# Butterfly glioblastoma: trends in therapeutic modalities, extent of resection and survival in the temozolomide era. a SEER-based study

## TL;DR

This study shows that surgery and chemotherapy improve survival for butterfly glioblastoma patients in the temozolomide era.

## Contribution

The study demonstrates that gross total resection and adjuvant therapies improve outcomes for butterfly glioblastoma in the TMZ era.

## Key findings

- Gross total resection (GTR) is significantly associated with improved overall survival in the late TMZ era.
- Adjuvant chemotherapy, radiation therapy, and surgery are linked to better survival in the TMZ era compared to pre-TMZ.
- The rate of GTR increased over time and was associated with higher rates of post-operative adjuvant therapy.

## Abstract

Butterfly glioblastoma (bGBM) is a rare type of GBM, thought to have extremely poor outcome and is generally considered “inoperable”. The aim of this study was to investigate survival outcomes in bGBM over a long period, and to look for potential benefits of gross total resection (GTR). The data of 521 bGBM patients diagnosed between 2000 and 2021 from the Surveillance, Epidemiology, and End Results (SEER) database were obtained. The cohort was divided into 3 subgroups based on the year of diagnosis: pre-temozolomide era (pre-TMZ; 2000–2006), early TMZ era (2007–2016) and late TMZ era (2017–2021). chemotherapy was significantly more common in the TMZ group (51.9% vs. 36%, p = 0.007). The TMZ group was associated with nearly significantly improved OS (HR = 0.795, p = 0.067). On multivariate analysis, only radiation therapy was associated with improved survival in the pre-TMZ group (HR = 3.029, p = 0.001). However, in the TMZ group, 4 variables were associated with improved survival: chemotherapy (HR = 1.523, p = 0.049), radiation therapy (HR = 1.676, p = 0.006), surgery (HR = 1.402, p = 0.004) and age (HR = 1.031, p < 0.001). Both subtotal resection and GTR were significantly associated with favorable prognosis when compared to no surgery (HR = 0.607, p < 0.001 and HR = 0.467, p < 0.001; respectively). The rate of GTR was significantly higher in the late TMZ group (19.2% vs. 10.2%, p = 0.0013). GTR was significantly associated with improved OS in the late TMZ subgroup (HR = 1.846, p = 0.028). bGBM cases in the TMZ era are associated with increased rate of adjuvant chemotherapy as well as with improved OS, in comparison to pre-TMZ cases. The rate of GTR cases has significantly increased in recent years, and is associated with significantly increased rate of post operative adjuvant therapy. GTR patients who have received any kind of adjuvant therapy had significantly better OS when compared to non-GTR patients. bGBM should be treated like other operable GBM cases, using the appropriate, advanced surgical techniques.

Clinical trial number: Not applicable.

The online version contains supplementary material available at 10.1007/s10143-025-03558-2.