Chapter 20: Cancer

INTRODUCTION

Cancer is the second leading cause of death globally and is responsible for nearly 9 million deaths annually—equivalent to 1 in 6 deaths worldwide.¹ In the USA, 38% of women and 42% of men will be diagnosed with cancer in their lifetimes.² With an ageing and rapidly expanding population, cancer is more prevalent than ever and incident cases are projected to rise by about 70% over the next two decades.¹

The first recorded case of cancer was in Egypt in 1500 BCE.³ Compared to the days of pharaohs and hieroglyphics, we may be living longer but many of us are also living sicker. Modern physical and social environments are not conducive to healthy lifestyles, and overwhelming levels of physical inactivity (among other non-communicable disease risk factors) are exposing our cells and biological processes to greater stress than in the past.

For many years we have understood that regular moderate to vigorous physical activity reduces the risk of breast and colon cancer. By 2018, that list had expanded to include a reduced risk for cancers of the bladder, blood, endometrium, head and neck, kidney, liver, lung, oesophagus and stomach.^{4, 5} The underlying biological mechanisms responsible for physical activity’s protective effects for cancer are being unravelled; epidemiologists and basic scientists now realise that physical activity has a much larger role to play in clinical oncology than initially thought.

In this chapter we explore:

• the clinical work-up of the patient with cancer, in brief

• physical activity’s role:

  • – in the primary prevention of different types of cancer

  • – as an adjunct treatment for cancer

  • – in maximising the quality of life in patients recovering from cancer

• considerations in prescribing physical activity to the patient with, or recovering from, cancer.

A BRIEF OVERVIEW OF CANCER

Cancer comes from the Greek word karkinos, meaning ‘crab,’ first used by Hippocrates to describe carcinomas.³ Cancer cells develop in a multistep process⁶ in which several mutations are required to gradually transform normal cells into malignant ones. This progressive series of alterations comprises inherited or acquired genetic mutations in tumour suppressor genes, oncogenes and/or mismatch repair genes.

Without the regulation of normal cell signalling, cancer cells continue to divide, replicate and accumulate, instead of undergoing apoptosis (programmed cell death) when damaged. In a nutshell, cancer can be thought of as cell programming gone wrong. This can occur in different cells throughout the body (Table 20.1).