Cancer

A Beginner's Guide

Paul Scotting

• Publisher: Oneworld Publications
• Year: 2017
• eBook ISBN: 9781786071415
• Edition: 2
• Topic: Medicine
• Subtopic: Diseases & Allergies

Cancer is a leading cause of death worldwide, and one of the most feared diagnoses a patient can face. The number of new cases is expected to rise by 70% over the next two decades, but few of us understand what it is, how it affects the body or what can be done to treat and even prevent it.In this illuminating introduction, Dr Paul Scotting explains the science behind the disease and explores the factors that can increase our risk of developing cancer. Fully revised and updated, Cancer: A Beginner's Guide details the latest breakthroughs, cutting-edge developments and promising new strategies that will help us combat and cure cancer in the future.

1

A brief history of cancer

The damage that causes cancer is usually due to toxic agents – carcinogens – including chemicals and radiation, which alter our genes. Cancer is the final result of the multiple damaging events these carcinogens cause in a single cell.

There are two opposing views of the history of cancer. One is that cancer has always been here: as long as there has been life, there has been cancer. The opposing view is that because many of the carcinogens that cause cancer have only become widespread in the environment since the Industrial Revolution in the eighteenth century, cancer is a disease of the modern age. It seems there is some truth in both views. For humans – and other animals – cancer has always been with us, but many of the more common cancers have only become prevalent in the last few hundred years.

The problem with trying to determine the extent to which cancers were present in earlier centuries is that before the late seventeenth century the way in which patients were examined would not have revealed most types of cancer. Also, the term ‘cancer’ was applied to a wide range of growths, many of which would not now be classified as cancers. The earliest recorded descriptions of cancer come from Ancient Egypt. One document, known as the Edwin Smith Papyrus, written between 3000 and 1500 BCE, is regarded as one of the oldest medical records. Edwin Smith, an American, was described as ‘an adventurer, a money lender and a dealer of antiquities’. In 1862, he bought the manuscript from a dealer in the city of Luxor in Egypt and, although he recognized its importance, a full translation (by James Henry Breasted) was not published until 1930, some years after Smith’s death. The manuscript’s descriptions of 48 patients include several suffering from a disease that would now be recognized as breast cancer.

Figure 1  Section from the Edwin Smith Papyrus, which describes 48 patients, including some with breast cancer

 

There is also some archaeological evidence to suggest that humans suffered from cancer in the Bronze Age (1900–1600 BCE). Strikingly, these archaeological examples are often of bone cancer, which is now relatively rare. However, we should beware of jumping to conclusions. Such observations do not imply that bone cancer used to be more common; the remains often include little other than bone, so there is not much scope to find clear evidence of any other kind of cancer. From Ancient Greece to Roman times, the majority of descriptions of cancer refer to the female breast. Aulus Cornelius Celsus (30 BCE–38 CE), commented on the relatively limited distribution of cancers diagnosed at this time, stating that cancer ‘occurs mainly in the upper structures about the face, nose, ears and lips and female breasts’. While most cases described were cancers of the breast, cancers of the uterus and digestive tract were also known. Despite this, even Galen, whose descriptions of cancer provided the basic reference for clinicians from their time of writing (131–203 CE) until the late eighteenth century, appeared to be largely unaware of cancers of the internal organs. By the seventh century, it was apparent that cancer could occur in many different organs. Paul of Aegina (625–690 CE) correctly noted that cancer arises in every part of the body, even the eyes and the uterus, but he went on to suggest that ‘it is especially common in women’s breasts because they are lax and quickly take up the coarsest matter’!

Little progress in understanding was then made over the next 1,000 years. One of the most useful observations, providing an indication of the thinking of the time, was made by Hieronymus Fabricius (1537–1619) of Padua, Italy, who stated that ‘the lung, the liver and the soft structures can scarcely become cancerous’. Despite the identification of cancers in a wide range of organs, they were still rare in comparison to cancers of the breast and uterus, the reasons for which will be discussed shortly.

