Central Nervous System

PV QA 2 - Poster Viewing Q&A 2

MO_13_2792 - Effect of Whole Brain Radiation Therapy on the Absolute Brain Volume Loss

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Effect of Whole Brain Radiation Therapy on the Absolute Brain Volume Loss
L. Pang, A. Stessin, A. T. Hsia, K. M. Mani, W. Hou, and S. Ryu; Radiation Oncology, Stony Brook University Hospital, Stony Brook, NY

Purpose/Objective(s): Whole brain radiation therapy (WBRT) is associated with neurocognitive toxicity. The underlying pathology and mechanism of radiation-induced neurotoxicity is diverse. We hypothesized that patients who underwent WBRT exhibit significant loss of brain parenchymal tissue, which may also contribute to the development of neurocognitive toxicity.

Materials/Methods: We conducted a retrospective study of 105 patients (male: 46, female: 59) who underwent WBRT for brain metastases or prophylactic cranial irradiation, who had both pre- and post-WBRT imaging studies. There were CT (74 pts) and MRI (31 pts) scans, pre- and post-WBRT for median duration of 6 months (range 1-137). The entire brain volume was contoured from the superior sagittal sinus to the foramen magnum. To measure true parenchymal volume, the ventricular system was excluded. The metastatic lesions were included in the brain volume. The brain volume change was plotted over time. We compared this volume change to that of the general aging population, reported in past systematic reviews. We also identified the contributing factors to the brain volume loss. A linear mixed-effect model was fitted for repeated measure of brain volume with adjustment for baseline characteristics. Pre- and post-WBRT volumes were compared using post-hoc t-test based on the model.

Results: Pretreatment average whole brain volume was 1280 cc ± 140, and the average brain volume of posttreatment was 1215.5 cc ± 149. The absolute brain volume was significantly reduced after WBRT by 64.5 cc ± 49.7 (p<0.0001). The mean annual percent of volume reduction was -5% ± 4 (p<0.0001). This annual change of brain volume reduction was in sharp contrast with the annual rate, from -0.9% to +1.1%, of an age-matched healthy population between 40-60 years of age. There were two distinct populations of rapid versus gradual volume loss within 6 months after WBRT, based on the median slope of volume loss 0.33. The rapid volume loss was associated with older age (65 years ± 9) compared to the group of gradual loss (56 years ± 13, p<0.05). Uni- and multivariate analyses showed no significant interaction between the volume change with gender, race, primary tumor type, or survival. Interestingly, patients with lesion number 0-2 had higher brain volume loss and percent volume change (-73.7 cc ± 48.3; -0.06% ± 0.04) compared to those with >5 lesions (-49.1 cc ± 37.3; -0.04% ± 0.03, p<0.05).

Conclusion: Patients who undergo WBRT are at higher risk for absolute and percent brain volume loss. Older age at WBRT appears to be an important contributing factor for a rapid volume loss. The results support avoidance or judicious use of WBRT, particularly for older patients and for limited number of brain metastases.

Author Disclosure: L. Pang: None. A. Stessin: None. K.M. Mani: None. W. Hou: None. S. Ryu: Honoraria; Varian. Speaker's Bureau; Varian. Advisory Board; Varian. President; International Stereotactic Radiosurgery Society. Board member; Scientific advisory board for Chrysalis BioTherapeutics.

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