What kind of cancers can be cured by radiation therapy?

Some early stage: There are multiple, but here are just some examples of cancers that are sometimes cured by radiation alone: early stage prostate cancer, early stage head and neck cancer, early stage gastric malt lymphoma.

Many: Many cancers are treated and "cured" successfully with radiation therapy alone. Usually these are early stage cancers and include cancers of the head and neck, the voicebox, the prostate, as well as lymphomas. Radiation in combination with chemotherapy and or surgery is standard of care for many cancers.