The treatment of tumors with focused ultrasound can stimulate the immune system and potentially enhance the body’s ability to identify and attack cancer.

Courtesy of the National Cancer Institute

When a tumor is ablated, the exposed proteins and cellular debris can act as antigens that may trigger an increased immune response to the tumor, both locally and at distant metastases. Furthermore, thermal ablation may cause local inflammation, stimulate the recruitment of immune effector cells, and activate anti-tumor adaptive immunity, all of which can increase the body’s ability to fight cancer.

Immunomodulation through focused ultrasound could noninvasively augment and enhance existing chemotherapy and immunotherapy treatments for the management of tumors. Several different ultrasound modalities, including thermal ablation, mechanical ablation (histotripsy), and mild hyperthermia, have been shown to trigger an immune response in the body by releasing antigens and danger signals from cancer cells. The effect of the focused ultrasound treatment appears to depend on the ultrasound modality used and the type of tumor being treated.

There are several proposed methods by which focused ultrasound may induce an immunotherapeutic response. Focused ultrasound treatments may stress or damage tumor cells, causing the release of danger-associated molecular patterns (DAMPs) such as heat shock proteins (HSP60 and 70), calreticulin, and ATP, which activate the innate immune system, increase the immunogenicity of the tumor, and improve immune cell trafficking to the tumor. Focused ultrasound may also mitigate tumor-induced immunosuppression by decreasing levels of immunosuppressive cytokines (e.g., VEGF, TGF-ß1, and TGF-ß2). Cancer cell destruction creates tumor debris that act as antigens for antigen presenting cells, enhancing both the innate and adaptive immune response. Mechanical focused ultrasound treatments can disrupt the extracellular matrix and make it easier for immune cells to infiltrate the tumor, particularly when there is dense stroma (e.g., pancreatic cancer).

Despite their promise, these effects may not be strong enough to control tumor growth on their own. Researchers are investigating the use of focused ultrasound in combination with other cancer treatments such as immunotherapeutics and CAR-T cells. Because of focused ultrasound’s ability to penetrate the blood brain barrier and other dense stroma, it is an attractive modality to potentially boost the delivery and effectiveness of immunotherapies in notoriously difficult to treat cancers. Additionally, research into immunotherapies has shown that they are more successful in patients who have a baseline immune response to the cancer, which focused ultrasound may be poised to provide.

The Focused Ultrasound Foundation has put together a landscape analysis of the focused ultrasound and immunooncology landscape as well as an annotated bibliography.


Novel Advances in Breast Cancer Treatment with David Brenin, MD | University of Virginia School of Medicine, Gregory Czarnota, MD, PhD | Sunnybrook Health Sciences Centre, Sunnybrook Research Institute, Ying Meng, MD | University of Toronto, Natasha Sheybani, PhD | University of Virginia

Fireside Chat: Focused Ultrasound for Cancer Immunotherapy with Jill O’Donnell-Tormey, PhD | Cancer Research Institute, Theresa LaVallee, PhD | Parker Institute for Cancer Immunotherapy, Jessica Foley, PhD | Focused Ultrasound Foundation

Immunotherapy for Brain Tumors by Michael Lim, MD | Johns Hopkins University

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Click here for additional references from PubMed.