Drug against Crohn's disease must be changed because of melanoma | Journal-News

DEAR DR. ROACH: I am a 67-year-old man in good physical shape. I suffer from Crohn's disease and have been taking a tablet of mercaptopurine for eight years. This is the only medication I take and if I eat a bland diet, exercise and avoid stress, I am fine.

I went to the dermatologist and she had to do biopsies of three possible melanomas. One needs to be excised and she sent an email to my gastroenterologist recommending that I stop taking mercaptopurine. My gastroenterologist recommended either infliximab or adalimumab-atto.

Do you think mercaptopurine causes skin cancer, and if so, what new prescription would you recommend? I don't want to change my medication unless I absolutely have to. — GG

ANSWER: The situation is complicated because people with Crohn's disease are at increased risk for melanoma, even without the effects of drugs that modulate the immune system – like all three drugs you mentioned.

It is true that mercaptopurine increases the risk of both melanoma and non-melanoma skin cancer. But these drugs do not cause skin cancer. The main risk factor for skin cancer is sunlight, which damages the DNA in skin cells and makes people more susceptible to cancer. The body has systems for repairing DNA, and these can be affected by mercaptopurine or the other drugs you mentioned, both of which are in the class of TNF inhibitors.

There is not enough evidence to say definitively which drug carries a higher risk, but it seems that TNF inhibitors probably carry a lower risk than mercaptopurine. I can't find any significant differences between infliximab or adalimumab-atto. The overall risk is small even with mercaptopurine; about 1 melanoma was found in 400 people taking the drug for 10 years.

You can ask your gastroenterologist about vedolizumab, which works differently and prevents white blood cells from entering and causing inflammation in the intestine. This treatment does not appear to carry an increased risk of cancer and is a preferred treatment in people with a history of cancer.

DEAR DR. ROACH: How is it that if I weigh myself first thing in the morning and then drink a 1 pound cup of coffee (I weighed it) I end up weighing over a pound more? This happens practically every day and doesn't make sense. From the weight, I must have eliminated more than I took in. I use a digital scale and it is accurate. — JL

ANSWER: This doesn't make sense. Although weight gain and loss sometimes seem to defy common sense, nothing violates the laws of physics. The scale may be fairly accurate, but it can be off ever so slightly if you add a pound to your weight. I suspect there is sometimes a rounding error.

For example, say you weigh 137.4 pounds and your scale rounds that up to 137 pounds. Then you drink 16 ounces of coffee, which is exactly one pound, and you now weigh 138.4 pounds. If there is a small error and the scale says your weight is, say, 138.6 pounds, your scale will appear to say you gained 2 pounds when it rounds your weight up to 139 pounds.

Dr. Roach regrets that he cannot respond to individual letters, but will include them in the column whenever possible. Readers may email questions to [email protected] or mail them to 628 Virginia Drive, Orlando, FL 32803.