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Laparoscopic renal ablation
LETTERS TO THE EDITOR
Laparoscopic Renal Ablation TO THE EDITOR:
Dr. Gill and colleagues1 present a large and promising experience using laparoscopic renal cryoablation to treat small renal masses. Most impressive was their ability to obtain postoperative biopsies in 23 (68%) of 32 patients and report no evidence of local or port site recurrence. However, readers must be cautious regarding the shortterm conclusions of efficacy. Although overall frozen needle biopsies are accurate in more than 75% of cases and have been shown to have excellent positive predictive value for carcinoma, Dechet et al.2 reaffirmed that there is a large degree of inaccuracy in renal biopsy even during open renal sampling for patients undergoing nephrectomy for renal masses. Consequently, the results of a negative postoperative biopsy do not necessarily preclude the presence of undetected cancer after cryoablation. More complicating when applying minimally invasive approaches for renal masses is the inability to evaluate the margin status of the ablated lesions. Without intraoperative thermocouples or magnetic resonance thermometry, it is impossible to know if effective therapy has been applied as the exact temperature of the iceball at the edge of the renal tumor is not known. Ultrasound cannot predict temperature, and, as such, the margin status is not always certain. Iceball extension 1 cm beyond the tumor margin is not always possible (their Table III) and does not guarantee that the lethal temperature is reached. We believe the optimal method to maximize tissue destruction is the use of a rapid freeze and slow thaw technique3 or intraoperative temperature monitoring of the iceball with thermocouples placed radiographically at the edge of the lesion. To complicate matters even more, most renal cryolesions do not resolve completely and leave a postcryoablation scar even after 1 year.3,4 Consequently, patients should also be advised about the need for frequent follow-up to ensure no interval tumor growth. If the cryoablation procedure fails to control the renal tumor, the patient should be advised of the potential need for further intervention. Frequent radiographic follow-up is important. Levin and associates5 reported one recurrence in 22 patients with post laparoscopic renal cryoablation biopsy. According to the abstract, the patient had a negative biopsy at 6 months, but was rebiopsied at 9 months for a suspicious nodule on a subsequent magnetic resonance imaging (MRI) scan. Renal cell carcinoma was demonstrated at that biopsy. The patient underwent radical nephrectomy and was found to have a 1.3-cm focus of clear cell renal carcinoma. Shingleton et al.6 have also reported their preliminary results of percutaneous renal cryoablation using MRI guidance. Of the 18 tumors ablated, one lesion required retreatment due to enhancement on follow-up computed tomography (CT) scan at 1 month. Recently, one of our patients was also found to have growth of the postcryoablation scar after 1 year. Despite the radiologic evidence of recurrence, that patient has deferred any surgical intervention. The 132
reason for these failures is unclear, but they could have resulted from inadequate tumor freezing or poor tumor targeting. Renal cryosurgery is still an evolving procedure and careful patient selection is paramount. REFERENCES 1. Gill IS, Novick AC, Meraney AM, et al: Laparoscopic renal cryoablation in 32 patients. Urology 56: 748 –753, 2000. 2. Dechet CB, Sebo T, Farrow G, et al: Prospective analysis of intraoperative frozen needle biopsy of solid renal masses in adults. J Urol 162: 1282–1285, 1999. 3. Rodriguez R, Chan DY, Bishoff JT, et al: Renal ablative cryosurgery in select patients with peripheral renal masses. Urology 55: 25–30, 2000. 4. Remer EM, Weinberg EJ, Oto A, et al: MR imaging of the kidneys after laparoscopic cryoablation. AJR Am J Roentgenol 174: 635– 640, 2000. 5. Levin HS, Meraney AM, Novick AC, et al: Needle biopsy histology of renal tumors 3– 6 months after laparoscopic renal cryoablation. J Urol. 163(suppl 4): 153, 2000. 6. Shingleton WB, and Sewell P: Renal tumor cryoablation utilizing interventional magnetic resonance imaging (IMRI). J Urol 163(suppl 4): 155, 2000.
