Influence of inguinal node anatomy on radiation therapy techniques

Abstract

A 1992 GOG (Gynecologic Oncology Group) study suggested that groin irradiation does not control microscopic inguinal node metastases as well as does surgical dissection. That trial has come under some scrutiny, as possible deficiencies in the radiation regimen used might have influenced results. The study received criticism for assigning a prescription point [Rx @ 3 cm below anterior skin surface] to patients which may not have given adequate coverage to the inguinal nodes. The inguinal node depths of 31 patients with cervical, vaginal, or vulvar malignancies were measured from their planning CT scans and then compared to depth of the prescription point designated by the radiation therapists in the aforementioned study. Twenty-four of eighty-one viable superficial inguinal node depth measurements were greater than 3 cm, and all of eighty-four deep inguinal node measurements were outside the three centimeter range. The results of this project would indicate that the depths of patients' inguinal nodes vary enough to justify alterations in some present external beam radiation therapy techniques. Indiscriminate prescription points will no longer suffice if groin radiation is to be effective, and treatment planning must utilize imaging studies to devise radiation regimens that provide optimal dose to the superficial and deep inguinal nodes.