Radiosurgery and stereotactic irradiation of multiple and contiguous brain metastases: A practical proposal of dose prescription methods and a literature review.

Abstract Purpose In literature, there are no guidelines on how to prescribe dose in the case of radiosurgery (SRS) or stereotactic irradiation of multiple and adjacent BM. Aim of this work is to furnish practical proposals of dosimetric methods for multiple neighboring BM, and to make a literature review about the SRS treatment of multiple BM, comparing radiotherapy techniques on the basis of different dosimetric parameters. Materials and methods A theoretical proposal of dosimetric approaches to prescribe dose in case of multiple contiguous BM is done. A literature review between 2010 and 2020 was performed on MEDLINE and Cochrane databases according to the PRISMA methodology, with the following keywords dose prescription, radiosurgery, multiple BM. Papers not reporting dosimetric solutions to irradiate multiple BM were excluded. Results Only one article in the literature reports a practical modality of dose prescription for multiple adjacent BM. Thus, we proposed other five practical solutions to prescribe radiation dose in case of two or more neighboring BM, describing advantages and drawbacks of each method in terms of different dosimetric parameters. The literature review about dosimetric solutions to irradiate multiple BM led to 56 titles; 14 articles met the chosen criteria and we reported their results in terms of dosimetric indexes and low doses to the normal brain tissue. Conclusions The six dosimetric approaches here described can be used by physicians for multiple contiguous BM, depending on the clinical situation. These methods may be applied in clinical studies to better evaluate their usefulness in practice.