Response to treatment: the role of q-PCR testing

Currently q-PCR is the most accurate test used to monitor response to a particular therapy and to detect any significant rise in BCR-ABL1 transcripts. Test results are used to make evidence based decisions in the context of the 2013 ELNet recommendations and NCCN Guidelines for the treatment of Ph+ CML.

Both ELNet and NCCN identify a major molecular response (MMR / MR3) within 12 months to be an optimal response and a realistic goal of
TKI therapy.

Under the best lab conditions q-PCR can detect as little as 0.001%IS (MR5) BCR-ABL1 transcripts in a sample, allowing for better detection of residual disease as well as the identification of patients who may be at risk of treatment failure or suboptimal response. Consistently rising levels of BCR-ABL1 transcripts identifies a need to address a probable cause, such as primary or acquired resistance or the possible lack of adherence to therapy.

Regularly missing more than three daily doses in one month is likely to affect optimal responses to therapy. In patients whose adherence to therapy was monitored, those whose adherence rate was greater than 90%, meaning that they took more than 90% of their prescribed doses in a month, were more likely to achieve the lower molecular levels of remission required for optimal response, such as MR3; MR4.5 or lower.