Proton beam therapy provides radiation by delivering a beam of proton particles rather than x-rays. The physical properties of proton beam therapy result in reduced dose being deposited in the normal tissue beyond the tumour, tumour bed or lymph nodes (target tissues). This is in contrast to x-rays where there is dose extension beyond the target tissues.

NHS England has carefully reviewed the evidence to treat breast cancer with proton beam therapy.  We have concluded that there is not enough evidence to make the treatment available at this time. This policy sets out the rationale for our decision.