Standard criteria are used to describe a tumor's response to a therapeutic intervention. This can aid in the communication of findings and to help determine the next steps to take. The criteria apply to chemo-, radiation and immunologic therapy.
Measurements of tumor burden:
(1) diameter of one or more selected lesions
(2) volume of one or more lesions
(3) levels of serum markers
Protocol:
(1) Determine the tumor burden at baseline before therapy.
(2) Determine the tumor burden 4 weeks after therapy.
Finding
Response
disappearance of all evidence of tumor
complete remission
decrease in total size of measured lesions >= 50%
partial response
decrease in total size of measured lesions 25-49%
minor response
no significant change in size and no new lesions
stable disease
increase >= 25% in one or more measurable lesions
progressive disease
appearance of new lesions
progressive disease
where:
• A change in tumor size with a < 25% increase or decrease would be classed as stable disease.
Limitations:
• Since some therapies can be extended out to several days or weeks, the time at which to measure response needs to be standardized. Usually it is based on completion of a course.
• These criteria work when all of the tumor foci behave similarly (all regress, all are stable or all progress). If some foci enlarge and some regress, there may be some confusion.
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