Can someone explain log reduction to me?

Hi Jeanette,

Log reduction is a mathematical term (so is log increase).

A 1 log reduction means 10 times smaller
A 2 log reduction means 100 times smaller
A 3 log reduction means 1000 times smaller

In the CML world we use it to see how well we are doing with respect to our treatment.

You compare your current results to the amount of CML you had when you were first diagnosed.

If you have a 3 log reduction it means that the amount of leukemia you had in your system at diagnosis has been reduced 1000 fold.

The numbers are produced by a PCR test.

Molecular remission means that the PCR test cannot detect any CML in your body. It doesn't mean that you are free from CML, it simply means that the PCR test couldn't detect any.

In terms of the log reduction, molecular remission occurs at the 5 log reduction stage.

Some milestones.

CCR - Complete Cytogenic Response - 2 log reduction
MMR - Major Molecular Response - 3 log reduction
- this is the level that you want to attain. It has been shown that
once you achieve this level of remission, there is virtually no chance
that you will ever relapse.
PCRU PCR Undetectible.

Make sure that you get your own copy of each of the results. You may not understand one report, but when you comepare two of them it is pretty evident as to what is happening.

Zavie

Please write me at zmiller@sympatico.ca I have some comments about the dose that you are receiving.

Zavie Miller (age 69)
67 Shoreham Avenue
Ottawa, Canada, K2G 3X3
dxd AUG/99
INF OCT/99 to FEB/00, CHF
No meds FEB/00 to JAN/01
Gleevec since MAR/27/01 (400 mg)
CCR SEP/01. #102 in Zero Club
2.8 log reduction Sep/05
3.0 log reduction Jan/06
2.9 log reduction Feb/07
3.2 log reduction Jun/07
3.6 log reduction Sep/07
e-mail: zmiller@sympatico.ca
Tel: 613-726-1117
Fax: 309-296-0807
Cell: 613-202-0204
Yahoo ID: zaviem
YM: zaviemiller
Skype: Zavie Miller

Hi Jeanette,
if you click on FAQ/Glossary button you will find an explanation of PCR's and how to interpret them. This was written by Anjana who runs the Asian cml support group (there is a link to her group from this site -go to 'links'). In this article, which she very kindly shared with us, Anjana explains about pcr's both qualatative-(positive or negative?) and quantative-(how much-at what level?) very clearly and in patient friendly terms.
it may be good to read the whole article but i have copied a snip from it which explains about log reductions, see below:

"....What about 3 log reduction? Both PCR negativity and 3 log reductions are goals, but as long as the PCR is stable or decreasing, IM (Glivec) is having disease control and there should be no worry......

....Ask for the sensitivity of the RtQPCR or real-time quantitative PCR (which shows the % of bcr/abl) and ensure that it can at least detect 1 leukaemic cell in 100,000 normal ones.
Then when you get your PCR value, ask what log reduction it is.
Remember, your value may be different from others doing PCRs in other labs. After that, track the PCR value in order to get the trend.

It is important to note that at very low PCR level there may be some variation in readings because of the nature of the technique and you should not worry if you become PCR negative and then have a low positive PCR value.
Remember, serial monitoring is the key and it is the 'trend' over time that is important.

A 3 log reduction or major molecular remission (MMR) by PCR may be desirable because from the Glivec Phase III trials, it was found that those patients who had this low level of disease had 100% progression-free survival 2 years after start of Glivec therapy."

this article was written some time ago and the prediction that consistantly low molecular levels of disease do predict progression free survival was correct. the IRIS trials data at 6 years shows that the percentage of patients who relapse is very low and is improving (getting even lower) year on year.
Also, PCR techniques have improved and many labs (such as the one at Hammersmith London, and the one at Mannheim, Germany amongst others) are particularly sensitive and can detect very low levels of disease.

Sandy

Dear Sandy

Thank you very much.
I am learning loads.
It's very interesting and very very positive news.

jeannette

Dear Julie,
first let me say that it is great news that your son has achieved molecular remission.
as for your question, as long as he can tolerate the adult dose (paedratric doses tend to be lower owing to less body weight/size etc.) i am sure his/your doctor will continue giving him 400mg indefinitely as his PCR levels have shown an improved response, but it may be best to discuss the long term with her/him.
i can imagine how much you must worry for the future. it must be so hard for you as a parent.
but there are many advances in CML therapy coming down the line.
best wishes,
Sandy ;o)