and specificity to detect residual tumors were 1.0 and 0.84, respectively, when the residual tumors were larger than 15% of the original tumor size . Conclusions: These preliminary results suggest that laser therapy can eliminate viable neoplastic tissue in vivo. To achieve better results, standardization in patient selection, power and energy applied, should be considered.
There are several advantages of ILT for breast cancer treatment, including preserving the structure and function of breast, no bleeding, no scaring and no radiation. More studies refining the technique should be conducted to allow the implementation of ILT as an alternative to surgical treatment in early breast cancer.
Citation Format: Danielle Matsumoto, Silvio Bromberg, Marcus Corpa, Rodrigo Garcia, Guilherme Mariotti, Monica Rudner, Angela Waitzberg, Afonso Nazário, Gil Facina. Ultrasound – guided Interstitial Laser therapy for Stage I Breast Cancer: a phase 2 trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-18-07.