Survival pattern of colorectal cancer in Sub-Saharan Africa: A systematic review and meta-analysis

1Introduction

The share of non-communicable diseases (NCDs) to global morbidity and mortality is increasing. In 2030, NCDs are predicted to be responsible for more than three-quarter of global mortality [1] , of which cancer is likely to be the most important contributor. In 2020, an estimated 19.3 million new cancer cases and 10.0 million deaths occurred, making cancers the second-leading cause of morbidity and mortality worldwide [2] . Colorectal cancer is the third most commonly diagnosed and second-leading cause of cancer deaths worldwide, with nearly 2 million new cases and above a million deaths in 2020 [23] .

In the past, NCDs including cancer were the disease priorities of developed countries, however, recently the burden is increasing in low- and middle-income countries (LMICs) and should be considered among major public health issues [4] . Adopting a sedentary lifestyle, urbanization, cultural transition towards unhealthy behavior, and an increase in life expectancy in LMICs might be the possible reasons for an increasing burden of NCDs including cancer 567 . Following an increase in individual income in LMICs, the dietary habit shifted towards unhealthy patterns such as an increased intake of fat, sugar, and animal-source packed foods [8] , which are known risk factors of cancer [910] . Furthermore, increasing industrialization in middle-income countries also contributes to the observed trend in cancer incidence and mortality [11] . Low and low-middle socio-development index (SDI) countries have shown the largest increase in the number of cancer cases and deaths occurred from 2009 to 2019 [12] . The sub-Saharan Africa (SSA) region in particular is in a demographic and epidemiologic transition marked by an increase in life expectancy due to a decline in mortality from communicable diseases leading to a more older population who are at higher risk of cancer [13] . As a result, the cancer burden in the region is expected to increase by 85% in 2030 [14] .

Existing challenges, including poor screening services, inadequate research, and limited population-based registry make the cancer burden to be underestimated in SSA and less attention is given in policies 15161718 . The rise in prevalence of cancer in the region puts pressure on already overwhelmed healthcare and economic infrastructure, and poses additional challenges to the health service delivery [19] . The mortality due to cancer is significantly higher in LMICs, accounting for nearly 70% of all cancer deaths [20] . Particularly, people younger than 65 years of age are most commonly affected [2122] , leading to a greater economic impact as a result of premature mortality and lost years of productivity. In contrast to other regions, the share of cancer death in Asia (58.3%) and Africa (7.2%) are higher than the share of incidence 49.3% and 5.7% respectively, which could be due to the difference in the distribution of cancer types and higher case fatality rates in those regions [2] .

The cancer prognosis in SSA is poor which could be due to delay in patients’ visit to healthcare facilities, inadequate access to diagnostic services, and minimal treatment options. Although investigating the survival pattern is crucial for patients and healthcare providers, comprehensive evidence is limited in SSA. Assessing survival patterns enables us to understand the prognosis over time and enables public health professionals and policy makers to understand the quality and effectiveness of care and treatments introduced. In this review, we synthesized the survival pattern of patients diagnosed with colorectal cancer in sub-Saharan Africa. Furthermore, we summarized the variation in survival pattern across time, country’s income level, and other study level factors.