Key Differences Between Histotripsy and Radiation Therapy

Mechanism of Action: Histotripsy uses focused ultrasound waves to mechanically destroy tissue through cavitation, without heat or ionizing radiation. In contrast, radiation therapy works by causing direct DNA damage through double-stranded breaks and indirect damage via reactive oxygen species.

Treatment Profile:

• Histotripsy: Non-invasive, non-thermal, no incisions or needles, typically outpatient single-session treatment with quick recovery

• Radiation Therapy: Can involve substantial radiation exposure, multiple fractions often needed, and toxicity can limit treatment volumes and locations

  
  

Precision and Tissue Preservation: Histotripsy can selectively destroy tumor tissue while sparing adjacent structures like blood vessels and bile ducts, with the advantage that it remains effective even near blood vessels (unlike thermal ablation which can be less effective in those situations).

Side Effects: Histotripsy doesn't cause common radiation side effects like burns or hair loss, nor does it trigger widespread symptoms like chemotherapy-related fatigue and nausea.

The Abscopal Effect: Important Differences

With Radiation Therapy: The abscopal effect occurs when radiation treatment shrinks not only the targeted tumor but also leads to shrinkage of untreated tumors elsewhere in the body, with the immune system playing an important role. However, the effect is extremely rare with radiation alone, as abscopal effects are often blocked by the immunosuppressive microenvironment inside the irradiated tumor. The effect has become more common when combined with immune checkpoint inhibitors.

With Histotripsy: The research suggests histotripsy may produce a stronger abscopal effect compared to radiation. In mouse studies comparing histotripsy to radiofrequency ablation and radiation therapy, researchers found no evidence for substantial T-cell infiltration at distal sites with radiation therapy, while histotripsy showed increased levels of antigen-specific CD8+ T cells in untreated tumors.

Why the Difference? During histotripsy treatment, tumors are liquefied, resulting in release of tumor antigens that generate an immune response in which the body attacks and destroys tumors located elsewhere. Importantly, histotripsy spares antigens—the proteins your immune system needs to identify and fight cancer—unlike treatments that use heat and X-rays.

The mechanical destruction of tissue by histotripsy appears to preserve tumor antigens better than the thermal or radiation-induced destruction, potentially leading to a more robust immune response against distant metastases.

Disclaimer: This article is for informational purposes only and is not medical advice. Always consult with qualified healthcare professionals about your individual situation and treatment options. Histotripsy is currently FDA-approved only for liver tumors. The system has not been evaluated by FDA for change in outcomes such as survival rates.