A pathology-based substrate for target definition in radiosurgery of brain metastases

Int J Radiat Oncol Biol Phys. 2006 Sep 1;66(1):187-94. doi: 10.1016/j.ijrobp.2006.03.050. Epub 2006 Jul 11.


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.

MeSH terms

  • Aged
  • Brain Neoplasms / secondary*
  • Brain Neoplasms / surgery*
  • Carcinoma, Non-Small-Cell Lung / secondary
  • Carcinoma, Non-Small-Cell Lung / surgery
  • Carcinoma, Small Cell / secondary
  • Carcinoma, Small Cell / surgery
  • Cranial Irradiation
  • Female
  • Humans
  • Lung Neoplasms / secondary
  • Lung Neoplasms / surgery
  • Male
  • Melanoma / secondary
  • Melanoma / surgery
  • Middle Aged
  • Radiosurgery / methods*
  • Radiotherapy Dosage
  • Sarcoma / secondary
  • Sarcoma / surgery
  • Survival Analysis