Osteosarcomas and adult soft tissue sarcomas: is there a place for high LET radiation therapy?

The treatment policy for non-operable or unresectable osteosarcoma and adult soft tissue sarcoma remains unclear or controversial, despite the progress achieved in multimodality treatments. The poor results obtained by radiotherapy alone led to consider these tumours as radioresistant and to use high Linear Energy Transfer (LET) particles, such as neutrons. These particles benefit from a higher Relative Biological Efficiency (RBE) and other biological properties tending to decrease radioresistance phenomenas. From the non randomized studies previously published, neutron-therapy seems to give better local control rates, compared to photons and/or electrons. But these results are not strongly convincing, due to the large heterogeneities in patient recruitment, histological types, sizes, sites and moreover to the high complication rates encountered in some studies, even if they are mainly imputable to the use of low energy machines. The use of high-energy hospital-based accelerators combined to the possibilities of accurate dose distribution offered by conformal therapy, the potential value of light ion beam therapy combining the dose distribution advantages of protons to the biological properties of high LET particles, represent the directions in which progresses might be made for further improvement of non-operable or unresectable osteosarcoma and soft tissue sarcomas treatment results.