Cancer is a non-communicable (non-infectious) disease, in other words it is not caused by pathogens. Cancer is caused when abnormal cells in the body divide by mitosis in an uncontrolled way by using the enzyme telomerase; this gives rise to tumours and, if the cells are malignant, cancers. Cancer is a major cause of death in the developed world. In 1999 7. 3 million people worldwide died from cancers. In high income European countries cancer is known as the second biggest killer. There are over 200 different cancers. The most common cancers are lung cancer and skin cancer.
There are about 42. ew cases of lung cancer reported in the UK per 1000 people each year and 5 new cases of skin cancer reported per 1000 people in the UK each year – and many cases go unreported. It is difficult to treat cancer because there are many different cancers. There are some common characteristics between them though; one being the presence of unregulated cell growth leading to the development of tumours. Not all tumours are cancerous – the greatest numbers are benign. Benign tumours are characterised by entirely localised growth and are usually separated from surrounding tissue by a surrounding capsule.
Benign tumours generally grow slowly and losely resemble the structure of the tissue they originate from. At worst benign tumours may press on blood vessels or nerves, interfering with their normal function. Cells from malignant tumours, however, invade other tissues, causing considerable damage; they metastasise – break off and spread to other parts of the body via the blood or lymph system and form secondary growths in other organs. A cancer becomes harder to treat the more spread over your body it is. Drugs can be given to reduce the rate of division of the cancer cells and radiation treatment can be used to kill the cells.
Research is ontinuing into several other methods of treating cancer. Because cancer cells are slightly different from normal cells, both in behaviour and appearance (wide variation in the shape and size of cell, large nucleus compared to size of cell), white lymphocytes may recognise them as foreign and kill them, this happens quite frequently in the body. The cancers doctors detect in the body are the ones that the bodies own defences have missed. To find out if a tumour is benign or malignant a surgeon has to do a biopsy (remove a small sample of the tumour for analysis).
Cancer cells, even when widely disseminated, may retain the physical and iological characteristics of their tissue of origin, therefore a pathologist can often determine the site of origin of metastatic tumours by microscopic examination of the cancerous tissue. The less closely a cancer resembles its tissue of origin the more malignant and rapidly invasive it tends to be. The causes of cancer are still not fully understood. Basically cancer is a genetic process. Something happens to change the way in which the cells behave. This may involve a change or mutation of the DNA in the nucleus of the cell.
Gene abnormalities can be inherited or they can be induced in a body cell by a virus or by damage from an utside source. No more than 20% of cancers are based on inheritance. In some hereditary disorders the chromosomes exhibit a high frequency of breakage, such diseases carry a high risk of cancer. Viruses are the cause of many cancers in animals. Research indicates that such viruses may contain a gene called viral oncogene capable of transforming normal cells to malignant cells. Ionising radiation is a puissant cause of cancer; it induces changes in DNA such as chromosome breaks and transpositions.
Radiation acts as an initiator of carcinogens. It is known chemical carcinogens are a main cause of cancer. Some chemicals act as initiators – inducing a change that progresses cancer after a latent period of years, the delay provides opportunity for exposure to other factors. Initiators produce irreversible changes in DNA. Some chemical carcinogens are promoters – they increase synthesis of DNA and stimulate expression of genes. Tobacco smoke contains many initiators and promoters; alcohol is an example of a promoter. Carcinogenic chemicals also produce chromosome breaks and translocations.
About 80% of cancers may be caused by environmental factors. There are seven symptoms that are early signs of cancer: . Change in bowel or bladder habits 2. A sore that does not heal 3. Unusual bleeding or discharge 4. Thickening or lump in the body somewhere 5. Indigestion or difficulty in swallowing 6. Obvious change in a wart or a mole 7. Nagging cough or hoarseness The earlier a cancer is diagnosed and treated the greater the chance of a cure. The biopsy remains the only definitive method for the diagnosis of a cancer.
Once a tissue diagnosis of cancer has been made, the extent/stage of the disease must be evaluated because prognosis and appropriate treatment vary with the stage of the disease. For each type of tumour the stage (I, II, III or IV) is defined in terms of findings with progressively more severe prognostic implications: small local tumour, more extensive local tumour, regional lymph node involvement, and distant metastases. The clinical stage, defined by information prior to surgical exploration, is used to decide appropriate initial treatment.
The traditional means of treating cancer are surgery, radiation and chemotherapy. The aim of surgery is to remove all of the malignant cells. Many cancers, though, are at too advanced stage at the time of diagnosis to permit cure by surgery. However surgery ay help to relieve symptoms, as of obstruction, or to reduce the size of the tumour in an effort to improve the response to subsequent radiation or chemotherapy. Ionising radiation, which may be either electromagnetic or particulate, is destructive to tissue. Tumours vary greatly in their sensitivity to radiation.
