Screening for Cancer: Considerations for Low- and Middle-Income Countries

Excerpt

The goal of cancer screening is to detect cancer or precancerous lesions in asymptomatic individuals at a point when cancer is more likely to be prevented or cured than if the patient waited for symptoms to develop (Morrison 1992). A screening intervention can be successful only if the disease is more likely to be cured when detected early, and for which effective treatment for early-stage disease is available, affordable, and acceptable to the individual, the community, and the jurisdiction of interest. This chapter briefly describes the principles and pitfalls of cancer screening, based largely on the experience in high-income countries (HICs); summarizes the evidence for screening “best buys” relevant to low- and middle-income countries (LMICs); and highlights opportunities to avoid some of the costly and vexatious problems associated with screening in HICs and LMICs. The chapter focuses principally on existing projects and recent literature on cancer screening in LMICs.

Policy considerations regarding whether and in what manner to implement a cancer screening program should be based on systematic evaluation of several factors, including at a minimum: the burden of the cancer in the population of interest (those at risk), the cost effectiveness of the proposed screening intervention, and how well a given screening test performs in the target population. How well the test works can be judged by how many individuals must be screened to prevent one death from that cancer, balanced with how many people who undergo screening have a positive or abnormal test result when they do not have cancer (false-positive test), and how many have a normal result when they in fact do have cancer (false-negative test). The number of individuals with positive results who will actually proceed to follow up and receive treatment is a critical issue to consider for a given population. Other critical considerations include the cost effectiveness of a screening intervention when moving from initial trials to scale and the health system requirements needed to ensure the success of a given program. (See chapters 11, 16, and 17 for more on health systems.)

In this chapter, we selected three cancer sites for which there is the most evidence for screening effectiveness in LMICs—breast, cervical, and colorectal—and three promising candidate conditions.