Irradiation effects of roentgen therapy on the growing spine.

Abstract

In administering roentgen therapy to retroperitoneal or paravertebral neoplasms in children, the radiologist is faced with these two questions: “What possible effects on the growth of the spine may result from the therapy?,” and “How can the tumor be irradiated in adequate dosage with minimal damage to the spine?” These were the questions which led to the present study. It consists of a follow-up of 45 patients who received roentgen therapy over the spine. Thirty-four living patients were observed over a period averaging six and a half years. Postmortem examination on 11 patients provided additional material used in the study. The experimental work concerning the effect of roentgen irradiation on the growth of bone in animals has been presented by Gates and Warren (1), Hinkel (2–4), Barr (5), Reidy (6), Gall (7), and coworkers. They have shown that when an epiphysis was exposed to 600 r or more of x-radiation, some retardation of growth usually occurred. Hinkel found that less than 500 r did not produce detectable stunting. The degree of stunting with higher doses seemed to depend on the age of the animal as well as on the dosage. Maximal effects, or complete inhibition of epiphyseal growth, were produced by 1,200 r or more. Quantitative relationships between the vulnerability to damage by irradiation of specific tissues in various animal species have not been studied extensively. Until it is shown that similar doses produce similar tissue responses independent of the species, or until a unit is devised which can serve as a common denominator for local tissue effects in all animal forms, effective irradiation dosage in man can only be determined empirically. This was one of the aims of this study. It is noteworthy that, in dogs and rats, severe disturbances of growth were elicited in the long bones by single roentgen treatments with dosages far lower than those delivered to the spine in the patients of this series. Clinical reports of growth disturbances in children resulting from roentgen irradiation have been infrequent, only 10 well documented reports having been found in the literature (8–17). In these, 16 patients are described in whom disturbances of bone growth occurred following irradiation. For 9 of these the depth dose delivered to the affected epiphysis was either stated or could be estimated from the data given. It ranged between 800 and 5,576 r. Because of the wide variation in dosage, a clear quantitative relationship between degree of stunting and dosage is not apparent. However, several features of these reported cases deserve mention. 1. One child, aged five months, who received a total tissue dose of 800 r showed definite growth retardation confined to the irradiated area. The irradiation was given in three doses, spaced over an eleven-month period, and involved the proximal epiphysis of the femur (14). entire pelvis and distal femoral epiphysis after irradiation totaling 1,610 r to the proximal portion of the femur.