From all indications, the ravage of cancer has been on the increase in recent years. Hardly a day goes by without someone dying of a type of cancer. In Nigeria alone, it is reported that no fewer than 80,000 people die from various forms of cancer annually, with an estimated 10 people dying from it every hour.
Yet, judging by reports from other developed countries, the rate of cancer deaths doesn’t have to be so high – provided that strategies and facilities are put in place for early detection and management. These strategies will be considered here, but first, let’s have an understanding of the scourge.
Cancer is a class of diseases characterised by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.
Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumours (except in the case of leukaemia where cancer prohibits normal blood function by abnormal cell division in the blood stream). Tumours can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function.
Tumours that stay in one spot and demonstrate limited growth are generally considered to be benign. More dangerous or malignant tumours form when two things occur:
- A cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion
- That cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.
When a tumour successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasised. This process itself is called metastasis, and the result is a serious condition that is very difficult to treat.
Why cancer spreads
Scientists reported in Nature Communications (October 2012 issue) that they have discovered an important clue as to why cancer cells spread. It has something to do with their adhesion (stickiness) properties. Certain molecular interactions between cells and the scaffolding that holds them in place (extracellular matrix) cause them to become unstuck at the original tumour site, they become dislodged, move on and then reattach themselves at a new site.
The researchers say this discovery is important because cancer mortality is mainly due to metastatic tumours, those that grow from cells that have travelled from their original site to another part of the body. Only 10 per cent of cancer deaths are caused by the primary tumours.
The scientists, from the Massachusetts Institute of Technology, say that finding a way to stop cancer cells from sticking to new sites could interfere with metastatic disease, and halt the growth of secondary tumours.
Malignant cells are more agile than non-malignant ones
Scientists from the Physical Sciences-Oncology Centres, USA, reported in the Scientific Reports (April 2013 issue) that malignant cells are much “nimbler” than non-malignant ones. Malignant cells can pass more easily through smaller gaps, as well as applying a much greater force on their environment compared to other cells.
Professor Robert Austin and team created a new catalogue of the physical and chemical features of cancerous cells with over 100 scientists from 20 different centres across the United States. The authors believe their catalogue will help oncologists detect cancerous cells in patients early on, thus preventing the spread of the disease to other parts of the body.
Prof. Austin said “By bringing together different types of experimental expertise to systematically compare metastatic and non-metastatic cells, we have advanced our knowledge of how metastasis occurs.”
What causes cancer?
Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide. This leads to a mass of abnormal cells that grows out of control.
Carcinogens are a class of substances that are directly responsible for damaging DNA, promoting or aiding cancer. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, and compounds in car exhaust fumes are all examples of carcinogens. When our bodies are exposed to carcinogens, free radicals are formed that try to steal electrons from other molecules in the body. Theses free radicals damage cells and affect their ability to function normally.
Genes – the family type
Cancer can be the result of a genetic predisposition that is inherited from family members. It is possible to be born with certain genetic mutations or a fault in a gene that makes one statistically more likely to develop cancer later in life.
Other medical factors
As we age, there is an increase in the number of possible cancer-causing mutations in our DNA. This makes age an important risk factor for cancer. Several viruses have also been linked to cancer such as: human papillomavirus (a cause of cervical cancer), hepatitis B and C (causes of liver cancer), and Epstein-Barr virus (a cause of some childhood cancers). Human immunodeficiency virus (HIV) – and anything else that suppresses or weakens the immune system – inhibits the body’s ability to fight infections and increases the chance of developing cancer.
What are the symptoms of cancer?
Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and how big the tumour is. Some cancers can be felt or seen through the skin – a lump on the breast or testicle can be an indicator of cancer in those locations. Skin cancer (melanoma) is often noted by a change in a wart or mole on the skin. Some oral cancers present white patches inside the mouth or white spots on the tongue.
