  Due to its precision and limited side effects, the particle therapy of cancer
is gaining popularity. The number of patients treated with protons and light
ions reached 150,000 worldwide. There are currently more than 80 facilities,
which offer this treatment and several dozen of new ones are in construction.
Mostly they are cyclotron-based facilities, which provide proton beams, and
only several are synchrotron-based facilities that provide both: proton and
carbon-ion beams. The advantage of carbon ions is their higher efficiency in
destroying the cancer cells, more localized shape of the Bragg peak and smaller
beam scattering in the body. Several of the large centers, which can provide
carbon, have experimented with other ions including helium. The advantage of
helium over protons is significantly larger precision of the treatment due to
lower scattering of alpha particles in the body, what is especially important
for pediatric patients. A facility with therapeutic beams limited to helium,
would be smaller and cheaper than carbon-based facility. Here we discuss this
option.
