Eur Radiol (2008) 18: 1431–1441 DOI 10.1007/s00330-008-0906-0 I N T E RV E N T I O N A L A. C. Schmitz D. Gianfelice B. L. Daniel W. P. Th. M. Mali M. A. A. J. van den Bosch Image-guided focused ultrasound ablation of breast cancer: current status, challenges, and future directions Received: 26 September 2007 Revised: 4 December 2007 Accepted: 15 January 2008 Published online: 20 March 2008 # The Author(s) 2008 A. C. Schmitz . W. P. T. M. Mali . M. A. A. J. van den Bosch Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands D. Gianfelice Department of Radiology, University Health Network C/O Toronto General Hospital, Toronto, Canada B. L. Daniel . M. A. A. J. van den Bosch Department of Radiology, Stanford University, Stanford, CA, USA M. A. A. J. van den Bosch (*) Department of Radiology, Lucas MR Imaging Center, 1201 Welch Road, Stanford, CA, 94305-5488, USA e-mail: mbosch@stanford.edu Tel.: +1-650-4987550 Fax: +1-650-7367925 Abstract Image-guided focussed ul- trasound (FUS) ablation is a non- invasive procedure that has been used for treatment of benign or malignant breast tumours. Image-guidance dur- ing ablation is achieved either by using real-time ultrasound (US) or magnetic resonance imaging (MRI). The past decade phase I studies have proven MRI-guided and US-guided FUS ablation of breast cancer to be technically feasible and safe. We provide an overview of studies asses- sing the efficacy of FUS for breast tumour ablation as measured by per- centages of complete tumour necrosis. Successful ablation ranged from 20% to 100%, depending on FUS system type, imaging technique, ablation protocol, and patient selection. Spe- cific issues related to FUS ablation of breast cancer, such as increased treat- ment time for larger tumours, size of ablation margins, methods used for margin assessment and residual tu- mour detection after FUS ablation, and impact of FUS ablation on senti- nel node procedure are presented. Finally, potential future applications of FUS for breast cancer treatment such as FUS-induced anti-tumour im- mune response, FUS-mediated gene transfer, and enhanced drug delivery are discussed. Currently, breast- conserving surgery remains the gold standard for breast cancer treatment. Keywords Image-guided therapy . Focussed ultrasound . Breast cancer . Tumour ablation . Magnetic resonance imaging Evolution of breast cancer treatment Breast cancer is the most frequently occurring malignant disease and leading cause of cancer-related death in women in the Western world. The number of new cases and deaths from breast cancer for women in the US in 2007 was estimated to be 178,480 and 40,460, respectively [1]. Radical mastectomy, i.e., breast amputation with or without excision of the pectoral muscle, has long been accepted as an appropriate therapy for breast cancer. This treatment was based on the theory of Dr. William Halsted that aggressive local therapy for control of breast cancer, chest wall and regional lymph nodes would have a substantial benefit on survival [2]. In the 1970s, an increased understanding of the natural history of breast cancer resulted in the use of breast-conserving surgery, i.e., local excision as proposed by Dr. Bernard Fisher, for treatment of breast cancer [3, 4]. After results of randomized studies demonstrated similar survival rates for both treatment groups, breast-conserving surgery combined with radiotherapy became standard treatment for patients with localized breast cancer [3]. Parallel to this development, nationwide breast cancer screening programmes were implemented in many Western countries in the 1990s, resulting in an increased proportion