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A tumour, also called a neoplasm, is a mass of tissue that results when abnormal cells divide without control. A cancer is a tumour that has the biological potential to invade adjacent tissues and spread via the blood or lymphatic system to other parts of the body; a cancer can also be called an invasive or malignant tumour or neoplasm. If the tumour does not have the potential to spread, i.e. it simply grows in its original location without being capable of piercing surrounding tissues, it is called benign. There is another kind of tumour, called an in situ tumour, which, unfortunately, is known by conflicting terminology. Some authorities describe it as non-invasive cancer while others state that it is not cancer. In any case, in situ tumours are usually treated as if they were very early stage cancer because some can undergo further change and become invasive.

A tumour’s behaviour refers to whether it is invasive, benign or in situ. Tumours are usually named according to the tissue or organ in which they develop (site) and are further characterised based on the type of cell that has become neoplastic (histology) and the specific mutations involved (genetics) (Table 1).

Table 1: Tumour characteristics: common terms
Characteristic Definition
Behaviour    
Malignant / invasive A malignant, invasive or cancerous tumour is characterised by its ability to spread to (metastasise) and ‘invade’ other parts of the body.
Benign A benign (non-cancerous) tumour will not spread, although it may interfere with nearby organs and structures in the body as it grows.
In situ A tumour that has not invaded surrounding tissue but in some people or conditions could undergo further change and become invasive. Some authorities call this non-invasive cancer while others say that it is not cancer.
Primary A primary tumour is located at the site where it first formed and contains cells of that same organ or tissue.
Secondary A secondary tumour results from an invasive tumour that has spread (metastasised) from the primary site. Although named for the organ or tissue where they are found (for example, the brain), secondary tumours are comprised of cells from the primary site (for example, the breast).
Histology      
Carcinoma Cancer that begins in the skin or in tissues that line or cover internal organs.
Sarcoma Cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
Myeloma Cancer that involves the plasma cells (found in bone marrow).
Lymphoma Cancer that involves lymphatic system cells (lymph nodes, spleen).
Leukaemia Cancer that begins in the blood-forming tissue, such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Leukaemia does not usually form a solid tumour.
Genetics    
Mutation A harmful change in ‘normal’ DNA (the molecular building blocks of all cells). Some mutations are inherited and can be passed from parent to child. Others are acquired during a lifetime, the result of other factors such as age, tobacco use, infection with viruses, or exposure to ultraviolet radiation (sunlight). Mutations in genes that regulate cell division may lead to cancer. There are four main gene types that increase the risk of cancer when mutated: tumour suppressor genes, proto-oncogenes, DNA repair genes and programmed death genes. These are described further below.
Tumour suppressor genes Tumour suppressor genes, such as the tumour protein p53 (TP53) gene, function normally to regulate cell replication and when mutated are unable to prevent uncontrolled replication and tumour formation. Mutations in the TP53 gene are found in more than 50% of tumours.
Proto-oncogenes Proto-oncogenes, such as the viral oncogene BRAF, have varying functions to stimulate cell growth and when mutated become cancer-inducing oncogenes that promote ongoing uncontrolled cellular replication and tumour formation. Mutations in the BRAF gene are found in approximately 50% of malignant melanomas.
DNA repair genes DNA repair genes, such as the mismatch repair (MMR) gene family, function normally to correct errors in cellular replication. When mutated these genes are unable to correct mutations in tumour suppressor genes or proto-oncogenes that may in turn lead to tumour formation. Mutations in the MMR genes (MSH2, MLH1 and MSH6) are known to cause familial (inherited) colorectal, breast and ovarian cancers.
Programmed death genes Programmed death genes, such as the B-cell lymphoma 2 (BCL2) gene, function normally to regulate cell death and maintain tissue integrity. When mutated these genes either prevent or are unable to induce cell death, leading to the replication of faulty cells and tumour formation. Mutations in the BCL2 gene are found in non-Hodgkin lymphomas and chronic lymphocytic leukaemias.

Sources: National Cancer Institute <http://www.cancer.gov/dictionary/>; Cortes J et al 2014. New approach to cancer therapy based on a molecularly defined cancer classification. CA: A Cancer Journal for Clinicians. 64(1): 70–74; Catalogue of somatic mutations in cancer (COSMIC) 2014 <http://cancer.sanger.ac.uk/cancergenome/projects/census/>.

