Today, one of the most promising questions in oncology is not only how can we eliminate a tumor?, but also how can we teach the immune system to recognize and fight cancer more effectively? This is where the combination of cryoablation and immunotherapy becomes especially interesting.

Cryoablation is a minimally invasive technique that destroys tumor tissue by freezing it to lethal temperatures. Immunotherapy, on the other hand, seeks to activate or restore the body’s immune response against cancer. When these two strategies are combined, the result may go beyond local tumor control. It may create an opportunity to transform the treated tumor into a source of immune activation.

 

What makes cryoablation different?

Cryoablation belongs to a broader group of image-guided ablation therapies used to treat solid tumors. These techniques are usually performed percutaneously, meaning that physicians insert specialized probes through the skin and guide them toward the tumor using imaging technologies such as ultrasound, computed tomography, or magnetic resonance imaging.

Compared with surgery, percutaneous ablation may offer lower morbidity, shorter recovery times, and precise treatment of selected lesions. However, cryoablation has a unique biological feature: unlike surgery, which removes the tumor from the body, cryoablation destroys tumor cells while leaving the damaged tumor material in place. This is important because the remaining tumor fragments can expose the immune system to tumor antigens that were previously hidden.

 

Freeze–thaw cycles and tumor destruction

The basic principle of cryoablation is simple, but biologically powerful. A cryoprobe is inserted into or near the tumor, where it produces extremely low temperatures. Modern devices commonly use argon gas to generate rapid cooling through the Joule-Thomson effect.

The tumor then undergoes freeze–thaw cycles, which cause direct cellular injury. During freezing, ice crystals form both inside and outside the cells. At slower freezing rates, extracellular ice draws water out of the cells, causing dehydration, shrinkage, and damage to membranes and organelles. At faster freezing rates, intracellular ice forms before the cell can adapt, producing severe mechanical damage from within. This combination of osmotic stress and ice-crystal injury can lead to extensive tumor cell death.

The thawing phase is just as important as the freezing phase. When the tissue warms again, small ice crystals can merge into larger crystals through a process known as recrystallization. These larger crystals cause additional damage to cell membranes and internal cellular structures.

Cells that became dehydrated during freezing may suddenly take up water during thawing, swell, and rupture. For this reason, many cryoablation protocols use more than one freeze–thaw cycle. The goal is to maximize tumor destruction while limiting damage to surrounding healthy tissue. However, the ideal number of cycles, freezing duration, and target temperature may vary depending on tumor type, tissue location, vascularization, and tumor volume.

 

How tumor cells die matters

From an immunological perspective, the way tumor cells die is extremely important. Cells located in the central zone of cryoablation are usually exposed to the most lethal temperatures and tend to die by necrosis. Necrotic cell death releases intracellular contents into the surrounding tissue, including tumor antigens and danger signals.

These signals can alert immune cells, especially dendritic cells, which are responsible for capturing antigens and presenting them to T cells. In contrast, cells located at the outer edge of the ablation zone may experience sublethal injury and die by apoptosis. Apoptosis is usually less inflammatory and, in some contexts, may even contribute to immune tolerance instead of immune activation. For this reason, the balance between immunogenic necrosis and tolerogenic apoptosis may influence whether cryoablation stimulates or weakens an antitumor immune response.

One of the most fascinating aspects of cryoablation is that it may act as an in vivo vaccination tool. When the tumor is frozen and damaged but remains inside the body, it can release a broad collection of patient-specific tumor antigens.

These antigens may be captured by dendritic cells, transported to the tumor-draining lymph nodes, and presented to T cells. If the immune context is favorable, this process can generate effector T cells capable of recognizing cancer cells. In other words, cryoablation may not only destroy tumor cells locally, but also help reveal the biological “identity” of the cancer to the immune system. This concept has important implications beyond the treatment of a single isolated lesion.

 

Antitumor immune memory

Preclinical studies have shown that cryoablation can induce tumor-specific immune protection. In some mouse models, animals treated with cryoablation developed resistance to tumor re-challenge. This means that when the same type of tumor was introduced again, the immune system was better prepared to reject it.

Importantly, this protection appeared to be tumor-specific, because the same animals remained susceptible to unrelated tumor cell lines. This suggests that cryoablation can generate immune memory directed against antigens from the treated tumor. Other studies showed that T cells taken from tumor-draining lymph nodes after cryoablation could reduce metastatic burden when transferred into other tumor-bearing animals, reinforcing the idea that cryoablation can initiate systemic antitumor immunity.

Despite its immune-stimulating potential, cryoablation alone is usually not sufficient to eradicate metastatic disease. The immune response generated by local tumor freezing may be real, but its magnitude and duration are often not strong enough.

Tumors are highly skilled at suppressing immune attack. They can exclude T cells, inhibit dendritic cell maturation, express checkpoint molecules, recruit immunosuppressive populations, and create a microenvironment that turns immune activation into immune exhaustion. This is why combining cryoablation with immunotherapy becomes so relevant. Cryoablation may provide the antigenic source and inflammatory spark, while immunotherapy may amplify, guide, and sustain the immune response.

One important combination strategy involves Toll-like receptor agonists, known as TLR agonists. TLRs are receptors mainly expressed by innate immune cells such as dendritic cells, macrophages, and neutrophils. These receptors recognize danger signals and microbial patterns, activating inflammatory pathways that can promote immune responses.

