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. 2021 Mar 3:17:40-47.
doi: 10.1016/j.tipsro.2021.02.008. eCollection 2021 Mar.

Impact of PTV margin reduction (2 mm to 0 mm) on pseudoprogression in stereotactic radiotherapy of solitary brain metastases

Justine Badloe  1   2 , Mirjam Mast  1 , Anna Petoukhova  3 , Jan-Huib Franssen  2 , Elyas Ghariq  4 , Noëlle van der Voort van Zijp  1 , Ruud Wiggenraad  1
Affiliations

Impact of PTV margin reduction (2 mm to 0 mm) on pseudoprogression in stereotactic radiotherapy of solitary brain metastases

Justine Badloe et al. Tech Innov Patient Support Radiat Oncol. .

Abstract

Purpose: To determine the influence of PTV-margin (0 mm versus 2 mm) on the incidence of pseudoprogression (PP) and local tumour control (LC) in patients treated with stereotactic radiotherapy (SRT) for solitary brain metastases.

Methods: Patients were treated on Novalis LINAC. Three dose schedules were used depending on the PTV-size. The PTV-margin was 2-mm prior to 2015 and 0-mm thereafter. MRI-scans were made every three months including a perfusion MRI-scan when pseudoprogression was suspected. We examined the relation of pseudoprogression and local control with the size of PTV-margin. Besides this, the association of dose-volume data of the whole brain (minus GTV) and pseudoprogression was investigated.

Results: 121 patients were analyzed (2-mm margin in 84 patients; 0-mm margin in 37 patients). There was no difference in GTV (7.6 cc versus 9.1 cc p = 0.2). At 24 months there was no difference in incidence of pseudoprogression (49% and versus 33%, p = 0.5) and local control in the 2-mm and 0-mm group (82% and versus 79%, p = 1.0). The size of PTV-margin was not associated with PP. Both margin and volume of brain receiving 12 Gy (V12) were not associated with pseudoprogression in patients treated with single fraction.

Conclusions: PTV-margin reduction did not reduce the incidence of pseudoprogression in LINAC-based-SRT for single brain metastases. We did not find a significant association of GTV-PTV margin or V12Gy with the incidence of pseudoprogression in solitary metastases treated with a single fraction. LC rates were similar, indicating margin reduction seems to be safe.

Keywords: Brain metastases; Margins; Pseudoprogression; Stereotactic radiotherapy.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Dose distributions for patients from 0-mm margin (a and c) and 2-mm margin (b and d) groups, Patients, (a) GTV = PTV = 0.17 cc CI = 44%, (b) GTV = 0.23 cc, PTV = 0.89 cc, CI = 61%, (c) GTV = PTV = 5.32 cc, CI = 76%, (d) GTV = 5.63 cc, PTV = 9.9 cc, CI = 81%.
Fig. 2
Fig. 2
a: Time to pseudoprogression after stereotactic radiotherapy b: Time to local control after stereotactic radiotherapy. c: Overall survival: Kaplan-Meier analysis. Dark Blue: 0-mm; Light Blue: 2-mm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3
Fig. 3
Boxplot correlation between V12 (cc) and yes/no pseudoprogression for single metastasis treated with a single fraction. Boxplot showing median, 1st and 3rd quartile and 95% CI. The asterisks with the numbers refer to single patients, their values are classified as “weak outliers”.
See this image and copyright information in PMC

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