High-dose and fractionation effects in stereotactic radiation therapy: Analysis of tumor control data from 2965 patients

Radiother Oncol. 2015 Jun;115(3):327-34. doi: 10.1016/j.radonc.2015.05.013. Epub 2015 Jun 6.

Abstract

Background and purpose: Two aspects of stereotactic radiotherapy (SRT) require clarification: First, are tumoricidal mechanisms at high-doses/fraction the same as at lower doses? Second, is single high-dose SRT treatment advantageous for tumor control (TCP) vs. multi-fraction SRT?

Material and methods: We analyzed published TCP data for lung tumors or brain metastases from 2965 SRT patients, covering a wide range of doses and fraction numbers. We used: (a) a linear-quadratic model (including heterogeneity), which assumes the same mechanisms at all doses, and (b) alternative models with terms describing distinct tumoricidal mechanisms at high doses.

Results: Both for lung and brain data, the LQ model provided a significantly better fit over the entire range of treatment doses than did any of the models requiring extra terms at high doses. Analyzing the data as a function of fractionation (1 fraction vs. >1 fraction), there was no significant effect on TCP in the lung data, whereas for brain data multi-fraction SRT was associated with higher TCP than single-fraction treatment.

Conclusion: Our analysis suggests that distinct tumoricidal mechanisms do not determine tumor control at high doses/fraction. In addition, there is evidence suggesting that multi-fraction SRT is superior to single-dose SRT.

Keywords: Dose; Fractionation; Model; Radiotherapy; SBRT; Stereotactic.

MeSH terms

  • Brain Neoplasms / radiotherapy*
  • Brain Neoplasms / secondary
  • Dose Fractionation, Radiation
  • Humans
  • Linear Models
  • Lung Neoplasms / pathology
  • Lung Neoplasms / radiotherapy*