This book by Paul Scotting is perhaps the best available "beginner's guide" to cancer biology and treatment. The book is clearly written, is reasonably short at only about 200 pages, and the price can't be beat. The technical level of the book is managable for general readers comfortable with science, and yet also sophisticated enough to offer new insights to people with biomedical background.
Here are highlights of some important points which probably aren't known to most people:
(1) There are many types of cancer, and the extent to which they're curable with current treatments varies widely.
(2) Generally, many factors contribute to cancer incidence, including genetic predisposition, environmental exposures, obesity, diet, exercise, and other lifestyle factors. A degree of randomness is involved in how these factors affect each individual. Cancers which are strongly genetically determined (eg, retinoblastoma) are relatively rare. Poor diet (eg, cooked red meat, alcohol, and lack of fruits and vegetables) may be substantially responsible for about a third of all cancer cases. Smoking accounts for about 90% of lung cancer, along with contributing to other types of cancer and other diseases. Radiation typically acts as a carcinogen by causing DNA strand breaks, resulting in chromosomal abnormalities. Only one type of bacteria and a few types of viruses are known to contribute to human cancer, but these pathogens are still responsible for a significant percentage of cancer cases.
(3) The evidence indicates that cancer has always been present in animals and humans, but some types of cancer have become much more common in the past few centuries, partly because of people of living longer, and partly because of negative trends in the factors noted above.
(4) The incidence of various types of cancer varies widely between countries, primarily due to the non-genetic factors noted above. In Western countries, the most common types of cancer are breast, lung, colorectal, and prostate.
(5) It often takes about 10 to 30 years for cancer to appear after initial exposure to a carcinogen.
(6) Gene expression and corresponding phenotype of cells is normally greatly influenced by external signals (eg, growth factors). In tumor cells, these signals are often either ignored or responded to abnormally, and the signals that tumor cells send out are likewise abnormal.
(7) Genetic mutations are clearly linked with cancer. However, (although not mentioned in this book) the extent to which these mutations are cause and/or effect is debated. For example, the dominant somatic mutation theory (SMT) of carcinogenesis argues that mutations are the primary cause of cancer. By contrast, the tissue organization field theory (TOFT) argues that abnormal signaling at the tissue level, especially related to control of proliferation, is primarily responsible for carcinogenesis, with mutations following as an effect.
(8) If the SMT is accepted, it's estimated that several mutations are typically required to produce a tumor cell (with fewer mutations typically corresponding to benign tumors). Mutations in DNA repair genes are nearly universal, and result in genetic instability and a mutator phenotype. Therefore, as a tumor progresses, many additional mutations tend to develop, including extensive chromosomal abnormalities.
(9) The vast majority of cancer deaths are due to carcinomas, which arise from epithelial tissues.
(10) Only about 1% to 3% of our genome codes for proteins, which means that most mutations don't contribute to cancer or other problems. Also, over 90% of tumors show telomerase activity.
(11) Apoptosis is a relatively "clean" cell death process which doesn't promote inflammation, whereas necrosis does promote inflammation. Inflammation in turn inhibits cell death and promotes cell division, and thus may significantly contribute to many types of cancer.
(12) Decreased cell adhesion is a factor contributing to tumor invasion and metastasis.
(13) The probability that a given tumor cell will complete the metastatic process is very low, but having a typically large number of tumor cells makes it likely that metastasis will occur, often at multiple sites.
(14) There are many commonalities between developmental biology and cancer biology, such as similar transcription factors involved in cell motility.
(15) It appears that the immune system is very effective in eliminating most microtumors, but not all of them, so cancer still commonly occurs.
(16) Though childhood cancers are much less common than adult cancers, cancer is still the most common cause of mortality among children. Childhood cancers often appear during the first three years of life, with incidence tapering off with greater age. Childhood cancers usually are biologically different from adult cancers, and tend to be simpler than adult cancers in terms of their genetic damage (and are thus more commonly curable). Leukemias are the most common childhood cancers and are associated with chromosomal abnormalities rather than DNA mutations. Scotting suggests (I think plausibly) that occurence of childhood cancers may be related mainly to higher rates of cell division and/or more intense growth signaling during embryonic and early childhood development, rather than exposure to environmental carcinogens.
(17) "From the earliest times, it has been recognized that the best way to deal with cancer is to catch it early and hit it hard." This is because such tumors (or "precancers") have less tumor cells to eliminate, are biologically simpler, are less heterogeneous, and are less likely to have invaded or metastasized.
(18) Radiotherapy and cytotoxic chemotherapy are usually mutagenic, so they can have at least three adverse effects with respect to malignancy: (a) contributing to development of secondary cancers, (b) selecting for tumor cells which are inherently resistant to treatment, and (c) adding mutations to existing cancers which make these cancers more aggressive. A double-edged sword indeed.