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Minimally Invasive Endoscopic Resection of Intraparenchymal Brain Tumors
Perspectives Commentary on: Minimally Invasive Endoscopic Resection of Intraparenchymal Brain Tumors by Plaha et al. World Neurosurg 82:1198-1208, 2014
Minimally Invasive Endoscopic Resection of Intraparenchymal Brain Tumors Douglas A. Hardesty, Corey T. Walker, Peter Nakaji
T
he endoscope in neurosurgery has at times been accused of being a tool looking for a purpose. In many applications, it has successfully refuted this accusation: it is hard to imagine a cogent argument against using endoscopy for a third ventriculostomy or intraventricular tumor biopsy in the right setting. Also, although the entire field of endonasal anterior skull base surgery has not yet reached full maturity, few would argue that the subspecialty does not have value. The endoscope works best in open spaces, either air or fluid, such as the ventricle or nose. Therein the illumination, magnification, and wide angles of visualization allow the endoscope to be used to its full advantage. In such spaces, the freedom of movement provided to the endoscopist overcomes much of the potential clumsiness that comes from working with a view that is not coaxial to the working angle. The cerebral parenchyma has no open cavity, and it is largely for this reason that the brain “space” itself has been left as the last great frontier for the endoscope. The bar to be reached for any technique used in the removal of intrinsic and metastatic brain tumors must be that the technique provides less neuroanatomical and neurological impact and equal or better efficacy than the traditional microscope-based approach. It is far from a foregone conclusion that the conditions for such success will be met with new endoscopic techniques. In the article in a recent issue of WORLD NEUROSURGERY by Plaha et al., a nontubular, endoscopic technique for resecting intraparenchymal brain tumors is applied and evaluated prospectively for safety and efficacy. Using this method, the authors demonstrated gross total resection (GTR) in 48% of cases and near-total (greater than 95%) resection in 70% of cases. They show that GTR rates in this study were comparable with those published by
Key words Endoscopic - Intraparenchymal brain tumors - Minimally invasive -
Abbreviations and Acronyms EBR: En bloc resection GTR: Gross total resection PMR: Piecemeal resection
other groups that used standard microsurgical resection for highgrade gliomas (where most evidence demonstrates that extent of resection plays a significant prognostic role). The authors conclude that the procedure can be performed safely, with only one major complication recorded secondary to anomalous anatomy (left anterior cerebral artery infarct), and a reported infection rate lower than that for other nonendoscopic craniotomy procedures at their institution. They conclude by suggesting that although their study does not imply superiority, it does support a role for this method of intraparenchymal tumor removal. The authors are to be applauded for attempting to drive forward this technique. Only by consistent practice in such a specialized area can we expect practitioners to reach a level of skill wherein they can accurately judge whether the surgical goals are achievable using a new technique. Through similar efforts, the established advances in ventricular endoscopy and endonasal skull base endoscopy were achieved where previously such surgeries seemed impossible. The rationale for this technique in intraparenchymal surgery seems more difficult to justify, but that does not mean it will not ultimately prove valuable. Arguments about a steep learning curve are not in and of themselves valid: it remains for the pioneers to show the way, and then they and others must refine and teach the technique. Nevertheless, we may legitimately also cast a very critical eye on such new techniques that their safety and efficacy be proven as quickly as possible. For endoscopic intraparenchymal tumor removal, we have some concerns. Inherent to the endoscopic technique is the piecemeal resection (PMR) approach of entering the tumor and creating a working space by debulking and removing the components of the tumor
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona, USA To whom correspondence should be addressed: Peter Nakaji, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 83, 4:479-480. http://dx.doi.org/10.1016/j.wneu.2014.08.056
WORLD NEUROSURGERY 83 [4]: 479-480, APRIL 2015
www.WORLDNEUROSURGERY.org
479
PERSPECTIVES