Cancer since the Renaissance

The eighteenth century saw a development in medicine that at last allowed a major leap in our understanding of cancer: the advent of autopsy (in which the body is dissected to determine the cause of death). Giovanni Battista Morgagni, Professor of Anatomy of the University of Padua, published The seats and causes of diseases investigated by anatomy, a well-described procedure for autopsy. Morgagni was a powerful intellectual force from the time of his graduation at the age of 19, with a degree in medicine and philosophy, to his 79th year, when he published his seminal work. He also found time to father 15 children and establish himself as a renowned archaeologist. Morgagni was widely respected for his works on anatomy, which provided accurate anatomical explanations for the features seen in disease, as opposed to the speculations, based on little real evidence, that were typical of earlier centuries. He spent his life recounting the outcomes of his many autopsies and providing anatomical descriptions of the human organs, both healthy and diseased, including cancers.

From the eighteenth century onwards, although descriptions of many different cancers appeared, including those of the face, rectum, stomach, penis and the female genitalia, descriptions of breast cancer still outnumbered all other types. It seems that those cancers that we now know to be linked to modern carcinogens were comparatively rare before the twentieth century, while others such as breast cancer (which appears to be more intrinsic to the body, with a strong genetic predisposition, chapter 9, p. 104–107; chapter 10, p. 120–121) were more common.

The number of carcinogen-driven cancers has fluctuated dramatically depending on exposure to particular agents. Lung cancer provides one very striking example of this. In 1878, a study of all cancers seen at autopsy in the Institute of Pathology of the University of Dresden in Germany identified only 1% as malignant lung tumours. By 1918, when the smoking of rolled cigarettes had become widespread, the percentage had risen to almost 10% and by 1927 to more than 14%, a number that remains similar in most Western countries today.

In some cases, cancers caused by occupational carcinogens appeared early in modern history and, thanks to the insight of clinicians of the time, were identified and dealt with. One example was a condition known to chimney sweeps as ‘soot-wart’. This was in fact cancer of the scrotum, first described by Percivall Pott in 1775. It soon became clear that this cancer was due to soot (now known to contain powerful carcinogens) becoming lodged in the ‘moist rugae’ of the scrotum. By the late nineteenth century, guidance from the chimney sweeps guild of Denmark for sweeps to take daily baths had resulted in great improvements, as was noted in a report in the British Medical Journal in 1892, entitled ‘Why foreign sweeps do not suffer from scrotal cancer’. This was a reflection of the rather less hygienic habits of British sweeps, who unfortunately continued to develop this cancer for some time. Interestingly, there was a clear recognition of the ability of cancer to spread within the body. Percivall Pott writes:

If there be any chance of putting a stop to or preventing this mischief, it must be by the immediate removal of the part affected; I mean that part of the scrotum where the sore is; for if it be suffered to remain until the virus has seized the testicle, it is generally too late even for castration. I have many times made the experiment; but though the sores, after such operation, have, in some instances, healed kindly and the patients have gone from the hospital seemingly well, yet, in the space of a few months, it has generally happened, that they have returned, either with the same disease in the other testicle or in the glands of the groin, to with such wan complexions, such pale leaden countenances, such a total loss of strength and such frequent and acute internal pains, as have sufficiently proved a diseased state of some of the viscera and which have soon been followed by a painful death.

Throughout the 1800s, many, like Percivall Pott, continued to believe that cancer was caused by an infectious agent. This belief was partly due to a phenomenon termed cancer à deux, in which married couples were noted both to develop cancer. We now understand that there are two good explanations for cancer à deux. First, the cancers concerned were often of the genitalia (such as in the cervix or penis), which are now known to be unusual cancers in which viral infection plays a significant role (see chapter 9), and, second, many couples would both have been exposed to the same carcinogens in their environment. The fact that cancer could be transferred from one region of the body to another, or to experimental animals, was also generally taken as evidence of an infectious cause rather than the ability of cancer cells to spread.

Finally, by the beginning of the twentieth century, developments in the detailed study of diseased tissue meant that the true composition of cancer, derived from our own cells, was clearly established.

A disease of the modern age?

