Check Up #24 - Complete response, incomplete or partial response to a cancer treatment; stable disease and progressive disease

There are varying degrees in the response of a cancerous tumour to a treatment. A complete response corresponds to the disappearance of all detectable signs of cancer in the body, while a partial or incomplete response is a decrease in the size of the tumour or in the amount of cancer in the body. To be considered a partial response, the measurable size of the tumor has to be reduced by at least 30% to 50% due to the treatment. 

The evaluation of the response to a treatment can be clinical (through imaging, mainly) or pathological (based on a tissue biopsy, which is more precise). However, both these methods have limitations, and there might always be residual cancer cells left in the body, which may later begin to proliferate again: the cancer may return after a while. That is why doctors, even in the case of a complete response, have to closely watch for signs of disease recurrence and prefer to say the patient is “in remission” rather than “cured”. Only if a patient remains in “complete remission” for five years or more, may some doctors say that the patient is cured.

When there is more than a 20% growth in the size or spread of the tumour since the beginning of the treatment, the response does not fill the criteria to be considered partial and the cancer is classified as a Progressive Disease. This is another way of saying that cancer does not respond to the treatment.

On the other hand, if the tumour reduction induced by the treatment is less than 30% (so that the response does not meet the criteria to be considered partial), but at the same time the increase of the cancer is still smaller than 20% (which means it does not meet the criteria for calling it progressive disease), the cancer is classified as being a Stable Disease.

Sources:

https://www.cancer.gov/
https://www.cancer.org
https://cancer.ca/
https://www.verywellhealth.com
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4844002

By Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.

Reviewed by: Dr. Alípio Araújo, Deputy-director of the Champalimaud Clinical Centre.