from within. This is in contrast to en bloc resection (EBR), which is used for many tumors when removed nonendoscopically. The PMR approach may be of special concern in tumors in which the recurrence risk is high. Two studies from the MD Anderson Cancer Center group have shown that in patients with metastatic brain tumors, PMR results in greater rates of leptomeningeal dissemination compared with EBR (3, 4). Similarly, in this population, they also showed an increased risk of local tumor recurrence with PMR (1.7 times greater), suggesting that EBR results in less intraoperative tumor spillage (2). Consequently, such lesions may not be optimally removed via endoscopy. Long-term follow-up of tumor recurrence and patient outcomes would be beneficial to determine whether this also holds true for the technique used by Plaha et al. The authors are to be congratulated on prospectively collecting data on their surgical technique, rather than performing a purely retrospective review. However, a prospective study must also be held to a higher standard than a retrospective review. The endoscopic resections presented are consecutive, but there is no discussion on how many patients underwent open microsurgical resection at the authors’ institution during the same time span. It seems unlikely that every tumor patient evaluated and recommended for surgery during the 21-month study period was deemed appropriate for the reported endoscopic technique. Inclusion criteria should be rigorously defined and reported for all prospective clinical studies. A perennial problem in endoscopic studies is the difficulty in generating metrics that allow head-to-head comparisons with traditional, nonendoscopic techniques. Endoscopy as a whole remains a very subspecialized area of neurosurgery and is still in a position of having to justify itself compared with the historical “gold standard” of open microsurgery. This justification is applied sparingly in the current work. For example, Plaha et al. contrast infection rates, GTR rates, operative blood loss, and surgical time between the endoscopic technique and traditional microneurosurgical approaches. However, the rate of extent of resection is provided from external sources, and not the authors’
REFERENCES 1. Garrett M, Consiglieri G, Nakaji P: Transcranial minimally invasive neurosurgery for tumors. Neurosurg Clin N Am 21:595-605, 2010: v.
2. Patel AJ, Suki D, Hatiboglu MA, Abouassi H, Shi W, Wildrick DM, Lang FF, Sawaya R: Factors influencing the risk of local recurrence after resection of a single brain metastasis. J Neurosurg 113:181-189, 2010.
480
www.SCIENCEDIRECT.com
own personal historical controls. For all such studies, these and other metrics, such as surgical times and blood loss, should be more robustly compared with historical controls or via randomization, rather than data simply provided by the authors without further analysis. Finally, a major theoretical advantage of an endoscopic resection is minimization of perilesional brain injury via retraction or manipulation. The current authors quantify the T2-signal change on postoperative magnetic resonance imaging and the tract size to deep lesions when identifiable. Without controls, it is impossible to truly state if this is less invasive than a neuronavigation-tailored, microneurosurgical approach, such as those advocated by our group and others (1). The current practice of the senior commentator (P.N.) at the Barrow Neurological Institute is to use the microscope in a primary role and to employ the endoscope as an adjunct to inspect the walls of the resection. However, this technique also remains to be rigorously evaluated against nonendoscope-assisted resection. The way we often make progress in medicine and surgery is through the initiative of individual physicians who are willing to push the limits and patients who are willing to let them. In a value- and evidence-based world of research funding, this schema may be more difficult to justify. The best way we can preserve such freedom is to apply rigorous discipline to the process of devising new techniques. This should involve carrying out studies within the setting of investigator-initiated clinical trials, with meticulous record-keeping, stringent entry criteria, and an unflinching regard for reporting outcomes—good or bad. In this regard, we must equally continue to move forward with new techniques and technology within the field of neuroendoscopy. The present study by Plaha et al. is another step forward in the field of minimally invasive tumor resection. To lend further progress, future studies must focus on long-term recurrence rates, cost-effectiveness, and patient quality of life to illuminate the true utility of this technique and allow us to identify the cases in which our patients will benefit most from its use.
3. Suki D, Abouassi H, Patel AJ, Sawaya R, Weinberg JS, Groves MD: Comparative risk of leptomeningeal disease after resection or stereotactic radiosurgery for solid tumor metastasis to the posterior fossa. J Neurosurg 108:248-257, 2008.
4. Suki D, Hatiboglu MA, Patel AJ, Weinberg JS, Groves MD, Mahajan A, Sawaya R: Comparative risk of leptomeningeal dissemination of cancer after surgery or stereotactic radiosurgery for a single supratentorial solid tumor metastasis.
Neurosurgery 64:664-674; discussion 674-676, 2009.
