Cancer: Tyes, Symptoms, Causes, Treatment, Stages & Prevention

Things to know about cancer

Illustration of cancer cells.
Cancer comes from overproduction and malfunction of the body's cells.

Cancer is the uncontrolled growth of abnormal cells anywhere in a body.
There are over 200 types of cancer.
Anything that may cause a normal body cell to develop abnormally potentially can cause cancer; general categories of cancer-related or causative agents are as follows: chemical or toxic compound exposures, ionizing radiation, some pathogens, and human genetics.
Cancer symptoms and signs depend on the specific type and grade of cancer; although general signs and symptoms are not very specific the following can be found in patients with different cancers: fatigue, weight loss, pain, skin changes, change in bowel or bladder function, unusual bleeding, persistent cough or voice change, fever, lumps, or tissue masses.
Although there are many tests to screen and presumptively diagnose cancer, a definite diagnosis is made by examination of a biopsy sample of suspected cancer tissue.
Cancer staging is often determined by biopsy results and helps determine the cancer type and the extent of cancer spread; staging also helps caregivers determine treatment protocols. In general, in most staging methods, the higher the number assigned (usually between 0 to 4), the more aggressive the cancer type or the more widespread is cancer in the body. Staging methods differ from cancer to cancer and need to be individually discussed with your health care provider.
Treatment protocols vary according to the type and stage of cancer. Most treatment protocols are designed to fit the individual patient's disease. However, most treatments include at least one of the following and may include all: surgery, chemotherapy, and radiation therapy.
There are many listed home remedies and alternative treatments for cancers but patients are strongly recommended to discuss these before use with their cancer doctors.
The prognosis of cancer can range from excellent to poor. The prognosis depends on the cancer type and its staging those cancers known to be aggressive and those staged with higher numbers (3 to 4) often have a prognosis that ranges more toward poor.

what is cancer, what causes cancer, cancerous cells

What Is Cancer & What Causes It?

When cells become cancerous

In the most basic terms, cancer refers to cells that grow out-of-control and invade other tissues. Cells become cancerous due to the accumulation of defects, or mutations, in their DNA. Certain:

inherited genetic defects (for example, BRCA1 and BRCA2 mutations),
infections,
environmental factors (for example, air pollution), and
poor lifestyle choices — such as smoking and heavy alcohol use — can also damage DNA and lead to cancer.

Most of the time, cells are able to detect and repair DNA damage. If a cell is severely damaged and cannot repair itself it undergoes so-called programmed cell death or apoptosis. Cancer occurs when damaged cells grow, divide, and spread abnormally instead of self-destructing as they should.

What is cancer?

Breast Cancer
These abnormal cells are termed cancer cells, malignant cells, or tumor cells. These cells can infiltrate normal body tissues.

Cancer is the uncontrolled growth of abnormal cells anywhere in a body. These abnormal cells are termed cancer cells, malignant cells, or tumor cells. These cells can infiltrate normal body tissues. Many cancers and the abnormal cells that compose the cancer tissue are further identified by the name of the tissue that the abnormal cells originated from (for example, breast cancer, lung cancer, colorectal cancer). Cancer is not confined to humans; animals and other living organisms can get cancer. Below is a schematic that shows normal cell division and how when a cell is damaged or altered without repair to its system, the cell usually dies. Also shown is what occurs when such damaged or unrepaired cells do not die and become cancer cells and show uncontrolled division and growth — a mass of cancer cells develop. Frequently, cancer cells can break away from this original mass of cells, travel through the blood and lymph systems, and lodge in other organs where they can again repeat the uncontrolled growth cycle. This process of cancer cells leaving an area and growing in another body area is termed metastatic spread or metastasis. For example, if breast cancer cells spread to a bone, it means that the individual has metastatic breast cancer to bone. This is not the same as "bone cancer," which would mean cancer had started in the bone.

