GLOBOCAN estimated 18.1 million new cases and 9.6 million cancer deaths worldwide in 2018 (1). Approximately half of the global burden of cancer was attributed to Asia in part due to 60% of the global population residing there and is projected to continue increasing as life expectancy improves (1). Cancer is the leading cause of mortality among both native and immigrant Asians irrespective of their country of residence (2–6). Those residing in Western countries where they are the ethnic minority are more likely to present with advanced stages of cancer and to have lower cancer screening rates in comparison to non-Hispanic whites (2–6). A study in Canada demonstrated breast cancer screening disparities among immigrant women by world region of origin and found that South Asian women, which included Indians, had the lowest screened as recommended rate at 48.5%. East Asian and Pacific women, which included Chinese, had a screened as recommended rate of 61.1% (7). In another study in the United States, regression models showed that foreign-born women from Southeast Asia, which included Singaporean Chinese, Indian and Malays, were more likely to be unscreened for cervical cancer (13.7%) compared to US-born women (7.6%) (8). Studies conducted in Western countries are often too underpowered to distinguish different Asian ethnic sub-groups (9, 10). Singapore is an opportune country to explore cancer screening behaviors among Asian ethnic sub-groups due to the nation’s large population of East Asians (Chinese), South Asians (Indians), and South East Asians (Malays).

In Singapore, cancer was the leading cause of death with 29.1% of total deaths in 2017 (11, 12). The Singapore Cancer Registry data showed that colorectal cancer (17.2%) had replaced lung cancer (14.8%) to become the most common cancer in men (13). Breast cancer (29.1%) and colorectal cancer (13.4%) remained the most common cancers in women (13). National Cancer Screening programmes have been launched to reduce morbidity and mortality in breast, cervical, and colorectal cancers. Through the Health Promotion Board (HPB), Singapore became the first Asian country to launch a population-wide national breast cancer screening programme in 2002 for females aged 50–69 years (14), which was shortly followed by the launch of a national cervical cancer screening programme in 2004 for females aged 25–69 years (15). From 2003, Singapore Cancer Society has been involved in large-scale opportunistic colorectal cancer screening. In 2011, HPB launched a national screening programme for colorectal cancer for individuals aged 50 and above (16). Although public awareness of screening and accessibility increased, the National Health Survey 2010 data showed that timely screening remained low with less than half of the population having had timely screening according to guidelines (17). Therefore, it is necessary to evaluate the progress of cancer screening.

This study aims to examine cervical, breast, and colorectal cancer screening behaviors in Singapore and identify how socio-demographic factors such as ethnicity and socio-economic status are associated with cancer screening rates. We will also examine the extent of the knowledge–behavior gap in cancer screening behavior. In doing so, we aim to better understand the determinants of cancer screening behaviors in the population of Singapore to improve screening programmes for the under-screened groups.

Respondents of the survey (N = 7,125) were mostly aged 40–69 years (85%) with a mean age of 57.7 ± 10.9 years and ethnically Chinese (73%) with a slight majority of females (58.9%) ( Table 1 ). The age, gender, and ethnic distribution of our survey sample resembled the population census during the same time period ( Supplemental Figures 1 – 3 ).

A majority of the screening-eligible female respondents reported having knowledge of Pap smear (80.0%) and mammography (93.6%). At least three quarters had ever been screened (cervical, 77.2%; breast, 75.2%); whereas, less than half had undergone screening as recommended (cervical, 43.0%; breast, 35.1%) ( Table 2 ).

Nearly half of the eligible respondents (49.0%) had ever been screened for colorectal cancer, but only 27.3% had screened within the recommended time period. More respondents had ever had FOBT (42.9%) compared to colonoscopy or sigmoidoscopy (22.1%). Among female respondents aged 50–69 years, only 10.7% had screened for all three cancers (cervical, breast, colorectal) within the recommended time period.

Although screening recommendation guidelines vary slightly between countries, our screened as recommended participation rates fell behind other high-income East Asian countries such as Taiwan in 2016 (cervical, 72.1%; breast, 39.3%; colorectal, 40.7%) (29), and South Korea in 2014 (cervical, 66.1%; breast, 66.0%; colorectal, 29.1%) (30). We also performed poorer compared to Western countries such as the United States in 2015 (cervical, 81%; breast, 71.6%; colorectal, 62.9%) (31) and the United Kingdom in 2017/18 (cervical, 71.4%; breast, 71.1%; colorectal, 57.7%) (32).

