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Purpose <p>Historically, clinical target volume (CTV) expansions for glioblastoma (GBM) have ranged from 2 to 3&#xa0;cm. Since 2017, our institution has adopted a 1&#xa0;cm CTV expansion beyond the gross tumor volume (GTV) and postoperative cavity on contrast-enhanced T1 Magnetic Resonance (MR) scan. Our study evaluates recurrence patterns using this approach.</p> Methods <p>We identified 50 patients who developed tumor recurrence following treatment between 01/01/2017–01/31/2024 at our institution. All patients underwent maximal safe resection followed by standard chemoradiation with 60&#xa0;Gy in 30 fractions, though dose reductions to 59.4&#xa0;Gy–54&#xa0;Gy were permitted to meet organ-at-risk constraints. All but three patients received concurrent temozolomide. Radiotherapy target volumes were defined as follows: GTV included gross tumor and postoperative cavity on contrast-enhanced T1 MR, CTV included GTV plus a 1&#xa0;cm expansion (edited for anatomical barriers), and the planning target volume included a 2&#xa0;mm expansion beyond the CTV. Recurrences were classified based on the recurrence volume within the 100% isodose: in-field (&gt; 80%), marginal (20–80%), and distant (&lt; 20%).</p> Results <p>Recurrence patterns were as follows: 80% (40/50) in-field alone, 10% (5/50) in-field and distant, 8% (4/50) distant alone, and 2% (1/50) marginal alone. The single marginal recurrence had 52% of its volume within the 100% isodose.</p> Conclusions <p>In GBM patients treated with a 1&#xa0;cm CTV margin on the gross tumor and postoperative cavity on contrast-enhanced T1 MR, we observed a very low marginal recurrence (2%). These findings support the continued use of a 1&#xa0;cm CTV expansion at our institution.</p>

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Pattern of recurrence with 1.0 cm CTV in brain glioblastoma treated with radiotherapy

  • 期刊论文

  • 发表日期：

    2025年8月11日

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  • Erica L. Braschi,
  • Olivia Trumble,
  • Anthony Casper,
  • Robert J. Amdur,
  • Christopher G. Morris,
  • Alexandra N. De Leo

摘要

Purpose

Historically, clinical target volume (CTV) expansions for glioblastoma (GBM) have ranged from 2 to 3 cm. Since 2017, our institution has adopted a 1 cm CTV expansion beyond the gross tumor volume (GTV) and postoperative cavity on contrast-enhanced T1 Magnetic Resonance (MR) scan. Our study evaluates recurrence patterns using this approach.

Methods

We identified 50 patients who developed tumor recurrence following treatment between 01/01/2017–01/31/2024 at our institution. All patients underwent maximal safe resection followed by standard chemoradiation with 60 Gy in 30 fractions, though dose reductions to 59.4 Gy–54 Gy were permitted to meet organ-at-risk constraints. All but three patients received concurrent temozolomide. Radiotherapy target volumes were defined as follows: GTV included gross tumor and postoperative cavity on contrast-enhanced T1 MR, CTV included GTV plus a 1 cm expansion (edited for anatomical barriers), and the planning target volume included a 2 mm expansion beyond the CTV. Recurrences were classified based on the recurrence volume within the 100% isodose: in-field (> 80%), marginal (20–80%), and distant (< 20%).

Results

Recurrence patterns were as follows: 80% (40/50) in-field alone, 10% (5/50) in-field and distant, 8% (4/50) distant alone, and 2% (1/50) marginal alone. The single marginal recurrence had 52% of its volume within the 100% isodose.

Conclusions

In GBM patients treated with a 1 cm CTV margin on the gross tumor and postoperative cavity on contrast-enhanced T1 MR, we observed a very low marginal recurrence (2%). These findings support the continued use of a 1 cm CTV expansion at our institution.