Cryotherapy of Kidney Cancer
Introduction and Technique
Renal Cryotherapy Overview
In the year 2007, there were an estimated 51,190 new cases and 12,890 deaths from kidney cancer 1. Historically, a large percentage of new renal cancer cases was discovered with metastases, however, contemporary series show increased rates of the detection of small (4cm) renal tumors primarily well before any apparent clinical signs or symptoms as a result of diagnostic testing (including the use of advanced cross-sectional imaging) for other conditions2,8. Traditionally, radical nephrectomy surgery has controlled renal cancer3, but as the transition to the early diagnosis of incidentally discovered small renal masses occurred, surgical treatment of renal masses also evolved. Nephron-sparing surgery, initially developed for patients with solitary kidneys or compromised renal function, emerged as the treatment of choice for renal masses smaller than 4 cm, even in patients with normal contralateral kidneys. Long term cancer control and renal function after partial nephrectomy has been equal to the results of radical nephrectomy4,5. Numerous nephron-sparing options now exist, including open partial nephrectomy, laparoscopic partial nephrectomy6, and minimally-invasive percutaneous techniques for tissue ablation such as cryotherapy.
Cryotherapy: A surgical procedure during which either percutaneously either laparoscopically assisted a few needles (cryoprobes) are inserted inside the tumour under ultrasound or CT scan control. A few biopsies are obtained in order to determine more accurately prognostic factors. Then Argon gas flows in these needles deep-freezing the cancer, and turning it into a permanent scar. This is a really minimally invasive treatment as usually the convalescence time is the shorttest one.
Techniques for Nonpercutaneous Renal Cryoablation
Exposure for renal cryoablation may be obtained open and laparoscopically (with robotic arm assistance). Initially cryosurgery via an open approach was described for patients with single renal units7. As described, the technique requires a flank incision large enough for kidney mobilization and tumor exposure, ultrasound is used to identify tumor location and to guide and verify cryoprobe placement. One large open renal cryoablation series included 29 patients with localized renal tumors8. In this study, the selected open approach (subcostal incision, transperineal mobilization) maximizes mobilization and exposure of the kidney and facilitates ultrasound monitoring. Seventeen cases were on protocol for cryoablation of masses of 4 cm or less (avg. 2.2 cm), twelve more were treated off-protocol but included in the report, either having already undergone cryoablation treatment, or not meeting inclusion criteria. Using a thermosensor at the tumor margin, a double-freeze sequence was performed using a liquid nitrogen-based unit to cool each cryoprobe to -140°C to -180°C until margin temperatures were verified at -40°C. The average hospital stay was 3.4 days. At a median intermediate follow-up of 16 months, all patients except one were radiologically tumor free. The single patient who was found to have a solid renal lesion that was unchanged in size at the 3-month postoperative MRI was determined to have a microscopic focus of renal cell carcinoma. After 12 months of observation, the patient elected a repeat open cryosurgical procedure with subsequent complete radiographic resolution of the cancer. The open approach allows a renal-sparing treatment with excellent sonographic monitoring.
The laparascopic robotically assisted approach offers the renal sparing benefits of open exposure, but with less morbidity. The kidney is generally approached transperitoneally for anterior and anterolateral tumors, or retroperitoneally for posterior and lateral tumors. After kidney mobilization and adequate tumor exposure, cryoprobes are placed into the tumor through the laparoscopic trocars or transcutaneously, placement is monitored visually and via laparoscopic ultrasound probes. One study of 32 patients (maximum tumor size of 4 cm) reported average hospital stay of 1.8 days and median two week time to full recovery. Following the double-freeze laparoscopic cryoablation, 20 patients had follow-up MRI at one year, five had no incidence of disease, and 15 had lesions that decreased in size by an average of 66%. Overall, the average study follow-up was 16 months (range 7-23) with no recurrence. Twenty-three patients underwent post-procedure biopsies of the small residual mass, which were all negative. Two other noteworthy studies describe monitoring of probe placement with an end firing ultrasound in three patients9, and sonographic guidance during laparascopic renal cryoablation of 26 tumors in 25 patients10.
Tissue cracking is a small concern, but it is important to note that fewer incidents of this are observed when an array of smaller gauge cryoprobes are used rather than a single larger (>,,,,3.2mm) probe, and there is little to no movement of the cryoprobe during the thaw cycle.11
Studies that report follow-up results affirm the promise of laparoscopic renal cryoablation. In one published report, three-year cancer specific survival in 51 patients undergoing cryotherapy for a unilateral, sporadic renal tumor was 98%. Renal function was not compromised and surgical complications were minimal12.
How cryosurgery works
Although minimally invasive, it is a procedure that requires expertise in venal ultrasound scanning, cryoneedle placement and experience in monitoring ice-ball formation.
Cryosurgery is also referred to as cryoablation or cryotherapy. It is a technique that involves using a carefully controlled freezing process as the surgery, instead of a scalpel. Cryogenic gases are circulated through tiny cryoprobes or needles within the prostate, which are introduced through the skin. The concept of using extreme cold to treat prostate cancer was developed in the 1960s, when liquid nitrogen was used to freeze the prostate in a rather unsophisticated manner, but its use was limited by high complication rates and unsatisfactory results.
However, the introduction of liquid argon and helium gas technology, linked to sophisticated and accurate prostate ultrasound scanning techniques, has allowed cryosurgery to develop, using a procedure that minimises complications and improves results.
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Post Procedure Imaging
Postoperatively, lesions require close monitoring to ensure tumor regression. The renal mass will not completely disappear for months or even years, because fibrosis can replace it, but the mass should progressively decrease in size. A 4 cm angiomyolipoma took over 2 years to resolve, although it steadily decreased in size. Failure to decrease after 6 months should mandate consideration for renal biopsy, repeat cryotherapy, or radical/partial nephrectomy. No set algorithm exists for post-procedure monitoring, but patients need close follow-up (every 3 months) for 12–18 months, followed by long-term surveillance, either until complete regression, or if a lesion becomes stable, annually to ensure no potential recurrence from a margin.