Radiation is useful when a tumour is located where it cannot be removed because surgery would damage vital adjacent tissue or because a tumour has begun to infiltrate adjacent structures that cannot be sacrificed. Preoperative radiation may rapidly sterilise the tumour cells and prevent them from seeding at surgery. It may also shrink the tumour and make surgery easier, or shrink the tumour and make surgery easier, or shrink an inoperable tumour so that it becomes operable. Chemotherapy is useful for tumours that have spread beyond the area accessible for surgery or radiotherapy.
A number of different types of anticancer drugs are used, but nearly all work by interfering with DNA synthesis or function. Rapidly dividing cells are therefore more sensitive to chemotherapy. Cancers have a larger proportion of dividing cells than do normal tissues, in which stem, or replenishing, cells are dormant and therefore resistant to drug effect. The most rapidly proliferating normal tissues are the bone marrow and the lining cells of the gastrointestinal tract. These are the most sensitive normal areas of chemotherapeutic effect and constitute the sites of toxicity that will limit the tolerable dose of most drugs.
To be effectively treated, a tumour must be more sensitive than the normal tissue. Some tumours may be many times more sensitive, but many are only slightly more sensitive. Fortunately, the normal bone marrow cells can divide faster than malignant cells and thus recover more rapidly. This permits a repeat cycle of the drug before the tumour has re- grown very much. Repeated cycles can steadily deplete the tumour before resistance occurs. Two major problems limiting the usefulness of chemotherapy are toxicity and resistance. Techniques that avoid or control toxicity and reduce the risk of resistance have steadily improved.
It is important to begin treatment as early as possible, to use the optimal dose of the drug, and to repeat cycles as quickly as possible, while giving the patient a chance to somewhat recover from toxicity. The use of multiple drugs is effective. Combination chemotherapy employs several drugs (often three to six at a time); each is effective as a single agent. The drugs used have different mechanisms of action, making cross-resistance less likely and different types of toxicity, so that each may be given at optimal dose without causing fatal addictive toxicity. Chemotherapy may be used with surgery or radiation as combined modality therapy.
It is often used as an adjuvant, or helper, when surgery is the primary therapy. As such it is usually given after surgery. This type of therapy has greatly increased the cure rate of breast cancer. The major purpose of chemotherapy as an adjuvant is to kill of micro- metastases that may have been established before surgery. Recently, chemotherapy has been used before surgery as a neoadjuvant. This therapy has the same effect as adjuvant chemotherapy but may also shrink a tumour, making it more easily operable. Many cancers arising from tissues that are hormone dependants are responsive to hormone manipulation.
Other approaches are still being researched for the treatment of cancer. The most important method for curing cancer though is preventive, for example stopping tobacco use, better diet, avoiding over-exposure to sunlight and the routine use of sunscreens, the environment can be improved by the elimination of carcinogenic hemicals e. g. asbestos. People without symptoms should have a cancer related check-up every 3 years from the ages 20 to 40 years, and every year from the age 40 years. The basics of UV sun rays The sun produces about three types of UV rays: UVA UVB UVC Ultraviolet Light is harmful to humans.
The ozone layer filters out UVC. UVA, however, has a long wavelength ray, so a certain amount reaches the earth’s surface. UVA is the predominant ray to reach earth. UVA causes damage to cellular membranes and DNA, and has been implicated in ageing of the skin and the development of skin cancer. Scientists believe it is UVB rays that are the paramount cause of premature ageing of the skin, sunburn, skin cancers and other sun induced skin problems, despite the fact that UVB rays constitute for only 1% of UV rays that reach our skin. The difference between suntan and sunburn Tanning is your body’s response to UV light.
Your skin darkens when you tan due to an increase in the production of melanin. It is a protective reaction to prevent further injury to your skin by UV rays as melanin absorbs light in the UV range. The complete physiological response to UV light takes about a week. A suntan is protective, however hey do not prevent skin cancer. Tanning and burning are two different processes. UVB rays are absorbed by the outer layers of the skin, causing the blood vessels that run close to the surface of the skin to swell, preventing the stimulation for tanning, so you burn.
Sunburn can start within several minutes of UV exposure or can continue to occur 24-72 hours after exposure to the sun. The sunburn you receive now may take 20 years or more to become skin cancer because it is very slow to develop. How to care for sunburn Unless accompanied by severe swelling, fever, or confusion; you can treat a sunburn by mmersing the area in cool water immediately following exposure and then treating the area with hydrocortisone cream for several days. If blisters form do not purposely pop them.
