The Effects of Varying Dosages of Irradiation upon Sternal-Marrow Regeneration

Abstract

In our earlier work concerning the effects of radiation therapy upon the sternal marrow (1, 2), it was found that an exposure dose of 3,000–4,700 R delivered in a period of three to four weeks to the sternal area resulted in severe depression of the sternal marrow in almost all cases. This present study attempts to define a critical irradiation dosage below which bone-marrow regeneration would consistently occur, and above which dosage marrow aplasia would persist. Materials and Methods This study includes 33 cases previously reported (2) and 28 new ones; a total of 61 patients. The 28 new patients include 20 with mammary cancer, irradiated after radical mastectomy; they received an exposure dose of 3,500 to 4,700 R to the sternum in twenty-one to thirty days with 250 kv equipment. The technic of irradiation was as previously recorded (1, 2). Four patients in whom sternal marrow was examined postmortem had received radiation for advanced cancer: 1 of the esophagus, 2 of the breast, and there was 1 case of osteogenic sarcoma. Their sternums were in the radiation field and received dosages varying from 1,700 R in sixteen days to 6,000 R in sixty-eight days. The radiation consisted of 1,000 kvp x rays in 1; 2,000 kvp x rays in 2; and 15 Mev electrons in 1. The remaining 4 patients volunteered to receive lower doses of radiation in order to determine its effects on the sternal marrow. Their malignant diseases were slow growing (1 carcinoma of the uterus, 1 carcinoma of the ovary, 1 hemangiopericytoma, and 1 patient with malignant carcinoid). With 250 kvp x ray, 2 of these patients received 1,000 R in two days; 1, 2,000 R in fourteen days; and the other, 2,400 R in fourteen days. The mean follow-up time of all 28 patients from termination of irradiation to sternal-marrow aspiration was twenty-six months, with a range from one to eighty-four months. The technic of marrow aspiration and the criteria for marrow classification were as described in previous papers (1, 2). Results In the 28 new cases, sternal-marrow regeneration occurred in all 5 patients who received a total dose of from 1,000 R in two days to 2,400 R in fourteen days (Table I). The sternal marrow aspirations of the remaining 23 showed no signs of regeneration after doses ranging from 3,000 to 6,000 R in twenty-one to sixty-eight days (Table I). In the previous study (2) only 2 of the 33 patients receiving over 3,500 R showed marrow regeneration (Table II). The summary of marrow regeneration versus radiation dosage in these two studies, consisting of 61 cases, is shown in Table II and Figure 1. Discussion Of the 61 patients studied, marrow regeneration was revealed in all 5 who received less than 2,400 R to the sternum. In the remaining 56 patients one marrow showed no regeneration after receiving 3,000 R in twenty-six days, while only 2 of the remaining 55 patients (3.6 per cent) who received 3,500 R or more showed sternal-marrow regeneration.