Cancer

Background

Cancer comprises a large group of diseases in which the body’s cells grow uncontrollably and may spread to other parts. There are more than 200 types of cancer (see most common), with each usually named for the organ or tissue where it forms.

Globally, cancer is the second leading cause of death, behind only cardiovascular disease. Breast, colorectal, lung, cervical, and thyroid cancer are the most common forms among women, while lung, prostate, colorectal, stomach, and liver cancer are the most common types among men. While overall medical advances have improved survival rates, incidences of certain cancers are increasing among young individuals.

Take a deep dive into cancer statistics here.

How Cancer Develops

Our bodies are made up of trillions of cells. The instruction manual for how our cells grow and divide is dictated by our genetic material or DNA. Occasionally, when a cell splits, it can make a mistake in its DNA, a mutation, that causes it to begin dividing abnormally.

Our body’s defense systems can typically handle a few mistakes, but when these defense mechanisms are overwhelmed, abnormal cells begin to grow and divide uncontrollably, resulting in cancer.

As cancer cells multiply, they group together in tumors (or lumps) that may migrate to other parts of the body using the blood and lymphatic system. This process of spreading to a distant site occurs in stages and is called metastasis (see how the different stages are defined).

Doctors typically determine the grade or stage of a cancer by taking a small tissue sample or a biopsy. In grade 1 tumors, the cells look close to normal, but the higher the number, the more abnormal the cells appear. Grade 4 tumors look the most abnormal.

Certain viruses, known as oncoviruses, such as Epstein-Barr virus (a common virus that can cause respiratory infections), HIV (responsible for AIDS), and HPV (a common virus accompanied by skin warts), can cause cancers. As many as 20% of all cancers can be attributed to viral infections.

There is no single cause of cancer. Risk factors may include unhealthy lifestyle choices like smoking, prolonged exposure to the sun without sunscreen, and excessive alcohol consumption, among others.

Family history also plays an important role in a person’s risk of developing cancer. Use this interactive calculator to gauge your risk level.

Treatments

The standard treatments for most cancers include surgery, chemotherapy, radiation, or a combination of these. The specific treatment depends on the cancer type, stage, and individual preference. Chemotherapy (“chemo”) refers to chemicals that interrupt cell division and shrink tumors, control advanced cancer, and prevent cancer recurrence.

Chemo works by killing all rapidly dividing cells in the body. Learn more about how it works here.

Many normal, fast-growing cells divide frequently—such as those in the bone marrow and lining the digestive tract—and are affected by chemo, accounting for its severe side effects. Radiation broadly targets all cells in its path by damaging their DNA, though normal cells mostly recover. Cells that acquire massive amounts of damaged DNA are unable to function and subsequently die.

For certain cancers—like breast and prostate cancers that use hormones to grow—hormone therapy can slow or stop the growth, or reduce its recurrence. Other approaches attempt to target specific cancer cell features that help cancer grow, divide, and spread. More recently, immunotherapies, which help the body’s own immune system fight cancers, have become common.

Future

Cancer death rates fell by about 30% between 1990 and 2020. Much of this improvement is attributed to a decline in smoking rates and medical improvements in early detection and treatment of certain cancers.

The pace of progress in recent years has been impressive. As immunotherapies become more widely used to treat cancers, new research disciplines that push boundaries are developing.

Cancer bioengineering aims to develop materials to manipulate cancer cells, improve drug development and devise better methods of delivering cancer treatments. New imaging techniques visualize tumor metabolism, revolutionizing cancer diagnosis. New methods are in development to target hard-to-reach tumors through radioimmunotherapy.