Other cancers have symptoms that are less physically apparent. Some brain tumours tend to present symptoms early in the disease as they affect important cognitive functions. Pancreas cancers are usually too small to cause symptoms until they cause pain by pushing against nearby nerves or interfere with liver function to cause a yellowing of the skin and eyes called jaundice. Symptoms also can be created as a tumour grows and pushes against organs and blood vessels. For example, colon cancers lead to symptoms such as constipation, diarrhoea, and changes in stool size. Bladder or prostate cancers cause changes in bladder function such as more frequent or infrequent urination.
As cancer cells use the body’s energy and interfere with normal hormone function, it is possible to present symptoms such as fever, fatigue, excessive sweating, anaemia, and unexplained weight loss. However, these symptoms are common in several other maladies as well. For example, coughing and hoarseness can point to lung or throat cancer as well as several other conditions.
When cancer spreads, or metastasises, additional symptoms can present themselves in the newly affected area. Swollen or enlarged lymph nodes are common and likely to be present early. If cancer spreads to the brain, patients may experience vertigo, headaches, or seizures. Spreading to the lungs may cause coughing and shortness of breath. In addition, the liver may become enlarged and cause jaundice and bones can become painful, brittle, and break easily. Symptoms of metastasis ultimately depend on the location to which the cancer has spread.
Classification of cancer
Cancers are categorised into five broad groups.
Carcinomas are characterised by cells that cover internal and external parts of the body such as lung, breast, and colon cancer.
Sarcomas are characterised by cells that are located in bone, cartilage, fat, connective tissue, muscle, and other supportive tissues.
Lymphomas are cancers that begin in the lymph nodes and immune system tissues.
Leukaemias are cancers that begin in the bone marrow and often accumulate in the bloodstream.
Adenomas are cancers that arise in the thyroid, the pituitary gland, the adrenal gland, and other glandular tissues.
Another classification is according to the affected organ as listed below:
Types of cancer
- Bladder Cancer
- Brain Cancer
- Breast Cancer
- Cervical Cancer
- Colorectal Cancer
- Lung Cancer
- Non-Hodgkin’s Lymphoma
- Ovarian Cancer
- Pancreatic Cancer
- Prostate Cancer
Diagnosis of cancer
Early detection of cancer can greatly improve the odds of successful treatment and survival. Physicians use information from symptoms and several other procedures to diagnose cancer. Imaging techniques such as X-rays, CT scans, MRI scans, PET scans, and ultrasound scans are used regularly in order to detect where a tumour is located and what organs may be affected by it. Doctors may also conduct an endoscopy, which is a procedure that uses a thin tube with a camera and light at one end, to look for abnormalities inside the body.
Extracting cancer cells and looking at them under a microscope is the only absolute way to diagnose cancer. This procedure is called a biopsy. Other types of molecular diagnostic tests are frequently employed as well. Physicians will analyse your body’s sugars, fats, proteins, and DNA at the molecular level. For example, cancerous prostate cells release a higher level of a chemical called PSA (prostate-specific antigen) into the bloodstream that can be detected by a blood test. Molecular diagnostics, biopsies, and imaging techniques are all used together to diagnose cancer.
After a diagnosis is made, doctors find out how far the cancer has spread and determine the stage of the cancer. The stage determines which choices will be available for treatment and informs prognoses. The most common cancer staging method is called the TNM system. T (1-4) indicates the size and direct extent of the primary tumour, N (0-3) indicates the degree to which the cancer has spread to nearby lymph nodes, and M (0-1) indicates whether the cancer has metastasized to other organs in the body. A small tumour that has not spread to lymph nodes or distant organs may be staged as (T1, N0, M0), for example.
TNM descriptions then lead to a simpler categorization of stages, from 0 to 4, where lower numbers indicate that the cancer has spread less. While most Stage 1 tumours are curable, most Stage 4 tumours are inoperable or untreatable.