Causes and risk factors

For most cancers the causes are not fully understood. However, some factors that increase the risk of developing cancer (risk factors) are well-recognised, and include:

  • tobacco smoking
  • alcohol consumption
  • diet, particularly those high in processed meats and high-fat foods
  • obesity and physical inactivity
  • chronic infections, which account for about 8% of all cancers
  • family history and genetic susceptibility
  • occupational exposures
  • sunlight
  • radiation
  • medical and iatrogenic factors (cancers relating to medical intervention)
  • reproductive and hormonal factors
  • environmental exposure.

It should be noted that having a risk factor does not mean that a person will develop cancer. Many people have at least one cancer risk factor but will never get cancer, while others with this disease may have had no known risk factors. The risk of developing cancer generally increases with increasing exposure to these factors.

Preventing cancer

Cancer prevention can mean a number of things. It can mean preventing cancer ever developing, or preventing disease progression, complications, recurrence or death once cancer has developed.

Preventing cancer developing is an area where the greatest gains in controlling and reducing cancer can be made, and can include:

  • Reducing risk factors for cancer, such as: quitting smoking, decreasing alcohol consumption and UV exposure, improving nutrition, increasing levels of physical activity and vaccinating against chronic infections (HPV for cervical cancer, and hepatitis for liver cancer).
  • Participating in cancer screening programs to detect cancer at an early and treatable stage or detecting pre-cancerous conditions before they progress to cancer.
  • Undergoing prophylactic surgery to remove tissue (such as breast or ovary) among those people at substantially increased genetic risk of cancer.

More information on risk factors and cancer prevention:

Detecting and diagnosing cancer

Detecting and diagnosing cancer can be a complicated process. There are a number of commonly used tests and processes to detect the presence of cancers, including imaging, endoscopy, blood and lymph tests, and screening tests. A definitive diagnosis of cancer can only be made through pathological examination of cells or tissue under a microscope, by a Pathologist. However, the increased use of specialised radiological or other imaging techniques and biochemical tests now permits more definite diagnoses to be made without the use of invasive pathology tests, in many cases.

The tests used to detect or diagnose cancer may be:

  • performed because an individual shows some signs, symptoms or risk factors for cancer
  • the result of an opportunistic or targeted (population-based) screening process of asymptomatic individuals.

These terms are described in Table 2.

Table 2: Detecting and diagnosing cancer: common terms
Term Definition
Detection The process of identifying an abnormality of tissue or cells that may be cancerous.
Diagnosis The process of identifying cancer based on its signs and symptoms. A definitive diagnosis of cancer can only be made by a pathologist (see Pathology).
Symptom A physical or mental problem or feature experienced by an individual that may indicate a disease or condition.
Asymptomatic No apparent signs (symptoms) of disease.
Screening Testing or examination of asymptomatic individuals for a specific cancer. The screening process may be indiscriminate, opportunistic (during a routine health check) or systematic (see, population-based cancer screening).
Population-based cancer screening Involves the systematic use of a test or series of tests to identify individuals at risk of cancer. The screening test is not intended to be diagnostic—it aims to identify individuals who should be referred for further investigation using diagnostic tests. The aim of population-based cancer screening is to reduce the burden of disease, either by detecting cancer at an earlier stage when treatment options are often more effective, or by detecting and treating abnormalities that if left may become cancerous.
Genetic testing The process of testing for the presence of particular genetic mutations. This form of testing is available to individuals at increased risk for inherited (familial) cancers, based on a strong family history of those cancers. The breast (and ovarian) cancer genes BRCA1 and BRCA2 are examples of genes with well-characterised mutations that can be ‘screened’ for in high-risk individuals. The presence of those mutated genes indicates an increased risk of developing breast or ovarian cancers. Similar to other screening tests, individuals receiving a positive test result may be referred for further investigation, or choose to undergo regular tests for pre-cancerous cells.
Pathology The study of disease process. A specialist in this field is called a pathologist. Sub-specialised diagnostic activities with relevance for cancer are histopathology/histology (microscopic examination and description of tissue) and haematopathology (the microscopic examination and description of blood and lymph).
Biopsy The removal of tissue for microscopic examination by a pathologist. There are different types of biopsy, based on the method used to remove tissue: incisional biopsy removes a small sample of tissue, excisional biopsy removes an entire section of tissue and needle biopsy removes a sample of tissue or fluid with a needle.

Source: National Cancer Institute <http://www.cancer.gov/dictionary/>.

Why are screening data not available for all cancers?

