2708 - Straight-Leg vs. Frog-Leg Radiotherapy Positioning in Locally Advanced Vulvar Carcinoma: A Prospective Randomized Trial Assessing Acute Toxicity and Lymphedema

Purpose/Objective(s): Frog-leg position has been used historically for patient setup for vulvar cancer radiotherapy. With the advent of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT), radiotherapy treatment constraints can now be met using different patient positions. Straight-leg setup offers greater convenience to patients and may reduce setup time. This study aims to evaluate the impact of straight- versus frog-leg treatment positioning on acute toxicity and lower limb lymphedema for patients receiving definitive radiotherapy concurrent with chemotherapy for locally advanced vulvar cancer.

Materials/Methods: Patients receiving definitive concurrent chemoradiation for locally advanced vulvar cancer were randomly assigned to either straight-leg or frog-leg radiotherapy positioning. Radiotherapy was planned via VMAT for all patients. Acute gastrointestinal (GI), genitourinary (GU) and skin toxicities were graded per the radiation therapy oncology group (RTOG) grading criteria, and were reported on a weekly basis for the 7 weeks of radiotherapy. Bilateral mid-thigh circumference was measured before treatment, after completion of radiotherapy, at 3 months and 6 months following treatment completion. Overall survival (OS) and local control (LC) were secondary endpoints. Statistical analyses were performed in a scientific 2-D graphing and statistics software using Logrank, Cox regression, Fisher’s exact, and Mann–Whitney tests.

Results: A total of 21 patients were enrolled, with 10 in the frog-leg position group and 11 in the straight-leg position group. The median age was 62 years (26 to 75), with no significant differences between groups (p > 0.05). The median primary dose for the entire cohort was 66 Gy, and the median nodal dose was 57 Gy, with no statistically significant differences between groups (p > 0.05). One patient had grade 2 GI toxicity in the frog-leg group and none in the straight-leg group. 7 patients developed grade 2 GU toxicity in the frog-leg group and six in the straight-leg group. Incidence of GI and GU toxicities (grade 2 or higher vs. grade 0-1) was not significantly different between groups (GI toxicity: p = 0.48; GU toxicity: p = 0.66). All patients in both groups developed grade 2 skin toxicity (p > 0.99). No patients had grade 3 or higher toxicity in any domain. Median thigh diameters were not statistically different between treatment groups bilaterally at any time points including before treatment, after completion of radiotherapy, at 3 months and 6 months following treatment completion (all p > 0.05). After a median follow-up of 23 months, outcomes at 6 months, 1 year and 2 years were as follows: 85.7%, 66.7% and 66.7% for LC, and 100.0%, 95.2% and 77.2% for OS, without significant differences between groups (p = 0.44 and 0.17, respectively).

Conclusion: Straight-leg patient setup is not inferior to the historical frog-leg patient positioning in terms of acute GI, GU and skin RTOG toxicities, as well as radiotherapy-related lower limb edema.