Chemoprevention of cancer--focusing on clinical trials.
Chemoprevention of cancer is reviewed from the viewpoints of action mechanisms and methodology of clinical trials in order to introduce promising agents discovered by in vitro and/or in vivo studies to applications in humans. The clinical trial procedure essentially follows the phase study which has been employed for chemotherapeutic drugs. Chemoprevention of bladder cancer, prostate cancer, gastric cancer, hepatocellular carcinoma, breast cancer, head and neck cancer, colorectal cancer and lung cancer is reviewed, mainly focusing on clinical trials. Previous clinical trials have shown the effectiveness of the following: polyprenoic acid (acyclic retinoid) for hepatocellular carcinoma; tamoxifen for breast cancer; retinoic acids for head and neck tumor; and aspirin, a COX-2 inhibitor, for colorectal cancer. Despite the advantageous effects of some of these agents, their toxic effects must also be of concern at the same time. For example, in a chemoprevention trial of lung cancer, beta-carotene was unexpectedly found to increase the risk of lung cancer among high-risk groups. It is also noted that large-scale clinical trials demand large research grants, which may not be affordable in Japan. Chemoprevention is still an emerging field of oncology where researchers in both basic and clinical sciences face great challenges.
National Cancer Center, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. tkakizoe@ncc.go.jp
Tadao
T
Kakizoe
D000818:Animals; D016588:Anticarcinogenic Agents / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000517:prevention & control; D002986:Clinical Trials as Topic / Q000639:trends*; D017322:Clinical Trials, Phase II as Topic; D017326:Clinical Trials, Phase III as Topic; D015179:Colorectal Neoplasms / Q000517:prevention & control; D005260:Female; D006258:Head and Neck Neoplasms / Q000517:prevention & control; D006801:Humans; D008175:Lung Neoplasms / Q000517:prevention & control; D008297:Male; D009369:Neoplasms / Q000517:prevention & control*; D011471:Prostatic Neoplasms / Q000517:prevention & control; D013629:Tamoxifen / Q000627:therapeutic use; D014212:Tretinoin / Q000627:therapeutic use; D001749:Urinary Bladder Neoplasms / Q000517:prevention & control; D019207:beta Carotene / Q000627:therapeutic use
D016588:Anticarcinogenic Agents; D000970:Antineoplastic Agents; D019207:beta Carotene; D013629:Tamoxifen; D014212:Tretinoin