Background

Cancer is amongst the most common causes of death globally and is predicted to be a major contributor to poor quality of life in the 21st century [1, 2]. Ovarian cancer is commonly occurring cancers among women. It has been estimated that 190,000 new cases of ovarian cancer are reported annually worldwide, and its incidence is more prevalent in developed countries. In most cases, because of lack of specific signs and symptoms and absence of proper screening, ovarian cancer is detected in later stages of the disease, which often leads to poor outcomes [3]. While the incidence rate of ovarian cancer is less than breast cancer, it is estimated to be three times more lethal, and by the year 2040, its mortality rate is predicted to increase significantly [4].

Ovarian cancer incidence and epidemiology patterns vary globally and are correlated with various risk factors that can contribute to development of the disease [5]. Non-Hispanic white women have been reported to have the highest prevalence of ovarian cancer (12.0 per 100,000), followed by Hispanic women (10.3 per 100,000), non-Hispanic blacks (9.4 per 100,000), and Asian / Pacific Island women (9.2 per 100,000). Additionally, ovarian cancer mortality has a different global pattern, and is the highest amongst black women, which is mostly due to the differences in prevention, diagnostic and treatment strategies [6].

There is growing evidence to suggest that the management of ovarian cancer should be personalized, taking into account the patient’s performance status. [7]. It is essential to be able to predict the incidence rate of ovarian cancer and its survival rate given this information can help develop and enhance strategies and interventions for prevention and early diagnosis of the disease. The survival rate of ovarian cancer is related to many factors, including the stage and degree of disease, age, histology, appropriate surgical treatment, appropriate chemotherapy, and tumor site [8]. Furthermore, several risk factors can contribute to the development of cancer. Identifying and addressing these risk factors can potentially aid in cancer prevention. Moreover, elucidating the mortality rates of the disease, and global incident patterns can help develop strategies aimed at prevention. Currently, there are no comprehensive studies on the survival rate of ovarian cancer in Asian countries. Therefore, this systematic review and meta-analysis were conducted to determine the survival rate of ovarian cancer in Asian countries.

Mehtods

The present study is a systematic review and meta-analysis of ovarian cancer survival rate. The method by which the present study is reporting is based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) checklist [9].

Search Strategy

In this study, authors surveyed five databases: Medline / PubMed, ProQuest, Scopus and the Web of Knowledge and Google scholar for grey literature and included studies published by the end of August 2021. Keywords that were selected to search databases included.

Ovarian Neoplasms [Mesh], Survival OR Survival Analysis OR Survival Rate, Asian Countries (Names of countries) (Appendix 1).

The data that were collected were entered onto EndNote, X7 software and duplicated articles were deleted. Two researchers examined the articles independently, using search strategies that are presented in Appendix 1.

Inclusion and exclusion criteria

This study included observational studies (cross-sectional, case-control, and cohort studies) on ovarian cancer survival that were published by the end of August 2021 and were published in English. Review and meta-analysis studies or studies that did not report sample size or survival confidence interval were excluded.

Quality evaluation and data extraction

The Newcastle-Ottawa Quality Assessment Checklist was employed to consider the quality of the selected manuscripts [10].

Two investigators performed the initial search of the studies. After screening studies and extracting results, the quality of the manuscripts were determined independently by two other investigators. If the two investigators were in disagreement, the preselected leader of the team would give their final opinion on the article.

All articles, which were included in this study were selected from a pre-determined checklist. This checklist encompassed the author’s name, publication year, study period, sample size, cancer type, country, and survival rates of 1, 3, and 5 year. Data extraction was done independently by two researchers.

Statistical analysis

The Cochran Q test (with a significance level of less than 0.1) and I2 statistics were used to determine the heterogeneity between studies. In the presence of heterogeneity, the Random-Effects Model was used by the Inverse-Variance Method, and if there was no heterogeneity, the fixed effects model was used. Meta-regression analysis and subgroup analysis were used in case of heterogeneity between studies. Analysis was performed on STATA software version 16 and MEDCALC version 14.