The following table (National Cancer Institute 2022) gives the estimated numbers of new cases and deaths for each common cancer type:

Cancer Type Estimated New Cases Estimated Deaths

Bladder
76,960
17,100

Breast (Female — Male)
287,850 – 2,710
43,250 – 530

Colon and Rectal (Combined)
151,030
52,580

Endometrial
65,950
12,550

Kidney (Renal Cell and Renal Pelvis) Cancer
79,000
13,920

Leukemia (All Types)
60,650
24,000

Lung (Including Bronchus)
236,740
130,180

Melanoma
99,780
7,650

Non-Hodgkin Lymphoma
80,470
20,250

Pancreatic
62,210
49,830

Prostate
268,490
34,500

Thyroid
43,800
2,230

The three most common cancers in men, women, and children in the U.S. are as follows:

Men: Prostate, lung, and colorectal
Women: Breast, lung, and colorectal
Children: Leukemia, brain tumors, and lymphoma

The incidence of cancer and cancer types are influenced by many factors such as age, gender, race, local environmental factors, diet, and genetics. Consequently, the incidence of cancer and cancer types vary depending on these variable factors. For example, the World Health Organization (WHO) provides the following general information about cancer worldwide:

Cancer is a leading cause of death worldwide. It accounted for 8.2 million deaths (around 22% of all deaths not related to communicable diseases; most recent data from WHO).
Lung, stomach, liver, colon, and breast cancer cause the most cancer deaths each year.
Deaths from cancer worldwide are projected to continue rising, with an estimated 13.1 million deaths in 2030 (about a 70% increase).

Different areas of the world may have cancers that are either more or less predominant than those found in the U.S. One example is that stomach cancer is often found in Japan, while it is rarely found in the U.S. This usually represents a combination of environmental and genetic factors.

The objective of this article is to introduce the reader to general aspects of cancers. It is designed to be an overview of cancer and cannot cover every cancer type. This article will also attempt to help guide the reader to more detailed sources about specific cancer types.

What are risk factors and causes of cancer?

Smoking
Tobacco or cigarette smoke contains at least 66 known potential carcinogenic chemicals and toxins.

Anything that may cause a normal body cell to develop abnormally potentially can cause cancer. Many things can cause cell abnormalities and have been linked to cancer development. Some cancer causes remain unknown while other cancers have environmental or lifestyle triggers or may develop from more than one known cause. Some may be developmentally influenced by a person's genetic makeup. Many patients develop cancer due to a combination of these factors. Although it is often difficult or impossible to determine the initiating event(s) that cause cancer to develop in a specific person, research has provided clinicians with a number of likely causes that alone or in concert with other causes, are the likely candidates for initiating cancer. The following is a listing of major causes and is not all-inclusive as specific causes are routinely added as research advances:

Chemical or toxic compound exposures: Benzene, asbestos, nickel, cadmium, vinyl chloride, benzidine, N-nitrosamines, tobacco or cigarette smoke (contains at least 66 known potential carcinogenic chemicals and toxins), asbestos, and aflatoxin

Ionizing radiation: Uranium, radon, ultraviolet rays from sunlight, radiation from alpha, beta, gamma, and X-ray-emitting sources

Pathogens: Human papillomavirus (HPV), EBV or Epstein-Barr virus, hepatitis viruses B and C, Kaposi's sarcoma-associated herpes virus (KSHV), Merkel cell polyomavirus, Schistosoma spp., and Helicobacter pylori; other bacteria are being researched as possible agents.

Genetics: A number of specific cancers have been linked to human genes and are as follows: breast, ovarian, colorectal, prostate, skin, and melanoma; the specific genes and other details are beyond the scope of this general article so the reader is referred to the National Cancer Institute for more details about genetics and cancer.

It is important to point out that most everyone has risk factors for cancer and is exposed to cancer-causing substances (for example, sunlight, secondary cigarette smoke, and X-rays) during their lifetime, but many individuals do not develop cancer. In addition, many people have genes that are linked to cancer but do not develop it. Why? Although researchers may not be able to give a satisfactory answer for every individual, it is clear that the higher the amount or level of cancer-causing materials a person is exposed to, the higher the chance the person will develop cancer. In addition, people with genetic links to cancer may not develop it for similar reasons (lack of enough stimulus to make the genes function). In addition, some people may have a heightened immune response that controls or eliminates cells that are or potentially may become cancer cells. There is evidence that even certain dietary lifestyles may play a significant role in conjunction with the immune system to allow or prevent cancer cell survival. For these reasons, it is difficult to assign a specific cause of cancer to many individuals.

Recently, other risk factors have been added to the list of items that may increase cancer risk. Specifically, red meat (such as beef, lamb, and pork) was classified by the International Agency for Research on Cancer as a high-risk agent for potentially causing cancers; in addition processed meats (salted, smoked, preserved, and/or cured meats) were placed on the carcinogenic list. Individuals that eat a lot of barbecued meat may also increase risk due to compounds formed at high temperatures. Other less-defined situations that may increase the risk of certain cancers include obesity, lack of exercise, chronic inflammation, and hormones, especially those hormones used for replacement therapy. Other items such as cell phones have been heavily studied. In 2011, the World Health Organization classified cell phone low-energy radiation as "possibly carcinogenic," but this is a very low-risk level that puts cell phones at the same risk as caffeine and pickled vegetables.

