High-frequency (20 MHz) high-intensity focused ultrasound: New Treatment of actinic keratosis, basal cell carcinoma, and Kaposi sarcoma. An open-label exploratory study

Background Skin cancer is common, growing, challenging, and in need of progress in early-stage treatment. 20 MHz high-intensity focused ultrasound (HIFU) is new and applied to actinic keratosis (AK) and skin cancers for the first time. HIFU of lower frequency is already used in the treatment of internal cancers. Materials and Methods Eight patients with 201 AK lesions, one patient with 7 basal cell carcinomas (reoccurrences after PDT), and one patient with 7 Kaposi sarcoma lesions (4 treated with radiotherapy in the past) were given 1-3 HIFU treatments. Twenty megahertz HIFU was dosed as 150 ms at 0.6-1.2 J/shot applied to target lesions. Probes with different target depths were available. The preferred shot energy and focal depth in AK were 0.9 J and 1.3 mm. A "Sandwich" strategy with HIFU applied in two depths were tried in cancers. The follow-up period was 3-6 months. Results All AK cleared except 5, giving a cure rate of 97%. Post-treatment lesion healed in 1-2 weeks with no scar. VAS pain was from 1 to 8, and in any case less than experienced with previous PDT. In both basal cell carcinoma (BCC) and sarcoma, healing was confirmed by histological verification. Discussion/conclusion 20 MHz HIFU was an effective and safe treatment of AK. This new treatment, applicable to any anatomical site, has promising advantages relative to PDT and has the potential to replace or supplement PDT in future. Case-observations indicated that HIFU can be useful in skin cancers as well.