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MO_6_2609 - Predictors for and Clinical Impact of Time between Surgical Resection and Radiation Therapy in Glioblastoma: Analysis of the National Cancer Database

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

Predictors for and Clinical Impact of Time between Surgical Resection and Radiation Therapy in Glioblastoma: Analysis of the National Cancer Database
S. M. Buszek1, K. A. Al Feghali1, H. Elhalawani1, N. C. Chevli1, P. K. Allen2, and C. Chung1; 1Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, 2Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX

Purpose/Objective(s): Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and standard of care treatment includes maximal safe surgical resection followed by adjuvant radiotherapy (RT) and chemotherapy. The optimal time interval between surgery and the initiation of adjuvant therapy remains unclear. This study aims to use the National Cancer Database (NCDB) to identify predictors for and clinical impact of time from surgical resection to initiation of RT in patients with newly diagnosed GBM.

Materials/Methods: The NCDB was queried for adult patients with diagnostic codes for GBM or grade IV glioma diagnosed from 2004 to 2015 who were treated with RT following surgical resection. Time intervals between surgery and the start of RT were grouped into ≤ 4 weeks, 4.1-6 weeks, 6.1-8 weeks, and >8 weeks. Univariate analyses (UVAs) and multivariate analyses (MVAs) were performed to investigate factors associated with the length of time between resection and radiation and impact of timing and other factors on survival.

Results: A total of 46,012 patients, with a median age of 61 years (range 18-90 years) met inclusion criteria. Median time interval from resection to RT was 29 days (range 2-620 days) and median survival was 14.4 months. On UVA, median survival was significantly different between time intervals (p<0.0001): 13.9 months for ≤ 4 weeks, 15.2 months for 4.1-6 weeks, 14.4 months for 6.1-8 weeks, and 14.7 months for >8 weeks. On MVA, ≤ 4 week interval was associated with worse survival than the intervals of 4-6 weeks or 6-8 weeks (HR 0.94 and p<0.001, HR 0.92 and p=0.002, respectively), but > 8 weeks was not associated with worse survival (≤ 4 weeks HR 1.05, p=0.2; 4.1-6 weeks HR 0.99, p=0.7; 6.1-8 weeks HR 0.96 p=0.4). Other factors associated with worse survival on MVA were older age (HR 1.03, p=<0.001), male gender (HR 0.92, p<0.001), KPS < 70 (HR 0.63, p<0.001), and less than a gross total resection (GTR; HR 1.2, p <0.001).

Conclusion: This large retrospective analysis of the NCDB suggests that patients with newly diagnosed GBM who start RT within four weeks of surgical resection have worse outcomes. This is consistent with prior studies that have reported detriment to overall survival if RT was started within 2 weeks of surgery. Beyond 4 weeks, the time frame from surgery was not found to be an independent prognostic variable for survival.

Author Disclosure: S.M. Buszek: None. K.A. Al Feghali: None. H. Elhalawani: None. P.K. Allen: None. C. Chung: None.

Samantha Buszek, MD

Biography:
Samantha M. (Bitter) Buszek, MD is a radiation oncology resident at MD Anderson Cancer Center in Houston, Texas. She completed her engineering and Medical Doctorate training in Cincinnati, Ohio. Her research interests include functional neuroimaging and patient satisfaction and quality of life. Her personal interests include medical device design and innovation, cancer survivorship, palliative care, and patient quality and safety.

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