Vaginal lymphatic channel location and its implication for intracavitary brachytherapy radiation treatment

In vaginal intracavitary brachytherapy using cylindrical applicators, it is common to prescribe dose to a depth of 0.5 cm to cover the lymphatic channels. However, the actual depth of the lymphatics within the vaginal wall has never been determined. In this study, we examined the depth distribution of lymphatics lying beneath the mucosal surface of the vagina.

Between January 24, 1996 and October 27, 2003, 31 patients underwent full-thickness vaginal biopsy or partial resection for both benign and malignant disease. In addition, in February 2004, vaginal samples from two autopsy specimens were stretched and pinned for formalin fixation and slide production. Forty-five slides of both stretched and nonstretched vaginal tissue were stained with D2-40 monoclonal antibody lymphatic endothelium marker. The percentages of lymphatics located within 1, 1-2, 2-3, and 3-4mm were calculated for all slides.

For the nonstretched samples, the percentages of lymphatics located within 1, 1-2, 2-3, and 3-4mm were 50.5%, 30.7%, 11.9%, and 6.9%, respectively. For the stretched samples, the percentages of lymphatics located within 1, 1-2, 2-3, and 3-4mm were 44.0%, 33.8%, 18.8%, and 3.4%, respectively. The differences of lymphatic percentages within and superficial to 1mm (p=0.60), 1-2mm (p=0.85), 2-3mm (p=0.89), and 3-4mm (p=0.99) were not statistically significant between the stretched and nonstretched states.

Our results show that approximately 95% of vaginal lymphatic channels are located within a 3mm depth from the vaginal surface. This suggests that dose prescribed to a depth less than 0.5 cm may be adequate and could permit treatment with less normal tissue toxicity in certain clinical situations.