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TO THE EDITOR: I read with interest the report by Cinalli et al.1 on their series of 27 children with thalamic tumors (Cinalli G, Aguirre DT, Mirone G, et al: Surgical treatment of thalamic tumors in children. J Neurosurg Pediatr 21:247–257, March 2018). I was disappointed that in their literature review they did not refer to our report on 72 pediatric thalamic tumors in the MRI era in Canada, which is one of the largest reported series of these tumors in children.2 Cinalli et al. have shown again that radical resection of
TO THE EDITOR: I read with interest the report by Cinalli et al.1 on their series of 27 children with thalamic tumors (Cinalli G, Aguirre DT, Mirone G, et al: Surgical treatment of thalamic tumors in children. J Neurosurg Pediatr 21:247–257, March 2018). I was disappointed that in their literature review they did not refer to our report on 72 pediatric thalamic tumors in the MRI era in Canada, which is one of the largest reported series of these tumors in children.2 Cinalli et al. have shown again that radical resection of unilateral thalamic tumors can be performed relatively safely, although in the Canadian experience 19% of patients had permanent neurological deficits, mainly motor, after resection. With our larger series, we were able to do a multivariate analysis, which showed that outcome was related only to the tumor grade and not to the extent of resection. In the light of these findings, we need to be cautious in how strongly we pursue gross-total resection, even for low-grade thalamic tumors. Perhaps the goal of surgery should be maximal resection without causing new permanent deficits.
INCLUDE WHEN CITING Published online August 17, 2018; DOI: 10.3171/2018.7.PEDS18310.
We are grateful to Dr. Steinbok for spotting this missing reference3 in our article. The truth is that our paper had a long gestation and several versions, and in the last check of recent literature I overlooked their reference that had been published online a few months before. I (G.C.) alone am responsible for that. I personally encouraged Dr. Steinbok to write a letter to the editor to keep alive the debate on this difficult and challenging condition. The very nice report on the Canadian experience differs from ours because it is a large, multicenter study collected over a long period of time (11 centers over a 24-year period, 1989–2012). Their study involves several differences among centers’ attitudes and surgeons’ experiences and the evolution of technology over the studied period when compared with our series, a single-center, single-surgeon series of patients treated over a shorter period (14 years, 2002–2016). Collection of their patients started in a period when the surgeon had fewer surgical and diagnostic tools (less intraoperative monitoring [IOM] experience, no endoscopy, lower-field MRI, no diffusion tensor imaging [DTI]) and was highly influenced by the general conservative attitude that, as reported both in our and their papers, slowly changed after publications in the mid-1990s and early years of the new century. Our patients were treated in a period during which technology offered much greater help to the surgeon and, above all, a general attitude in favor of attempts for radical surgery was already largely established.
For these reasons, we would be very cautious about generalizing their conclusions. Their survival rate for low-grade tumors was 84%. In our 18 patients with low-grade tumors, only 1 patient died, due to malignant transformation of a low-grade thalamic ganglioglioma that was partially resected and conservatively followed up at the beginning of our series. This patient’s course contributed significantly to a very drastic change in surgical attitude toward low-grade thalamic neoplasms at our institution. Moreover, Steinbok and colleagues’ data clearly show that radical resection offers significantly higher chances of survival (80% vs 50%). These 2 points could be sufficient to close the discussion.
However, a major point needs to be stressed, which is the different use of staged surgery in the 2 series. In the study of Steinbok et al.,3 programmed staged surgery was never performed, and only 5 patients underwent reoperation, but only at the time of progression. We feel, in agreement with Puget et al.,2 that staged surgery, far from being a fallback, should be considered as an elective treatment strategy in many cases of deep-seated or giant lesions in children, and low-grade thalamic tumors represent the ideal lesion to demonstrate its effectiveness. In fact, after selecting the ideal approach that spares eloquent areas and the corticospinal tract on the basis of DTI findings, the main danger during surgery resides in the removal of the deepest part of the lesion at the tumor-parenchymal interface. The very last layer of tumor can be especially difficult to recognize at the end of the procedure, and its manipulation for dissection and removal can be especially dangerous for deeply located nerve fibers where the precision of IOM is questionable. Our strategy in these cases consists of planning the maximal safe resection, usually allowing removal of 80%–90% of the lesion in the first procedure, and removing the residual lesion, usually through the same approach, after a period ranging from 1 to 2 months after obtaining new MR images. During the second procedure, the residual tumor is much easier to recognize in terms of color and consistency and usually bulging into the surgical cavity, making total resection safer and feasible in our experience.
As a general rule, in thalamic low-grade gliomas incompletely resected at first surgery, we always perform a second-look surgery with the aim of complete resection before considering any adjuvant treatment (chemo-/radiotherapy).
For the aforementioned reasons, we feel that the retrospective review of the Canadian experience3 kindly brought to our attention by Dr. Steinbok offers an extraordinary historical perspective of a single nation on the treatment of this pathology. Nevertheless, in the field of low-grade tumors, we feel that their conclusions should be toned down and reviewed in the light of more recent and homogeneous experiences, where concentration in high-volume centers, systematic use of preoperative DTI, IOM, and intraoperative imaging offer significant support to the surgeon compared with 25 years ago, and we favor resection instead of conservative treatment. We agree instead with Dr. Steinbok that the role of surgery in the field of high-grade lesions remains debatable. In fact, although good surgical removal of a high-grade lesion seems to have a favorable impact on overall survival and progression-free survival,1 their infiltrative pattern and their dimensions carry higher surgical risks in our experience, both for neurological function and life.