Cryoablation is generally favored due to its safety near central structures and its ability to “sculpt” large enough ice to cover all tumor margins. Our renal cryoablation series have shown no greater tumor recurrence for larger tumors, unlike the greater recurrence noted for heat-based ablations.
These are nearly all primary renal cell carcinomas (RCC), but we have treated rare metastatic tumors that have spread from other primary cancers (i.e., from cancers that arose in breast, melanoma, etc.). If a kidney tumor is solid, enhancing and growing, it’s highly likely to be an RCC rather than a benign renal tumor (i.e., oncocytoma, nonfat-containing angiomyolipoma, etc.). This high probability generally allows us to be cost effective and offer the diagnostic biopsy at the same time as the ablation in a single procedure. The choices for a renal mass include:
- Conservative follow-up with a repeat scan in 6-12 months. This is particularly beneficial for tumors <3 cm and/or elderly patients, or those with significant comorbidities or other serious health problems.
- Biopsy alone for diagnosis: if the tumor is < ~1.5 cm, there is a greater likelihood of benign or non-diagnostic sampling, thereby favoring conservative follow-up. In our recent series, only 5% of biopsies done at the time of ablation had benign diagnosis, for which the cryoablation may have been unnecessary. However, any growing solid tumor would still be considered a surgical candidate and a benign biopsy may not fully reflect the tumor potential (e.g., oncocytic RCC).
- Biopsy with ablation: if the tumor has not been previously diagnosed, this is the most common choice since it spares the patient an additional procedure and likely associated risk since biopsy alone may have just as high a complication related as cryoablation which causes more coagulation. The down side is approximately 5% of our patients may receive “over treatment” for benign tumors.
Usually these are solitary tumors, but depending on the size, several tumors may be treated in the same or multiple sessions.
Approximately 4 cm, an additional CT/MRI of the chest and/or abdomen may be necessary to better evaluate potential lung metastases or local tumor spread.
Nearly any location within the kidney. This may require additional protection measures as noted below.
- An exception would be if the tumor has invaded a renal vein, the inferior vena cava or portions of the urinary collecting system.
- As above, tumors that have spread to the local lymph nodes or elsewhere in the body (i.e., lungs, adrenal glands, pancreas, etc.) may require additional considerations of systemic therapy.
- Hydrodissection: if the tumor is located near adjacent bowel or ureter, a small catheter (5F) may be placed between the tumor and bowel/ureter for infusing saline to protect that space, thereby preventing the ablation zone (ice or heat) from proceeding into the bowel. In our recent large renal cryoablation series, hydrodissection was used in a third (34%) of cases.
- Balloon interposition: rarely, when fluid is not sufficient to keep away adjacent bowel, a balloon may be placed via a different puncture site and placed through an introducing tube or sheath.
- Ureteral stent: if a tumor has a margin lying close enough to the ureter (i.e., the tube that drains urine from the kidney to the bladder) that the ablation zone may affect the ureter and its drainage of the kidney, a ureteral stent (i.e., a thin tube from the kidney to the bladder) will need to be placed by a urologist prior to the cryoablation. We found this necessary for 9% of our recent large renal cryoablation series. In rare circumstances, a special stent may be used to allow continuous flushing of warm saline to further prevent possible ureteral damage.