The relative differences of tumors in sensitivity to roentgen and radium rays are worthy of special study by the clinician, pathologist and radiotherapist. Much information has already been accumulated concerning the reaction of various cells and tissues to radiation. Embryonal tumors, as well as tumors composed of rapidly growing cells, are sensitive to radiotherapy. Lymphoid cells are particularly susceptible to radiation. On the contrary, neurosarcoma, glioma and melanoma are radioresistant.
Stewart1 defines radiosensitivity as that combination of circumstances resident in the tumor or the host which permits marked or total local tumor regression under doses of radiation sufficiently small to preserve the integrity of the tissues of the host. Degrees of radiosensitivity are recognized. Ewing2 classified tumors in decreasing order of radiosensitivity as follows: (1) lymphoma, (2) embryonal tumors, (3) cellular anaplastic tumors, (4) basal cell carcinoma, (5) adenoma and adenocarcinoma, (6) desmoplastic tumors, such as squamous carcinoma