Brain Stereotactic Radiosurgery

SRS delivers single doses or a limited number of fractions, with high doses delivered to a limited treatment volume through the use of multiple converging beams. This results in a rapid dose drop-off at the edge of the target volume and a clinically insignificant dose to adjacent normal tissue. Major advances in stereotactic localization, noninvasive neuroimaging, and radiation physics have made it possible to selectively irradiate a clearly defined target, largely sparing surrounding normal tissue thanks to a rapid dose drop-off. Therefore, SRS requires precise lesion localization and patient positioning during treatment.

Gammaknife Icon at Genesis Care Cromwell where some of the brain Stereotactic Radiosurgery treatments are performed.
Gammaknife Icon at Genesis Care Cromwell where some of the brain Stereotactic Radiosurgery treatments are performed.

SRS can treat deep lesions or lesions near critical brain structures that are not amenable to surgical resection. SRS is often delivered as a single high dose of radiation, but it can also be delivered in two to five fractions (stereotactic RT, SRT) for larger targets or near critical normal tissues, such as the brainstem or optic nerve. This hypofractionation strategy was originally called hypofractionated RT, but the term stereotactic RT is currently used and is reserved for highly fractionated regimens based on the differential sensitivity of tumor and normal tissue to radiation.

The SRS dose is defined by the amount of radiation delivered to the margin of the target lesion; this is known as the prescription dose. Typically, the marginal dose delivered in a single session ranges from 11 Gy (for benign lesions) to 70 Gy (for thalamotomy, in the treatment of movement disorders).

BIBLIOGRAPHIC REFERENCES:

  1. Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy. A Comprehensive Guide. Trifiletti D, Chao SE, Sahgal A, Sheehan JP. Springer. 2019.
  2. LEKSELL L. The stereotaxic method and radiosurgery of the brain. Acta Chir Scand 1951; 102:316
  3. SABR Consortium UK, 2016 and SABR Consortium UK, 2019
  4. NCCN guidelines available at http://www.nccn.org/professionals/physician_gls/f_guidelines.asp
  5. Potters L, Kavanagh B, Galvin JM, et al. American Society for Therapeutic Radiology and Oncology (ASTRO) and American College of Radiology (ACR) practice guideline for the performance of stereotactic body radiation therapy. Int J Radiat Oncol Biol Phys 2010; 76:326
  6. Andrews DW, Scott CB, Sperduto PW, et al. Whole brain radiation therapy with or without stereotactic radiosurgery boost for patients with one to three brain metastases: phase III results of the RTOG 9508 randomised trial. Lancet 2004;363(9422):1665e1672
  7. Patil CG, Pricola K, Sarmiento JM, Garg SK, Bryant A, Black KL. Whole brain radiation therapy (WBRT) alone versus WBRT and radiosurgery for the treatment of brain metastases. Cochrane Database Syst Rev 2012;9. CD006121
  8. Yamamoto et al. Stereotactic radiosurgery for patients with multiple brain metastases (JLGK0901): a multi-institutional prospective observational study. Lancet Oncol; 15:387-95, 2014.