Introduction: Magnetic resonance-guided laser induced thermal therapy (MRgLITT) can be used to treat progressive in-field recurrences, regardless of underlying physiology. We analyze volumetric trends from time of radiosurgery to laser ablation to understand the behavior of progression prior to laser therapy.
Methods: A retrospective review of patients who underwent MRgLITT for treatment of post GammaKnife (GKS) recurrent metastatic tumors between November 2010 and October 2016 was performed. Lesion volumes were calculated using OsiriX Software. Volumetric trends were obtained by plotting individual lesion volumes from the nadir volume after radiosurgery to volume at laser ablation.
Results: A total of 25 post-radiation recurrent lesions in 20 patients demonstrated exponential growth and 14 tumors in 13 patients followed linear growth. For lesions following exponential growth, at an average of 305 days before ablation, the average nadir volume was 0.28 cm3 (SEM=0.07) and mean volume at ablation was 2.81 cm3 (SEM= 0.42). The average adjusted coefficient of determination was 0.94 (SEM= 0.013). The mean value for doubling factor was 72.53 days (SEM= 13.84). In the linear growth cohort, at an average of 165 days before ablation, the mean nadir volume was 1.25 cm3 (SEM= 0.27) and the average volume at ablation was 6.42 cm3 (SEM= 1.40). The mean coefficient of determination was 0.91 (SEM= 0.02) and average growth rate was 0.032 cm3 per day. Of all metastatic lesions from non-small cell lung cancer (n=17), 82% followed exponential growth and 18% showed linear growth. Breast cancer metastases (n=8) demonstrated an even distribution of exponential and linear growth. All other etiologies had three or fewer cases.
Conclusions: The exponential decay and linear regressions are accurate representations of tumor progression behavior following radiation. These preliminary results can be valuable in predicting tumor growth, based on primary tumor type, and determining an optimal time window for MRgLITT treatment.
Patient Care: This preliminary research can be valuable in understanding post-radiation recurrent tumor growth patterns to determine a time window when patients can be optimally treated with MRgLITT.
Learning Objectives: 1. Understand growth patterns of post-radiation progressive in-field recurrences
2. Recognize association between primary origin of brain metastasis and progression behavior (exponential vs. linear)