According to the World Health Organization, cancer (or tumor or neoplasm) is not only a disease but a group of diseases that can start in almost all organs or tissues of the body and is characterized by the uncontrolled growth of abnormal cells that cross their usual boundaries to invade adjacent parts of the body and / or spread to other organs, with a process called metastasization.
Cancer is a genetic disease caused by the accumulation of genetic anomalies (mutations and chromosomal alterations) and epigenetic changes affecting genes that control proliferation, differentiation, cell death and the integrity of genetic heritage. Mutations can be spontaneous or derive from replication errors or DNA damage caused by “carcinogenic” agents, internal or external.
Carcinogenesis, that is the transformation of a healthy cell into a cancer cell, is a long and complex multi-step process that requires the accumulation of more mutations in the DNA of the cells. The mutations that the cell has accumulated make it unable to repair DNA damage or to go to cell death; the consequent survival and uncontrolled replication of the abnormal cell can give rise to a tumor mass. The mutation is generally “somatic”, it is not transmitted hereditary, but, in a minority of cases, a mutation may be present at a “constitutional” level, in all the cells of the individual and therefore may have been inherited by one or both parents.
There are three stages of carcinogenesis:
- Initiation: the cells undergo mutations at the DNA level
- Promotion: the cells with mutations begin to multiply and to give rise to other cells also containing DNA alterations
- Progression: a grouping of tumor cells is formed
Benign and malignant tumors
It is not certain that the mass that has formed from this process is malignant. Often the neoformations are benign, that remain well localized in the organ where they were formed, bounded inside a capsule and without invading nearby tissues.
They are tumors characterized by slow growth and favourable prognosis.
The most common benign tumor forms are:
- Adenoma, papilloma: of epithelial origin
- Lipoma, fibroma, angioma, chondroma, osteoma: of mesenchymal origin
- Meningioma, neuroma: they develop in the nervous tissue
- Nevus: develops in the skin
Over time, a benign tumor can remain that way or transform in malignant and for this reason it is not uncommon for a benign mass to be removed.
The process of transforming a benign tumor into a malign one can be rapid or take many years.
The term cancer is used only when the tumor is malignant.
The malignant neoformations, unlike the benign ones, have the ability to develop in an uncontrolled manner, in some cases without spreading to other tissues besides that of origin (examples of cancers in situ: breast cancer, melanoma, colon cancer, etc.). In other cases, the ability of the tumor to expand at a distance, ie outside the site of onset of the primitive tumor, allows the invasion of distant organs with a process that takes the name of metastatization and the new masses that are formed are called metastases.
The prognosis is often poor. In most cases, in fact, the presence of metastases is a sign of disease at a very advanced stage.
The spread of the tumor can occur:
- Through the bloodstream
- Through the lymphatic system
- Endocavitary way: direct dissemination inside a body cavity or natural conduit
Regardless of the way of diffusion, the tumor can spread to any part of the body even though the most common sites of metastasis are liver, lung, bones and brain.
The most common malignant forms of cancer are:
- Carcinoma: of epithelial origin
- Sarcoma: of mesenchymal origin
- Myeloma, lymphoma, leukemia: they develop in lymphohaemopoietic tissue
- Astrocytoma and glio-neuro-retinoblastoma: they develop in the nervous tissue
- Melanoma: develops in the skin
What are the causes of cancer?
As we have already said, cancer is a genetic disease caused by the accumulation of a critical number of mutations, but why do these mutations appear? In some cases they are due to random errors during the life cycle of the cells, in other cases they can be caused by exposure to mutagenic environmental factors or they can be inherited by one or both parents.
The genes that, if altered, are involved in the onset of cancer are the following:
- Oncogenes: they are genes that, in normal condition, are activated to replicate cells when needed. If they undergo mutations, they induce the cells to multiply without control.
- Oncosuppressors: they are genes that, in normal conditions, are activated to block cell replication. If they undergo mutations they can no longer put a stop to cell growth.
