Is 3D-CRT still a reasonable option for high-grade gliomas in contact with the brainstem in the absence of IMRT/VMAT?

INTRODUCTION

High-grade gliomas (HGGs) abutting the brainstem present a planning challenge because target coverage must be balanced against brainstem dose constraints. This study assessed whether three-dimensional conformal radiotherapy (3D-CRT) remains a reasonable option when intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) are unavailable, and whether partial-arc VMAT (P-VMAT) offers advantages over full-arc VMAT (F-VMAT) in lateral HGGs.

METHODS

Thirty-seven patients with lateral HGGs in direct brainstem contact, treated between 2021 and 2025, were planned using 3D-CRT, IMRT, P-VMAT, and F-VMAT. Evaluation included uncomplicated target conformity index (UTCI), plan quality index (PQI), integrated dosimetric indices for tumor and organs (IDITumor and IDIOrgans), target coverage, organs-at-risk (OARs) sparing, and integral dose (ID).

RESULTS

IMRT, P-VMAT, and F-VMAT achieved superior target quality versus 3D-CRT, with limited differences among the modulated techniques. P-VMAT showed the most favorable UTCI and ID values (p < 0.05). IDITumor was highest with 3D-CRT, whereas IDIOrgans and PQI showed no significant differences (p > 0.05), although PQI numerically favored IMRT. For the brainstem, 3D-CRT produced the least favorable high-dose values, with a significantly higher maximum dose (Dmax) than the modulated radiotherapy techniques (p < 0.05). Conversely, 3D-CRT yielded lower doses to distant non-brainstem OARs. P-VMAT achieved the lowest healthy-tissue mean dose (Dmean), indicating reduced normal-brain dose spread.

CONCLUSIONS

For lateral HGGs abutting the brainstem, modulated techniques are preferable for target quality and brainstem Dmax sparing. Nevertheless, 3D-CRT may remain a reasonable option when IMRT/VMAT are unavailable, particularly because it may better spare distant OARs despite inferior brainstem Dmax control.

PLAIN LANGUAGE SUMMARY: Some brain tumours grow very close to the brainstem, making radiation treatment harder to plan safely. This study compared four radiation treatment methods to see how well they treated the tumour while protecting nearby healthy tissue. This study found that newer treatment methods generally gave better tumour coverage and better brainstem protection than a traditional method, although the traditional method protected some more distant healthy areas. This matters because it can help clinicians choose safe and effective treatment options when different technologies are available.