Charungthai Dejthevaporn. Long term outcomes of thymectomy in myasthenia patients . Doctoral Degree(Clinical Epidemiology). Mahidol University. : Mahidol University, 2003.
Long term outcomes of thymectomy in myasthenia patients
Abstract:
The purpose of this study is to evaluate the long term outcomes of thymectomy
in Thai myasthenia gravis (MG) patients in terms of clinical remission and clinical
relapse rate after thymectomy. The study design was retrospective cohort. The study
population was MG patients age 15 years or older, who underwent thymectomy at
Ramathibodi Hospital between January 1st, 1969 and August 31st, 2002. Survival
analysis by Kaplan-Meier method was used to estimate probability of clinical
remission and clinical relapse after thymectomy. Cox proportional hazard model was
used to determine factors associated with clinical remission and clinical relapse.
There were 250 MG patients included in this study. Most (80%) of them were
women. The mean age at thymectomy was 34.5 (±11.27) years. Follow up time after
thymectomy was 1.7 years (range 1-36). The clinical remission rate was 52 episodes
per 100 persons-months. The median time from thymectomy to first clinical remission
was 8.5 months and 50% of the patients remained in remission for around 3.7 months
and then had clinical relapse. The probabilities of clinical remission at 1 and 5 years
were 73% and 96%, respectively. Pre-operative Osserman grade 0, disease duration
less than 3 years, pre-operative prednisolone and immuno-modulation treatment were
significant prognostic factors of clinical remission. The clinical relapse rate was 2
episodes per 100 person-months. The probabilities of clinical relapse at 1 and 5 years
were 17% and 67%, respectively. Deteriorated disease condition before thymectomy
and thymoma were significant prognostic factors of clinical relapse. These findings
suggested that thymectomy should be considered a part of treatment of MG to induce
clinical remission. Early diagnosis, early thymectomy as well as pre-operative
treatment with prednisolone and immuno-modulation to improve clinical severity
would result in better prospects for clinical remission.