Proving that a substance does not cause or is not related to increased cancer risk is difficult. For example, antiperspirants are considered to possibly be related to breast cancer by some investigators and not by others. The official stance of the NCI is that "additional research is needed to investigate this relationship and other factors that may be involved." This unsatisfying conclusion is presented because the data collected so far is contradictory. Other claims that are similar require intense and expensive research that may never be done. Reasonable advice might be to avoid large amounts of any compounds even remotely linked to cancer, although it may be difficult to do in complex, technologically advanced modern societies.

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What specialists treat cancer?

A doctor who specializes in the treatment of cancer is called an oncologist. He or she may be a surgeon, a specialist in radiation therapy, or a medical oncologist. The first uses surgery to treat cancer; the second, radiation therapy; the third, chemotherapy and related treatments. Each may consult with the others to develop a treatment plan for the particular patient.

In addition, other specialists may be involved depending upon where the cancer is located. For example, ob-gyn specialists may be involved with uterine cancer while an immunologist may be involved in the treatment of cancers that occur in the immune system.

Your primary care physician and main oncologist will help you to determine what specialists are best to be members of your treatment team.

How do health care professionals diagnose cancer?

Some cancers are diagnosed during routine screening examinations. These usual tests are routinely done at a certain age. Many cancers are discovered when you present to your health care professional with specific symptoms.

A physical exam and medical history, especially the history of symptoms, are the first steps in diagnosing cancer. In many instances, the medical caregiver will order several tests, most of which will be determined by the type of cancer and where it is suspected to be located in or on the person's body. Also, most caregivers will order a complete blood count, electrolyte levels, and, in some cases, other blood studies that may give additional information.

Imaging studies are commonly used to help physicians detect abnormalities in the body that may be cancer. X-rays, CT and MRI scans, and ultrasound are common tools used to examine the body. Other tests such as endoscopy, which with variations in the equipment used, can allow visualization of tissues in the intestinal tract, throat, and bronchi that may be cancerous. In areas that cannot be well visualized (inside bones or some lymph nodes, for example), radionuclide scanning is often used. The test involves ingestion or IV injection of a weakly radioactive substance that can be concentrated and detected in the abnormal tissue.

The preceding tests can be very good at localizing abnormalities in the body; many clinicians consider that some of the tests provide presumptive evidence for the diagnosis of cancer. However, in virtually all patients, the definitive diagnosis of cancer is based on the examination of a tissue sample taken in a procedure called a biopsy from the tissue that may be cancerous and then analyzed by a pathologist. Some biopsy samples are relatively simple to procure (for example, a skin biopsy or intestinal tissue biopsy done with a device called an endoscope equipped with a biopsy attachment). Other biopsies may require as little as a carefully guided needle, or as much as a surgery (for example, brain tissue or lymph node biopsy). In some instances, the surgery to diagnose cancer may result in a cure if all of the cancerous tissue is removed at the time of biopsy.

The biopsy can provide more than the definitive diagnosis of cancer; it can identify the cancer type (for example, the type of tissue found may indicate that the sample is from a primary [started here] or metastatic type of brain cancer [spread from another primary tumor arising elsewhere in the body] and thereby help to stage cancer. The stage, or cancer staging, is a way for clinicians and researchers to estimate how extensive the cancer is in the patient's body.

Is cancer that has been found localized to its site of origin, or is it spread from that site to other tissues? Localized cancer is said to be at an early stage, while one which has spread is at an advanced stage. The following section describes the general staging methods for cancers.

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How do physicians determine cancer staging?

There are a number of different staging methods used for cancers and the specific staging criteria vary among cancer types. According to the NCI, the common elements considered in most staging systems are as follows:

Site of the primary tumor
Tumor size and number of tumors
Lymph node involvement (spread of cancer into lymph nodes)
Cell type and tumor grade (how closely the cancer cells resemble normal tissue cells)
The presence or absence of metastasis

However, there are two main methods that form the basis for the more specific or individual cancer type staging. The TMN staging is used for most solid tumors while the Roman numeral or stage grouping method is used by some clinicians and researchers on almost all cancer types.