Cancer treatment depends on the type of cancer, the stage of the cancer (how much it has spread), age, health status, and additional personal characteristics. There is no single treatment for cancer, and patients often receive a combination of therapies and palliative care. Treatments usually fall into one of the following categories: surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or gene therapy.
Surgery is the oldest known treatment for cancer. If a cancer has not metastasised, it is possible to completely cure a patient by surgically removing the cancer from the body. This is often seen in the removal of the prostate or a breast or testicle. After the disease has spread, however, it is nearly impossible to remove all of the cancer cells. Surgery may also be instrumental in helping to control symptoms such as bowel obstruction or spinal cord compression.
Innovations continue to be developed to aid the surgical process, such as the iKnife that “sniffs” out cancer. Currently, when a tumour is removed surgeons also take out a “margin” of healthy tissue to make sure no malignant cells are left behind. This usually means keeping the patients under general anaesthetic for an extra 30 minutes while tissue samples are tested in the lab for “clear margins”. If there are no clear margins, the surgeon has to go back in and remove more tissue (if possible). Scientists from Imperial College London say the Knife may remove the need for sending samples to the lab.
Radiation treatment, also known as radiotherapy, destroys cancer by focusing high-energy rays on the cancer cells. This causes damage to the molecules that make up the cancer cells and leads them to commit suicide. Radiotherapy utilises high-energy gamma-rays that are emitted from metals such as radium or high-energy x-rays that are created in a special machine. Early radiation treatments caused severe side-effects because the energy beams would damage normal, healthy tissue, but technologies have improved so that beams can be more accurately targeted. Radiotherapy is used as a standalone treatment to shrink a tumour or destroy cancer cells (including those associated with leukaemia and lymphoma), and it is also used in combination with other cancer treatments.
Chemotherapy utilises chemicals that interfere with the cell division process – damaging proteins or DNA – so that cancer cells will commit suicide. These treatments target any rapidly dividing cells (not necessarily just cancer cells), but normal cells usually can recover from any chemical-induced damage while cancer cells cannot. Chemotherapy is generally used to treat cancer that has spread or metastasised because the medicines travel throughout the entire body. It is a necessary treatment for some forms of leukaemia and lymphoma. Chemotherapy treatment occurs in cycles so the body has time to heal between doses. However, there are still common side effects such as hair loss, nausea, fatigue, and vomiting. Combination therapies often include multiple types of chemotherapy or chemotherapy combined with other treatment options.
Immunotherapy aims to get the body’s immune system to fight the tumour. Local immunotherapy injects a treatment into an affected area, for example, to cause inflammation that causes a tumour to shrink. Systemic immunotherapy treats the whole body by administering an agent such as the protein interferon alpha that can shrink tumours. Immunotherapy can also be considered non-specific if it improves cancer-fighting abilities by stimulating the entire immune system, and it can be considered targeted if the treatment specifically tells the immune system to destroy cancer cells. These therapies are relatively young, but researchers have had success with treatments that introduce antibodies to the body that inhibit the growth of breast cancer cells. Bone marrow transplantation (hematopoietic stem cell transplantation) can also be considered immunotherapy because the donor’s immune cells will often attack the tumour or cancer cells that are present in the host.
Several cancers have been linked to some types of hormones, most notably breast and prostate cancer. Hormone therapy is designed to alter hormone production in the body so that cancer cells stop growing or are killed completely. Breast cancer hormone therapies often focus on reducing oestrogen levels (a common drug for this is tamoxifen) and prostate cancer hormone therapies often focus on reducing testosterone levels. In addition, some leukaemia and lymphoma cases can be treated with the hormone cortisone.
The goal of gene therapy is to replace damaged genes with ones that work to address a root cause of cancer: damage to DNA. For example, researchers are trying to replace the damaged gene that signals cells to stop dividing (the p53 gene) with a copy of a working gene. Other gene-based therapies focus on further damaging cancer cell DNA to the point where the cell commits suicide. Gene therapy is a very young field and has not yet resulted in any successful treatments.