David Y. Chan, M.D. Ronald Rodriguez, M.D. Louis R. Kavoussi, M.D. Department of Urology Hopkins Bayview Medical Center Baltimore, Maryland PII S0090-4295(01)01139-6
REPLY BY THE AUTHORS: The above letter reiterates the various points already clearly emphasized in our prior publications on this topic.1–3 However, given the current developmental nature of renal cryoablation, re-emphasis is worthwhile, even necessary. As such, this opportunity is welcomed. Meticulous attention to patient selection, laparoscopic technique, and rigorous postoperative follow-up is essential. At our institution, this procedure is indicated for a solitary, small (less than 4 cm), exophytic renal mass located away from the collecting system. Intraoperatively, after a precryoablation needle biopsy for tissue diagnosis (permanent section, not frozen section), a double rapid freeze–slow thaw cycle, with the iceball extending approximately 1 cm beyond the laparoscopically and ultrasonographically visible edge of the tumor is performed. We disagree that placement of a thermocouple at the edge of the tumor is an “optimal method” to determine reliable tumor kill. In our practical experience, there are two problems with thermocouple needles. First, thermocouple readings may be unreliable, with significant variations in temperature readings between thermocouples placed immediately adjacent to each other. Second, the circumference of the tumor literally has innumerable points of physical contact with the kidney along its threedimensional inner border abutting the renal parenchyma. Leaving untreated cancer behind at any one of these points would constitute inadequate treatment. As such, measuring the temperature at one of these points with a single thermo-
© 2001, ELSEVIER SCIENCE INC. ALL RIGHTS RESERVED
UROLOGY 58: 132–134, 2001
•
0090-4295/01/$20.00
Laparoscopic Renal Ablation TO THE EDITOR:
Dr. Gill and colleagues1 present a large and promising experience using laparoscopic renal cryoablation to treat small renal masses. Most impressive was their ability to obtain postoperative biopsies in 23 (68%) of 32 patients and report no evidence of local or port site recurrence. However, readers must be cautious regarding the shortterm conclusions of efficacy. Although overall frozen needle biopsies are accurate in more than 75% of cases and have been shown to have excellent positive predictive value for carcinoma, Dechet et al.2 reaffirmed that there is a large degree of inaccuracy in renal biopsy even during open renal sampling for patients undergoing nephrectomy for renal masses. Consequently, the results of a negative postoperative biopsy do not necessarily preclude the presence of undetected cancer after cryoablation. More complicating when applying minimally invasive approaches for renal masses is the inability to evaluate the margin status of the ablated lesions. Without intraoperative thermocouples or magnetic resonance thermometry, it is impossible to know if effective therapy has been applied as the exact temperature of the iceball at the edge of the renal tumor is not known. Ultrasound cannot predict temperature, and, as such, the margin status is not always certain. Iceball extension 1 cm beyond the tumor margin is not always possible (their Table III) and does not guarantee that the lethal temperature is reached. We believe the optimal method to maximize tissue destruction is the use of a rapid freeze and slow thaw technique3 or intraoperative temperature monitoring of the iceball with thermocouples placed radiographically at the edge of the lesion. To complicate matters even more, most renal cryolesions do not resolve completely and leave a postcryoablation scar even after 1 year.3,4 Consequently, patients should also be advised about the need for frequent follow-up to ensure no interval tumor growth. If the cryoablation procedure fails to control the renal tumor, the patient should be advised of the potential need for further intervention. Frequent radiographic follow-up is important. Levin and associates5 reported one recurrence in 22 patients with post laparoscopic renal cryoablation biopsy. According to the abstract, the patient had a negative biopsy at 6 months, but was rebiopsied at 9 months for a suspicious nodule on a subsequent magnetic resonance imaging (MRI) scan. Renal cell carcinoma was demonstrated at that biopsy. The patient underwent radical nephrectomy and was found to have a 1.3-cm focus of clear cell renal carcinoma. Shingleton et al.6 have also reported their preliminary results of percutaneous renal cryoablation using MRI guidance. Of the 18 tumors ablated, one lesion required retreatment due to enhancement on follow-up computed tomography (CT) scan at 1 month. Recently, one of our patients was also found to have growth of the postcryoablation scar after 1 year. Despite the radiologic evidence of recurrence, that patient has deferred any surgical intervention. The 132
reason for these failures is unclear, but they could have resulted from inadequate tumor freezing or poor tumor targeting. Renal cryosurgery is still an evolving procedure and careful patient selection is paramount. REFERENCES 1. Gill IS, Novick AC, Meraney AM, et al: Laparoscopic renal cryoablation in 32 patients. Urology 56: 748 –753, 2000. 2. Dechet CB, Sebo T, Farrow G, et al: Prospective analysis of intraoperative frozen needle biopsy of solid renal masses in adults. J Urol 162: 1282–1285, 1999. 3. Rodriguez R, Chan DY, Bishoff JT, et al: Renal ablative cryosurgery in select patients with peripheral renal masses. Urology 55: 25–30, 2000. 4. Remer EM, Weinberg EJ, Oto A, et al: MR imaging of the kidneys after laparoscopic cryoablation. AJR Am J Roentgenol 174: 635– 640, 2000. 5. Levin HS, Meraney AM, Novick AC, et al: Needle biopsy histology of renal tumors 3– 6 months after laparoscopic renal cryoablation. J Urol. 163(suppl 4): 153, 2000. 6. Shingleton WB, and Sewell P: Renal tumor cryoablation utilizing interventional magnetic resonance imaging (IMRI). J Urol 163(suppl 4): 155, 2000.
David Y. Chan, M.D. Ronald Rodriguez, M.D. Louis R. Kavoussi, M.D. Department of Urology Hopkins Bayview Medical Center Baltimore, Maryland PII S0090-4295(01)01139-6
REPLY BY THE AUTHORS: The above letter reiterates the various points already clearly emphasized in our prior publications on this topic.1–3 However, given the current developmental nature of renal cryoablation, re-emphasis is worthwhile, even necessary. As such, this opportunity is welcomed. Meticulous attention to patient selection, laparoscopic technique, and rigorous postoperative follow-up is essential. At our institution, this procedure is indicated for a solitary, small (less than 4 cm), exophytic renal mass located away from the collecting system. Intraoperatively, after a precryoablation needle biopsy for tissue diagnosis (permanent section, not frozen section), a double rapid freeze–slow thaw cycle, with the iceball extending approximately 1 cm beyond the laparoscopically and ultrasonographically visible edge of the tumor is performed. We disagree that placement of a thermocouple at the edge of the tumor is an “optimal method” to determine reliable tumor kill. In our practical experience, there are two problems with thermocouple needles. First, thermocouple readings may be unreliable, with significant variations in temperature readings between thermocouples placed immediately adjacent to each other. Second, the circumference of the tumor literally has innumerable points of physical contact with the kidney along its threedimensional inner border abutting the renal parenchyma. Leaving untreated cancer behind at any one of these points would constitute inadequate treatment. As such, measuring the temperature at one of these points with a single thermo-
© 2001, ELSEVIER SCIENCE INC. ALL RIGHTS RESERVED
UROLOGY 58: 132–134, 2001
•
0090-4295/01/$20.00