The Effect of Radiation on the Lymph and on the Lymph Vessels

In spite of the fact that the majority of cancer deaths occur because of lymphatic metastasis, the effects of radiation upon the lymphatic vessels are still imperfectly known. Essentially the question is: Is it possible to “seal” the lymph vessels by irradiation? In an attempt to answer this question a number of experiments were conducted at the Radiological Institute of the University of Modena during the last five years with 200-kv radiation, a cobalt bomb, and by a 15-Mev betatron. Rabbits and guinea pigs were employed as experimental animals, and, in addition, 30 human uteri were examined following irradiation and hysterectomy for cancer. The technics of examination included injection of latex in the lymph vessels followed by maceration of the tissues. The circulating lymph was studied by phase contrast microscopy. For study of the circulating lymph 40 guinea pigs were given whole-body irradiation with a 1,500 curie cobalt bomb for a dose of 7,500 r at one sitting. Lymph specimens were studied five and twenty hours after irradiation (15 animals in each group). A few drops of Sky Blue dye were administered intratracheally, and the animals were killed under ether anesthesia. The lymph was aspirated from the prenodal pulmonary lymphatics, which were visualized by the dye, and placed on microscopic slides. Counts were then made of the normal and abnormal lymphocytes. The lymph of animals killed five hours following irradiation showed a constant diminution of the number of lymphocytes and a few abnormal cells. These changes were much more marked after twenty hours when a large number of lymphocytes had degenerated into cellular debris. The macrophages, on the other hand, were numerous and active, incorporating cellular debris and damaged lymphocytes which showed a distinct tendency to clumping. These observations are in accord with previous studies by the present authors with 200 kv, and with those by Braibanti et al. (3) who also employed 200 kv and similar doses. It seems, therefore, that the effects of cobalt and of 200-kv irradiation on the circulating lymph are essentially the same, consisting in the destruction of lymphocytic cells. This is probably associated with an impaired production of new lymphocytes. An attempt was made to compare the effects on lymph vessels of irradiation of varying wave lengths. One hundred twenty rabbits were divided into 24 groups of 5 each. The irradiated area in all animals measured 4 × 6 cm. and included the pelvis. The rectum, uterus, bladder, iliac lymphatics, and para-aortic lymphatics were thus subjected to irradiation. The dose was calculated for 2 cm. below the skin. The first three groups were given 3,000 r with 1.3 Cu filtration, 75 cm. distance, at 500 r per day. Groups 4–6 received 6,000 r with the same factors and at the same daily dose rate. Groups 7–9 received 3,000 r with a 1,500-curie cobalt bomb at 500 r per day.