Schedule of Stereotactic Radiotherapy: A study considering the factors of repair and cell proliferation

Naoyuki Shigematsu, Etsuo Kunieda, Tetsuya Kawada, Masayuki Kitamura, Atsushi Kubo, Takushi Dokiya, Hisao Ito

Research output: Contribution to journalArticlepeer-review


Stereotactic radiosurgery (SRS: stereotactic irradiation [STI]delivered in a single high dose) was initially developed by Leksell for non-malignant brain lesions, but there has been increasing interest in using it to treat small primary brain tumors or metastases. Recently, stereotactic radiotherapy (SRT: fractionated STI) has been recommended on the basis of radiobiological considerations for tumors in which both normal glial cells and tumor cells reside within the tumor margin. Strangely, the factors 'repair' and 'cell proliferation' have been neglected in the radiobiological evaluations of STI reported so far, mainly because of the complexity of the calculations. 'Half-time repair' which is the key value in the 'repair' factor may be larger for nervous tissue than for many other normal tissues because nerve cells have decreased ability to recover from damage. 'Cell proliferation' should be an important factor when the total radiation period is extended by applying SRT. In this study, we created models based on estimated 'half-time repair' and 'cell doubling time' and attempted to determine optimal SRT schedules. When repair and cell proliferation factors are also taken into consideration, the recommended SRT schedules would be 7 Gy × 7 fractions every other day for malignant tumors and 3.5 Gy × 12 fractions every other day for benign tumors. However, clinically, these schedules should be modified according to factors in individual cases, e. g., tumor size, presence of tumor necrosis, the patient's general condition, prognosis, and so on.

Original languageEnglish
Pages (from-to)516-520
Number of pages5
JournalNippon Acta Radiologica
Issue number9
Publication statusPublished - 1998


  • Brain tumor
  • Radiation biology
  • Stereotactic radiotherapy

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Oncology


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