Demystifying Cancer: Basics you need to know about Cancer.

Understanding cancer

Cancer is the result of abnormal processes within the body that cause cells to divide in a faulty, uncontrolled way, often combined with a weak or malfunctioning immune system. Because it can affect almost any organ — including the brain, breast, colon, liver and lung — there are over 100 different types.

It is also increasingly common. In 2018, the number of people newly diagnosed with cancer worldwide rose to 18.1 million, up from 14.1 million in 2012 — a rise that has led some to describe cancer as the disease of the century.

The body is made up of billions of cells that are constantly dividing, a process normally kept under tight control. At any point this process can be disrupted, and cells can begin to divide abnormally. These atypical cells become cancerous, or malignant, when the faulty division involves changes in the cell's DNA. Each cell's DNA contains many genes, which hold the instructions for how a cell grows, divides and behaves. Cancer is caused by a change, or mutation, in this DNA. Such mutations can be present before birth or develop afterwards:

• Gene mutations before birth: these are inherited from our parents and carried from birth. They account for a comparatively small proportion of cancers.
• Gene mutations after birth: these develop through outside influences such as smoking, chemicals, radiation, obesity, hormone imbalance and chronic inflammation.

Types of cancer

Cancer is grouped into four main types according to where it begins:

• Carcinoma: cancer that arises in epithelial tissue, such as the skin or the lining of internal organs including the colon, lung, liver and prostate.
• Sarcoma: cancer that starts in the connective tissue that supports and connects the body, such as muscle, fat, bone, cartilage, nerves, joints, blood vessels and lymph vessels.
• Leukaemia: cancer of the white blood cells, which begins when healthy white blood cells change and grow uncontrollably. There are four main types: acute myeloid leukaemia, chronic myeloid leukaemia, acute lymphocytic leukaemia and chronic lymphocytic leukaemia.
• Lymphoma: cancer that begins in the lymphatic system, the network of vessels and glands that helps the body fight infection and cancer.

Signs and symptoms

Symptoms vary depending on which organ is affected, but some general warning signs include:

• fatigue
• a lump or area of thickening that can be felt under the skin
• unintended weight loss or gain
• skin changes, such as yellowing, darkening or redness, sores that do not heal, or changes to existing moles
• changes in bowel or bladder habits
• a persistent cough or trouble breathing
• difficulty swallowing
• hoarseness
• persistent indigestion or discomfort after eating
• persistent, unexplained muscle or joint pain
• persistent, unexplained fever or night sweats
• unexplained bleeding or bruising

Risk factors

Several factors can increase the likelihood of developing cancer:

• Age: although cancer can occur at any age, it becomes more likely in later life, particularly from around 60 years old.
• Lifestyle: everyday habits play an important role. Drinking more than one alcoholic drink a day — for men over 65 and for women of any age — can increase the risk.
• Environment: our surroundings can be harmful even when our own lifestyle is healthy, such as breathing in second-hand smoke from someone nearby.
• Existing health conditions: chronic conditions such as inflammation of the colon, or viral infections such as human papillomavirus (HPV), can raise the risk.

Possible complications

Cancer can lead to a range of complications, which differ according to the type of cancer and may occur alone or together:

• Pain: cancer or its treatment can cause pain.
• Fatigue: common across almost all types of cancer, though usually manageable. It may also follow treatments such as chemotherapy or radiotherapy, in which case it is usually temporary.
• Weight loss: cancer can divert nutrients away from healthy cells, depriving them of nourishment.
• Nausea: some cancers, such as stomach cancer, can cause a feeling of nausea.
• Spread (metastasis): as cancer advances it can spread to nearby organs, or travel through the blood or lymphatic vessels to more distant parts of the body.
• Immune reactions: in rare cases the immune system begins to attack healthy cells, a condition known as paraneoplastic syndrome.
• Recurrence: people who have had cancer remain at risk of it returning.

How cancer is diagnosed and staged

Diagnosing cancer usually involves a combination of approaches:

• Physical examination: a doctor checks for lumps or other abnormalities, such as changes in skin colour or enlarged organs.
• Blood tests: certain blood tests can point to cancer, or to an abnormality in a specific organ that may be caused by cancer.
• Imaging: scans allow doctors to see inside the body and identify any mass or abnormal lump that may be cancer. Common imaging tests include PET (positron emission tomography), CT (computed tomography), MRI (magnetic resonance imaging), X-ray and ultrasound. Further testing is needed to confirm a diagnosis.
• Biopsy: a sample of the suspicious tissue is collected and examined in a laboratory to confirm whether or not it is cancer.

Once cancer is confirmed, it is staged to establish how advanced it is and which treatments are suitable. Cancer is usually staged from 0 to 4, with a higher number indicating more advanced disease. The most widely used system is TNM:

• T refers to the size of the tumour.
• N refers to whether nearby or more distant lymph nodes are affected.
• M stands for metastasis — whether the cancer has spread to other organs.

Treatment options

Cancer may be treated with a single approach or, more often, a combination of several. The main options include:

• Surgery: removing the tumour or affected mass.
• Chemotherapy: using drugs — taken orally or given by injection or infusion — to kill cancer cells.
• Radiotherapy: using high-energy beams, such as X-rays, to kill cancer cells.
• Immunotherapy: using immune cells, or drugs that prompt the immune system, to attack cancer cells.
• Hormone therapy: some cancers, including certain breast, ovarian and prostate cancers, depend on hormones to grow. This therapy uses drugs to block either the production of those hormones or their effects.
• Targeted drug therapy: using drugs designed to act on specific genetic features of a cancer.
• Alternative therapy: other approaches such as herbal medicine, physical treatments like hyperthermia, and metabolic treatments.