Response Means in Cancer Treatment

Doctor reading chest xrays
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After treatment completion, an individual is generally assessed for a response after a period of time to allow the maximal regression of the tumor. At the end of that period, if there is some disease remaining but a reduction of disease by 30% or more on clinical examination or x-rays and scans, it is called partial response (or partial regression).

What Does a Partial Response Mean?

Partial response (PR) implies that further treatment will probably be required to attempt a cure. In some slow-growing tumors (including low-grade lymphomas) no further treatment may be immediately necessary until the disease starts increasing in size again.

Understanding Terms Describing Cancer Treatment

There are so many terms used to describe cancer treatment that it gets terribly confusing. Thankfully many of these means about the same thing. Some of these include:

  • Complete response means that cancer has responded to treatment and no evidence of cancer can be seen on imaging studies.
  • Complete remission means all target lesions have disappeared. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to <10 mm.
  • Partial response (PR): At least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters.
  • Partial remission means the same things as a partial response.
  • NED (No evidence of disease) means exactly that, and can be the same as a complete response or a complete remission. Imaging studies are "normal" but that doesn't mean cancer is gone, just that no evidence can be found on imaging studies that we currently have.
  • Progressive disease means that cancer has at least a 20% increase in the sum of diameters of target lesions, taking as reference the smallest sum on study (this includes the baseline sum if that is the smallest on study). In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of at least 5 mm. (Note: the appearance of one or more new lesions is also considered progression). 
  • Stable disease means that a tumor has essentially not changed, and there is neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD, taking as reference the smallest sum diameters while on study. Stable disease could still mean that cancer has responded, for example, if cancer would have been expected to get worse but has stayed the same.
  • Recurrence means that cancer has reappeared after a period of being in remission or being NED.
  • Relapse means the same thing as recurrence.

Making Plans After a Partial Response

As noted above, what happens after a partial response is largely dependent upon the type of cancer you have. For the same reason, a partial response could be particularly good or particularly bad. It all depends not only on your specific cancer but on the molecular profile of your specific cancer. If you are searching for information on your cancer keep this in mind.

Numbers and statistics online do not take into account the tremendous variations between people, even those with the same type of cancer. In addition, what you read online will often refer to statistics. Statistics are numbers not people and are averages. Very few people are "average."

And statistics are put together using data from how people with your cancer responded in the past to treatment. These numbers do not take into account any new treatments since the time the data was recorded, so they may not be relevant to you.

Recurrence of Leukemia or Lymphoma

We are talking about the partial response, but in the back of many of our minds is the fear of recurrence. How can you cope with the fear of recurrence or the fear of progression? What happens when leukemia or lymphoma recur?

Many people find it helpful to talk about the elephant in the room. Open up and expose these fears. Sometimes talking to a counselor is helpful if you catch yourself worrying. Thankfully we live at a time when survival rates for many cancers are improving, and new treatments are being approved more rapidly than ever.

Clinical trials are in progress not only for treatments we hope will improve survival but for treatments with fewer side effects than in the past.

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  • National Cancer Institute. Imaging Response Criteria.