Embedded Files
Fractionated Radiosurgery
Fractionated Radiosurgery
The term 'Fractionated Radiosurgery' commonly appears in various studies or conferences. In reality, with present classifications, it should be 'Stereotactic Radiotherapy'. Before Frameless Radiosurgery was defined, it was always 'Single fraction treatment', whether LINAC or Gamma Knife. Relocatable frames and image verification during treatment enabled and refined Frameless Radiosurgery. To make a consensus, ICRU defined Fractionated Treatment as 'fractionated radiosurgery when fractions are 5 or less'. However, there were others categorized like Staged radiosurgery for Dose Staging and Volume Staging, but both were single fractions. Fractionated radiosurgery is mostly used for Stereotactic Body Radiation Therapy (SBRT).
In March 2020, DEGRO (The German Society for Radiation Oncology), a working group for Radiosurgery and Stereotactic Radiotherapy, and the DGMP (The German Society for Medical Physics), a working group for Physics and Technology in Stereotactic Radiotherapy, came to a consensus where the term 'Radiosurgery' was defined as only for intracranial treatments. (Strahlenther Onkol (2020)196:417–420 )
Stereotactic radiosurgery (SRS) as a treatment of intracranial malignant or benign tumours and functional or vascular disorders with one single irradiation fraction.
Fractionated stereotactic radiotherapy (FSRT) as a treatment of intracranial malignant or benign tumours and functional or vascular disorders.
Stereotactic body radiotherapy (SBRT) as a treatment of extracranial malignant or benign tumours and functional or vascular disorders.
Generally, Stereotactic Radiotherapy is defined as
"a method of percutaneous external beam radiotherapy, in which a clearly defined target volume is treated with high precision and accuracy with a biologically high radiation dose in one single or a few fractions with locally curative intent".
Unfortunately, the term 'Radiosurgery' is still used loosely used for fractionated treatment in modern radiation machines which claim to be stereotactic enabled. There is no standardization as they convert a regular, single fraction dose to multiple fractions with their own judgment and call it 'radiosurgery'. Ideally, there should be a single fraction to call it radiosurgery. The most common argument is dose escalation without a fair idea about how it will help in improving the result.
Split-dose recovery (also known as Elkind recovery) is defined as causing a decrease in the radiation's effect i.e. if a single dose is split into two fractions separated by time. Split-dose recovery has been described in several cell systems and is at least partly due to the repair of single and double stranded DNA breaks.
It is a known fact that every time we add a fraction, there are more chances for the cell to survive, and that is the main reason for increasing the dose when fractionation is applied. It may be of some importance for large malignant tumours, but fractionation for small benign tumours is absolutely not supported by science. I wish to add here that this decision is not about machines, as all modern machines (Gamma Knife [Elekta AB, Stockholm, Sweden], CyberKnife [Accuray Inc., Sunnyvale, CA, USA], Edge [Varian Inc., Palo Alto, CA, USA] & ZAP-X [Zap Surgical, California USA] and Versa HD [Elekta AB]), are capable of single fraction accurate delivery. Then why Fractionation? Does science support it?
For the same α/β ratio, dose escalation while increasing number of fractions does not improve the Biological Equivalent Dose (BED). Hence, if you fractionate, dose escalation doesn't yield a better outcome. A single fraction is more superior to fractionation.
Page updated
Google Sites
Report abuse