Therapeutic margins in clinical radiotherapy with conventional types of radiations and their implications for neutron therapy

Abstract

For various groups of tumors, clinical characteristics are discussed which are important with respect to responses to fractionated treatments with supervoltage X-rays and with respect to problems to be expected with fast neutron treatments. Physical characteristics of supervoltage X-ray beams, with small penumbra, skin sparing and large depth dose, provde important advantages which are unlikely to be equalled by fast neutron beams. As a consequence the usefulness of fast neutrons might be limited in cases where either a critical structure is near the tumor bearing volume or where large areas of skin receive doses equal to the tumor dose. Different groups of tumors are distinguished which currently are highly curable or are not suitable for neutron treatment for other reasons, whereas others are discussed which seem to be candidates for neutron therapy, although methods are not available to predict their responses.