Chapter 51: Cancer

INTRODUCTION

Cancer and its associated issues have an important impact on public health practice that is global. Worldwide cancer is among the top causes of death. Cancer is a major health concern in both developed and developing countries. Cancer etiology studies describe cancer within different populations along with identifying the causes of cancer. Cancer prevention takes this a step further and looks at ways to reduce or eliminate some of the risk factors for cancer. The public health approach is to prevent cancer.

Cancers or neoplasms are diseases characterized by abnormal proliferation of cells. If the proliferating cells invade surrounding tissues and spread through lymphatics or blood vessels, the resultant tumor is malignant; if they do not, it is benign. Some benign neoplasms may be fatal, including histologically benign brain tumors that grow and displace normal brain tissue in the confined space of the skull, and hepatocellular adenomas that rupture and cause bleeding into the peritoneal cavity. Some benign tumors such as intestinal polyps are considered premalignant lesions and confer a high risk of progression to malignancy. The term cancer usually implies a malignant or invasive tumor.

DESCRIPTIVE EPIDEMIOLOGY

Classification

Cancers are classified according to their organ or tissue of origin (site or topography code) and histological features (morphology code). A number of classification schemes have been developed, the most recent and widely used of which appears in Chap. 2 of the International Classification of Diseases, 10th revision (ICD-10), which is largely a topography code,¹ and the International Classification of Diseases for Oncology, 3rd edition (ICD-O), which contains an expanded version of the topography code in ICD-9 as well as a detailed morphology code.²

Sources of Incidence and Mortality Rates

Mortality rates are calculated from death certificate records and population census data. Mortality rates from various countries have been compiled periodically.³ Cancer mortality rates for the United States are published by the United States’ National Cancer Institute (NCI) and Centers for Disease Control and Prevention (CDC).^4–6

Population-based cancer registries, which have been established in many countries, provide information on incidence rates. These have been compiled in Cancer in Five Continents, which is jointly published periodically by the International Agency for Research on Cancer (IARC) and the International Association of Cancer Registries (IACR).⁷ In the United States, the best source of cancer incidence rates is the Surveillance, Epidemiology, and End Results (SEER) program of the NCI, which supports a network of 18 population-based cancer registries throughout the country. Results from this program are published annually and more detailed monographs are published periodically^4,8,9 and available online (https://seer.cancer.gov/). Both incidence and mortality statistics for the United States are summarized for the lay public and projected rates are published annually by the American Cancer Society.¹⁰

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