Dear Doctors: Why don’t we hear more about cryoablation as a treatment for prostate cancer? It appears to be much easier than major surgery, so it seems like it would be a good option. What does the procedure entail? I am also interested in knowing about the advantages and disadvantages.

Dear Reader: Prostate cancer is the second-most-common type of cancer in men. Only skin cancers occur more often. This type of cancer arises in the prostate gland, which is about the size and shape of a walnut and is located beneath the bladder.

Because the prostate sits amid a complex network of nerves and structures that contribute to both sexual and urinary function, removing tumors in this type of cancer can be challenging. Depending on size and specific location of the cancer and whether it has spread, prostate cancer treatment can result in urinary incontinence and loss of sexual function.

Therapies may consist of one or more approaches, including surgery, radiation, chemotherapy, hormone therapy or immunotherapy. Cryoablation, also known as cryotherapy, can also be an option in certain cases. This is a procedure in which abnormal tissues are subjected to extremely cold temperatures, which destroys the cells.

Cryotherapy is performed under either regional or general anesthesia. It may be an outpatient procedure, or it can sometimes require an overnight hospital stay. Guided by ultrasound imagery, the physician inserts thin, hollow needles, known as cryoprobes, into a specific region of the prostate gland. The cryoprobes infuse freezing gas into the cells of the prostate gland, which kills them.

There are two forms of cryotherapy for prostate cancer. One type, known as whole-prostate cryotherapy, treats the entire gland. This kills both the cancer cells and the healthy tissues. Freezing the tissues of the prostate gland often damages the nearby nerves that control erections. As a result, erectile dysfunction occurs more often after whole-prostate cryotherapy than when the gland is surgically removed.

The other type of cryotherapy, known as focal cryotherapy, targets only the cancer cells. This allows less of the healthy tissue in the prostate to be destroyed. With focal cryotherapy, the risk of the loss of sexual function is minimized, but not eliminated. This approach is typically reserved for cancers that are small, well-defined and have not spread.

In both types of cryotherapy, a catheter filled with warm saltwater is used to protect the urethra. This is the tube that empties the bladder. The catheter is left in place for several weeks after the surgery, which ensures that the patient can empty his bladder as he recovers.

You are correct that cryotherapy is less invasive than surgery. It is also less painful and has a faster recovery period. However, it is not suitable for all patients. Factors such as the size, location and typing of the patient’s cancer, as well as the size of their prostate, play a role in whether cryotherapy can be an option. It is also unclear at this time if the long-term survival rates of this approach match those of either radiation or surgery.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I have read that older adults may not get enough vitamin D in winter. My father-in-law is 73 years old. He’s from Florida, but he’s spending a year with us here in Maine. He can’t be outdoors all the time like he is at home. How important is vitamin D? How do we know if he’s getting enough?

Dear Reader: Your question keys right into why vitamin D is often referred to as the “sunshine vitamin.” It’s a nutrient essential to human health and well-being and is produced by the body in response to exposure to sunlight. Vitamin D helps the body absorb calcium and maintain proper blood levels of both calcium and phosphorus. These functions are critical to the growth and maintenance of healthy teeth and bones. Newer research shows the vitamin has an anti-inflammatory effect, helps the body fight infection and can reduce cancer cell growth in some situations. Vitamin D receptors are found in tissues throughout the body and in several major organs. This suggests additional roles for the nutrient that have not yet been identified.

How much vitamin D someone needs depends on their age. Children, teens and adults up to the age of 70 are advised to get 600 international units, or IU, per day. Absorption becomes less efficient as we age, so older adults, like your father-in-law, are advised to get 800 IU per day. For infants up to 12 months old, the recommendation is 400 IU of vitamin D per day. While the nutrient is found in some foods, such as fatty fish, beef liver, egg yolks, cheeses and some mushrooms, most of us don’t eat enough of these to fulfill our daily requirement. To compensate, a range of commonly consumed prepared foods are fortified with the nutrient. These include dairy products, many breakfast cereals and some brands of prepared orange juice.

And then, of course, there’s sunshine. When the ultraviolet rays in sunlight hit the surface of the skin, they trigger a complex chemical reaction. With an assist from the kidneys, liver and other cellular structures, our bodies manufacture vitamin D. For those with light skin, 15 to 30 minutes of full sunlight on bare arms, legs or torso at least two or three times per week will do the trick. Melanin offers a protective effect, so people with darker skin need longer exposure. People with any kind of history or risk of skin cancer should rely on diet and supplements to get their daily allowance.

It’s important to note that several factors can interfere with natural vitamin D production. Clothing and sunscreen either partially or completely block UV light, which hinders or prevents vitamin D formation. In northern latitudes like your own, with shorter days, weaker sunlight and bad weather that keeps people indoors, getting enough vitamin D naturally can become a challenge. Your father-in-law can learn his vitamin D status with a simple blood test. If it’s low, his health care provider will offer guidance on supplementation. These can include fortified foods, vitamins or, in cases of serious deficit, vitamin D injections.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I had COVID-19, and now I’ve got long COVID. I have neuropathy and brain fog, and when I try to exercise, I get exhausted right away. My doctor said it just takes a while to get back on your feet, like after you’ve had the flu, but this feels different. What is the latest news on long COVID?

Dear Reader: As we enter the fourth year of living with COVID-19, it’s clear the initial illness isn’t the only health risk for those who contract the disease. They also face the chance of developing long COVID, the constellation of symptoms that can continue long after the initial illness has ended.

Symptoms include the physical and neurological effects that you have described. The condition can also adversely affect the heart, respiratory and circulatory systems, stamina, endurance, cognition and mental and emotional health. Long COVID does not appear to be linked to the severity of a case of COVID-19. And to make things even more complex, the symptoms can take a few weeks, or even months, to appear.

The newest data shows that 1 in 5 people who recovered from COVID-19 later develop long COVID. With more than 100 million cases of COVID-19 in the U.S. to date, that puts the number of long COVID patients well into the millions. Because the condition is so new, doctors are still struggling to understand what is happening to their patients. And, as with all new diseases, the learning curve is steep. This puts a burden on both patients seeking help and the medical workers trying to treat them. Here at UCLA, as is occurring in medical centers and hospitals throughout the U.S., long COVID treatment is rapidly emerging as a subspecialty of its own.

When it comes to physical activity, a new study backs up your experience -- that is, long COVID can severely reduce the ability to exercise, no matter the person’s prior level of fitness. It also offers clues into the mechanics of what is happening. Researchers at the University of California, San Francisco analyzed data from studies that compared the exercise performance of about 800 adults who have had COVID-19. Roughly half recovered completely, while the others developed long COVID. While running or cycling, the long COVID group had a diminished ability to use oxygen in the blood to fuel muscles. Additionally, their cardiac function, including heart rate, wasn’t able to meet the needs of the exercise. Why this happens is not yet clear, but each new bit of information suggests new paths forward.

At this time, the guidance for long COVID patients is to take a modulated return to exercise. This can mean adding as little as a few extra steps to a walk or run or a few extra strokes of a swim every few days or weeks. Research shows that pushing yourself can delay progress. Physical therapy is also emerging as an important tool for recovery. Long COVID continues to be the subject of many of the letters we receive. We’re keeping an eye on new developments and will continue to share them in future columns.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)