Geyer C, Papadimitrakopoulou V, Hong W K
Thoracic and Head and Neck Medical Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Semin Radiat Oncol. 1998 Oct;8(4):292-301. doi: 10.1016/s1053-4296(98)80027-1.
The concept of field cancerization and the multistep carcinogenesis theory are the premises on which the development of chemoprevention efforts has been based. The first concept underlies the fact that patients who have been cured of a cancer in the aerodigestive tract are still at risk of developing additional primary tumors in the same field, and the multistep carcinogenesis theory implies that the conceivable arrest of one of the steps by chemoprevention might be enough to impede the development of cancer. There is ongoing research for development of new candidate-chemopreventive substances in most areas of oncology. Most of the clinical experience in chemoprevention of head and neck cancer is based on the use of retinoids. Retinoids in high doses have demonstrated activity in treating oral premalignant lesions (OPLs) but with frequent side effects and early relapse after cessation of therapy. Subsequent trials showed better tolerability of retinoids in lower doses. Ongoing trials are currently evaluating whether chemoprevention over 3 years might have longer-lasting effect both on OPLs and in the prevention of second primary tumors.
场癌化概念和多步骤致癌理论是化学预防研究发展所基于的前提。第一个概念基于这样一个事实，即已治愈上消化道癌症的患者仍有在同一区域发生其他原发性肿瘤的风险，而多步骤致癌理论意味着通过化学预防阻止其中一个步骤的发生可能足以阻碍癌症的发展。肿瘤学的大多数领域都在进行开发新的化学预防候选物质的研究。头颈部癌化学预防的大多数临床经验都基于维甲酸的使用。高剂量维甲酸已显示出治疗口腔癌前病变（OPL）的活性，但常有副作用且治疗停止后早期复发。随后的试验表明低剂量维甲酸的耐受性更好。正在进行的试验目前正在评估3年以上的化学预防是否对OPL和预防第二原发性肿瘤都有更持久的效果。