Compared to the cancer screening participation rates measured in the 2004 and 2010 national health surveys (17, 33), our screened as recommended participation rates did not indicate significant improvements ( Supplemental Table 3 ). For example, the proportion of women who had gone for mammogram as recommended was 35.1% in our study, down from 39.6% in 2010. The proportion of Singapore residents who underwent colorectal screening as recommended was 27.3% in our study, up from 20.2% in 2010. Although the health promotion efforts over the years may have resulted in only modest changes in the screened as recommended participation rates, it is reassuring to observe that between 2004 and 2016, the ever screened rates have seen an upward trend (cervical, 70.1 vs 77.1%; breast, 54.2 vs 75.2%) in tandem with a downward trend in the size of the knowledge–behavior gap (cervical, 10.7 vs 2.8%; breast, 25.7 vs 18.4%). Improvements were also seen in colorectal cancer screening participation rates between 2004 and 2016 in ever screened with FOBT (17.3 vs 42.9%) and ever screened with sigmoidoscopy/colonoscopy (11.2 vs 22.1%).

Our results demonstrate that screening knowledge and behaviors differ substantially by socio-economic status and ethnicity in Singapore. Higher educational level and household income were found to be significantly associated with screening as recommended for cervical, breast, and colorectal cancers. Malay ethnicity was associated with a lower likelihood of screening as recommended as compared with Chinese ethnicity. Cancer screening disparities associated with socio-economic status and ethnicity were reported in previous studies in Singapore (25–27, 34–38), as well as internationally (39, 40). However, limitations to the existing local literature include small sample sizes of the Malay and Indian ethnic minorities with oversampling of the Chinese ethnic majority, assessment of a single cancer screening modality, and age of the data. These limit the ability to generalize findings to the population and develop targeted population health interventions. Our study attempts to better estimate the true population effect sizes through our large representative sample size of 5,203 Chinese, 1,014 Malay, and 777 Indian respondents in the community setting.

Over the years, the Singapore Ministry of Health has endeavored to address the need to improve cancer screening participation rates, which culminated in the 2017 launch of the Enhanced Screen for Life Programme by the Health Promotion Board. This enabled eligible Singaporeans to screen for cervical, breast, and colorectal cancer from as low as $0–$5 per screening visit (41). Although affordability is an important consideration to address the socio-economic disparities, the continued low participation rates suggest there are additional barriers to address. A survey conducted at four polyclinics in Singapore reported that the most commonly cited reasons for not attending breast cancer screening programmes were lack of any breast problems, lack of time, and fear of pain (37). Another local mixed-methods study on barriers to breast and cervical cancer screening reported that fear of unnecessary treatments, ineffective treatments for early stage cancer, and low test sensitivity for early stage cancer were barriers to screening (28).

The proportion of those reporting having a family history of cancer was similar across cervical, breast, and colorectal cancer screening respondents; however, the association between a positive family history of cancer and cancer screening was only found to be significant among colorectal cancer screening respondents. While other studies have also reported this association among Asian women (26, 42), local screening rates particularly among the higher risk first degree relatives of colorectal cancer patients continue to be low (43, 44). Barriers include poor understanding of the screening guidelines, lack of health promotion messaging by healthcare professionals, fear of the test and the diagnosis, scheduling difficulties, feeling invulnerable since young and asymptomatic, unawareness of genetic risk, and the high cost of colonoscopy (43–45). Risk perception should be emphasized in health promotion messaging among Asian ethnicities as perceived susceptibility to breast, cervical, and colorectal cancers was found to be the lowest among Asian women as compared with White, African American, and Latino women (42).

Observing past studies in tandem with our current study, there is a repetitive trend of Malay ethnicity being less likely to participate in cancer screening when compared to the Chinese ethnic majority and their Indian counterparts (17, 26, 27, 33, 46, 47). For female cancer screening, this may be partly explained by the knowledge–behavior gap demonstrated in our study. This gap may be linked to cultural beliefs among Asian women, which should be appropriately understood in order to craft effective policies and health promotion messages. Previous studies have reported cancer screening barriers related to social stigma, personal modesty, fatalistic attitudes, beliefs that breast cancer is a Western women-affliction, beliefs that mammograms cause cancer, and a preference to be unaware of a fatal disease diagnosis to postpone accompanying fears (28, 34, 37, 48–52). However, these findings are limited to predominantly Chinese respondents. In the neighboring country Malaysia with a high proportion of ethnic Malays, their National Health & Morbidity Survey in 2006 showed that only 7.9% of eligible women had underwent mammography as recommended, and only 12.8% had underwent Pap smear as recommended in 2011 (53). Malaysian studies have reported that Malay women are apprehensive about doing Pap smears especially if they are single or unmarried as it indicates sexual activity. A woman’s partner or family members also hold great influence over decisions to screen due to strong family ties. Lack of knowledge among partners and male family members as well as perceived inaccessibility to a female health-care provider are commonly reported barriers (54–56). Similarly, the presence of male technicians/radiographers was found to be a barrier to mammogram screening (57).

