| Summary: | 碩士 === 國立臺灣大學 === 公共衛生學系 === 86 === Introduction: To prevent oral cancer, elimination of precancerous lesion i.e.l
eukoplakia is feasible preventive strategy. It is necessary to make a clearund
erstanding of natural history from normal, leukoplakia, to oral cancer toknow
the efficacy of dental check-up for leukoplakia in reducing oral cancer.But, s
everal limitations in previous studies are rare cases, long-term follow-up, an
d treated effect of leukoplakia. An alternative approach is proposed totackle
these problems.Objectives: The aims of this thesis are (1) to estimate the eff
ect of relevantrisk factors on the occurrence of leukoplakia; (2) to investiga
te how riskfactors affect malignant transformation ; and (3) to estimate the i
ncidenceof leukoplakia and malignant transformation simultaneously based on a
three-state Markov chain model.Material and Methods: Three retrospective follo
w-up cohorts from 1988 to 1998are identified from one medical center in Taipei
. Using leukoplakia andperiodontal disease cohort, a matched case-control stud
y is design to answerthe first objective. The leukoplakia cohort is linked to
cancer registry andchart review to identify oral carcinoma to answer the secon
d objective. Athree-state case-control study design is performed for the third
objective.A conditional logistic regression is performed to estimate the infl
uence ofrisk factors on leukoplakia. Two accelerated failure models are employ
ed toestimate the incidence of malignant transformation. A three-state Markovc
hain model adapted to case-control study is developed to estimate theincidence
of leukoplakia and malignant transformation.Results: the adjusted odds ratios
for chewing betel nut and smoking on theoccurrence of leukoplakia are 34.(95%
CI: 4.5~259.0) and 3.6 (95%CI: 1.0~12.5). Using Weibull model, the incidence
of malignant transformation ofleukoplakia increases with year. The adjusted ha
zard ratio for chewing betelnut is 5.04 (95% CI: 1.27~20.06). Using of three-s
tate case-control method,the incidence of leukoplakia for this cohort is 0.18%
(95%CI: 0.15%~0.21%),and malignant transformation is 11.1% (95%CI: 9.27%~13%)
.Conclusion: From practical viewpoint, this thesis demonstrates betel nut asa
risk factor not only for the occurrence of leukoplakia but for malignanttransf
ormation. For the occurrence of leukoplakia, getting rid of chewingbetel nut w
ould avoid 77% leukoplakia. The efficacy of treatment onleukoplakia could redu
ce 76% malignant transformation. This implies annualdental check-up for leukop
lakia could lead to 57% reduction of oral cancers.From methodological viewpoin
t, three-sate Markov chain model adapted toestimate transition parameters base
d on a retrospective case-control study,can be applied to other chronic diseas
es.
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