ArcaMax

DEAR DR. ROACH: I have read about using the immune system's response as a mechanism to battle cancer (such as brain and pancreatic) and to reduce the devastating impact that cancer and its treatment has on humans. I understand current drug trials show promising results. How do doctors and scientists use the immune system to treat cancer? -- J.W.

ANSWER: The concept of using the immune system to treat cancer is old, but the ability to do so has dramatically improved in the past few years. There are a few specific types of treatments that I'd like to highlight:

Immune checkpoint inhibitors are treatments that release inhibitions on the immune system. (These "strengthen" the immune system, which has beneficial but also potentially toxic effects.) For melanoma, the most dangerous form of skin cancer, these treatments have revolutionized treatment and led to dramatically improved outcomes in people whose melanoma has spread. Response rates are up to 60% in a disease where the prognosis used to be dismal.

The unleashed immune system can destroy cancer very effectively, but it also can attack healthy organs, with many people (between 10% to 60% depending on drugs and doses) developing damage to the skin, lungs, liver, thyroid, colon and heart. These toxicities range from mild to life-threatening.

The body's own immune cells can be genetically engineered to kill cancer cells. Chimeric antigen receptor T cells (CAR T cells) can be specifically changed to recognize cancer cells. This can lead to complete remission with some cancers, especially some leukemias and lymphomas. Unfortunately, they can also attack the body, leading to neurological damage that can be very serious.

Developing cancer vaccines is a highly promising strategy for personalizing the immune system to attack a person's own cancer. Although the United States has recently made dramatic cuts to its support of this research, researchers in other countries continue to study this. It can be used in combination with other traditional or immune-based treatments.

The immune system can be used to help treat cancer effectively, but there is still the potential for serious side effects.

DEAR DR ROACH: I am 89 years old and doing reasonably well, but I have noticed some loss of energy and a bit of my balance. I try to walk, do some exercises, and then hit the hot tub every day to help relax my joints. I recall reading an article about a study concluding that 15 minutes in a hot tub equated, cardio-wise, to a 15-minute jog. I would really appreciate your opinion on this proposition. -- J.D.

ANSWER: I read the study that I think you are referencing, from Coventry, England, and I think the headline writers overstated the more cautious conclusions of the actual study. Being in a hot tub or sauna does increase the heart rate and the ability of the heart to exert itself when done daily for four weeks in people with heart failure.

Other studies have found that healthy volunteers also get small but significant improvements in their cardiac reserve, similar to (but not quite as much as) what would be expected with exercise.

The benefits of exercise are well-known and large and go beyond the effects of the heart, while the benefits of regular hot-tub or sauna bathing appear to give some but not all the benefits of regular exercise. At age 89, there is a risk of heat-related injuries, including lightheadedness and falling, so I would urge caution for new users not to use too high of a heat or stay in for too long, especially when first starting.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.

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