The difference in the knowledge–behavior gap between ethnicities alludes to potential health literacy issues related to language barriers in Pap smear testing. Limited English proficiency and low health literacy among Asian women have been identified as barriers to cancer screening in several international studies where English is the predominant language (58–63). We also observed the phenomenon of Chinese women proceeding with Pap smear testing, despite not being fully aware of the purpose of the test. This may be linked to high trust among Chinese women towards their primary physician, which was reported by a study among Redhill residents in Singapore who were predominantly Chinese. Over half of the respondents rated trust towards primary care doctors and the medical profession as high or very high (64), which has been supported by other studies that reported high regard towards general practitioners in the Asian context (65, 66).

In our study, the knowledge–behavior gap was higher for mammography (18.4%) than for Pap smear (2.8%). Previous studies have suggested logistical and operational issues as reasons for the difference between uptake of Pap smear versus mammograms (34, 51, 52). The widespread availability of Pap smear tests as a bedside procedure in general practice clinics has made it readily accessible in contrast to the limited availability of mammography. In addition, most patients are able to state preferences or choose female doctors to perform the Pap smears; however, there is no freedom of choice for radiographer doing the mammograms. Having a male radiographer has been shown to be a barrier to screening in both Western and Asian cultures (67–70).

Strategies to further narrow the knowledge–behavior gap should include developing tailored cancer screening promotion campaigns for the Malay ethnic group, which can be done in close consultation with employers, religious, and community authorities to ensure the messages stay culturally relevant (71–77). To further incentivize cancer screening behavior, we must inculcate a culture of cancer screening through community screening initiatives so that they are seen as a form of social event (71, 78, 79). Targeted and frequent mass media campaigns have been shown to be effective in increasing awareness and compliance for cancer screening (71, 80, 81) as well as being frequently exposed to reminders with cues to action (23, 24, 71, 82, 83). Addressing polyclinic proximity and screening appointment logistics may contribute to improving mammography uptake (51). Further studies will need to be done on Malay-specific barriers and facilitators for screening across the three screening modalities as our analysis showed that only 10.7% screened as recommended for all three, and Malays had a higher propensity to not be screened. Existing studies in Singapore had predominantly Chinese respondents and focused on specific screening modalities (23–28). Further studies comparing cancer screening knowledge and behavior between Malays residing in Singapore versus Malays residing in Malaysia would help to elicit environmental and cultural influences.

Cancer screening knowledge and behaviors differ substantially between Asian ethnic sub-groups even within the confines of the island state of Singapore. Asian ethnicity represents a heterogeneous group with different religious and cultural traditions, and our results suggest that it is important to distinguish different ethnic sub-groups in future studies of screening behavior. Ethnic Malays are therefore, a key target population for further research and interventions to narrow the knowledge–behavior gap. Design of targeted cancer screening programmes and health promotion messaging by healthcare providers should include sensitivity to ethnic differences as well as female-specific cancer screening facilitators and barriers, which will help to further increase the uptake of cancer screening. The population-based cancer screening programmes are essential to Singapore’s preventive health strategy. The availability of subsidized rates has allowed more members of the population to access cancer screening, but the overall cancer screening rates still remain low. Socio-economic factors such as educational and income level remain important aspects that policy makers and healthcare organizations should address to improve cancer screening.

The datasets used in this article are available from the corresponding authors on reasonable request.

The studies involving human participants were reviewed and approved by National Health Group Domain Specific Review Board (2015-00095) and the National University of Singapore IRB (S-19-340). The patients/participants provided their written informed consent to participate in this study.

TC participated in the design of this study, performed the statistical analysis, interpreted the data, and drafted the manuscript. LT participated in the design of the Community Health Study, coordination, and data collection. RD is the principal investigator of the Community Health Study and participated in the manuscript revision of this study. WJS participated in the design of this study, the statistical analysis, interpretation of the data, and the manuscript revision. All authors contributed to the article and approved the submitted version.

The publication of this report was funded by the National University of Singapore Start-Up and the Ministry of Education Tier 1 grants. The Community Health Study was supported by grants from the Ministry of Health, Singapore, National University of Singapore and National University Health System, Singapore. The funding bodies had no role in the interpretation of the data and the formulation of this report.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.