Additional analysis

The year in which the study was published was utilized in Meta-Regression analysis due to the high heterogeneity of the studies.

Bias Risk among Studies

The Random Effects Model is utilized to reduce the risk of bias in studies [11, 12]. Egger diffusion bias evaluation test was also utilized to determine the risk of diffusion bias (publication bias) [13].

Results

Study selection

2377 articles were found after searching all international databases, and after omitting duplicated articles, 667 articles were included in the review stage. After careful examination of the titles and abstracts of the selected articles, 426 articles were considered for the next step. At this stage, the full text of the articles was reviewed, and 108 retrospective cohort articles were part of the final analysis. The references of imported articles were also reviewed to add applicable studies. The study selection process is shown in Fig. 1.

Fig. 1
figure 1

Flowchart of the included eligible studies in systematic review

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Study characteristics

The articles were chosen from January of 1989 to August 2021. 108 studies over the mentioned period were eligible. 56 articles from China, 13 articles from Hong Kong, 21 papers from India, 13 articles from Iran, 2 articles from Israel, 57 articles from Japan, 29 papers from South Korea, 2 papers from Kuwait, 16 papers from Singapore, 11 articles from Taiwan, 16 papers from Thailand, and 14 articles from Turkey were reviewed. Descriptive information for these studies is provided in Table 1. The median follow-up period in the studies was 9 years.

Table 1 Basic Information of Included Studies
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Quality Appraisal

The results of the quality assessment of manuscripts are shown in Appendix 2. Based on the review using the relevant checklist, 79 studies were determined to be of good quality, and 29 articles had average quality.

Heterogeneity

The result of the chi-squared test and I2 index elucidated that there is significant heterogeneity between studies. According to the analysis, 1 year survival of ovarian cancer was: I2 = 99.93%, P < 0.001; 3 years was: I2 = 99.96%, P < 0.001); and 5 years was: I2 = 99.92%, P < 0.001). As a result, a random-effects model was used for all analysis.

Results of the Meta-Analysis

First, the articles were sorted based on the year of publication, and then the survival was differentiated into 1, 3, and 5 years. Meta-regression was also completed based on the year of the study.

1-year Survival Rate of Ovarian Cancer in Asian Countries

From the total number of articles that were included in the final analysis of this paper, 41 studies showed that based on a random-effect model, the 1-year survival was 73.65% (95% CI, 68.66–78.64). (Fig. 2)

Fig. 2
figure 2

1,3 and 5-year Survival Rate of Ovarian Cancer in Asian Countries

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3-year Survival Rate of Ovarian Cancer in Asian Countries

From the total number of articles that were included in the final analysis of this paper, 50 studies showed that based on a random-effect model the 3-year survival was 61.31% (95% CI, 55.39–67.23).(Fig. 2).

5-year Survival Rate of Ovarian Cancer in Asian Countries

From the total number of articles that were included in the final analysis of this paper,159 showed that based on a random-effect model, the 5-year survival was 59.60% (95% CI, 56.06–63.13).(Fig. 2).

Ovarian Cancer survival rate by Asian Country

Results of ovarian cancer survival rate in 12 countries are shown in Table 2; Fig. 3. The highest 1, 3, and 5 years survival rates are respectively in Iran (93.80), Turkey (84.0), and Turkey (85.27), and the lowest survival rates are respectively seen in Singapore (63.23) and India (46.72).

