Abstract
BackgroundThe optimal treatment volume for Glioblastoma multiforme (GBM) is still a subject of debate worldwide. The current study was aimed to determine the distances between recurring tumors and the edge of primary lesions, and thereby provide evidence for accurate target area delineation.MethodsBetween October 2007 and March 2019, 68 recurrent patients with GBM were included in our study. We measured the distance from the initial tumor to the recurrent lesion of GBM patients by expanding the initial gross tumor volume (GTV) to overlap the center of recurrent lesion, with the help of the Pinnacle Treatment Planning System.ResultsRecurrences were local in 47(69.1%) patients, distant in 12(17.7%) patients, and both in 9(13.2%) patients. Factors significantly influencing local recurrence were age (P = 0.049), sex (P = 0.049), and the size of peritumoral edema (P = 0.00). A total number of 91 recurrent tumors were analyzed. All local recurrences occurred within 2 cm and 94.8% (55/58) occurred within 1 cm of the original GTV based on T1 enhanced imaging. All local recurrences occurred within 1.5 cm and 98.3%(57/58) occurred within 0.5 cm of the original GTV based on T2-FLAIR imaging. 90.9% (30/33) and 81.8% (27/33) distant recurrences occurred >3 cm of T1 enhanced and T2-Flair primary tumor margins, respectively.ConclusionsThe 1 cm margin from T1 enhanced lesions and 0.5 cm margin from T2-Flair abnormal lesions could cover 94.8 and 98.3% local recurrences respectively, which deserves further prospective study as a limited but effective target area.
Highlights
Glioblastoma multiforme (GBM) is a common type malignancy with dismal prognosis in the primary brain tumors worldwide [1,2,3]
The recurrent lesions were defined as “in-field” if > 80% of the intersecting area was covered by the 95% isodose line, “marginal” if 20–80% of the intersecting region was inside of the 95% isodose line, or “distant” if< 20% of the intersectant volume was included in the 95% isodose line [13]
Sixty-eight cases of recurrent GBM initially treated with postoperative radiotherapy between October 2007 and March 2019 were available for analysis
Summary
Glioblastoma multiforme (GBM) is a common type malignancy with dismal prognosis in the primary brain tumors worldwide [1,2,3]. The European Organization for Research and Treatment of Cancer (EORTC) employs a single target volume with 2–3 cm radiation margins around the primary tumor bed (based on abnormalities on post-contrast MRI) [4]. The Radiation Therapy Oncology Group (RTOG) implements the initial clinical target volume (CTV) and the boost field separately by adding a 2-cm margin to postoperative peritumoral edema and residual tumor [11]. The University of Texas MD Anderson Cancer Center adds a 2 cm margin around the gross tumor volume (GTV) to generate CTV, which comprises the surgical cavity and the postoperative residual tumor, while excluding any edema. The optimal treatment volume for Glioblastoma multiforme (GBM) is still a subject of debate worldwide. The current study was aimed to determine the distances between recurring tumors and the edge of primary lesions, and thereby provide evidence for accurate target area delineation
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