Confirmatory trial of narrower side margin excision for head and neck basal cell carcinoma in the Japanese (East Asian) population: JCOG2005 (J-BASE-MARGIN).
Authors: Nakamura Yasuhiro , Sano Yusuke , Kataoka Tomoko , Shibata Taro , Fukuda Haruhiko , Matsushita Shigeto , Fujisawa Yasuhiro , Takenouchi Tatsuya , Omodaka Toshikazu , Yamamura Kentaro , Aoki Megumi , Uchi Hiroshi , Tsutsui Keita , Yoshikawa Shusuke , Ogata Dai , Yanagisawa Hiroto , Omatsu Jun , Ito Takamichi , Namikawa Kenjiro , Yamazaki Naoya 
Published: June 2022

TPS9604 Background: Basal cell carcinomas (BCCs), the most common type of skin cancer, frequently occur on the head and neck. Because distant metastases are extremely rare, complete excision with clear margins is the standard treatment for BCCs. In the NCCN Guidelines, the recommended surgical treatment strategies include standard excision with wider margins ( > 4 mm) or Mohs surgery or other forms of peripheral and deep en face margin assessment (PDEMA) for head and neck BCCs. However, these strategies are based on studies in the Caucasian population, with BCCs mostly arising as non-pigmented lesions and/or with poorly defined clinical borders. Conversely, in East Asians, most BCCs tend to present as pigmented lesions with well-defined clinical tumor borders. Recent retrospective studies from East Asia have reported positive side margin proportions and local recurrence proportions in BCCs excised with narrower margins that are lower than guidelines-recommended margins. Our previous study investigating 1000 East Asian BCCs also indicated that the estimated positive side margin proportions with 2- and 3-mm surgical margin excision in East Asian BCCs were 3.8% and 1.4%, respectively. Those findings may lead to very limited need for Mohs micrographic surgery or PDEMA in East Asian head and neck BCCs; however, there have been no clinical trials regarding fixed narrower margin excision for those cohorts. Methods: This is an investigator-initiated, prospective, multicenter, non-randomized phase III confirmatory trial evaluating the efficacy and safety of narrower surgical margins for the treatment of East Asian patients with head and neck, solitary, primary BCCs with sizes ranging from 3 mm to 20 mm. Eligible patients are aged ≥20 years (≤85 years in men or ≤90 years in women). Narrower margin excisions of 2 mm and 3 mm are applied to BCCs with well-defined clinical borders (cohort A) and poorly defined borders (cohort B), respectively. The primary endpoint is the 5-year local recurrence proportion, and the secondary endpoints are positive side margin proportion and incidence of adverse events. We anticipated an expected 5-year local recurrence proportion of 0.8% in both cohorts and a threshold of 3.3% in cohort A and 4.1% in cohort B. The planned sample size is 410 patients (cohort A, 250; cohort B, 160) to provide a power of 80% with one-sided alpha of 5%, assuming a 5% competing risk of death from other diseases. The planned accrual period is 5 years, and the follow-up period is 10 years; primary analysis will be performed at the completion of 5-year follow-up for all registered patients. The trial began in March 2021, and 225 patients (cohort A, 170; cohort B, 55) have already been enrolled as of January 2022. Clinical trial information: UMIN000043511.