Cryoablation is one of the most studied ablative tools used in the treatment of renal cell carcinoma. Renal cryoablation involves the rapid freezing of renal tumors to below -40°C. After cooling, ice crystals rapidly form inside and outside the cells, causing the tumor cells to dehydrate and rupture.
Rationale for treatment
This rapid freezing method acts as a direct tumor killer by disrupting the intracellular structure by disrupting the cell membrane and cutting off the cellular blood supply, oxygen and water. It then rapidly melts, damaging the inner layer of tumor blood vessels and making subsequent tumor recovery difficult.
A second freezing and melting cycle kills the remaining tumor cells, while freezing constricts microvessels, slows blood flow, and microthrombi form, blocking blood flow and causing ischemic necrosis of tumor tissue.
Repeated freezing and thawing of tumor cells results in cell rupture and cell membrane lysis, prompting the release of intracellular and occluded antigens, stimulating the body to produce antibodies and improving immune recognition.
Operation method
The renal cryoablation method was initially applied to fix the kidney laparoscopically and isolate the adjacent organs. A cryoprobe is inserted inside the tumor under direct vision or ultrasound guidance, and then argon gas is injected into the renal tumor through a tiny channel in the center of the probe to freeze and destroy the tumor. The operator can accurately control the extent of freezing and the degree of kidney tissue damage throughout the procedure.
Open kidney cryoablation is less commonly used because it loses its minimally invasive significance. More recently, the percutaneous puncture route has begun to be used for tumors that are relatively close to the body surface and are more fixed, with cryoprobes inserted directly percutaneously into the tumor for cryoablation.
Population
The scope of cryoablation is similar to that of radiofrequency ablation and is primarily used for renal cancers that are intolerant of surgical resection, have other systemic disease, are not amenable to surgery, or refuse surgery. In addition, it can be used as appropriate for large intrarenal masses that have failed radiotherapy or chemotherapy, or for those with bilateral tumors.
Similar to radiofrequency ablation, cryoablation has been shown to achieve a significant and desirable treatment outcome in a select group of patients.
Side effects
Among the complications, the most common is low back pain, followed by perirenal hematoma and cardiovascular system complications. When postoperative patients experience some discomfort, such as pain, hematuria, etc., they need to talk to their doctors and manage the symptoms as early as possible to try to avoid serious postoperative complications.
Cryoablation or radiofrequency ablation, which is better?
Cryoablation and radiofrequency ablation both use energy to kill the tumor and protect the normal kidney tissue. The advantages of this procedure are less invasive and faster recovery. Among all minimally invasive procedures for kidney cancer, cryoablation is widely used because it has the lowest complication rate and the best control of surgical risk. In addition, cryoablation is less painful and results in less bleeding than radiofrequency ablation.
The radiofrequency ablation technique has some disadvantages compared with cryoablation:
- First, cryoablation can be observed on imaging such as ultrasound and MRI, whereas the lack of visual or imaging-specific changes in the tissue after radiofrequency ablation makes it difficult to assess the extent and degree of tissue damage.
- Second, the heat is dispersed through the probe to the surrounding tissue, the heat absorption effect may diminish the effect of RF ablation, and the disruption of blood vessels is difficult to ensure. Another disadvantage is that the tumor killing process typically takes about 30 days.
- In addition, animal studies have demonstrated that radiofrequency ablation is more likely to damage the renal collecting system than cryoablation, resulting in a theoretically higher incidence of urinary fistula.
Currently, both cryoablation and radiofrequency ablation are under development, their efficacy has not been conclusively proven, and they are generally used only in patients who are not candidates for the procedure, such as those of advanced age or with other serious health problems.
How is it followed up?
The follow-up for ablation therapy is really much the same as the postoperative follow-up. Ablation is generally indicated for small, low-risk, stage I renal tumors, and follow-up after ablation is based on the presence of residual tumor or recurrent tumor in the area of the ablated lesion. Patients who have undergone rigorous screening do not have a high chance of developing distant metastases after ablative surgery.
After a successful ablation procedure, the site where the tumor was originally located does not absorb contrast and therefore does not enhance. Based on this, enhancement of the mass site is often indicative of local recurrence of the tumor, and further puncture biopsy of the mass site is needed to clarify the diagnosis. After 5 years of follow-up, if there are no signs of recurrence or metastasis, we can breathe a little easier.