Table 2 Result of meta-analysis and heterogeneity of survival rate of ovarian Cancer in Asian Countries base on each country and year of survival
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Fig. 3
figure 3

1-year survival rate, 3-year survival rate, and 5-year survival rate of ovarian Cancer in Asian Countries

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Metaregression Ovarian Cancer Survival Rate in Asian Countries

Although in the recent years, the 1-year survival (Reg Coef = 0.6756, p = 0.119) and 3-year survival (Reg Coef = 0.6012, p = 0.287) has increased, this increase was not statistically significant. Also the 5 year survival rate has decreased (Reg Coef = − 0.1205, p = 0.678), while this decerease was also not signifant. (Fig. 4)

Fig. 4
figure 4

Bubble plot of standard error by point estimate for assessment of meta-regression (1, 3, and 5-year Ovarian cancer survival rate) [A: 1-year survival rate, B: 3-year survival rate, C: 5-year survival rate]

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Publication Bias

Ultimately, we chose the funnel plots to evaluate the release bias for 1, 3, and 5 years ovarian cancer survival rate in Asian countries. The results of the egger test confirmed this bias (Appendix 3).

Bias for 1 year: 1.86, 95% CI = -11.14 to 14.87; P = 0.7738.

Bias for 3 years: 2.40, 95% CI = -11.76 to 16.56; P = 0.7346.

Bias for 5 years: 2.64, 95% CI = -2.16 to 7.46; P = 0.2795.

Discussion

In the present study, we conducted a meta-analysis to evaluate the 1, 3 and 5 year survival rate of ovarian cancer across 12 Asian countries. The mean 1-year survival in this study was estimated to be 73.65%. According to the results, Iran’s 1-year survival rate was estimated to be the highest and was 93.80% and Singapore’s 1-year survival rate was evaluated to be the lowest and was 63.23%. In a 2013 cohort study of women with ovarian cancer in Denmark, Grann et al. found that the overall 1-year survival rate between 2000 and 2002 was 73% and between 2009 and 2011 was 69% [14]. In a 2012 study, the 1-year survival rate of ovarian cancer between 1978 and 2002 was evaluated to be 74.6% in Finland, 75.6% in Norway, 79.3% in Sweden, 60.7% in Ireland., 60.7% in England, 62.9% in Northern Ireland, 60.8% in Scotland, 62.9% in Wales, 70.9% in Austria, 69.7% in Germany, 69.5% in the Netherlands, 78.5% in Switzerland, 64.9% in the Czech Republic, 4.64% in Poland, 1.56% in Slovakia, 69.6% in Italy, 68.8% in Slovenia and 63.6% in Spain [15]. In 2017, another study by Stewart et al. reviewed ovarian cancer survival rate between 2001 and 2009 in 37 states, which includes 80% of the population of the United States. The survival rate for ovarian cancer in women between 15 and 90 years old was 72.3% from 2001 to 2003 and increased to 73.3% from 2004 to 2009 [16]. The estimated 1-year survival rate in the present study is higher than in the previous studies. Only Finland, Sweden, and Switzerland have slightly higher survival rates.

The 3-year survival rate of ovarian cancer in this study was estimated to be 61.31%. The highest and lowest 3-year survival rates in our study were found to be 84% in Turkey and 46.72% in India respectively. According to a study published in 2014 by Anuradha et al., women with invasive epithelial ovarian cancer in 2005 had a 3-year cancer survival rate of 57% in Western Australia and 50% in South Australia [17]. Cabasag et al. studied 3-year survival rate of ovarian cancer between 2014 and 2010 in Australia, Canada, Denmark, Ireland, New Zealand, Norway, and the United Kingdom where the results were 56.4%, 50.1%, 53.6%, 44.8%, 45.5%, 57.2%, and 47.3% respectively [18].

The 5-year survival rate of ovarian cancer in the present study is 59.60%. Turkey, with 85.27%, has the highest, and India, with 36.06%, has the lowest 5-year survival rate. In the United States, the incidence of ovarian cancer is relatively low, with a 5-year survival rate of 53% in patients undergoing surgery and 8% in patients that do not undergo surgery. In Canada, the 5-year survival rate of ovarian cancer was estimated to be between 37 and 43%, and in Japan, the United Kingdom, France, and Sweden was respectively 55%, 43%, 43%, and 45% [19]. Studies which were conducted in the Netherlands and Korea illustrated that the 5-year survival rate in the Netherlands rose from 18% to 1993 to 28% in 2004, and reported the 5-year survival rate of ovarian cancer in Korea in 2011 to be 60% [20, 21].

