Abstract
INTRODUCTION:
Breast Cancer (BC) is the most prevalent cancer and the second leading cause of cancer-related death among Iranian women. A valid estimation of the 5-year survival rate can improve the current BC treatment programs. The present study aimed to assess the 5-year survival rate through a systematic review of published studies.
METHODS:
A systematic search of Medline/PubMed, Scopus, and Science direct as well as Iranian databases was conducted to identify the original articles evaluating the 5-year survival rate of BC among women in Iran. Random effects model was used to estimate the pooled 5-year survival rate. The eligible articles were analyzed using the Stata software.
RESULTS:
Our comprehensive literature search identified 11 eligible articles 2 of which were excluded due to reporting the results of a single study. The remaining 9 articles that contained 4815 women diagnosed with BC during 1991–2014 were included in the meta-analysis. The combined 5-year survival rate of BC was estimated to be 67.60%.
DISCUSSION/CONCLUSION:
The survival rate of BC was relatively low in Iran compared to developed countries. Hence, more effective measures have to be taken to increase these patients’ survival.
Introduction
Rationale
Due to population growth and aging, the burden of cancer is expected to increase worldwide, especially in developing countries [1,2]. In 2012, an estimated 14.1 million new cases of cancer and 8.2 million deaths resulting from cancer occurred worldwide [2–4]. Among cancers, Breast Cancer (BC) accounted for the highest morbidity and mortality among women in both more- and less-economically developed countries [2,5–8]. Approximately 40,000 deaths are attributed to BC annually [9] and DALYs of the disease followed an increasing trend from 1990 to 2010 [3].
BC is the most prevalent cancer and the second cause of cancer-related death among Iranian women [10–13]. The results of a meta-analysis on the incidence of BC in Iranian population showed that the age standardized rate of BC was 26.4 per 100,000 [14]. Indeed, the age standardized mortality rate of BC increased from 1.40 to 3.52 per 100,000 among Iranian women from 1995 to 2004 [3]. Unfortunately, BC in Iranian women occurs at least one decade earlier compared to women in developed countries [15]. These statistics indicate that more attention should be paid to BC care programs in Iran.
Survival rate is one of the most important indices for evaluating the quality of cancer-control and cancer treatment programs [6,10,15,16]. Survival analysis is a set of methods for analyzing time to event data where the event can be death, relapse of the disease, etc. [3]. Additionally, 5-year survival rate represents the percentage of the individuals who survive 5 years after the initial diagnosis of cancer [16].
Objectives
In the past two decades, many studies have been conducted on the survival rate of BC in Iranian women. In these studies, the 5-year survival rate of BC varied from 51% to 87%. Yet, a more accurate estimation of the survival rate of BC is required in order to reduce the burden of the disease at the national level. Precise estimation of BC survival rate can lead to improvement in the current treatment programs. Therefore, we conducted a systematic review and meta-analysis of the studies in Iran to determine a valid estimation of the 5-year survival rate of BC among women.
Materials and methods
Search strategy
We conducted an extensive literature search using Medline/PubMed, Scopus, and Sciencedirect for English-Language Articles (ELAs) from inception to March 2016. We used the following Medical Subject Headings (MeSH) terms for our initial search: (breast cancer OR breast tumor OR breast neoplasms) AND (survival analysis OR survival rate OR survival OR prognosis OR Kaplan-Meier Estimate). The search strategy was limited to ELAs in each database.
For Persian-Language Articles (PLAs), we did a comprehensive search of citations from SID (www.sid.ir), Irandoc (www.irandoc.ac.ir), IranMedex (www.iranmedex.com), and MagIran (www.magiran.com). In addition, the reference lists of the relevant studies as well as review articles were scanned to identify additional eligible articles. In case the results of a single study were repeated in more than one publication, the required data for analysis were extracted from the most recent article.
Study selection and eligibility criteria
Since there is no scoring guide for quality assessment in meta-analyses, the studies were considered to be eligible for inclusion in our study if they contained sample size, overall 5-year survival rate for BC, and 95% Confidence Interval (CI) or Standard Error (SE) for the 5-year survival rate.
Data collection process
The potentially relevant articles were obtained and the quality of the papers was assessed independently by two investigators. These investigators were blinded to names, affiliations, and addresses of the investigators and the name of the publisher journals. It should be mentioned that any discrepancies were resolved by either discussion or a third reviewer. Then, the data were gathered using pre-designed and pre-tested paper forms.
