FEMORAL VESSEL DEPTH AND THE IMPLICATIONS FOR GROIN NODE RADIATION

Purpose: To quantify, based on pretreatment computer tomographic measurements, potential groin node depths, which will aid in optimal treatment planning for patients requiring groin node radiation. Methods and Materials: The pretreatment computer tomographic scans of 50 gynecologic cancer patients were reviewed to determine the distance of each femoral vessel beneath the overlying skin surface, as an indicator of potential groin node depth. Correlative data regarding height and weight were obtained from patient medical records, and were used to calculate the Quetelet index, defined as (weight in kg)/(height in m)(2). Treatment parameters of 5 patients who failed prophylactic groin radiation in a recently published study were assessed to determine if underdosage represented a possible cause of failure. Results: Individual femoral vessel depths ranged from 2.0 to 18.5 cm. When the depths of all four femoral vessels were averaged in each patient, the mean ''4-vessel average'' depth for this patient population was 6.1 cm. The median Quetelet index for the group was 25.6, and there was a strong correlation between femoral vessel depth and patient Quetelet index. Recalculation of doses provided to the 5 patients failing prophylactic groin radiation in the Gynecologic Oncology Group study showed that all had received potential tumor doses < 4700 cGy, with 3 patients being underdosed by > 30%. Conclusion: While surgery is often indicated in the management of patients with potential groin node metastases, the role of prophylactic groin radiation should not be rejected. Data from this study may aid in the optimal design and implementation of groin node radiotherapy.