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Radiation Necrosis Following Stereotactic Radiosurgery or Fractionated Stereotactic Radiotherapy with High
Leonie Johannwerner1, Elisa M Werner1, Oliver Blanck2,3
1Department of Radiation Oncology, University of Lubeck, 23562 Lubeck, Germany.
Biology
|May 27, 2023
Summary
Fractionated stereotactic radiotherapy (FSRT) with higher biologically effective doses (BED) shows a lower risk of radiation necrosis for brain metastases larger than 20 mm compared to single-fraction radiosurgery (SRS). FSRT may be a safer option for these larger lesions.
Area of Science:
- Radiation Oncology
- Neurosurgery
- Medical Physics
Background:
- Previous studies established 18 Gy (BED 45 Gy12) as the maximum tolerated dose for single-fraction radiosurgery (SRS) of brain metastases (21-30 mm) in patients with prior irradiation.
- Radiotherapy-naive lesions may tolerate higher biologically effective doses (BED) than previously irradiated lesions.
- Investigating higher BED SRS and fractionated stereotactic radiotherapy (FSRT) for de novo brain metastases is warranted.
Purpose of the Study:
- To compare the risk of grade ≥ 2 radiation necrosis (RN) between SRS and FSRT for radiotherapy-naive brain metastases.
- To evaluate the impact of lesion size on RN rates for both SRS and FSRT.
- To determine the safety and efficacy of higher BED FSRT for larger brain metastases.
Main Methods:
- Retrospective analysis of 169 patients with 218 brain metastases treated with SRS (19-20 Gy) or FSRT (30-48 Gy in 3-12 fractions) with BED > 49 Gy12.
- Patients were stratified by treatment modality (SRS vs. FSRT) and lesion size (≤ 20 mm vs. > 20 mm).
- Radiation necrosis rates were assessed at 1 and 2 years post-treatment using per-patient and per-lesion analyses.
Main Results:
- Overall RN rates were similar between SRS and FSRT (8% vs. 7% at 1 year, 13% vs. 10% at 2 years per-patient).
- For lesions ≤ 20 mm, RN rates were comparable between SRS and FSRT (4% vs. 0% at 1 year, 15% vs. 11% at 2 years per-patient).
- For lesions > 20 mm, FSRT demonstrated significantly lower RN rates than SRS (9% vs. 50% per-patient, p=0.012). Lesion size > 20 mm was a significant predictor of RN after SRS but not FSRT.
Conclusions:
- Fractionated stereotactic radiotherapy (FSRT) with BED > 49 Gy12 is associated with a low risk of radiation necrosis for brain metastases.
- FSRT appears safer than SRS for brain metastases larger than 20 mm, with lesion size not impacting RN risk in the FSRT group.
- Higher BED FSRT may be a preferred treatment option for larger, radiotherapy-naive brain metastases to minimize radiation necrosis.
