When you talk to your doctor about treatment for chronic myelogenous leukemia (CML), you may hear him say that your goal is to get into remission. If you're like most folks, you've got a general idea of what the term means, but you may be fuzzy on the details. For CML, also called chronic myeloid leukemia, there are some concrete milestones that you need to reach.

"We try to be very, very specific in CML because most patients hear the term 'remission' and they feel the cancer is gone," says Gail J. Roboz, MD, director of the Leukemia Program at Weill Cornell Medical College in New York City. "But actually in CML there are specific categories of remission."

Your doctor will use blood test results to figure out which one you're in. He'll refer to these different groups as "responses."

Complete hematologic response. It means your blood cell count is back to normal and tests don't show any abnormal white blood cells. Also, if your spleen was swollen, it's now at its original size.

Complete cytogenetic response. You've reached this milestone when your blood or bone marrow -- the inside of your bone where blood cells are made -- no longer has any cells with the "Philadelphia" chromosome. That's the one that carries a gene called "BCR-ABL," which plays a role in the process that creates abnormal white blood cells.

Major molecular response. The amount of BCR-ABL gene in your blood is low.

"The most important milestone we've derived with the new treatments is the major molecular response," says Michael J. Mauro, MD, of Memorial Sloan Kettering Cancer Center in New York City. "That's when the leukemia is 1,000 times smaller than when we started. It's a significant enough remission where the odds of the leukemia growing again or transforming into an advanced phase are dramatically lower."

Complete molecular response. Your doctor will say you're in this category when the BCR-ABL gene doesn't show up in your blood.

Mauro says patients generally achieve blood remission in a few weeks and cytogenetic remission in a few months. Doctors look for major molecular remission within the first year or two, and research is under way to see if it's OK to stop treatment after you've been in it for a period of time.

How Do I Know if I'm Having a Relapse?

It's likely to show up in a blood test, so it's important to see your doctor for regular checkups.

"We define relapse in general as 'backward movement,' and ... the patient is unlikely to have any change in the way they feel," Mauro says.

Your doctor will use the same categories he used when talking about remission to describe a relapse.

For example, he could refer to a "hematologic" relapse in your blood cell count.

Or he could tell you that you've had a "cytogenetic" relapse, which means you again have cells with the Philadelphia chromosome.

He could also say you have a "molecular" relapse, which means you have some of the BCR-ABL gene in your blood.

Next Steps

If you have one of these changes, your doctor will repeat the test to rule out error.

"It's very important to not jump to a conclusion based on a single lab reading. That's a mistake patients make because they are worried," Roboz says. "They see their white blood cell count go up at one visit, but it might just be they caught a cold from their kids and their white blood cell count is responding normally."

If changes are confirmed, doctors may do a bone marrow biopsy to look for changes in the chromosomes so they can figure out what treatment might work better for you.

"Some patients respond quickly to a change in medication and do well, and there are others who need to try one or two times with different medications," Roboz says. "But it is not true that a relapse is definitely devastating news. There are plenty of patients who will be switched to a different CML medication and do extremely well."

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