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A pathology-based substrate for target definition in radiosurgery of brain metastases
Brigitta G Baumert1, Isabelle Rutten, Cary Dehing-Oberije
1Department of Radiation Oncology (MAASTRO), GROW, University Hospital Maastricht, Maastricht, The Netherlands. brigitta.baumert@maastro.nl
Purpose:
To investigate the need of a margin other than for accuracy reasons in stereotactic radiosurgery (SRS) of brain metastases by means of histopathology.
Methods And Materials:
Evaluation of 45 patients from two pathology departments having had brain metastases and an autopsy of the brain. Growth patterns were reviewed with a focus on infiltration beyond the metastases boundary and made visible with immunohistochemical staining: the metastasis itself with tumor-specific markers, surrounding normal brain tissue with a glial marker, and a possible capsule with a soft tissue marker. Measurements were corrected by a tissue-shrinkage correction factor taken from literature. Outcomes parameters for infiltration were mean and maximum depths of infiltration and number of measured infiltration sites.
Results:
In 48 of 76 metastases, an infiltration was present. The largest group of metastases was lung cancer. Small-cell lung cancer (SCLC) and melanoma showed a maximum depth of infiltration of > or =1 mm, and other histologies <1 mm. For non-small-cell lung cancer (NSCLC), melanoma, and sarcoma, the highest number of infiltrative sites were observed (median, 2; range, 1-8). SCLC showed significantly larger infiltrative growth, compared with other diagnostic groups. In NSCLC, the highest percentage of infiltration was present (70%).
Conclusions:
Infiltrative growth beyond the border of the brain metastasis was demonstrated in 63% of the cases evaluated. Infiltrative growth, therefore, has an impact in defining the clinical target volume for SRS of brain metastases, and a margin of approximately 1 mm should be added to the visible lesion.
Insights
Histopathology revealed infiltrative growth in 63% of brain metastases, necessitating a margin beyond visible borders for stereotactic radiosurgery (SRS). A 1 mm margin is recommended for accurate treatment planning in brain metastases SRS.
Area of Science:
- Neurology
- Oncology
- Pathology
Background:
- Brain metastases pose significant challenges in stereotactic radiosurgery (SRS).
- Accurate delineation of tumor boundaries is crucial for effective SRS planning.
- The extent of microscopic infiltration beyond visible tumor margins remains an area of investigation.
Purpose of the Study:
- To histopathologically investigate the necessity of a margin beyond accuracy considerations in stereotactic radiosurgery for brain metastases.
- To determine the extent of infiltrative growth in brain metastases.
Main Methods:
- Evaluation of 45 patient autopsy brain samples with metastases.
- Immunohistochemical staining to visualize tumor, glial, and soft tissue markers.
- Analysis of infiltration depth and number of sites, with correction for tissue shrinkage.
Main Results:
- Infiltration beyond metastasis boundaries was observed in 63% of cases (48/76 metastases).
- Small-cell lung cancer (SCLC) and melanoma showed infiltration depths of >= 1 mm.
- Non-small-cell lung cancer (NSCLC) exhibited the highest infiltration percentage (70%).
Conclusions:
- Microscopic infiltrative growth beyond visible brain metastases is common.
- This infiltrative growth impacts the definition of the clinical target volume for SRS.
- A margin of approximately 1 mm should be added to the visible lesion for SRS planning.
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