Dear Doctor: It's a real nightmare trying to pry our two grandsons away from their online video games when they are visiting. There's always a fight followed by hours of sulking and crankiness. Our son and his wife say it's easier to just let the kids play. Could they be addicted?

Dear Reader: Anyone who has ever interacted with a digital screen, be it a smartphone, tablet or computer, knows all too well the lure -- and allure -- of electronic devices. They draw you in, engage your brain at a startlingly deep level, and time and awareness just vanish. Up the ante with the dynamic visuals and mesmerizing world of a video game, and non-gamers often find themselves in a losing battle for the time and attention of their loved ones.

When it comes to the question of addiction, no less an authority than the World Health Organization has recently added "gaming disorder" as a new mental health condition to the 11th edition of its International Classification of Diseases, or ICD. However, the bar for someone to earn this new -- and somewhat controversial -- diagnosis is quite high. According to the ICD, gaming disorder is "a pattern of gaming behavior ('digital-gaming' or 'video-gaming') characterized by impaired control over gaming, increasing priority given to gaming over other activities to the extent that gaming takes precedence over other interests and daily activities, and continuation or escalation of gaming despite the occurrence of negative consequences."

Not only that, the digital devotion must be so powerful that it severely impairs all interactions, including with family and friends, at work or school, and in areas of self-care. Finally, the behavior must take place for at least one year before an official diagnosis is possible.

With that definition in mind, it's unlikely that your grandkids qualify as addicted. But that doesn't make the situation you describe any less challenging. The boys are choosing a world visible and meaningful only to themselves over the cooperative dynamics of family life. Lost in the flow of the game, their universe is a potent mix of questions, answers, penalties, risks and rewards. And with the way these games are engineered, particularly the role-playing games, there is no logical place to stop -- or even pause.

On the plus side, immersive games can expand the imagination, foster collaboration and sharpen cognitive skills. But when kids are parked in front of a screen, they're missing out on activities, experiences and events that will help them become healthy and productive adults. In your case, the challenge seems to be that the parents don't see enough of a problem to intervene. However, when the boys are visiting your home, you can make a point of engaging them in the analog world.

Give them a set time for gaming and be firm when that time limit is up. Then be prepared with something interesting for them to do. Think of activities with distinct start and finish times, and with concrete end products or the potential for rewards. Show them that even in the real world, they can achieve the video gaming world's enthralling sense of flow.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Is it just me or has it been forever since we've seen any real advances in cancer treatments? The new miracle drugs work only in very specific cases and the rest of us cancer patients are left with 20th-century treatments. Are there breakthroughs we aren't hearing about?

Dear Reader: When it comes to big cancer breakthroughs, it can seem like there isn't much new to report. As you correctly point out, the newest treatments emerging from the fields of precision medicine and immunotherapy are geared to cancers with very specific characteristics. However, when it comes to the future of cancer treatment, there's a revolution in progress.

Powered by the decoding of the human genome, which has allowed scientists to explore the human body at the cellular level, our understanding of what cancer is, how it behaves and how to stop it is growing exponentially. One bright spot is recent research funded by the National Institutes of Health, which has collected detailed data about more than 10,000 tumors arising from 33 different types of cancer. The analysis of that data, known as the PanCancer Atlas, is found in a collection of 27 different scientific papers. The information contained within was 10 years in the making. Taken together, these papers outline the findings of more than 150 researchers and examine the selected cancers at the molecular level.

One important advance has been how we talk about various cancers. Rather than approach tumors based solely on the part of the body where they originate, the shift is to classify them based on their molecular similarities to one another. For instance, after analyzing the tumors in the database, it was discovered that one type of tumor with a specific genetic profile was located in 25 different parts of the body. According to the body-location way of thinking, this one tumor would have had multiple treatment approaches.

Researchers also found a marked diversity in the genetic glitches in the tumors they studied, in the ways that the tumors grow, and in the cellular pathways they either use or outright hijack to ensure their survival. This line of inquiry has made possible the creation of important sub-groupings of various cancers, which aids in the search for targeted treatments. It has also helped scientists to identify potential vulnerabilities in various types of cancer.

Instead of focusing on how to poison the rogue cells with radiation or chemotherapy, researchers are now looking at ways to starve tumors, weaponize the immune system and even rewrite the tumor's own genetic code. So-called "smart" cancer drugs, which just a few years ago seemed like a fantasy, are now in the testing stages. One promising line of inquiry is looking into ways to harness tiny microparticles to deliver cancer-fighting drugs directly to the tumor, and even to deliver tiny imaging agents for more precise visualization.

Many of the cancer researchers and oncologists we know agree that we are presently in the midst of a revolution into our understanding of this complex and challenging disease. The "war on cancer" that we grew up hearing about may not yet be won, but battle by battle, things have never looked better.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My son, who plays several sports, recently broke his right arm. Now he's worried that the muscles will waste away while it heals. I read that exercising his left arm could help his broken arm. When I told him this, he scoffed. It does seem crazy, but is it true?

Dear Reader: Improbable as it sounds, a new study found that when a limb on one side of the body is immobilized, as in the case of your son's broken arm, it's possible to preserve muscle strength and size by exercising the corresponding limb on the other side of the body.

This is a phenomenon known as "cross education," which has been written about since at least 1894. Since then, a number of studies have backed up the existence of cross education. Whether through voluntary muscle contractions through exercise, imagined contractions via targeted visualization or contractions that were electrically stimulated, activating the muscles of the opposite limb preserved both strength and muscle mass in the immobilized body part.

In this newest study, researchers in Canada studied the forearms of 16 male and female college students for four weeks. All were right-handed, and none had recent experience with resistance training. Using CT scans, ultrasound and a weight machine, the researchers measured the dimensions and strength of the muscles in the participants' forearms. The students were then fitted with casts on their left forearms to immobilize their wrists, hands, thumbs and fingers up to the knuckles. Each was randomly assigned to either a training group or to a control group. The training group took exercise classes three times a week that focused on certain muscle groups in the wrist, hand and forearm of the free limb. The control group did not take part in those classes and was asked to refrain from any other exercise as well.

A month later, after the casts were removed, measurements showed that participants in the control group had lost about 20 percent of the strength in their left forearms and had lost 3 percent of their muscle mass. For the participants who had exercised those specific muscle groups in their right forearms, however, both strength and mass measurements in their immobilized forearms were virtually unchanged. Even more interesting was the fact that the muscle groups in the right hand that were deliberately not exercised had measurably atrophied in the left hand. Only the same muscles that were exercised in the free limb maintained their strength and mass in the limb that was in a cast.

How and why cross education takes place is not yet known. Although sensors placed inside the casts of the resistance training group showed that there was indeed some muscular contraction taking place while the students exercised their free hands, these were too weak to have a physical effect.

So what's going on? Most popular among the many theories that have been floated is the idea that something is happening in the neural circuits of our brains. In the meantime, let your son know that, thanks to cross education, he has a way to emerge from his cast stronger than he expected.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)