Citation: World Neurosurg. (2015) 83, 4:479-480. http://dx.doi.org/10.1016/j.wneu.2014.08.056 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.08.056
Minimally Invasive Endoscopic Resection of Intraparenchymal Brain Tumors Douglas A. Hardesty, Corey T. Walker, Peter Nakaji
T
he endoscope in neurosurgery has at times been accused of being a tool looking for a purpose. In many applications, it has successfully refuted this accusation: it is hard to imagine a cogent argument against using endoscopy for a third ventriculostomy or intraventricular tumor biopsy in the right setting. Also, although the entire field of endonasal anterior skull base surgery has not yet reached full maturity, few would argue that the subspecialty does not have value. The endoscope works best in open spaces, either air or fluid, such as the ventricle or nose. Therein the illumination, magnification, and wide angles of visualization allow the endoscope to be used to its full advantage. In such spaces, the freedom of movement provided to the endoscopist overcomes much of the potential clumsiness that comes from working with a view that is not coaxial to the working angle. The cerebral parenchyma has no open cavity, and it is largely for this reason that the brain “space” itself has been left as the last great frontier for the endoscope. The bar to be reached for any technique used in the removal of intrinsic and metastatic brain tumors must be that the technique provides less neuroanatomical and neurological impact and equal or better efficacy than the traditional microscope-based approach. It is far from a foregone conclusion that the conditions for such success will be met with new endoscopic techniques. In the article in a recent issue of WORLD NEUROSURGERY by Plaha et al., a nontubular, endoscopic technique for resecting intraparenchymal brain tumors is applied and evaluated prospectively for safety and efficacy. Using this method, the authors demonstrated gross total resection (GTR) in 48% of cases and near-total (greater than 95%) resection in 70% of cases. They show that GTR rates in this study were comparable with those published by
Key words Endoscopic - Intraparenchymal brain tumors - Minimally invasive -
Abbreviations and Acronyms EBR: En bloc resection GTR: Gross total resection PMR: Piecemeal resection
other groups that used standard microsurgical resection for highgrade gliomas (where most evidence demonstrates that extent of resection plays a significant prognostic role). The authors conclude that the procedure can be performed safely, with only one major complication recorded secondary to anomalous anatomy (left anterior cerebral artery infarct), and a reported infection rate lower than that for other nonendoscopic craniotomy procedures at their institution. They conclude by suggesting that although their study does not imply superiority, it does support a role for this method of intraparenchymal tumor removal. The authors are to be applauded for attempting to drive forward this technique. Only by consistent practice in such a specialized area can we expect practitioners to reach a level of skill wherein they can accurately judge whether the surgical goals are achievable using a new technique. Through similar efforts, the established advances in ventricular endoscopy and endonasal skull base endoscopy were achieved where previously such surgeries seemed impossible. The rationale for this technique in intraparenchymal surgery seems more difficult to justify, but that does not mean it will not ultimately prove valuable. Arguments about a steep learning curve are not in and of themselves valid: it remains for the pioneers to show the way, and then they and others must refine and teach the technique. Nevertheless, we may legitimately also cast a very critical eye on such new techniques that their safety and efficacy be proven as quickly as possible. For endoscopic intraparenchymal tumor removal, we have some concerns. Inherent to the endoscopic technique is the piecemeal resection (PMR) approach of entering the tumor and creating a working space by debulking and removing the components of the tumor
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona, USA To whom correspondence should be addressed: Peter Nakaji, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 83, 4:479-480. http://dx.doi.org/10.1016/j.wneu.2014.08.056
WORLD NEUROSURGERY 83 [4]: 479-480, APRIL 2015
www.WORLDNEUROSURGERY.org
479
PERSPECTIVES
