What is Composite Complete Remission (CRc) in cancer research?
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Composite Complete Remission (CRc) is the sum of
- Complete Remission (CR), i.e. the primary disease is no longer active and the blood counts have normalized.
- Complete Remission with incomplete hematological recovery (CRi), i.e. the primary disease is no longer active but at least one of the blood cell lines has not recovered to normal levels.
- *Complete Remission with incomplete platelet recovery (CRp),*i.e. the primary disease is no longer active but the platelet count has not recovered to normal levels.
Note that some authors include CRp in CRi while others list it separately.
Source: NCT00989261: Efficacy Study for AC220 to Treat Acute Myeloid Leukemia (AML) (ACE) (CRc = CR + CRi) or Cortes et al (2018) (CRc = CR + CRi + CRp)
Example:
If you have a CR rate of $50%$ and and a CRi rate of $5%$, the CRc rate is $50% + 5% = 55%$. If you have a CR rate of $50%$ and and a CRi rate of $4%$ and a CRp rate or $2%$, the CRc rate is $50% + 4% + 2% = 56%$.
How is full recovery of the blood cell lines defined?
This depends on the type of primary disease (and sometimes there are slightly conflicting definitions).
For example, Döhner et al (2017) present these numbers for CRi in acute myeloid leukemia:
- Neutrophils $\leq \frac{1000}{\mu l}$ (in other words, grade 2 or higher grade neutropenia)
- Platelets $\leq \frac{100,000}{\mu l}$
If these criteria for CRi are not fulfilled (even if the blood counts have not reached normal levels), the state is defined as CR.
Note that in this case there are no limits for *erythrocyte count recovery,*hence the patient might require blood transfusions due to low levels of hemoglobin even though according to this definition he is considered to be in a state of complete remission (CR).
The meaning of CR as opposed to CRi, CRp or CRc is therefore more relevant as endpoint of a medical study, but not so much as indicator that the patient has recovered to a point that allows discontinuation of treatment.