Using Smaller than Standard Radiation Treatment Margins Does Not Change Survival Outcomes in High-grade Gliomas

Publication date: Available online 5 June 2018
Source:Practical Radiation Oncology
Author(s): Kripa Guram, Mark Smith, Timothy Ginader, Kellie Bodeker, Darrin Pelland, Edward Pennington, John M. Buatti
PurposeStudies evaluating treatment margins for high grade gliomas (HGG) are limited. We hypothesize patients with HGG treated with GTV to PTV expansion of 1cm or less will have similar progression-free survival (PFS) and overall survival (OS) as those treated according to standard RTOG or EORTC protocols. Furthermore, PFS and OS of subgroups within the study population, with GTV1 to PTV1 margins of 1.0cm and 0.4cm, will have equivalent survival outcomes.MethodsTreatment plans and outcomes for patients with pathologically confirmed HGG were analyzed (n=267). Survival (PFS and OS) was calculated from first radiation treatment. Chi-square test or Fisher's exact test was used to calculate associations between margin size and patient characteristics. Survival was estimated using Kaplan–Meier and compared using the log-rank test. All analyses were performed on the univariate level.ResultsMedian PFS and OS was 10.6 and 19.1months, respectively. By disease, median PFS and OS were 8.6 and 16.1months for glioblastoma (GBM) and 26.7 and 52.5months for anaplastic glioma (AG). Median follow-up was 18.3months. Treatment margin had no effect on outcome, with the 1.0cm GTV1-PTV1 margin subgroup (n=212) showing a median PFS and OS of 10.7 and 19.1months and the 0.4cm margin subgroup (n=55) showing a median PFS and OS of 10.2 and 19.3months. In comparison with the standard treatment with 2–3cm margins, there was not a significant difference in outcomes.ConclusionsThere is no apparent difference in survival when utilizing smaller margins compared to larger margins defined by RTOG and EORTC guidelines. While there remains no class I evidence that outcomes after treatment with smaller margins are identical to those after treatment with larger margins, this large series with long-term follow-up suggests reducing margins is safe and further investigation is warranted.



https://ift.tt/2LoNgiy