Cancer screening involves the use of a single test to identify individuals at risk of cancer. Population-based screening is an organised, integrated process with strict assessment criteria. In Australia, these criteria are defined in the Australian Population-based Screening Framework (APHDPC Screening Subcommittee 2008), which advises:

  • The screening program will provide more benefit than harm to the people being screened.
  • The condition should be an important health problem and have a recognisable latent or early symptomatic stage.
  • The screening test should: be highly sensitive and highly specific to find early stages of the disease, provide consistent results, be safe, find most disease present at the time of the screening test, be normal when there is no disease present, and be acceptable to the target population including important sub-groups.
  • Systems should be in place for evidence-based follow up assessment of all people with a positive screening.
  • Treatment should be effective, available, easily accessible and acceptable to all patients with the recognised disease or condition.

In Australia, three cancers (breast, cervical and bowel cancers) meet these criteria, and have organised, national population screening programs. While other cancers, such as prostate cancer and lung cancer, are also important health problems for which treatment is available, they do not meet the other criteria for population-based screening programs. Testing for these cancers, and others, are available as opportunistic screening (see, Table 2: Detecting and diagnosing cancer: common terms). Data on the number of tests requested or carried out may be available, however these are not collected or compiled nationally, and the results are not reportable.

Treating cancer

Treatment and management options after a diagnosis of cancer are dependent on:

  • cancer type
  • the virulence of the cancer
  • stage (extent or spread) and grade at diagnosis
  • cancer genetics
  • individual factors—age, life expectancy, general health status and personal beliefs.

Terms are described in Table 3. In Australia, there are clinical guidelines promoting best-practice management of a number of cancers, including breast, lung, testicular, prostate, bladder cancers and mesothelioma.

Table 3: Treating cancer: common terms
Term Definition
Oncology A branch of medicine that specialises in the diagnosis and treatment of cancer. Sub-specialties include: medical oncology (the use of medication to treat cancer), radiation oncology (the use of radiation therapy to treat cancer), and surgical oncology (the use of surgery to treat cancer).
Stage The extent of a cancer in the body. Staging can be determined by clinical or pathological examination of the tumour and is based on tumour size, the presence of cancer cells in lymph nodes and the degree of metastasis (spread). Cancers are conventionally allocated categories 0, I, II, III or IV, and may be classified as localised, regional or metastatic, depending on the extent of spread.
Grade The microscopic description and classification of tumour cell abnormality—that is, how different the tumour cells appear from normal, healthy cells—and an indicator of how quickly a tumour might grow and spread. This information can be used in determining treatment plans.
Virulence The ability of cancer to cause damage to its host. A virulent cancer is fast-growing and invasive. These cancers are also referred to as ‘aggressive’. A non-virulent or less-virulent cancer is slower-growing and less likely to be invasive or metastasise. A slow-growing cancer may be referred to as ‘indolent’.
Chemotherapy A type of treatment that uses chemicals to kill cancer cells.
Radiotherapy The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumours. The radiation source may be applied externally, or internally.
Surgery A form of treatment that involves an operation, and may involve the removal of tissue, change in the organisation of the anatomy or placement of prostheses.
Remission A decrease in or disappearance of the signs and symptoms of cancer. Remission may be partial (a reduction in some or many symptoms) or complete (all symptoms have disappeared). Remission is not the same as a cure. Even in complete remission cancer cells may still be in the body.
Recurrence Cancer that has returned (recurred) after a period of remission. The cancer may recur at the primary site, or elsewhere in the body, as a secondary tumour.
Targeted (molecular-based) treatments Improved understanding of the molecular characteristics of tumours, and the genetic causes, have led to targeted, precision or personalised treatments for some cancers. An example is the use of Herceptin to treat HER-2 type breast cancers (those that have a mutation of the HER-2 gene).

Source: National Cancer Institute <http://www.cancer.gov/dictionary/>.

What treatment and management data are available nationally?

There are comprehensive national data on treatments provided through admitted patient hospitalisations. These include surgery (such as mastectomy), and non-surgical care (such as radiotherapy and chemotherapy). In some instances, data from MBS or PBS claims can be used to infer treatment and management of cancers. For example, radioactive seed implantation of the prostate (MBS items 15338 and 37220) or use of antineoplastic agents (PBS group L01).

However, these data are not a complete source for treatment or management of cancer. Treatments in day clinics or private consulting rooms, management by general practitioners, complications from treatments, and the frequency of recurrence of cancer after treatment are not available at a national level. Pilot projects to collect these data on a small scale are currently underway, with the aim of expanding the methodology to national data collection if feasible.

More detailed definitions of cancer and related terminology: