DEAR DR. ROACH: I was diagnosed with small cell lung cancer. After radiation and chemotherapy my chest CT scan is now clear. My radiologist recommended prophylactic brain radiation even though my head CT scan is clear. When I asked how much this would decrease my chances of brain metastasis, he couldn’t give me an answer. He did say that I could develop cognitive impairment from the brain radiation.

Is the prophylactic brain radiation worth the risk of losing some cognitive function? What are the chances of developing brain metastasis without this radiation versus with the radiation? My radiologist is supposed to get back to me. I want to make an informed decision. — R.L.

ANSWER: I am sorry about your diagnosis, but I applaud you for asking for more information. It is disappointing that the radiologist did not immediately answer you. It is absolutely essential in order for you to make an informed decision.

Small cell lung cancer frequently spreads to the brain. Doctors have been using radiation to the brain for decades to kill any cancer cells that may be there unseen. In people with “limited stage” small cell cancer, the use of brain radiation reduced the incidence of recognized brain disease from 59% to 33%; treatment also improved the three-year survival rate from 15% to 21%.

In a different study of people with “extensive stage” small cell lung cancer, the proportion of people who developed cancer in the brain was 40% in the group not treated with brain radiation and 15% in the group who did get the radiation. The survival rate was improved as well, from 13% to 27% at one year.

Cancer and chemotherapy both can have effects on brain function, including not being able to think as clearly or solve problems as well (cognitive impairment). However, brain radiation does cause problems in more people than the other cancer treatments alone; for example, the ability to recall words immediately was decreased by 30% in people treated with brain surgery and radiation compared with 8% in people treated with surgery alone. Other brain functions similarly showed greater decline among those treated with radiation.

The improvement in survival rates and freedom from cancer spreading to the brain is significant; however, there is some increased loss of cognitive function. Most people choose to undergo radiation.

I must note that these studies were from years ago. Treatment for this type of cancer is better now than it was, and the ability to deliver radiation while sparing critical areas of the brain is better as well. I hope this information helps you make a decision.

DEAR DR. ROACH: Why isn’t there a blood test or X-ray to find pancreatic cancer before it’s too late? — A.D.

ANSWER: Screening for pancreatic cancer is appropriate for those few people with a history of familial pancreatic cancer or other cancer risk syndromes, such as Peutz-Jeghers syndrome. For people at average risk, no blood test or radiology study has been identified that has more benefit than harm. Pancreatic cancer is uncommon — only about 1 person in 10,000 per year are diagnosed. So, many people would need to be screened in order to find a case. The tests are not perfect; so, many people need further invasive testing to prove they don’t have pancreatic cancer. More people are harmed from the follow-up testing than get benefit from finding pancreatic cancer early.

If new tests are proven to be so good that invasive testing will not be necessary, we can consider the costs against the benefits.

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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 or send mail to 628 Virginia Dr., Orlando, FL 32803.

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