NCS Recommendations for 3D superficial treatments 

Superficial lesions are defined as lesions close to the skin surface, with a maximum depth of approximately 5 cm. In general, radiation oncology uses either electron beam therapy or intensity modulated photon beam therapy to treat these types of lesions, but, orthovolt and brachytherapy are used as well. Currently institutes are switching from hand calculation to Monte Carlo based treatment planning systems for electron beam therapy.

Due to density variations, skin sparing and steep depth dose gradients, electron beam planning results in inhomogeneous dose volume histograms, which become visible in 3D planning. In addition the 95% and 100% isodose volumes for electron beam therapy are small resulting in modality specific normalization levels. Moreover, we are dealing with dose schemes that are based on a treatment history of hand calculations.

Some centers are quitting electron beam treatment while relying on photon based IMRT or VMAT solutions for the same lesions, and volume based dose prescription rules are applied. Those isodose volumes are large less inhomogeneous compared to the electron beam treatments.

Both techniques require special expertise for the beam data collection and validation of the treatment planning. Our first goal is drafting guidelines for those measurements and the consequent validation. This topic is primarily oriented to the field of medical physics;

A second goal is to survey the current clinical situation, and propose a safe method for introducing 3D electron treatment planning without compromising both TCP and NTCP. In addition guidelines will be provided to enable the comparison of electron and photon beam treatments in light of historical dose schemes. For this topic input of the radiation oncologists is required.

Finally a brief comparison with orthovolt and brachy therapy can be drafted if an inquiry reveals that those techniques are still used in daily practice.

Topics to be covered

  • Measurement guidelines
  • Validation of the beam model
  • Treatment planning recommendations
  • Agreement and differences with photon beam, Orthovolt and brachytherapy treatments

 

Geert Pittomvils 0032 9 332 6561 Geert.Pittomvils@uzgent.be

Wim Jansen 0031 88 779 0176 w.jansen@radiotherapiegroep.nl