ESMO 2014 Report: Proton beam therapy: Emperor’s new clothes

by Denis Wheatley:  In her introduction, Yolane Lievens (Belgium) explained that when we have to defer from making comment because of the need to be discrete (the Emperor parading himself in the nude), it is as if the obvious must not be stated. Is therefore this the case with proton beam therapy; is it beneficial, and if it is why is it not in the public arena for discussion? (Hence this was a controversy session). Two speakers, Drs De Ruysscher and Habrand, argued purportedly for and against the greater use of proton beam therapy, but in retrospect they both were not against it, but also found that it only had certain advantages over photon therapy that had to be carefully weighed against some limitations in its applicability and application. One controversy was whether it delivered with more accuracy than photon therapy, on which almost half the delegates were unsure. The speakers had indicated that in certain respects it was, such as the penetration depth beyond the tumour being shorter. Much the same percentage of the delegates considered proton therapy should be reserved for specific types of tumours, but equally the same percentage thought it too expensive, only perhaps having its place in personalized medicine (as noted in current news items).  Most agreed it needs to be investigated to a much greater extent in preclinical trials. One advantage mentioned by De Ruysscher was the more confined, localised delivery of protons, with less collateral damage to normal tissues (especially when accurate spot scanning check the tumour parameters), the intensity of the beam being the trade-off in this case. Some cardiotoxicity was, however, mentioned.

There is little disagreement that the technology involved in proton beam therapy is awesome, but it was thought that, like all innovative technology, time would show it could be made more compact, easier to manage and cheaper. There was also a trade-off here in that the follow-up of cases treated with this procedure should develop fewer post-therapy problems which would effectively reduce the overall cost per patient.  The tumours that were considered best treated by proton beam therapy include ocular melanomas, skull and spine carcinomas, chordomas and some pediatric tumours.  Whether it will prove suitable for prostate remains controversial (in trial), and there is hope that it can be used more in lung, liver, esophagus and head and neck tumours.  The overall conclusion was that proton therapy does have its place, can be better than photon therapy in some cases, is expensive at present and may have fewer post-treatment adverse effects