Statistical analysis
The heterogeneity between the studies was tested by X2 statistics. I2 statistics were also used to determine the total percentage of variation across the studies that resulted from heterogeneity rather than chance. Because the assumption of homogeneity was not valid (I2 > 50% and p < 0.1), the random effects model was used for pooled estimation of the 5-year survival rate of BC. Our findings of the meta-analysis have been presented in classical forest plots, with point estimates and 95% CIs for each study and the overall estimation. All the analyses were performed using Stata software, version 12 (Stata Corp LP, College Station, Texas).
Results
Study selection
Our literature search resulted in 226 citations 9 of which met the inclusion criteria for the meta-analysis. The summary profile of the search has been presented in Fig. 1.
Out of the 21 articles reporting the 5-year survival rate of BC among Iranian women, only 5 had 95% CI. In 3 other articles, the 95% CI was computed based on the SE of the 5-year survival rate. We contacted and emailed the corresponding authors of other studies to get sufficient data for the meta-analysis. Unfortunately, only 1 of them reported SE for the 5-year survival rate after 2 weeks. After quality assessment, all 9 articles met the inclusion criteria of the meta-analysis.
Study characteristics
The 9 studies included 4815 women diagnosed with BC during 1991–2014. These studies mainly aimed to evaluate the survival rate of women with BC. The main characteristics of these studies have been presented in Table 1. Among these articles, 3 were conducted in Fars province (south of Iran), 2 in Tehran province (the capital of Iran), 1 in Ardabil province (north–west of Iran), 1 in Kurdistan province (west of Iran), and 1 in Bushehr province (south of Iran). Also, one study was carried out in 5 provinces in different geographical regions in Iran. The minimum and maximum of the overall 5-year survival rate of BC was reported to be 51% and 75%, respectively (Table 1). The basic characteristics of disease in original studies was shown in Table 2.
Synthesis of results
Our results showed heterogeneity among the studies regarding the 5-year survival rates (X2 = 47.69 with df = 8, p < 0.001; I2 = 83.2% , p < 0.001). Using the random effects model, the pooled 5-year survival rate was estimated as 67.60% (95% CI: 65.90%, 69.29%). The effect size and weight of each study included in the meta-analysis have been depicted in Fig. 2.
Discussion
Herein, we conducted a systematic review and meta-analysis on the studies published on survival rate of BC in Iran.
Summary of evidence
Our findings showed great heterogeneity among the original studies regarding the 5-year survival rate. This difference could be attributed to the difference in the clinical/pathological characteristics of the patients under these studies (Table 2). In our meta-analysis, the pooled estimate of the 5-year survival rate of BC was 67.60%. In the studies conducted in India, Thailand, and Oman, the overall 5-year survival rates of BC were 46%, 62.9%, and 64%, respectively [10,17,18]. This indicated a better survival rate of the disease in Iran compared to these countries. However, this rate was lower in Iran compared to most developed countries. The overall 5-year survival rates of BC were 90%, 88.1%, and 84% in the US, Germany, and UK, respectively [19–21]. One of the most important reasons for poor BC survival in Iran is delay in diagnosis [22]. In some countries, on the other hand, the survival rate of the disease has increased with the onset of screening programs in 1994 [15]. Moreover, lack of Iranian women’s awareness about the early symptoms of BC cause them to seek for treatment in advanced stages of the disease [22]. Studies have shown that self-examination could play an important role in early detection and increasing the survival of BC [23–25]. However, cultural barriers prevent regular self-examination in the majority of women in Iran [22,23]. A study conducted in Iran indicated that less than 10% of health staff did self-examination regularly [26]. Fear about been diagnosed with BC could also result in delay in visiting a physician [22]. In other words, women in Iran cannot easily consult a physician about their sensitive medical problems, such as breast diseases [12,22]. Furthermore, shortage of cancer treatment units and screening programs compared to developed countries can justify the lower survival rate of BC in Iran [12,27].
Conclusion
In conclusion, the results of the current meta-analysis demonstrated that the overall 5-year survival rate of BC was relatively low in Iran. Thus, more effective measures must be taken in order to increase the survival of these patients. The present study had some limitations. The first limitation was that some studies reporting the survival rate of BC did not meet the inclusion criteria of the meta-analysis. Indeed, there was no reported survival rate of BC in some areas of the country, which could affect the study results.
All research done by the authors.
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Footnotes
Acknowledgement
Hereby, the authors would like to thank Ms. A. Keivanshekouh at the Research Improvement Center of Shiraz University of Medical Sciences for improving the use of English in the manuscript.