Baseline pretreatment contrast enhancing tumor volume including central necrosis is a prognostic factor in recurrent glioblastoma: evidence from single and multicenter trials.

BACKGROUND: The prognostic significance of baseline contrast enhancing tumor prior to second- or third-line therapy in recurrent glioblastoma (GBM) for overall survival (OS) remains controversial, particularly in the context of repeated surgical resection and/or use of anti-angiogenic therapy. In the current study, we examined recurrent GBM patients from both single and multicenter clinical trials to test whether baseline enhancing tumor volume, including central necrosis, is a significant prognostic factor for OS in recurrent GBM. METHODS: Included were 497 patients with recurrent GBM from 4 data sources: 2 single-center sites (University of Toronto, University of California Los Angeles) and 2 phase II multicenter trials (AVF3708G, Bevacizumab ± Irinotecan, NCT00345163; XL184-201, Cabozantinib, NCT00704288). T1 subtraction maps were used to define volume of contrast enhancing tumor, including central necrosis. Cox multivariable and univariate analyses were used to evaluate the relationship between tumor volume prior to second- or third-line therapy and OS. RESULTS: Both continuous measures of baseline tumor volume and tumors dichotomized into large (≥15cc) and small (<15cc) tumors were significant predictors of OS (P<.0001), independently of age and treatment. Univariate analysis demonstrated significant OS differences (P<.05) between large (≥15cc) and small (<15cc) tumors in patients under all therapeutic scenarios. Only patients treated with cabozantinib who previously failed anti-angiogenic therapy did not show an OS dependence on baseline tumor volume. CONCLUSIONS: Baseline tumor volume is a significant prognostic factor in recurrent GBM. Clinical trial treatment arms must have a balanced distribution of tumor size, and tumor size should be considered when interpreting therapeutic efficacy.

Contrast-enhancing tumor growth dynamics of preoperative, treatment-naive human glioblastoma.

BACKGROUND: Little is known about the natural growth characteristics of untreated glioblastoma before surgical or therapeutic intervention, because patients are rapidly treated after preliminary radiographic diagnosis. Understanding the growth characteristics of uninhibited human glioblastoma may be useful for characterizing changes in response to therapy. Thus, the objective of the current study was to explore tumor growth dynamics in a cohort of patients with untreated glioblastoma before surgical or therapeutic intervention. METHODS: Ninety-five patients with glioblastoma who had measurable enhancing disease on >2 magnetic resonance imaging scans before surgery were identified. Tumor growth rates were quantified in 4 different ways (the percentage change per day, the absolute rate of change per day, the estimated volumetric doubling time, and the radial expansion rate) using 3 different approaches (bidirectional product, enhancing disease, and total lesion volume). RESULTS: The median volumetric doubling time was 21.1 days, the percentage change in tumor volume was 2.1% per day, and the rate of change in total lesion volume was 0.18 cc per day. The length of follow-up between magnetic resonance imaging examinations should be >28 days to detect progressive disease with high specificity. Small initial tumor sizes (<3 cm in greatest dimension) are biased toward a large percentage change at follow-up. CONCLUSIONS: Presurgical, treatment-naive glioblastoma growth dynamics can be estimated in a variety of ways with similar results. The percentage changes in tumor size and volume depend on baseline tumor size and the time interval between scans. Cancer 2016;122:1718-27. © 2016 American Cancer Society.