Although it is clear that cancer has been observed since records began, it is also evident that cancer became increasingly common during the twentieth century. One explanation for this increase is that improvements in quality of life and healthcare have resulted in our living to a greater age. Before about 1800, average life expectancy was fairly stable at around 40 to 45 years; since most cancers do not occur until we reach old age, there was much less opportunity for it to occur in centuries gone by. In short, other diseases got us before cancer had a chance. Of course, even in ancient history, some people did live to old age, so there was still the opportunity for carcinogenic damage to accumulate over many decades. A range of cancers was seen, but their numbers seem to have been far fewer than we see now. In the nineteenth and twentieth centuries, life expectancy doubled in many parts of the world to the 70 or 80 years we can now anticipate in developed countries such as the UK. Our bodies now provide the necessary time for cancer to develop and so it has become one of the most common causes of death.

Another explanation for the recent increase in cancer numbers is that exposure to most common carcinogens is relatively new. For example, sunlight has become a greater cause of skin cancer now than it was many years ago. This is because sudden or strong exposure to ultraviolet light contributes to skin cancer in those who are not normally exposed to it. In years gone by, exposure to the sun was continuous for those living and working outdoors. Pigment therefore accumulated, which protected the skin cells from the effects of ultraviolet light. Also, fashion and the rules of social decency meant that people in the northern hemisphere covered up most of their skin when outdoors – the phenomenon of sunbathing only became popular after the 1920s. It seems that this change in our habits has given rise to one of the most dramatic increases in cancer occurrence: incidence of malignant skin cancer has increased more than fourfold in the UK since the mid-1970s. Because it usually takes 15 to 30 years for a cancer to appear after the initial exposure to a carcinogen, this increase possibly reflects a change in habits dating back to the 1950s and 1960s, a period that coincided with an upsurge in foreign travel and a significant decline in the amount of clothing worn when in the sun. Our awareness of the risks of sunburn does now seem to be affecting our behaviour; the sunblocks we use are much more effective and we pay more attention to protecting children from sunburn. We can only hope that this will lead to a decrease in the incidence of aggressive skin cancer over the next 25 years.

But what about breast cancer, which, above all other cancers, is frequently described in historical texts? Although breast cancer has always been one of the most common cancers, it seems probable that it too was significantly less common in earlier times than it is now. As I will discuss in chapter 9, early childbirth and prolonged breastfeeding both protect against breast cancer. In economically developed countries, the nature of families and pregnancy changed dramatically in the nineteenth and twentieth centuries. In the USA, average family size fell from 7 children in the early 1800s to 3.5 children by 1900 and, as the twentieth century progressed, to the current level of around 2. The trend towards smaller family size and later first pregnancies means that women have largely lost the benefits of these protective factors against breast cancer.

Although it seems that breast cancer, in particular, is likely to have been prevalent in historic times, by the beginning of the twentieth century the range of cancers with which we are now familiar was evident and scientists and clinicians had begun to view cancer as our own cells gone wrong. However, an almost total lack of understanding meant surgical removal of tumours was the only means of treatment. Not until the advent of recombinant DNA technology (‘gene cloning’), in the late 1970s, did we at last have the means to gain real insights into cancers’ biology; insights that, at last, have heralded the advent of new therapies, with the promise of more on the horizon.

Summary

It appears that cancer has always been associated with human life. However, it is most prevalent in older people and it is more common following exposure to environmental carcinogens that damage DNA. Cancer has therefore become a much more prevalent problem in most countries since the industrial age, when life expectancies and exposure to carcinogens both increased. We now understand what most of these causes are, so public health messages and public policy could begin to protect us from their effects. Unfortunately, it is not always easy to get the public to heed these messages.

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Table of contents

• Cover
• Halftitle
• Series page
• Title page
• Contents
• Second edition notes
• Introduction
• 1. A brief history of cancer
• Part 1. The selfish cell
• 2. The circle of life
• 3. The immortal cell
• 4. Surviving and spreading
• Part 2. The enemy forces
• 5. Mutation, mutation, mutation
• 6. Chemical carcinogens
• 7. Radiation
• 8. Catching cancer
• Part 3. Who gets cancer?
• 9. We are all different
• 10. Inheriting cancer
• 11. It shouldn’t happen to children
• Part 4. Winning the war
• 12. Attacking cancer
• 13. Prevention and cure: future prospects
• Appendix 1
• Appendix 2
• Appendix 3
• Appendix 4
• Glossary
• Further reading
• List of figures and tables
• Acknowledgements
• Copyright