Many cancers require more than one kind of treatment

DEAR DOCTORS: Our dad was diagnosed with lung cancer and will be getting chemo and radiation. I’m not really sure how they work, or why he has to have both. Should we get a second opinion?

DEAR READER: We use the word “cancer” to refer to a group of diseases in which abnormal cells within the body begin to divide uncontrollably. They are able to evade the body’s natural defenses, and, over time, they can spread throughout the body. The goal of cancer treatment is to prevent these rogue cells from dividing. This is achieved either by killing the cancer cells outright, or disrupting their DNA, and thus their ability to divide. Radiation and chemotherapy are two of the most common cancer treatments. Although each works to stop the progress of the disease, they act in different ways.

Chemotherapy is a systemic treatment. That means that the specialized drugs used in chemotherapy are administered via the bloodstream so that they can reach and act upon cells throughout the body. More than 100 different chemotherapy medications fall into five major categories. Each of these drug categories behave in a different way, but all share the same objective. That is, to disrupt the life cycle of cells within the body that divide rapidly, which includes cancer cells.

Chemotherapy drugs are quite powerful. Because they circulate to all parts of the body, they act on all of the rapidly dividing cells in the body, including those that are not cancer. This includes hair roots, which is why hair loss occurs in many cancer patients undergoing chemo. Other common side effects include nausea, vomiting, fatigue, anemia and infection.

Radiation therapy, by contrast, is a localized treatment. It targets a specific part of the body where cancer cells are found. The powerful energy -- delivered via Xrays, gamma rays, electron beams or protons -- destroys cancer cells and damages their DNA as well. This prevents the rogue cells from dividing and growing, and thus stops their spread.

Some radiation treatments involve ingesting, injecting or implanting a radioactive substance, which either locates or binds to cancer cells. Although the effect on noncancerous cells isn’t as severe in radiation therapy as it is in chemotherapy, healthy cells do get damaged. This results in side effects such as skin problems at the delivery site and fatigue.

Depending on the type of cancer and how far it has spread, it’s not unusual for several treatments to be used together. This includes chemotherapy and radiation therapy, as well as surgery, immunotherapy, hormone therapy and targeted drug therapies.

In certain types of lung cancer, studies have found that using chemotherapy along with radiation therapy can improve survival rates. While radiation is effective at targeting solid tumors, chemotherapy can act upon cancer cells throughout the body, including those that haven’t yet been identified.

Lung cancer treatment is a rapidly advancing field. For that reason, it’s often helpful for patients to have their case and treatment plan reviewed by a physician or medical team that specializes in the disease. To avoid unexpected costs, check with your insurer for guidance on which doctors and facilities are covered by your plan.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health.