- Genes involved in cell repair mechanisms: they are genes that, in normal condition, are activated to repair any DNA damage. If they undergo mutations they lose their ability to repair DNA, so the cells can transform into tumors.
- Genes involved in the process of apoptosis (programmed cell death): they are genes that, in normal condition, when the cell undergo irreparable damage, are activated to trigger cell death, thus avoiding damage to the organism. If these genes undergo mutations they are no longer able to “kill” the damaged cell which consequently continues to grow abnormally.
What are the risk factors?
Risk factors are all those factors that increase the probability of developing cancer because they increase the risk of mutation.
Some of these factors cannot be modified, ie they do not depend on human will thereby cannot be modified in any way. Others, instead, can be modified, ie they depend on the human will and on them it is possible to intervene to reduce the risk of fall ill.
It is not possible to identify a single risk factor involved in tumor genesis; cancer is in fact a multifactorial disease, ie there are many risk factors that add up and determine the onset of the disease.
- Age: aging is one of the most important risk factors for the development of cancer. This is demonstrated by the fact that the incidence of tumors increases drastically after the age of 55. This relationship is explained by the fact that as the years go by the defense capabilities and repair mechanisms in our body decrease while we continue to be exposed to carcinogenic factors.
Age is an unmodifiable risk factor.
The forms of cancer typical of adulthood are:
- Hereditary factors that is genes inherited from one or both parents. If there are cancer cases in the family it is possible that the genes responsible for this tumor are inherited from the children. Inheriting a mutated gene from a family member does not mean get cancer for sure in the course of life, but only having a greater risk of developing it. In fact, so that the tumor can develop, it is necessary not only to inherit the gene but also to accumulate other errors.
Familiarity is an unmodifiable risk factor.
However, genetic tests are available to identify possible mutations. A positive result indicates that there is a greater risk of developing the tumor while a negative result does not exclude that one cannot get cancer but certainly is less at risk because the altered genes have not been inherited. Knowledge of the genetic test result can allow the implementation of prevention protocols and participation in early screening programs, as well as lifestyle changes.
The possibility to undergo these tests must be evaluated with the doctor when there is a real risk of getting sick.
The main hereditary forms are:
- Colon cancer
- Breast cancer
- Ovarian and uterine cancer
- Prostate cancer
- Stomach cancer
- Pancreatic tumor
- Thyroid tumor
- Lifestyle plays an important role in the development of cancer in several respects. If everyone adopted a healthier lifestyle the diagnosis of cancer would be much lower.
The factors related to lifestyle that have the greatest impact are the following:
- Smoke with which many carcinogens such as tar, arsenic, benzene and cadmium are inhaled. Some carcinogens contained in cigarette smoke act directly on the DNA causing mutations, others interfere with the DNA repair mechanisms, others still prevent the removal of toxic substances.
Smoking is correlated above all with the development of lung cancer, oral cavity, throat, esophagus, pancreas, colon, bladder, kidney and breast.
- Alcohol abuse contributes to tumor development through different mechanisms: in the mouth, throat and liver it irritates the mucous membranes preventing damaged cells from repairing themselves correctly, increases the permeability of mucous membranes to other carcinogens and, once metabolized in the colon, leads to the formation of acetaldehyde which is a carcinogen.
- A diet that, if incorrect, would seem to be related to the increase of inflammatory processes and the production of growth factors. The main forms of cancer associated with an unbalanced diet are at the esophagus, stomach, colorectal, liver, prostate, breast, ovary and uterus.
- Overweight and obesity because they are conditions that generate a chronic inflammatory state and a series of hormonal imbalances in the body. Those with a body mass index above average have a greater risk of developing cancer, especially in the pancreas, liver, esophagus, breast, ovary and prostate.
- Sedentary lifestyle: it is a condition associated with increased adiposity which in turn can facilitate carcinogenesis through increased inflammation and hormonal imbalances. A sedentary lifestyle increases the risk of developing mainly ovarian, prostate, uterus and colorectal cancers.