from within. This is in contrast to en bloc resection (EBR), which is used for many tumors when removed nonendoscopically. The PMR approach may be of special concern in tumors in which the recurrence risk is high. Two studies from the MD Anderson Cancer Center group have shown that in patients with metastatic brain tumors, PMR results in greater rates of leptomeningeal dissemination compared with EBR (3, 4). Similarly, in this population, they also showed an increased risk of local tumor recurrence with PMR (1.7 times greater), suggesting that EBR results in less intraoperative tumor spillage (2). Consequently, such lesions may not be optimally removed via endoscopy. Long-term follow-up of tumor recurrence and patient outcomes would be beneficial to determine whether this also holds true for the technique used by Plaha et al. The authors are to be congratulated on prospectively collecting data on their surgical technique, rather than performing a purely retrospective review. However, a prospective study must also be held to a higher standard than a retrospective review. The endoscopic resections presented are consecutive, but there is no discussion on how many patients underwent open microsurgical resection at the authors’ institution during the same time span. It seems unlikely that every tumor patient evaluated and recommended for surgery during the 21-month study period was deemed appropriate for the reported endoscopic technique. Inclusion criteria should be rigorously defined and reported for all prospective clinical studies. A perennial problem in endoscopic studies is the difficulty in generating metrics that allow head-to-head comparisons with traditional, nonendoscopic techniques. Endoscopy as a whole remains a very subspecialized area of neurosurgery and is still in a position of having to justify itself compared with the historical “gold standard” of open microsurgery. This justification is applied sparingly in the current work. For example, Plaha et al. contrast infection rates, GTR rates, operative blood loss, and surgical time between the endoscopic technique and traditional microneurosurgical approaches. However, the rate of extent of resection is provided from external sources, and not the authors’
REFERENCES 1. Garrett M, Consiglieri G, Nakaji P: Transcranial minimally invasive neurosurgery for tumors. Neurosurg Clin N Am 21:595-605, 2010: v.
2. Patel AJ, Suki D, Hatiboglu MA, Abouassi H, Shi W, Wildrick DM, Lang FF, Sawaya R: Factors influencing the risk of local recurrence after resection of a single brain metastasis. J Neurosurg 113:181-189, 2010.
480
www.SCIENCEDIRECT.com
own personal historical controls. For all such studies, these and other metrics, such as surgical times and blood loss, should be more robustly compared with historical controls or via randomization, rather than data simply provided by the authors without further analysis. Finally, a major theoretical advantage of an endoscopic resection is minimization of perilesional brain injury via retraction or manipulation. The current authors quantify the T2-signal change on postoperative magnetic resonance imaging and the tract size to deep lesions when identifiable. Without controls, it is impossible to truly state if this is less invasive than a neuronavigation-tailored, microneurosurgical approach, such as those advocated by our group and others (1). The current practice of the senior commentator (P.N.) at the Barrow Neurological Institute is to use the microscope in a primary role and to employ the endoscope as an adjunct to inspect the walls of the resection. However, this technique also remains to be rigorously evaluated against nonendoscope-assisted resection. The way we often make progress in medicine and surgery is through the initiative of individual physicians who are willing to push the limits and patients who are willing to let them. In a value- and evidence-based world of research funding, this schema may be more difficult to justify. The best way we can preserve such freedom is to apply rigorous discipline to the process of devising new techniques. This should involve carrying out studies within the setting of investigator-initiated clinical trials, with meticulous record-keeping, stringent entry criteria, and an unflinching regard for reporting outcomes—good or bad. In this regard, we must equally continue to move forward with new techniques and technology within the field of neuroendoscopy. The present study by Plaha et al. is another step forward in the field of minimally invasive tumor resection. To lend further progress, future studies must focus on long-term recurrence rates, cost-effectiveness, and patient quality of life to illuminate the true utility of this technique and allow us to identify the cases in which our patients will benefit most from its use.
3. Suki D, Abouassi H, Patel AJ, Sawaya R, Weinberg JS, Groves MD: Comparative risk of leptomeningeal disease after resection or stereotactic radiosurgery for solid tumor metastasis to the posterior fossa. J Neurosurg 108:248-257, 2008.
4. Suki D, Hatiboglu MA, Patel AJ, Weinberg JS, Groves MD, Mahajan A, Sawaya R: Comparative risk of leptomeningeal dissemination of cancer after surgery or stereotactic radiosurgery for a single supratentorial solid tumor metastasis.
Neurosurgery 64:664-674; discussion 674-676, 2009.
Citation: World Neurosurg. (2015) 83, 4:479-480. http://dx.doi.org/10.1016/j.wneu.2014.08.056 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.08.056