Monitoring response to targeted therapies

As time goes on you won’t need to go to the clinic as often and eventually you may only need a check-up every couple of months.

At these appointments your doctor will ask about your general health and if you’ve had any new symptoms or side effects from treatment. You’ll usually have blood taken to check the numbers of blood cells (a full blood count or FBC) and for a PCR blood test. From time to time you may also have a bone marrow sample taken. Your doctor can tell you how often this might be needed.

The results of these tests help your doctors judge how well your leukaemia is responding to treatment so they can make any changes if needed.

Levels of response Back to top

The aim of your treatment is to put the CML into remission. Remission means there aren’t any signs of CML in your blood. To measure how effective the treatment has been, doctors look for different levels of response:

Haematological response

The white blood cell count in the blood is usually high when people first develop CML, and the first level of response is seen in the blood counts. If there’s a haematological response, it means the full blood count has returned to normal and no leukaemia cells can be seen. If your spleen was larger than normal when you were first diagnosed, this should also have gone back to its normal size.

Most people get a haematological response within three months of starting imatinib|.

Cytogenetic response

This is the next level of response. It refers to the amount of Philadelphia chromosome| in your blood and bone marrow.

When your treatment begins to work, the number of Philadelphia chromosome positive (Ph+) cells in your bone marrow decreases. Usually, at least 20 cells from your bone marrow sample are examined by your doctor to see if there’s been a cytogenetic response.

There are different levels of cytogenetic response depending on the percentage of Ph+ cells in the bone marrow:

• Complete cytogenetic response - no Ph+ cells.
• Partial cytogenetic response - between 1–35% Ph+ cells (between 1 and 35 in 100).
• Minor cytogenetic response - between 36–65% Ph+ cells (between 36 and 65 in 100).
• Minimal cytogenetic response - between 66–95% Ph+ cells (between 66 and 95 in 100).
• No cytogenetic response - more than 95% Ph+ cells (more than 95 in 100).

It takes longer (sometimes many months) to get a cytogenetic response than a haematological response. About 80% (8 out of 10) people taking imatinib for CML in the chronic phase| get a complete cytogenetic response.

Molecular response

A molecular response is the next aim of treatment after someone gets a cytogenetic response.

Even after someone has a cytogenetic response, there can still be leukaemia cells in their blood. But because there may only be one leukaemia cell among many thousands of normal blood cells, a very sensitive test is needed to detect the leukaemia.

The polymerase chain reaction (PCR) blood test is able to detect one leukaemia cell in up to one million (1,000,000) normal blood cells. It does this by measuring a substance (transcript) made by the BCR-ABL gene in the leukaemia cells.

When you’re first diagnosed, and about every three months afterwards, you’ll have blood taken for PCR testing.

Because it’s so sensitive, the PCR test may continue to show up signs of leukaemia for many months after your treatment starts, even though you’re feeling well.

There are two different levels of molecular response:

• A complete molecular response means the PCR test can’t detect any of the BCR-ABL gene in your blood.
• A major molecular response is when there are tiny amounts of the BCR-ABL gene in the blood.

Continuing to take treatment Back to top

You’ll usually keep taking the TK inhibitor for as long as it’s working to control the leukaemia. This is important even if your PCR blood tests don’t show any signs of leukaemia.

There’s a risk that if you stop treatment or change your dose without your doctor’s advice, leukaemia cells may develop again and not respond as well to treatment in the future.

It can be difficult to remember to take your tablets every day. You may find it helps to make taking them part of your daily routine so it becomes a habit. Here are some ideas:

• Take your tablets at the same time you usually do something else - for example, when you eat your lunch or dinner.
• Put your tablets in a place where you’ll see them every day.
• Mark off each dose you take on a calendar or use a 7-day pill container.
• Keep a supply of tablets with you when you travel and take your medicine in your carry-on luggage when you fly.

Your prescriptions will be organised through the hospital, so you may have to go there to collect the tablets each time you need more. Tell your doctor, nurse or pharmacist if it’s difficult for you to get to the hospital