From 2000 to 2007, the 5-year survival rate for European women with ovarian cancer was 38%. However, the 5-year survival rate for this cancer was lower in Ireland and the United Kingdom, where it was reported to be 31%, as compared to the results of our current study. Moreover, in Eastern Europe, Southern Europe, Central Europe, and Northern Europe, the 5-year survival rate were estimated to be 34.4%, 38%, 40.5%, and 41.1% respectively [22]. In Western and Southern Australia, the 5-year survival of invasive epithelial ovarian cancer is estimated to be 46% and 40%, respectively. Additionally, the 5-year survival rate of ovarian cancer between 2003 and 2008 was approximately 44% in United States, 43% in England, 45% in Canada, 55% in Japan, 37% in Denmark, and 45% Sweden [17]. Srivastava et al. found that the 5-year survival rate in Caucasian women has surged from 40.7 to 45% from 1992 to 2008; however, the 5-year survival rate decreased in African American women from 47.9 to 40.3% over the same period and decreased to 36% from 2006 to 2012 [23]. In a 2020 study, Bian et al. studied the effects of a previous malignancy on ovarian cancer survival rate between 2004 and 2015. They reported a 5-year survival rate of ovarian cancer with a previous malignancy to be 35.1%, and with no previous malignancy to be 43.2% [24]. A retrospective study conducted in China, which analyzed 63 pathological cases of ovarian cancer from 2000 to 2018, reported a 5-year survival rate of 69% in patients who underwent surgery for treatment. The study also found an overall 5-year survival rate of 80% for all patients [25].

A 2020 cohort study by Beachler et al. reported an overall 5-year survival rate of 47.7% in advanced ovarian cancer patients in the United States from 2018 to 2010 [26].

The findings of our study indicate that the survival rate of ovarian cancer is higher in Asian countries when compared to those in Europe, America, Australia, and Africa.

Ovarian cancer is generally less common in Asia and the Middle East and has better outcomes than in the United States and Europe. Ovarian cancer is also diagnosed in women in Asia and the Middle East at a younger age, which may be a contributing factor to better survival rates [19]. Generally, this difference in survival could be related to different risk factors, increased cancer incidence, or more specific reporting of the death rates, which needs to be thoroughly investigated in future studies. It can also be caused by different treatment methods such as the use of lymphadenectomy [27, 28], which can lead to different survival in patients in different regions.

The strength and limitations

The type and quality of the studies included in this study are among the study’s limitations. Also, the volume of sample studies and the number of studies conducted in each country can affect the results of the present study. In addition, more than half of Asian countries have not published any studies on ovarian cancer survival rate, so more accurate studies are needed for precise assessment, especially in unreported countries. The power of the present study is the introduction of observational studies with follow-up design (cohort) and meta-regression analysis to identify heterogeneity sources.

Conclusion

Ovarian cancer can be one of the most important cancers among women and can be fatal if diagnosed late. The survival rate of ovarian cancer in the present study shows that in most cases, Asian countries have a higher survival rate than European countries, and these results can be a basis for developing treatment strategies and health interventions. One of the reasons for the higher survival of this cancer in Asian countries can be due to the difference in the type of cancer as well as the cancer BIRAD. Also, the difference in diet and lifestyle in Asian countries compared to European countries can be another reason for the difference in survival in these two continents. It seems that a healthier life than an industrial life can have an effect on cancer survival. However, it is highly preventable by recognizing risk factors. With improved disease management, early detection and better treatment, ovarian cancer mortality can be better managed and even prevented. It is also recommended for future studies to investigate different treatments and make better decisions for more effective treatment that can bring more survival for patients. In addition, it is recommended to investigate risk factors, genetic differences, differences in the type of cancer and degree of cancer, and nutritional differences for further studies.