In Reply: Thalamic Glioblastoma: Clinical Presentation, Management Strategies, and Outcomes

To the Editor:

We thank the readers¹ for their interest and comments regarding our study.² While the majority of patients (47) in our study underwent needle biopsy, we also identified 10 cases were a craniotomy and resection was performed. In this subset of patients, postoperative imaging demonstrated subtotal resection in all cases, which is not unexpected considering the eloquent structure of the thalamus. While the goal of our study was not to compare survival between patients undergoing biopsy or resection, we did not find any survival differences between these 2 groups. A recent study by Biwu Wu et al,³ “High-grade thalamic gliomas: Microsurgical treatment and prognosis analysis,” evaluated 49 patients with thalamic high-grade gliomas undergoing microsurgical resection. While the definition of extent of resection differed from commonly utilized radiographic criteria in routine practice (GTR- gross total resection, NTR- near total resection, and STR- subtotal resection),⁴ it appears that none of the patients had complete radiographic removal of the tumor (GTR). Moreover, the majority of patients (except for 9) had some surgical complication (hemiplegia – 18 cases, infection –17, speech problems – 3, disturbance of consciousness – 7, postoperative hemorrhage – 6, and visual deterioration – 1). Additionally, the OS was lower than the OS observed in our group of patients, in which the majority of patients underwent biopsy (9 vs 12 mo). Such survival difference is surprising considering that Anaplastic Astrocytomas were also included in the study done by Biwu Wu et al³ as opposed to ours,² which only evaluated glioblastomas. A recent study by Zhang et al,⁵ evaluated 33 adult patients with unilateral thalamic gliomas and concluded that GTR can be achieved with an acceptable complication rate and can potentially lead to better prognosis. In such study, GTR was reported in 19 cases which led to better prognosis compared to patients undergoing partial resections. Complications were not uncommon including a case of perioperative death following resection. The 1 and 2 yr overall survival rates in such study (which also included a large number of WHO grade III tumors) were 68.1% and 25.9% compared to 51.55% and 21.1% in ours. A prior study from the same institution (Beijing Tiantan Hospital, Capital Medical University) by Cao et al⁶ reported a postoperative mortality rate of 4.5%, with transient hemiparesis in about 50% of patients with a similar OS than our study (12 mo), and again included grade III gliomas which typically have a better OS than GBM. The reports of these surgical series demonstrate that aggressive removal of thalamic glioblastoma may be questionable considering the aggressive behavior of the disease and the short time that might be available to recover prior to administration of adjuvant therapies.² EOR has consistently shown to be a favorable prognostic indicator in large retrospective and population based studies,^7-10 but it is important to acknowledge that such studies have typically excluded patients with deep-seated tumors, who typically undergo more conservative approaches such as needle biopsy or even upfront chemoradiation. Approaches to the thalamus have been well described¹¹ and recent advances in functional imaging and surgical technology coupled with intraoperative neurophysiological monitoring and intraoperative cortical and subcortical brain mapping might allow surgical interventions in the thalamus to be more feasible with an acceptable risk profile. Certainly, patients with large tumors, mass effect, and associated cystic components are likely to have worse outcomes without intervention and surgical judgment is critical as some form of resection may be indicated for selected patients. Less invasive strategies for deeply located lesions such as the transsulcal parafascicular approach using naturally existing corridors with tubular retractors¹² and laser interstitial thermal therapy have garnered interest recently,¹³ and should be considered.

Further analysis of chemoradiation data was not necessary in our study, as the great majority of our patients underwent standard adjuvant therapy including chemoradiation. A total of 50 patients underwent adjuvant Temozolomide and external radiation therapy. Three patients went to hospice early in their diagnosis and did not receive further treatments. Details from outside institutions regarding adjuvant therapy on four patients were not available.² The median preop KPS for all patients was 80. Similar to other glioblastoma series, KPS was also associated with survival.¹⁴ Details of postoperative KPS were not available in all patients and therefore were not included in the analysis. Moreover, we did not have reliable records of postoperative KPS, particularly for patients undergoing craniotomy, as none of those patients were managed primarily in our institution.

Disclosure

The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.