Defining clinically significant tumor size in vestibular schwannoma to inform timing of microsurgery during wait-and-scan management: moving beyond minimum detectable growth

Abstract

OBJECTIVE Detection of vestibular schwannoma (VS) growth during observation leads to definitive treatment at most centers globally. Although ≥ 2 mm represents an established benchmark of tumor growth on serial MRI studies, 2 mm of linear tumor growth is unlikely to significantly alter microsurgical outcomes. The objective of the current work was to ascertain where the magnitude of change in clinical outcome is the greatest based on size. METHODS A single-institution retrospective review of a consecutive series of patients with sporadic VS who underwent microsurgical resection between January 2000 and May 2020 was performed. Preoperative tumor size cutpoints were defined in 1-mm increments and used to identify optimal size thresholds for three primary outcomes: 1) the ability to achieve gross-total resection (GTR); 2) maintenance of normal House-Brackmann (HB) grade I facial nerve function; and 3) preservation of serviceable hearing (American Academy of Otolaryngology–Head and Neck Surgery class A/B). Optimal size thresholds were obtained by maximizing c-indices from logistic regression models. RESULTS Of 603 patients meeting inclusion criteria, 502 (83%) had tumors with cerebellopontine angle (CPA) extension. CPA tumor size was significantly associated with achieving GTR, postoperative HB grade I facial nerve function, and maintenance of serviceable hearing (all p < 0.001). The optimal tumor size threshold to distinguish between GTR and less than GTR was 17 mm of CPA extension (c-index 0.73). In the immediate postoperative period, the size threshold between HB grade I and HB grade > I was 17 mm of CPA extension (c-index 0.65). At the most recent evaluation, the size threshold between HB grade I and HB grade > I was 23 mm (c-index 0.68) and between class A/B and C/D hearing was 18 mm (c-index 0.68). Tumors within 3 mm of the 17-mm CPA threshold displayed similarly strong c-indices. Among purely intracanalicular tumors, linear size was not found to portend worse outcomes for all measures. CONCLUSIONS The probability of incurring less optimal microsurgical outcomes begins to significantly increase at 14–20 mm of CPA extension. Although many factors ultimately influence decision-making, when considering timing of microsurgical resection, using a size threshold range as depicted in this study offers an evidence-based approach that moves beyond reflexively recommending treatment for all tumors after detecting ≥ 2 mm of tumor growth on serial MRI studies.

Predicting Extent of Microsurgical Resection of Sporadic Vestibular Schwannoma

“…Institutional review board approval was obtained (16-007363) to examine a consecutive series of patients with sporadic VS treated via microsurgical resection from January 2000 to May 2020 with a preoperative goal of GTR. As described in a previous article using this cohort (13), patients were excluded if they carried a diagnosis of neurofibromatosis type 2, previously underwent radiosurgery of their VS, had intralabyrinthine tumor extension, had a pre-treatment House-Brackmann (HB) Grade > I, or had inadequate records precluding complete extraction of necessary baseline patient and tumor characteristics.…”

Predicting surgical decision-making in vestibular schwannoma using tree-based machine learning

“…This finding is in line with recently published results involving a large cohort from a high-volume center in which the optimal tumor size thresholds associated with various improved clinical outcomes in VS surgery were ascertained. 10 Authors of that study used logistic regression models to determine that tumors within 3 mm of a 17-mm maximum tumor size threshold were more amenable to a resection that resulted in better outcomes for their patients. 10 Although evaluating our surgical cohort's outcomes was outside the scope of this work, we are assured to see that our active treatment-prompting tumor size threshold lines up with other centers in guiding our institution's practice.…”

“…1 Recently, evidence-based methods have been gaining popularity in guiding VS surgical decision-making with a particular focus on machine learning (ML) approaches. 10,11 Still, treatment algorithms from diverse centers and populations are desired to discern which patient and tumor-related variables should reliably prompt active VS treatment. Tree-based ML provides a powerful set of tools to accomplish classification (categorical outcomes) or regression (continuous outcomes) tasks in multidimensional clinical settings.…”

Technology Behavior Model—Beyond Your Sight with Extended Reality in Surgery

“…Their eye does not move and focus on the surgical operation. In some delicate surgeries the clarity of human eyes cannot meet the demand, and surgeons need to use a microscope to perform the surgery [4], for instance, vestibular schwannoma of the brain [5], dental pulp nerve endings [6], and intracranial dural arteriovenous fistulae [7]. Nevertheless, the microscope is too bulky and has a small operable interface which is not conducive to surgical operations.…”