Why would I have EVLA over foam sclerotherapy? Foam sclerotherapy treatment is cheaper than EVLA treatment, but in the majority of patients, EVLA is much more effective. Foam sclerotherapy is only suitable as the primary treatment option for a small minority of patients. A duplex ultrasound scan is necessary to determine whether you are suitable for treatment by foam solely. The success rate of treating the underlying cause of varicose veins solely with foam sclerotherapy is low.