Dear Doctor: 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 X-rays, 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.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My wife just had her yearly checkup, and when her blood test results came back, she was told that she had recently suffered a heart attack. How can that be, since she never had any symptoms?

Dear Reader: Your wife had what is known as a “silent” heart attack. Just as the name suggests, it’s a heart attack that occurs without the person realizing it happened. In many cases, though, it turns out the episode wasn’t all that silent after all. It’s true that the person didn’t experience the numb left arm or sudden chest pain that we all recognize from movies and television, often referred to as the “Hollywood” heart attack. However, upon review, many people will realize they were aware of different, subtler symptoms that signaled a heart attack was taking place.

A heart attack occurs when something causes the flow of blood to the heart to become blocked. Without the oxygen and nutrients supplied by a network of blood vessels known as the coronary arteries, the heart muscle begins to die. This causes an array of symptoms. The most commonly known symptoms of heart attack include pain and pressure in the chest, and pain or discomfort in one or both arms. Additional symptoms include pain or discomfort in the neck, jaw, back or stomach; nausea; light-headedness; dizziness; shortness of breath; sudden sweating; and fatigue. These can be so mild, brief or even innocuous that the person never connects them to a heart attack.

Studies suggest that silent heart attacks are more common in women than in men. Women are also more likely to experience symptoms that are unrelated to chest pain. People who have had a silent heart attack may later recall feeling dizzy or short of breath, having a bout of stomach pain or nausea, or experiencing a neck ache or unusual fatigue. These symptoms are easy to attribute to other causes, such as a case of the flu, stress, indigestion or a strained muscle. However, as in your wife’s case, blood tests will reveal elevated levels of a protein known as troponin T or troponin I. These are released into the blood when the heart muscle is damaged.

The risk factors for any type of heart attack are the same. These include a prior heart attack, a family history of heart disease, using tobacco products, high blood pressure, high blood cholesterol, being overweight, poor diet and lack of exercise. Age and race also play a role.

After someone has had a heart attack, they can make lifestyle changes to lower risk. These include quitting smoking; reaching and maintaining a healthy weight; adopting a healthful diet; managing chronic health conditions, such as diabetes; and becoming physically active. If appropriate, medications to control high blood pressure and high blood cholesterol will be prescribed.

If anyone has the symptoms of a silent heart attack, it’s important not to ignore them. Early treatment will not only lessen the amount of damage that is done to the heart, it may well save your life.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Would you please consider doing a recap about the coronavirus -- especially about how it spreads? There’s a lot of information floating around, and it’s getting hard to sort through the noise.

Dear Reader: It’s true that we’ve been deluged in recent months with coronavirus coverage. Whether in print, on TV, on the radio or online, the information ranges from accurate to speculative to deliberately false. All of this adds up not only to potential confusion, but also to mental fatigue. You’re not alone in feeling overwhelmed by the topic. And to be honest, just running through the facts as we know them thus far will be helpful to us, as well.

Let’s start at the beginning. The novel coronavirus goes by the name SARS-CoV-2, which stands for severe acute respiratory syndrome coronavirus 2. It’s referred to as “novel” because it has never been seen in humans before. This means we have no acquired resistance or immunity to this particular virus. The disease that SARS-CoV-2 causes is known as COVID-19. COVID stands for “coronavirus disease,” and the number 19 refers to the year that it first appeared, which is 2019. In fact, the first public information about the disease was released on Dec. 31, 2019, the last day of that year.

A growing body of evidence suggests the virus most commonly spreads via the tiny respiratory droplets we emit whenever we speak, cough, sneeze and breathe. These droplets can be inhaled, or may be transferred to the mucous membranes of the nose, mouth and eyes via touch. That’s why washing your hands and not touching your face are both so important. This is also why the Centers for Disease Control and Prevention now recommends that people in public places wear facial coverings, which constrain the movement of the respiratory droplets we all release. Since not everyone infected with SARS-CoV-2 develops physical symptoms, it is possible for these individuals to unknowingly transmit the virus. Again, that’s why facial coverings for everyone are so important -- you’re protecting the people around you. The typical range of expelled respiratory droplets is less than 6 feet, which has led to the buffer zone we are now all asked to observe.

Symptoms of COVID-19 appear about two weeks after infection. They include fever, dry cough, tiredness and shortness of breath. Also common is a sudden loss of the sense of taste and smell. Patients also report headache, muscle aches, chills and chest pain. Although older adults and anyone with a serious underlying medical condition appear to be at higher risk of serious COVID-19 complications, it’s possible for anyone of any age to become ill. And the disease appears to have a broader scope than the pneumonia it’s best known to cause. A rare inflammatory condition is now being seen children. And in a number of adults, a range of adverse reactions brought on by sudden and unexpected blood clot formation have been reported. Unfortunately, there is no cure for COVID-19 at this time. Anyone with symptoms should seek immediate medical care.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)