When TLR agonists are combined with cryoablation, they may help dendritic cells mature and present tumor antigens more effectively. In preclinical tumor models, cryoablation combined with TLR9 stimulation improved survival and increased dendritic cell maturation markers such as CD80 and CD86. Another model using imiquimod, a TLR7 agonist, showed greater protection when combined with cryoablation than with either treatment alone. This supports the idea that cryoablation may need an immune adjuvant to become a stronger antitumor vaccine.

Another promising avenue is the combination of cryoablation with adoptive cell therapies. Dendritic cell-based therapies are especially logical because these cells are the main antigen-presenting cells of the immune system. After cryoablation releases tumor antigens, dendritic cells can capture them and present them to T cells.

Some preclinical models combining cryoablation with intratumoral dendritic cell transfer have shown improved survival and resistance to tumor re-challenge. Natural killer cells, cytokine-induced killer cells, and γδ T cells are also being explored because they can recognize and destroy cancer cells through mechanisms that do not always depend on classical antigen presentation. This may be especially useful in tumors that reduce MHC expression to escape recognition by T cells.

Immune checkpoint inhibitors are another key partner for cryoablation. Drugs targeting CTLA-4, PD-1, or PD-L1 work by releasing the immune “brakes” that limit T-cell activity. However, these treatments often work best when there is already a pre-existing antitumor immune response.

If a tumor is immunologically “cold,” meaning it has low T-cell infiltration or poor antigen presentation, simply releasing the brakes may not be enough. Cryoablation could help address this problem by generating tumor antigen release and local inflammation. In preclinical models, combining cryoablation with CTLA-4 blockade improved survival compared with either treatment alone. Early clinical studies in breast cancer and melanoma have suggested that this combination may be tolerable and show signs of efficacy, although more research is still needed.

 

Figure 1. Cryoablation damages tumor cells through freeze–thaw cycles, releasing tumor antigens and danger signals. These signals may help dendritic cells activate T cells and support a broader antitumor immune response.

 

Local treatment with systemic potential

This concept becomes even more powerful when considering metastatic disease. In some cases, treating one tumor lesion locally may help generate immune responses that travel through the body and affect distant, untreated lesions. This phenomenon is often known as the abscopal effect.

Cryo-immunotherapy can be understood as a strategy in which local cryoablation releases tumor antigens, dendritic cells process those antigens, T cells become activated in tumor-draining lymph nodes, and systemic immunotherapy helps those T cells function more effectively against both the treated tumor and distant tumor lesions.

Even with this potential, cryo-immunotherapy is not a universal solution. Several critical questions remain unresolved. Which tumor should be treated: the primary tumor or a metastasis? How much tumor tissue should be frozen? Which temperature and freeze–thaw protocol best promotes immune activation instead of immune tolerance?

Should one lesion be treated multiple times, or should several lesions be treated over time? What is the best timing for administering immunotherapy in relation to cryoablation? These questions matter because the immune response does not depend only on destroying the tumor. It also depends on how tumor cells die, which antigens are released, which immune cells are present, and whether the surrounding microenvironment supports or blocks immune activation.

Personalization is also essential. Two patients with the same cancer diagnosis may have very different immune landscapes. One tumor may have a high mutational burden and many recognizable neoantigens, while another may be less immunogenic. One patient may have a strong baseline immune capacity, while another may show immune exhaustion or suppression due to advanced disease or previous treatments.

For this reason, it is important to analyze blood and tissue samples before and after treatment to understand each patient’s immune profile and adapt therapy accordingly. Tumors can also vary within the same patient, meaning that one metastasis may respond while another escapes. Biopsies from treated and resistant lesions may therefore help guide future therapeutic decisions.

Cryoablation is much more than a freezing technique. It is a local therapy with the potential to influence systemic immunity. By destroying tumor tissue in place, cryoablation can release tumor antigens, stimulate inflammatory signals, and create an opportunity for immune recognition.

However, this immune response is often incomplete on its own. That is why the future of cryoablation will likely depend on rational combinations with immunotherapies such as TLR agonists, dendritic cell strategies, NK cells, CIK cells, γδ T cells, and checkpoint inhibitors. The goal is not simply to freeze a tumor, but to convert local tumor destruction into a personalized immune event. If carefully optimized, cryo-immunotherapy could become an important part of precision oncology, especially for patients with metastatic disease, where both local control and systemic immune activation are urgently needed.

 

Main reference:

Yakkala, C., Chiang, C. L., Kandalaft, L., Denys, A., & Duran, R. (2019). Cryoablation and Immunotherapy: An Enthralling Synergy to Confront the Tumors. Frontiers in immunology, 10, 2283. https://doi.org/10.3389/fimmu.2019.02283

 

Other references:

Sidana A. (2014). Cancer immunotherapy using tumor cryoablation. Immunotherapy, 6(1), 85–93. https://doi.org/10.2217/imt.13.151

Medlej, Z. A. A., Medlej, W., Slaba, S., Torrecillas, P., Cueto, A., Urbaneja, A., Garrido, A. J., & Lugnani, F. (2023). Cryoablation and Immunotherapy: An Enthralling Synergy for Cancer Treatment. Current oncology (Toronto, Ont.), 30(5), 4844–4860. https://doi.org/10.3390/curroncol30050365