## 4 Discussion
In this study, the median survival period of patients with pleural mesotheliomax was 8.0 months (95% confidence interval: 6.2 to 9.8), which is less than one year. This is similar to other findings in that the prognosis is very poor at about one year [11; 12; 13; 14; 15; 16]. However, some studies have reported median survival times greater than 1 year [17; 18]. These differences in survival periods are thought to be influenced by the characteristics, including the stage, comorbidities, and the degree of treatment of the mesotheliomax subjects. In our study, the 1-year, 2-year, and 5-year survival rates of subjects were 43.5%, 23.6%, and 12.5%, respectively. [PERSON] et al. [19] found that the 1-year, 2-year, and 5-year survival rates of 303 patients with malignant pleural mesothelioma were 73.1%, 22.9%, and 12.0%, respectively, which was higher at one year than in this study, but the 2-year survival rate was marginally lower than was seen in this study. In addition, in [PERSON] et al. 's study [20] of patients with malignant pleural mesothelioma, the 1-year, 2-year, and 5-year survival rates were 45.4%, 24.8%, and 9.6%, respectively, indicating that the 1-year and 2-year survival rates were slightly higher than in our study. However, the 5-year survival rate tended to be slightly lower. In the study of [PERSON] et al. [12], the 5-year survival rate was 12.1% for pleural mesotheliomax, which was similar to the 5-year survival rate of 12.5% in our study. In the study of [PERSON] and [PERSON] [2], the 5-year survival rate of pleural mesotheliomax was 5%, and in the study of [PERSON] et al. [16], the 5-year survival rate of pleural mesotheliomax was 5.4% for men and 6.0% for women, both of which were lower than in this study. In addition, in the study of patients with malignant pleural mesothelioma by [PERSON] et al. [21], the 1-year and 2-year survival rates were 48.8% and 23.3%, respectively, which were slightly higher than in our study, and the 2-year survival rates were similar. In the study of [PERSON] et al. [13], the 1-year survival rate was 41.4%, which was slightly lower than in this study. In the study of [PERSON] et al. [15], the 1-year and 2-year survival rates of patients with malignant pleural mesothelioma were 21.3% and 3.5%, respectively, which were lower than in this study. The sex distribution of the subjects of this study was 69.0% male and 31.0% female. In general, diseases caused by occupational hazards tend to occur more frequently in men than in women [19]. However, among the prognostic factors affecting the survival of patients with malignant pleural mesothelioma in this study, sex was not a significant factor in Cox multivariate analysis. However, several studies have reported that sex is often associated with prognosis [2; 22; 23; 24; 25; 26; 27]. Most of these studies reported that women had higher survival rates, but in women, there is the possibility of early detection [28] and also the possibility of histologically suitable tumors [2]. In addition, women were more likely to have lower asbestos exposure or a slower progression [29]. It has also been suggested that women may enjoy a protective effect due to estrogen [27] and possibly a protective effect from the interaction between estrogen and the estrogen receptor in the tumor [30]. In a study by [PERSON] et al. [31], women with malignant mesothelioma had a longer survival period than men, and they suggested that this may be due to a lower level of smoking in women or a different level of exposure to the environment. In a study by [PERSON] et al. [32], the sex ratio of malignant mesotheliomax in Korea was about 1.9:1, and predominantly male. Studies in other countries have reported a sex ratio of 4 to 3:1 [12; 18]. [PERSON] et al. [10] found that the high percentage of women with malignant mesotheliomax in Korea is because the percentage of cases exposed to environmental asbestos is relatively higher in women than in men, and women are less likely to be exposed to asbestos occupationally.