A 52-year-old woman from Delhi presents with a 3-year history of progressive swelling and heaviness in the left lower limb, worse at the end of the day. On examination, she has dilated, tortuous veins over the medial aspect of the thigh and calf, with mild pitting edema. Trendelenburg test is positive. Duplex ultrasound shows reflux in the greater saphenous vein (GSV) lasting >0.5 seconds. She has no history of DVT. What is the most appropriate next step in management?