Overview
The primary goals of cancer screening are to reduce mortality and morbidity of a cancer in the population, through detection of pre-cancer (e.g. cervical intraepithelial neoplasia) or early-stage cancer (e.g. breast cancer) in asymptomatic individuals, so that timely diagnosis and early holistic treatment can be offered to improve health outcomes of those apparently healthy individuals.1, 2 Notably, not all cancers can be screen-detected. Likewise, screening for some cancers among average-risk asymptomatic individuals may not lead to reduction in mortality. Early diagnosis represents another important cancer control strategy, which aims at detecting cancer in symptomatic patients at the earliest possible, potentially curable stage to allow timely effective treatment, leading to improved survival and quality of life.3
To be effective, cancer screening must be delivered as a structured pathway starting from: (1) Identifying the target population who will benefit from the service; (2) Informing and inviting them to participate; (3) Administering the screening test; (4) Following-up with test results and referral for further testing among those with abnormal results; to (5) Ensuring timely pathologic diagnosis, staging and access to effective treatment.2, 3 Enabling the target population to participate in cancer screening (i.e. uptake) is a crucial step for its successful implementation. Common barriers to cancer screening uptake included lack of perceived need for cancer screening, lack of knowledge on the disease, fear of cancer screening, limited access to cancer screening procedure, never recommended to undergo screening by healthcare professionals and financial costs of the cancer screening.4-6 Conversely, enhanced knowledge of cancer and importance of cancer screening, accessible cancer screening programme, healthcare provider recommendations and family support can significantly enhance screening rates.7 Apart from improving accessibility of screening services, community-based education on cancer screening in the form of counselling or educational materials, the use of reminder systems to encourage appointments, and reduced financial barriers to cancer screening were proven effective for promoting uptake.8, 9
Meanwhile, there is no cancer screening test with perfect performance (i.e. 100% specificity, sensitivity, positive predictive value (PPV) and negative predictive value (NPV)). Even with the best technology, there will always be false-positive results, necessitating further investigations and leading to over-diagnosis and over-treatment, which increase the risk of complications associated with invasive investigations and treatment, cause unnecessary psychological distress, as well as strain healthcare resources. Conversely, false-negative results may provide a misleading sense of security, and delay essential diagnoses and ultimately cause harm.2 These challenges highlight the need for evidence-informed assessment of the benefits and potential harm before introducing a cancer screening test in local cancer screening programmes. Equally important is the need for the development of evidence-based educational materials adapted to different health literacy levels to inform, communicate and support decision making by the target groups.2
In Hong Kong, the Cancer Expert Working Group on Cancer Prevention and Screening (CEWG) was established in 2002 under the Cancer Coordinating Committee chaired by the Secretary for Health, to regularly review local and international scientific evidence, assess and formulate local recommendations on cancer prevention and screening applicable to the local setting.10 Recommendations on screening were made based on local epidemiology, scientific evidence on effectiveness of screening and early treatment as well as cost-effectiveness. In this chapter, screening recommendations of the following women-specific cancers: (1) breast cancer; (2) cervical cancer; (3) ovarian cancer; as well as the third commonest cancer among Hong Kong women – (4) colorectal cancer will be presented.