Overall incidence and mortality trends
The incidence and mortality trends of CS increased significantly during the study duration (1975-2018), and the results are illustrated in Figure 1. According to data from SEER-9 incidence database, the overall incidence of CS showed a rise, with an APC of 3.4% (95% CI:2.8-3.9, p < 0.05) (Figure 1A). CS incidence was 0.36 cases per 100,000 in 1975, whereas it was 0.83 cases per 100,000 in 2018. Meanwhile, based on data from SEER-9 incidence-based mortality database, the overall mortality of CS followed a similar pattern of increase at an APC of 3.2% (95% CI:2.8-3.6, p < 0.05) (Figure 1B). CS mortality exhibited a rising trend from 0.07 cases per 100,000 in 1975 to 0.54 cases per 100,000 in 2018.
Incidence and mortality trends by demographic characteristics
Our study further evaluated both incidence and mortality trends by sex, race, and age from 1975 to 2018 and results are as follows (Figure 2).
Firstly, both trends were steady in male patients (APC=-0.1%, 95% CI:-1.2%-1.0%, p > 0.05; APC=0.2%, 95% CI:-0.8%-1.3%, p > 0.05, respectively), but elevated rapidly in female patients (APC=4.0%, 95% CI:3.4%-4.6%, p < 0.05; APC=3.9%, 95% CI:3.3%-4.4%, p < 0.05, respectively). Besides, both rates were higher in women than in men (Figure 2A, 2B).
Seconded, both trends increased sharply in White (APC=3.1%, 95% CI:2.5%-3.6%, p < 0.05; APC=3.0%, 95% CI:2.6%-3.4%, p < 0.05, respectively) and Black (APC=4.1%, 95% CI:3.2%-5.1%, p < 0.05; APC=3.5%, 95% CI:2.6%-4.4%, p < 0.05, respectively) people. Among other races, weakly increasing trends were seen (statistic could not be calculated). In addition, both rates were higher in Black than in White or in other races (Figure 2C, 2D).
Thirdly, both trends elevated markedly in patients aged 50-69 (APC=3.4%, 95% CI:2.8%-4.0%, p < 0.05; APC=3.0%, 95% CI:2.4%-3.6%, p < 0.05, respectively) and ≥70 (APC=3.4%, 95% CI:2.9%-3.9%, p < 0.05; APC=3.2%, 95% CI:2.8%-3.7%, p < 0.05, respectively) years. Furthermore, a steep increase with advanced age was found in both rates (Figure 2E, 2F).
Incidence and mortality trends by tumor characteristics
Subsequent analysis was performed to further identify the incidence and mortality trends by grade and stage from 1975 to 2015, and the findings are summarized in Figure 3. The duration between 2016 and 2018 was not included because the sample size with available grade and stage was small.
Firstly, no significant increase or decrease was noted in low grade (statistic could not be calculated), then, a obvious rise was detected in high grade (APC=7.1%, 95% CI:6.2%-8.0%, p < 0.05; APC=6.9%, 95% CI:5.9%-7.8%, p < 0.05, respectively). Moreover, both rates were higher in high grade than in low grade (Figure 3A, 3B).
Secondly, both trends were observed with statistical increase in early (APC=2.6%, 95% CI:1.8%-3.3%, p < 0.05; APC=2.3%, 95% CI:1.6%-3.1%, p < 0.05, respectively) and advanced (APC=4.7%, 95% CI:4.0%-5.3%, p < 0.05; APC=4.4%, 95% CI:3.8%-5.0%, p < 0.05, respectively) stages. Additionally, both rates were higher in advanced stage than in early stage (Figure 3C, 3D).
Incidence, mortality, and survival analyses by primary site
Between 1975 and 2018, a total of 5,281 patients with CS were enrolled from SEER-9 incidence database. As for tumor location, the most common site was female genital system (78.0%), followed by respiratory system (6.0%), digestive system (4.0%), urinary system (4.0%), and breast (3.0%) (Figure 4A). The primary site that contributed the most to the incidence rate was respiratory system in males and female genital system in females (Figure 4B).
In the current study, both incidence and mortality had rising trends in female genital system (APC=4.5%, 95% CI:3.7%-5.2%, p < 0.05; APC=4.2%, 95% CI:3.6%-4.9%, p < 0.05, respectively), while they showed stable trends in other sites during 1975-2018. Furthermore, both rates were higher in female genital system than in other sites (Figure 4C, 4D).
Figure 4E shows that the relative survival of CS patients for the main primary sites. The breast tended to enjoy the longest survival, while digestive system had worst survival than other sites.