Relationship between radiation dose and microbleed formation in patients with malignant glioma
Michael Wahl1, Mekhail Anwar1, Christopher P Hess2,3
1Department of Radiation Oncology, University of California, San Francisco, CA, USA.
Background:
Cranial irradiation is associated with long-term cognitive changes. Cerebral microbleeds (CMBs) have been identified on susceptibility-weighted MRI (SWI) in patients who have received prior cranial radiation, and serve as radiographic markers for microvascular injury thought to contribute to late cognitive decline. The relationship between CMB formation and radiation dose has not previously been quantified.
Methods:
SWI was performed on 13 patients with stable WHO grade III-IV gliomas between 2 and 4 years after chemoradiotherapy to 60 Gy. The median age at the time of treatment was 41 years (range 25 - 74 years). CMBs were identified as discrete foci of susceptibility on SWI that did not correspond to vessels. CMB density for low (<30 Gy), median (30-45 Gy), and high (>45 Gy) dose regions was computed.
Results:
Twelve of 13 patients exhibited CMBs. The number of CMBs was significantly higher for late (>3 years from treatment) compared to early (<3 years) timepoints (early median 6 CMBs; late median 27 CMBs; p = 0.001), and there were proportionally more CMBs at lower doses for late scans (p = 0.006). 88% of all CMBs were observed in regions receiving at least 30 Gy, but the CMB density within medium and high dose regions was not significantly different (p = 0.33 and p = 0.9, respectively, for early and late time points).
Conclusions:
CMBs predominantly form in regions receiving at least 30 Gy, but form in lower dose regions with longer follow-up. We do not observe a clear dose-response relationship at doses above 30 Gy. These findings provide important information to assess the risk of late microvascular sequelae from cranial irradiation.
Insights
Cerebral microbleeds (CMBs) after cranial radiation predominantly form in areas receiving at least 30 Gy. With longer follow-up, CMBs appear in lower dose regions, suggesting delayed microvascular injury.
Area of Science:
- Neuro-oncology
- Radiation oncology
- Neuroradiology
Background:
- Cranial irradiation can cause long-term cognitive deficits.
- Cerebral microbleeds (CMBs) on MRI indicate microvascular injury post-radiation, linked to cognitive decline.
- The dose-response relationship for CMB formation after cranial radiation is not well-defined.
Purpose of the Study:
- To quantify the relationship between radiation dose and cerebral microbleed (CMB) formation.
- To investigate the impact of radiation dose on microvascular injury markers.
Main Methods:
- Susceptibility-weighted MRI (SWI) was used to identify CMBs in 13 glioma patients 2-4 years post-chemoradiotherapy (60 Gy).
- CMB density was calculated for low (<30 Gy), median (30-45 Gy), and high (>45 Gy) radiation dose regions.
- Patients' ages at treatment ranged from 25 to 74 years, with a median of 41 years.
Main Results:
- CMBs were detected in 12 of 13 patients.
- Significantly more CMBs were observed at later time points (>3 years post-treatment) compared to earlier ones (median 27 vs. 6 CMBs, p=0.001).
- CMBs were more prevalent in lower dose regions on later scans (p=0.006), with 88% occurring in areas receiving ≥30 Gy. No significant difference in CMB density was found between medium and high dose regions.
Conclusions:
- Cerebral microbleeds primarily develop in areas receiving at least 30 Gy of radiation.
- Over extended follow-up periods, CMBs emerge in lower-dose regions, indicating a delayed microvascular response.
- A clear dose-response relationship for CMBs was not evident at radiation doses exceeding 30 Gy.
