Recurrence analysis of glioblastoma cases based on distance and dose information

Abstract

Background and purpose: Radiation therapy for glioblastoma (GBM) typically involves large target volumes. The aim of this study was to examine the recurrence pattern of GBM following modern radiochemotherapy according to EORTC guidelines and provide dose and distance information for the choice of optimal target volume margins.

Materials and methods: In this study, the recurrences of 97 GBM patients, treated with radiochemotherapy from 2013 to 2017 at the Medical Center- University of Freiburg, Germany were analysed. Dose and distance based metrices were used to derive recurrence patterns.

Results: The majority of recurrences (75%) occurred locally within the primary tumor area. Smaller GTVs had a higher rate of distant recurrences. Larger treated volumes did not show a clinical benefit regarding progression free and overall survival.

Conclusion: The identified recurrence pattern suggests that adjustments or reductions in target volume margins are feasible and could result in similar survival rates, potentially combined with a lower risk of side effects.

Keywords: Glioblastoma; Radiotherapy; Recurrence; Target volume.

Fig. A5.

Results of the distance-dose analysis with respect to minimum, maximum and mean doses. The horizontal red line is equivalent to the suggested 2 cm margin in literature (for details and literature see 1).

Fig. A6.

Results of the distance-dose analysis with respect to median, standard deviation and relative volume RV. The horizontal red line is equivalent to the suggested 2 cm margin in literature (for details and literature see 1).

Fig. A7.

Results of the distance-dose analysis with respect to the overlapping relative volume. The horizontal red line indicates the recommended 2 cm margin in literature (for details and literature see 1).

Fig. A8.

Two dimensional slice showing the recurrence (white), the COM of which is 4 mm away from the $\mathrm{G}\mathrm{T}\mathrm{V}$ (grey) surface.

Fig. 1.

a: Schematical representation of the distance recurrence analysis. For illustration reasons the image is shown in R² (instead of R³ - further details see text). b: Example of the marginal analysis (for illustration reasons the image is shown in R² (instead of R³). White: $\mathrm{G}\mathrm{T}\mathrm{V}$. Light-grey: $V_{HD}$ covered with 57 Gy. Dark-grey: Volume created by the marginal analysis using $d_{margin}\left(GTV,H_{HD}\right)$.

Fig. 2.

Examples for locations of recurrences (white) with respect to the $\mathrm{G}\mathrm{T}\mathrm{V}$ (grey). Left: central recurrence within the $\mathrm{G}\mathrm{T}\mathrm{V}$. Right: marginal recurrence.

Fig. 3.

Kaplan Meier survival curves of Time to progression (left) and time to death (right), measured in months for both groups (smaller and larger or equal to the median $d_{margin}\left(GTV,H_{HD}\right)$. Shaded areas are the respective 95 % confidence levels. For details see text.

Fig. 4.

a: Results of the distance-dose analysis with respect to the mean dose. The horizontal red line indicates the suggested 2 cm margin in literature (for details and literature see 1). b: Here the $d(GTV,Rec)$ of the recurrences from the $\mathrm{G}\mathrm{T}\mathrm{V}$ is plotted as a function of the absolute $\mathrm{G}\mathrm{T}\mathrm{V}$ Volume measured in ml.