Dose homogeneity analysis of adjuvant radiation treatment in surgically resected brain metastases: Comparison of IORT, SRS, and IMRT indices

Basem A Dahshan; Joshua S Weir; Robert P Bice; Paul Renz; Daniel T Cifarelli; Linda Poplawski; Joshua Hack; John A Vargo; Christopher P Cifarelli

doi:10.1016/j.brachy.2020.11.004

Dose homogeneity analysis of adjuvant radiation treatment in surgically resected brain metastases: Comparison of IORT, SRS, and IMRT indices

Brachytherapy. 2021 Mar-Apr;20(2):426-432. doi: 10.1016/j.brachy.2020.11.004. Epub 2021 Jan 14.

Authors

Basem A Dahshan¹, Joshua S Weir¹, Robert P Bice¹, Paul Renz², Daniel T Cifarelli³, Linda Poplawski¹, Joshua Hack¹, John A Vargo⁴, Christopher P Cifarelli⁵

Affiliations

¹ Department of Radiation Oncology, West Virginia University, Morgantown, WV.
² Department of Radiation Oncology, Allegheny General Hospital, Pittsburgh, PA.
³ Department of Neurosurgery, West Virginia University, Morgantown, WV.
⁴ Department of Radiation Oncology, UPMC, Pittsburgh, PA.
⁵ Department of Radiation Oncology, West Virginia University, Morgantown, WV; Department of Neurosurgery, West Virginia University, Morgantown, WV. Electronic address: cpcifarelli@hsc.wvu.edu.

Abstract

Purpose: Although surgery remains a treatment option for symptomatic brain metastases, the need for adjuvant radiation after surgery is widely accepted as standard. Despite a multitude of randomized trials aimed at identifying the ideal radiation treatment plan for surgically resected metastases, the development of new delivery regiments necessitates a periodic re-evaluation of dosimetric performance/outcome. Here, we compare the homogeneity index (HI) across three platforms: single-session stereotactic radiosurgery (SRS), multisession stereotactic radiotherapy, and intraoperative radiotherapy (IORT).

Methods and materials: Patients treated with IORT after surgical resection of brain metastases were identified and dosimetric parameters collected from the dose-volume histograms based on the development of conformal plans for adjuvant radiation using Gamma Knife-SRS (GK-SRS), linear accelerator based intensity-modulated radiation therapy, and IORT. HIs were calculated using four established methods and compared across platforms within the patient cohort. Statistical analyses were performed using analysis of variance.

Results: The mean maximal doses for the GK-SRS and IMRT plans were 30 Gy and 29 Gy with margin prescription doses of 16 Gy and 24 Gy, respectively. The IORT dose was 30 Gy to the applicator surface. HIs varied based on calculation methods, but maintained consistency when comparing across platforms with IORT having the lower mean HI value (0.56; 95% confidence interval (CI) 0.55-0.60) in single-fraction treatment, compared with GK-SRS (0.77; 95% CI 0.76-0.80). The mean multisession IMRT HI was lower than both single-fraction treatment modalities at 0.41 (95% CI 0.40-0.42).

Conclusions: When using the HI as the primary dosimetric parameter for adjuvant radiation plans after surgical resection of brain metastases IORT offers improved dose homogeneity compared with GK-SRS in single-fraction treatment, whereas fractionated LINAC-based IMRT was superior with respect to the HI in comparison among all three methods.

Keywords: Brain metastases; Gamma Knife; Homogeneity index; IMRT; IORT; Radiation.

Publication types

Research Support, N.I.H., Extramural

MeSH terms

Brachytherapy* / methods
Brain Neoplasms* / radiotherapy
Brain Neoplasms* / surgery
Humans
Radiosurgery*
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Intensity-Modulated*

Abstract

Publication types

MeSH terms

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