To Evaluate the Safety and Efficacy of Histotripsy for the Symptom Relief of Inoperable Abdominal Tumors

When solid tumors cause pain or other symptoms due to compression or mass effect, and surgical resection is not feasible, the primary clinical recommendation for malignant tumors is chemotherapy or local radiotherapy to delay tumor progression, improve quality of life, and prolong survival. For benign tumors, however, there are no other effective treatment options.

For unresectable tumors, local ablation techniques such as Radiofrequency Ablation (RFA) are considered as potentially curative alternatives. However, the main drawback of RFA is its invasive nature, which may sometimes cause bleeding or tumor seeding along the needle tract. Moreover, when tumors are adjacent to blood vessels, the efficacy of ablation is often compromised. Therefore, its application is currently limited mainly to small liver cancers.

Histotripsy is an emerging tumor ablation technology that utilizes High-Intensity Focused Ultrasound (HIFU) for non-invasive treatment of solid tumors. The mechanism involves physically focusing ultrasound energy to a precise location within biological tissue, where high-power and low-frequency ultrasound creates mechanical disruption (histotripsy) and cavitation effects to fragment the tissue and destroy tumor cells. Under real-time ultrasound imaging guidance and using multiple appropriate scanning strategies, the focal point moves within the treatment area to ablate tumor tissue. The destroyed tumor tissue is gradually absorbed by the body. Since this method does not require needle insertion or electrode placement and does not involve radiation or thermal injury, it is considered non-invasive and holds the potential to overcome current limitations of ablation techniques.

This clinical trial utilizes the Edison System developed by HistoSonics Inc., USA. The technology underwent its first multicenter Phase I human trial in 2018, treating 11 patients with advanced, multifocal liver tumors who were ineligible for surgical resection. All targeted liver tumors were successfully ablated with no device-related adverse events. Based on these results, a global multicenter, single-arm, non-randomized prospective trial (HOP4LIVER trial) was initiated in 2021 to assess the efficacy and safety of this system in treating primary and metastatic liver tumors. Imaging was conducted within 36 hours post-treatment to confirm technical success, and patients were monitored for 30 days, during which only three treatment-related adverse events occurred. A six-month post-operative evaluation showed a success rate of 95.5%. Consequently, the system received FDA De Novo approval in October 2023.

According to the HOPE4LIVER clinical trial, this treatment has demonstrated significant efficacy across various cancer types, including colorectal cancer with intrahepatic metastases (38%), pancreatic cancer (19%), and breast cancer (15%). Other cases included melanoma, neuroendocrine tumors, lung cancer, hemangiopericytoma, ovarian cancer, and bronchial cancer, indicating the potential applicability of this technique for other tumor types.

As the system has not yet been registered or approved by the Taiwan Ministry of Health and Welfare, investigators propose a research project targeting patients with intra-abdominal benign or malignant tumors who are unsuitable for surgical resection and are experiencing tumor-related symptoms. investigators aim to apply HIFU histotripsy for tumor ablation, monitor for any post-operative complications and symptom relief, assess tumor response after one month, and follow up on survival rates to evaluate the clinical feasibility and safety of this system.