Defining Glioblastoma Resectability Through the Wisdom of the Crowd: A Proof-of-Principle Study

Abstract

Background: Extent of resection (EOR) correlates with glioblastoma outcomes. Resectability and EOR depend on anatomical, clinical, and surgeon factors. Resectability likely influences outcome in and of itself, but an accurate measurement of resectability remains elusive. An understanding of resectability and the factors that influence it may provide a means to control a confounder in clinical trials and provide reference for decision making.

Objective: To provide proof of concept of the use of the collective wisdom of experienced brain tumor surgeons in assessing glioblastoma resectability.

Methods: We surveyed 13 academic tumor neurosurgeons nationwide to assess the resectability of newly diagnosed glioblastoma. Participants reviewed 20 cases, including digital imaging and communications in medicine-formatted pre- and postoperative magnetic resonance images and clinical vignettes. The selected cases involved a variety of anatomical locations and a range of EOR. Participants were asked about surgical goal, eg, gross total resection, subtotal resection (STR), or biopsy, and rationale for their decision. We calculated a "resectability index" for each lesion by pooling responses from all 13 surgeons.

Results: Neurosurgeons' individual surgical goals varied significantly ( P = .015), but the resectability index calculated from the surgeons' pooled responses was strongly correlated with the percentage of contrast-enhancing residual tumor ( R = 0.817, P < .001). The collective STR goal predicted intraoperative decision of intentional STR documented on operative notes ( P < .01) and nonresectable residual ( P < .01), but not resectable residual.

Conclusion: In this pilot study, we demonstrate the feasibility of measuring the resectability of glioblastoma through crowdsourcing. This tool could be used to quantify resectability, a potential confounder in neuro-oncology clinical trials.

Keywords: Crowdsourcing; EOR; Extent of resection; Glioblastoma; Glioma; Resectability.

FIGURE 1.

Flowcharts showing the sequence of questions associated with each set of MRIs. GTR, gross total resection; STR, subtotal resection.

FIGURE 2.

The percentage of patients for whom each surgeon selected GTR, STR, and biopsy. A, surgeons are ranked by AI in descending order from left to right. B, a scatter plot representation of the AI for each individual surgeon, with the surgeons ranked by AI as above. A lower value on AI signifies a neurosurgeon who has more aggressive surgical goals, and a higher value represents more conservative surgical goals. AI, aggressiveness index; GTR, gross total resection; STR, subtotal resection.

FIGURE 3.

MRI images in 3 planes for the most resectable (patient 17), least resectable (patient 19), and most controversial patient (patient 18), as determined by level of variance. See Table 1 for variance of responses for surgical goals. A heat map illustrating each surgeon's management plan for these 3 patients is also included, with white representing biopsy, light gray representing subtotal resection, dark gray representing gross total resection, and black representing no response. Surgeons are ranked by AI from most aggressive ( top ) to least aggressive ( bottom ). AI, aggressiveness index; GTR, gross total resection; RI, resectability index; STR, subtotal resection.

FIGURE 4.

Reasons cited for not selecting GTR as the surgical goal for residual disease on postoperative imaging. For each patient, bars depict the percentage of surgeons selecting a response on a multiple-choice menu presented for choosing the reason for not electing to pursue GTR. Patients for whom all surgeons reported that GTR was achieved, patients for whom all surgeons agreed that the residual disease was resectable, and patients who underwent a biopsy were excluded from the analysis. GTR, gross total resection.

FIGURE 5.

Scatter plots with linear regressions relating the percentage of residual enhancing tumor to NIH score (slope = 8.4 [−8.9 to 25.7], R = 0.233, P = .322) A; MSM score (slope = 14.4 [2.5-26.3], R = 0.515, P = .020) B; and resectability index (RI) (slope = 49.4 [32.1-66.7], R = 0.817, P < .001)C. Slope is defined as percentage of tumor/RI unit. MSM, motor-speech-middle cerebral artery component.