The TNM system is based on the extent of the tumor (T), the extent of spread to the lymph nodes (N), and the presence of distant metastasis (M). A number is added to each letter to indicate the size or extent of the primary tumor and the extent of cancer spread (a higher number means a bigger tumor or more spread).

The following is how the NCI describes the TNM staging system:

Primary tumor (T)
- TX – Primary tumor cannot be evaluated
- T0 – No evidence of primary tumor
- Tis – Carcinoma in situ (CIS; abnormal cells are present but have not spread to neighboring tissue; although not cancer, CIS may become cancer and is sometimes called pre-invasive cancer)
- T1, T2, T3, T4 – Size and/or extent of the primary tumor
Regional lymph nodes (N)
- NX – Regional lymph nodes cannot be evaluated
- N0 – No regional lymph node involvement
- N1, N2, N3 – involvement of regional lymph nodes (number of lymph nodes and/or extent of spread)
Distant metastasis (M)
- MX – Distant metastasis cannot be evaluated (some clinicians do not ever use this designation)
- M0 – No distant metastasis
- M1 – Distant metastasis is present

Consequently, a person's cancer could be listed as T1N2M0, meaning it is a small tumor (T1), but has spread to some regional lymph nodes (N2), and has no distant metastasis (M0).

The Roman numeral or stage grouping method is described by the NCI as follows:

SEER groups cancer cases into five main stages chart Stage Definition Stage 0

Carcinoma in situ.

Stage I

Higher numbers indicate more extensive disease: Larger tumor size and/or spread of cancer beyond the organ in which it first developed to nearby lymph nodes and/or organs adjacent to the location of the primary tumor

Stage II Stage III Stage IV

Cancer has spread to other organs (s).

As mentioned above, variations of these staging methods exist. For example, some cancer registries use surveillance, epidemiology, and end results program (SEER) termed summary staging. SEER groups cancer cases into five main categories:

In situ: Abnormal cells are present only in the layer of cells in which they developed.
Localized: Cancer is limited to the organ in which it began, without evidence of spread.
Regional: Cancer has spread beyond the primary site to nearby lymph nodes or organs and tissues.
Distant: Cancer has spread from the primary site to distant organs or distant lymph nodes.
Unknown: There is not enough information to determine the stage.

Staging of cancer is important; it helps the physician to decide on the most effective therapeutic protocols, provides a basis for estimating the prognosis (outcome) for the patient, and provides a system to communicate the patient's condition to other health professionals that become involved with the patients' care.

What are cancer treatment options?

The cancer treatment is based on the type of cancer and the stage of cancer. In some people, diagnosis and treatment may occur at the same time if the cancer is entirely surgically removed when the surgeon removes the tissue for biopsy.

Although patients may receive a unique sequenced treatment, or protocol, for their cancer, most treatments have one or more of the following components: surgery, chemotherapy, radiation therapy, or combination treatments (a combination of two or all three treatments).

Individuals obtain variations of these treatments for cancer. Patients with cancers that cannot be cured (completely removed) by surgery usually will get combination therapy, the composition determined by the cancer type and stage.

Palliative therapy (medical care or treatment used to reduce disease symptoms but unable to cure the patient) utilizes the same treatments described above. It is done with the intent to extend and improve the quality of life of terminally ill cancer patients. There are many other palliative treatments to reduce symptoms such as pain medications and antinausea medications.

Are there home remedies or alternative treatments for cancer?

There are many claims on the Internet and in publications about substances that treat cancer (for example, broccoli, grapes, ginseng, soybeans, green tea, aloe vera, and lycopene and treatments like acupuncture, vitamins, and dietary supplements). Almost every physician suggests that a balanced diet and good nutrition will help individuals combat cancer.

Although some of these treatments may help reduce symptoms, there is no good evidence they can cure any cancers. Patients are strongly recommended to discuss any home remedies or alternative treatments with their cancer doctors before beginning any of these.

What is the prognosis for cancer?

The prognosis (outcome) for cancer patients may range from excellent to poor. The prognosis is directly related to both the type and stage of cancer. For example, many skin cancers can be completely cured by removing the skin cancer tissue; similarly, even a patient with a large tumor may be cured after surgery and other treatments like chemotherapy (note that a cure is often defined by many clinicians as a five-year period with no reoccurrence of cancer). However, as the cancer type either is or becomes aggressive, spread to lymph nodes, or is metastatic to other organs, the prognosis decreases. For example, cancers that have higher numbers in their staging (for example, stage III or T3N2M1; see staging section above) have a worse prognosis than those with low (or 0) numbers. As the staging numbers increase, the prognosis worsens, and the survival rate decreases.