When they do pop use antibacterial soap to keep them clean. Aspirin will help mitigate pain and swelling. Moisturising creams and aloe containing products may help soothe the sunburn and replenish the skin. Severe sunburn is usually indicated when a person experiences excessive exposure to the sun. Intemperate swelling, fever, chills, nausea, confusion, or immediate blistering may indicate that you are suffering with severe sunburn. You should seek medical help. The sun can dry out your skin so you should keep your skin moist.
Moist skin is an important part of healthy skin. Most over-the-counter skin lubricants are adequate. Keeping your skin from drying out by applying moisturiser before your skin becomes dry is better than doing it afterwards. You should pay particular attention to your face, and especially your lips, to make sure they do not “dry-out” in the extremes of winter and summer. Photosensitivity reaction Photosensitivity reactions are immunological or toxicity reactions which result from the presence of a photosensitising agent and UV light.
Photosensitivity reactions are characterised by reddish skin with elevated poison ivy like bumps and can occur in areas that were not exposed to the sun. They rarely produce discomfort, however phototoxic reactions (another type of photosensitivity reaction) are usually accompanied by symptoms similar to sunburn. The long-term effects of exposure to the sun Exposure to UV rays adds up over time, most people receive approximately 80% of their lifetime exposure to the sun by the time their 18 years old! UV light and sunburn can damage your skin, this damage can then lead to skin cancer.
Apart from skin ancer, overexposure to the sun can cause: * Skin to become dry, wrinkly, thicker, saggy, with splotches of pigmentation, * Pre-cancerous growths, * Photosensitivity reactions, * Cataracts, * Eyelid cancers, * Burnt retinas, * Acute and systematic immune depression, * Exacerbation of chronic medical conditions, * Sun exposure can also induce herpes “flair-ups”. How many people are affected by sun induced skin problems Incidence and mortality rates for skin cancer have risen steeply in the UK during the past few decades. Scientists estimate that 1 in 5 people will develop skin cancer during their ifetime.
The sun is responsible for more than 90% of all skin cancers. Serious sunburn once in your life can increase the risk by as much as 50%. Tanning beds and lights Exposure to the radiation of a tanning booth may be more risky than exposure to the sun. UVA can cause “direct” injury to underlying blood vessels, collagen breakdown, reduced skin elasticity, inflammation of the stratum corneum, retinal damage, a decreased amount of Langerhans’ cell (immunological cells). UVA rays, which are the main rays tanning beds and lights emit, compound the damage of UVB rays. Prolonged xposure to UVA by itself can cause skin cancer.
Tanning creams Tanning pills or oral compounds that claim to brown the skin are dangerous, most of them have been removed from the market, however beware of any “pills” that claim to darken the skin. Most tanning creams are skin dyes or cosmetics. They do not stimulate melanin production and therefore do not provide any protection against UV rays. Skin cancer The skin has two main layers, the epidermis and the dermis, and several kinds of cells. The epidermis is the top layer of skin. It contains three types of cells: squamous cells flat, scaly cells on the surface), basal cells (round cells), and melanocytes (which give your skin colour).
If you have skin cancer the skin cells become malignant. There are three main types of cancer: Basal cell carcinoma, Squamous cell carcinoma and melanoma. Major risk factors for getting skin cancers The effect UV light has on your skin is dependent both upon the intensity and the duration of your exposure. How your skin reacts to the amount of exposure received is related to your genetic background. Even if you rarely sunburn you should still protect the sensitive areas such as your lips, nose, and the palms of your hands.
If there is a history of skin cancer in your family, you are probably at higher risk. About 1 in every 10 patients diagnosed with melanoma has a family member with a history of the disease. Lighter coloured skin puts individuals at a higher risk for some types of skin cancers. People with a large number of moles or freckling have a higher risk for getting skin cancers. A history of sunburns increases your risk – one study showed that 6+ sunburns during a lifetime doubles a persons risk of malignant melanoma. The more UV exposure the greater the chance of getting sun induced skin damage.
The level of UV light today is higher than 50 years ago, which was higher than 100 years ago. With less atmospheric ozone, a higher level of UV light reaches the earth’s surface. The reduction of the ozone layer is not the only influencing environmental facto, elevation, latitude, and cloud cover have an effect. UV light is stronger as elevation increases. The thinner atmosphere at higher altitudes cannot filter UV as effectively as it can at sea level. The rays of the sun are also strongest near the equator. Cloud cover helps to reduce UV; the density of the clouds affects the amount of UV filtered out.