Tumours with a favourable prognosis with five-year survival greater than or equal to 90% for which it is important to limit sequelae toxicities in long-term survivors, especially cardiological patients, are potential applications of proton therapy. This is for example the case of Hodgkin’s disease with cervicomediastinal localization.

Some non-aggressive brain tumours (meningiomas, paragangliomas, also called chemodectomas, neurinomas, also called schwannomas, craniopharyngiomas, etc.) can benefit from proton therapy for better preservation of neurocognitive functions, i.e. long-term memory and brain flexibility.
This is also the case of left breast cancers with ganglionic invasion of the internal mammary chain to reduce long-term cardiac toxicity. Radiotherapy reduces the risk of recurrence by 25% and improves breast cancer survival by a few percent.
When the ganglia are invaded, as the heart is located behind the left breast, it receives a small dose of irradiation when current techniques are used. This dose, although low, has been identified as responsible for cardiac toxicity, in particular during irradiations of the internal mammary chain. The breast and lymph nodes are irradiated more homogeneously and at a more optimal dose by using protons than by using photons, even with intensity modulation. The dose actually delivered is therefore closer to that which is theoretically sought, which can potentially lead to more healing. The average dose delivered to the heart is lower using protons than using photons, and remains acceptable even when irradiating the internal mammary chain. The lack of clinical data from irradiated patients does not however allow us to formally conclude that proton therapy can cure more patients, or that it reduces the rate of late cardiac complications. Its theoretical and physical benefits will need to be assessed in clinical trials before possibly being used routinely.