A study on early ultrastructural changes in squamous cell carcinoma of the uterine cervix following radiation therapy

An electron microscopic study was made on early post-irradiation changes in cancer cells of the parabasal cell type in a series of 30 patients with squamous cell carcinoma of the uterine cervix receiving irradiation by the bilateral eccentric pendulum method. The earliest post-irradiation change in cancer cells of the parabasal cell type was an increase in electron density of the matrix of mitochondria, which became noticeable at a dose of 500r. Changes associated with a dose of around 1000r included a decrease in electron density of mitochondria, disruption of their cristae, enlargement or vacuolization of the endoplasmic reticulum and an increase in the number of free ribosomes. At a dose of about 1500r, mitochondria apparently became disrupted, lysosomes appeared and prominently increased in number. The nucleus also began to undergo changes, displaying separation of the two layers of the nuclear membrane and coarse clumping of chromatin in the vicinity of the nuclear membrane. At a dose of about 2000r, a widening of intercellular spaces and breakdown of cell membrane became noticeable. Changes in mitochondria and in endoplasmic reticulum were even more prominent, while lysosomes were rather decreased in number. The nucleus often displayed separation of two layers of the nuclear membrane and was occasionally destroyed. From these results it is considered that radiation therapy for cervical cancer causes cancer cells of the parabasal cell type to undergo changes in their cytoplasm, followed by destruction of their nuclei. (auth.)