This article offers a general introduction to cancers, consequently, the details — such as life expectancy for each cancer — cannot be covered. However, cancers, in general, have a decreasing life expectancy as the stage of the cancer increases. Depending on the type of cancer, as the prognosis decreases, so does life expectancy. On the positive side, cancers that are treated and do not recur (no remissions) within a five-year period, in general, suggest that the patient will have a normal life expectancy. Some patients will be cured, and a few others may get recurrent cancer. Unfortunately, there are no guarantees.

There are many complications that may occur with cancer; many are specific to the cancer type and stage and are too numerous to list here. However, some general complications that may occur with both cancer and its treatment protocols are listed below:

Fatigue (both due to cancer and its treatments)
Anemia (both)
Loss of appetite (both)
Insomnia (both)
Hair loss (treatments mainly)
Nausea (both)
Lymphedema (both)
Pain (both)
Immune system depression (both)

Is it possible to prevent cancer?

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Most experts are convinced that many cancers can either be prevented or the risk of developing cancers can be markedly reduced. Some of the cancer prevention methods are simple; others are relatively extreme, depending on an individual's view.

Cancer prevention, by avoiding its potential causes, is the simplest method. First on most clinicians and researchers' list is to stop (or better, never start) smoking tobacco. Avoiding excess sunlight (by decreasing exposure or applying sunscreen) and many chemicals and toxins are excellent ways to avoid cancers. Avoiding contact with certain viruses and other pathogens also are likely to prevent some cancers. People who have to work close to cancer-causing agents (chemical workers, X-ray technicians, ionizing radiation researchers, asbestos workers) should follow all safety precautions and minimize any exposure to such compounds. Although the FDA and the CDC suggest that there is no scientific evidence that definitively says cell phones cause cancer, other agencies call for more research or indicate the risk is very low. Individuals who are concerned can limit exposure to cell phones by using an earpiece and simply making a few cell phone calls as possible.

There are two vaccines currently approved by the U.S. Food and Drug Administration (FDA) to prevent specific types of cancer. Vaccines against the hepatitis B virus, which is considered a cause of some liver cancers, and vaccines against human papillomavirus (HPV) types 16 and 18 are available. According to the NCI, these viruses are responsible for about 70% of cervical cancers. These viruses also play a role in cancers arising in the head and neck, as well as cancers in the anal region, and probably in others. Today, vaccination against HPV is recommended in teenagers and young adults of both sexes. The HPV virus is so common that by the age of 50, half or more people have evidence of being exposed to it. Sipuleucel-T is a new vaccine approved by the FDA to help treat advanced prostate cancer. Although the vaccine does not cure prostate cancer, it has been shown to help extend the lifespan of individuals with advanced prostate cancer.

People with a genetic predisposition to develop certain cancers and others with a history of cancers in their genetically linked relatives currently cannot change their genetic makeup. However, some individuals who have a high possibility of developing genetically linked cancer have taken action to prevent cancer development. For example, some young women who have had many family members develop breast cancer have elected to have their breast tissue removed even if they have no symptoms or signs of cancer development to reduce or eliminate the possibility they will develop breast cancer. Some doctors consider this as an extreme measure to prevent cancer while others do not.

Screening tests and studies for cancer are meant to help detect cancer at an early stage when the cancer is more likely to be potentially cured with treatment. Such screening studies are breast exams, testicular exams, colon-rectal exams (colonoscopy), mammography, certain blood tests, prostate exams, urine tests, and others. People who have any suspicion that they may have cancer should discuss their concerns with their doctor as soon as possible. Screening recommendations have been the subject of numerous conflicting reports in recent years. Screening may not be cost-effective for many groups of patients or lead to unnecessary further invasive tests, but individual patients' unique circumstances should always be considered by doctors in making recommendations about ordering or not ordering screening tests.

Where can people find more information about cancer?

There are many ways a person can find more information about cancer, but if they have any immediate concerns about having cancer, their first source of information should be their doctor. In addition to the references listed at the end of this article, the following is a list of information sources that are well recognized as authorities for cancer information by most clinicians:

American Cancer Society (http://www.cancer.org/Cancer/index)
National Cancer Institute (http://www.cancer.gov/)

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