Application of Vaginal Cylinders for Intracavitary Radiation Therapy

Vaginal intracavitary radiation therapy is applied for two reasons: (1) to treat carcinoma directly in the vagina, the subvaginal mucosa and, in adenocarcinoma of the endometrium, the lymphatic and (2) to add radiation to point A in the isodose curve.

The largest cylinder that can comfortably fit the vagina should be used to achieve the most favorable isodose curve with the lowest surface dose. An intrauterine tandem can be inserted through the vaginal cylinder and can be loaded as the length of the uterus dictates. If the uterus is absent, the cylinders can be used alone to apply radiation therapy to the vagina.

The purpose of applying intracavitary therapy to the vagina is to irradiate the vaginal canal with ionizing radiation. In general, attempts are made to deliver 4000 cGy of radiation to the depth dose of 1.5 cm.

Physiologic Changes. The physiologic changes in this procedure are the same as for all procedures in which ionizing radiation is passed through normal and malignant tissue.

Points of Caution. The vaginal cylinders should be constructed so that they will fill the entire vaginal canal up to, but not beyond, the introitus. Care should be taken that no radium source extends beyond the vaginal introitus for fear that ulceration of the labia minora and majora will occur.

Fixation of the device should be made to ensure that the cylinder will not slip toward the introitus. This usually can be performed by suturing the labia together in the midline.

Technique

Cylinders of varying diameter can be easily constructed out of Silastic. The cylinder can be fashioned so that they can be added to each other in tandem to accommodate different vaginal lengths.

If a Fletcher uterine tandem is to be used, it should be inserted into the entire length of the endometrial canal. The vaginal cylinders can then be loaded on the tandem. The radium sources can be inserted through the center of the tandem in a manner that will deliver the desired isodose curve for the uterus, cervix, and vagina.