Each of these lifestyle factors can be changed.
- Environmental factors. The environment around us, the place where we work, the materials we come into contact with could also increase the risk of cancer.
The factors most involved are:
- Atmospheric pollution especially that due to microparticles dispersed in the air covered on their surface with numerous toxic and carcinogenic substances such as polycyclic aromatic hydrocarbons. Inhalation of these microparticles is an important risk factor especially for the development of lung cancer.
- Exposure to carcinogenic chemicals such as formaldehyde, benzene, aluminum, chromium, nickel, radon, radium, asbestos, leather and wood dusts.
Particular categories of workers are often exposed to these pollutants.
- Ionizing radiation and X-rays that directly damage the DNA structure or alter the cellular environment by promoting cell transformation. Radiation can induce any form of tumor even if the organs most affected are bone marrow and thyroid.
- Excessive sun exposure. Despite exposure to the sun is good for the body especially for the production of vitamin D, staying too many hours under UV light could increase the risk of developing skin cancers.
- Infectious agents capable of transforming normal cells into cancer cells. The carcinogenic infectious agents identified to date are the Epstein-Barr virus associated with Burkitt’s lymphoma, the Hepatitis B and C viruses, the Papilloma virus associated with cervical cancer, the penis, the vagina, the Helicobacter Pylori associated with the gastric tumor and HIV-1 responsible for various cancers.
Contracting one of these infections does not surely mean developing a tumor but only increases the risk.
Many of these risk factors are modifiable or only in part.
In every patient with a neoplasm, there are factors that influence the prognosis, ie the development, the evolution of the disease and the outcome of the treatments. These factors are called prognostic factors and can be positive or negative, ie they can positively or negatively influence the evolution of the disease.
Prognostic factors are divided into three categories:
- Factors related to the disease:
- Histological features of the tumor. It is one of the most important prognostic factors.
- Clinical stage, ie the extent of the disease. It is one of the most important prognostic factors.
- Location of the tumor.
- Laboratory parameters such as LDH, VES, alkaline phosphatase, PSA, CEA etc.
- Patient related factors:
- Sex: Male patients have often the worst prognosis.
- Age: children and the elderly have a worse prognosis.
- General health conditions
- Factors related to treatment
It is estimated that in 2017 in Italy more than 369,000 new cases of malignant tumors will be diagnosed, of which about 46% in women.
Currently in Italy the most frequent cancer in men, regardless of age, is that of the prostate followed by the colon-rectum, lung, bladder and kidney or urinary tract. In women, however, the most frequent is breast cancer followed by the colon-rectum, lung, thyroid and body of the uterus.
According to 2014 ISTAT data, approximately 29% of the total deaths that occurred this year were due to cancer (177,301 out of 600,000 deaths). In women, tumors are the second leading cause of death (25% of all deaths) after cardiovascular diseases (40%) while in men, cardio-vascular diseases and tumors are both the leading cause of death as they cause about the same number of deaths (34%).
The first cause of oncologic death in the Italian male population is lung cancer (27% of total cancer deaths) followed by colorectal cancer (11%), prostate (8%), liver (7%) and stomach (6%). In the female population, however, the first cause of cancer death is breast cancer (17% of total cancer deaths) followed by colorectal cancer (12%), lung (11%), pancreas (7%) , stomach (6%).
The 2017 data, compared to the previous ones, show a considerable increase in the survival of people who have had a cancer diagnosis (+ 24%). The only tumor for which survival has been reduced (- 10%) is that of the cervix. The number of patients living after a diagnosis of stomach, larynx and ovary cancer remains stable.
Not distinguishing by type of cancer and sex, the 5-year survival, that is the number of people alive after 5 years from the diagnosis, is equal to 60%, while the 10-year survival is 35%.
The percentage of patients recovered, ie with a life expectancy similar to the healthy population, is 27%.
* The numbers of cancer 2017 – AIOM Working Group, AIRTUM, AIOM FOUNDATION