Using cancer-specific immune system cells to treat cancer
Scientists from the RIKEN Research Centre for Allergy and Immunology in Yokohama, Japan, explained in the journal Cell Stem Cell (January 2013 issue) how they managed to make cancer-specific immune system cells from iPSCs (induced pluripotent stem cells) to destroy cancer cells.
The authors added that their study has shown that it is possible to clone versions of the patients’ own cells to enhance their immune system so that cancer cells could be destroyed naturally.
Hiroshi Kawamoto and team created cancer-specific killer T-lymphocytes from iPSCs. They started off with mature T-lymphocytes which were specific for a type of skin cancer and reprogrammed them into iPSCs with the help of “Yamanaka factors”. The iPSCs eventually turned into fully active, cancer-specific T-lymphocytes – in other words, cells that target and destroy cancer cells
Prevention of cancers
Cancers that are closely linked to certain behaviours are the easiest to prevent. For example, choosing not to smoke tobacco or drink alcohol significantly lower the risk of several types of cancer – most notably lung, throat, mouth, and liver cancer. Even if you are a current tobacco user, quitting can still greatly reduce your chances of getting cancer.
Skin cancer can be prevented by staying in the shade, protecting yourself with a hat and shirt when in the sun, and using sunscreen. Diet is also an important part of cancer prevention since what we eat has been linked to the disease. Physicians recommend diets that are low in fat and rich in fresh fruits and vegetables and whole grains.
Certain vaccinations have been associated with the prevention of some cancers. For example, many women receive a vaccination for the human papillomavirus because of the virus’s relationship with cervical cancer. Hepatitis B vaccines prevent the hepatitis B virus, which can cause liver cancer.
Some cancer prevention is based on systematic screening in order to detect small irregularities or tumours as early as possible even if there are no clear symptoms present. Breast self-examination, mammograms, testicular self-examination, and Pap smears are common screening methods for various cancers.
Targeting cancers for new drug therapies
Researchers at The Institute of Cancer Research reported in Nature Reviews Drug Discovery (January 2013) that they have found a new way of rapidly prioritising the best druggable targets online. They managed to identify 46 previously overlooked targets.
The researchers used the canSAR database together with a tool and were able to compare up to 500 drug targets in a matter of minutes. With this method, it is possible to analyse huge volumes of data to discover new drug targets, which can lead to the development of effective cancer medications.
The scientists analysed 479 cancer genes to determine which ones were potential targets for medications. Their approach was effective – they found 46 new potentially “druggable” cancer proteins.
Not only will this approach lead to much more targeted cancer drugs, but also considerably cheaper ones, the authors added.
Having examined cancers generally, we shall zero in on breast cancer, because of its common occurrence among women, the world over. The essence of this is for proper enlightenment, as well as keeping women abreast of early detection techniques.
More than 261,000 women are diagnosed with breast cancer each year, according to the American Cancer Society, making it the second most common malignancy in women after skin cancer. While all cancers arise from an uncontrolled growth of abnormal cells, each patient’s treatment and prognosis can differ radically depending on her type of breast cancer, how advanced it is and a variety of other factors.
Symptoms and Types
All breast cancers are not created equal, either in symptoms or category. Though some cases emerge without any noticeable symptoms, breast changes that warrant a doctor’s attention include a lump, swelling or thickening; dimpling or skin irritation; breast pain; nipple pain or an inverted nipple; red or flaky nipple or surrounding skin; or a discharge other than breast milk, according to the National Breast Cancer Foundation.
It is important to note that even these symptoms don’t necessarily mean a malignancy is present and often signal a benign condition, such as a cyst or infection.
Just as breast cancer has many symptoms, the disease is comprised of many specific types. Defined by whether it begins in the lobules or ducts, the parts of the breast responsible for milk production, these types include:
- DCIS, or Ductal Carcinoma in Situ. This non-invasive malignancy is the earliest and most curable form of the disease because is confined to the duct and rarely spreads. DCIS comprises about 20 per cent of all breast cancers, invasive and non-invasive, diagnosed annually.
- IDC, or Infiltrating Ductal Carcinoma, is an invasive malignancy because it has spread beyond the ducts. It accounts for almost 80 per cent of all invasive breast cancers. IDC appears as rounded or star-shaped areas on mammograms, with the star-like lesions signalling a poorer prognosis.
The remaining five types of invasive breast cancer comprise about 20 per cent of all total cases. According to the National Breast Cancer Foundation, they include the rare and aggressive Inflammatory Breast Cancer, or IBC, which unlike other forms is often visible on the outside of the breast. IBC causes the breast to look red or inflamed due to blocked lymph vessels in the skin and mimics certain breast infections such as mastitis.
Diagnosis and Tests
Breast cancer screening tests, which are done on symptom-free women, can help to diagnose early cases. Early detection methods include clinical exams by medical professionals, self-breast exams and screening mammograms, which are recommended for women age 40 and over, according to the American Cancer Society. Women with a family history of the disease can also undergo genetic testing to determine if they are at increased risk of developing it.
If a screening method reveals possible breast cancer, several tests can help confirm or disprove the diagnosis. These include:
- Imaging tests such as mammograms, MRI scans or breast ultrasound. Each of these methods produces internal pictures of the breast that help doctors see a potential mass.
- Biopsies, which entails taking cells from suspicious lumps to study in a pathology lab to determine if they are malignant. Cells are extracted through special needles or during surgery.
If cancer is confirmed, doctors will assess the cells to determine key information such as the type of cancer and its grade, which signals how fast it is growing. They will also learn if the tumour is caused by a genetic mutation passed through families or is hormone receptive. According to the American Cancer Society, the presence of hormone receptors on breast cancer cells usually indicates a better prognosis because certain drugs can prevent oestrogen or progesterone from promoting cancer growth.
Typically, women with a positive breast cancer diagnosis will also undergo a battery of tests to determine if the cancer has spread to surrounding tissues, organs or bone. Common sites for breast cancer metastases are the bones, the lungs and the liver.
Treatments & Medications
With more than 2.5 million breast cancer survivors in the United States, it’s clear that researchers have developed effective treatments and drugs that can either cure the disease or prevent it from quickly recurring. Treatments either target the cancer locally or systemically, depending on the location of the breast tumour, its size and the extent of the disease.
Local treatments include surgery and radiation, which attempt to remove or destroy the cancer in the breast without affecting the rest of the body. Surgery can include a breast-sparing lumpectomy or the more aggressive mastectomy, which removes the entire breast and is usually done in more advanced cases, according to the National Breast Cancer Foundation.
Systemic treatments are given by mouth or through the bloodstream and target cancer cells throughout the body. These include chemotherapy, which uses toxic drugs such as cyclophoshamide (sometimes referred to by its brand name, Cytoxan) or methotrexate. Cancer fueled by the hormones oestrogen or progesterone can be treated with hormone suppressors such as tamoxifen or raloxifene (Evista).
More recent systemic treatments include biological therapy, which uses the immune system to fight the cancer and targets breast cancer cells containing high levels of a certain protein. Commonly used biologics are bevacizumab (Avastin) or trastuzumab (Herceptin).
Depending on a variety of factors, including type and stage of cancer, her care regimen might include only one of these treatments or a combination of several.
Some breast cancer risks, such as age and heredity, can’t be controlled. But as with so many other diseases, eating right and exercising can help lower the chances of developing breast cancer. According to the Mayo Clinic, other risk-reducing tips include:
- Limiting alcohol intake to less than one drink per day
- Limiting dietary fat
- Maintaining a healthy weight
- Foregoing hormone therapy at menopause
- Limiting exposure to pesticides and antibiotics
Collated by TemitopeObayendo with additional information from Webmd.com and livescience.com