Cancer risks from betel quid chewing beyond oral cancer: a multiple-site carcinogen when acting with smoking.

Objectives: This cohort study is to assess the extent of cancer risks of betel quid chewing (without tobacco added) beyond oral cancer, as such information was limited from case-control studies.

Methods: The cohort, selected from participants in a medical screening program since 1994, consisted of 177,271 adult men with 19.2% chewers of betel quid. As of 2006, out of 4,840 deaths, 1,901 cancer deaths were identified. Mortality hazard ratios (HR) were estimated by Cox proportional hazard model. Life expectancy was calculated by life table method.

Results: One-third of smokers chewed (33%) but most of chewers smoked (90%). Risk for all cancer doubled among chewers (HR = 2.00). Risks of at least six cancer sites were increased among chewers: oral cavity (HR = 12.52), esophagus (HR = 5.64), liver (HR = 2.27), pancreas (HR = 2.67), larynx (HR = 6.24), and lung (HR = 2.43) with risks increased with increasing betel quid amount consumed. All-cancer age-adjusted mortality rates in Taiwan increased 25%, including 223% increase in oral cancer, during the last 20 years when chewing rate increased five- to tenfolds. Chewing on top of smoking increased the risks synergistically, and these two were responsible for at least half (50%) of all cancer deaths among 2 million chewers in Taiwan. Life expectancy of chewers was shorter than non-chewers by 5.93 years at age 20 and 5.55 years at age 40.

Conclusion: In addition to oral cancer, significant increases were seen among chewers for cancer of the esophagus, liver, pancreas, larynx, lung, and all cancer. Chewing and smoking, as combined by most chewers, interacted synergistically and was responsible for half of all cancer deaths in this group. They were responsible for the recent increases in oral, esophageal, pancreatic, and liver cancer in Taiwan. Chewing and smoking shortened their life span by nearly 6 years.