Dumb Question about response rates

[Elaine]

Does a response rate of say 10 per cent mean that 10 per cent of people have a response (shrinkage etc) or does it mean that tumors shrink by 10 per cent?

[Angie Daughter of Bill]

Hmmmmmmmm......are you talking about a medication that has a 10% response rate? If so, it sounds to me like the medication would work for 10% of the people who took it. ?????? JOHN>>>>>>HELLOOOOOO???? Maybe John will jump in here and help you on this.

Angie

[karenl]

Well Elaine, just to confuse the issue even more, my reaction was that it meant a 10% response rate in tumour size. Just a guess. I'm sure someone out there knows for sure!!

Karen

[JaneC]

My understanding is that 10% of the people will respond to the drug. My doctor told me that response is considered to be "shrinkage" or even just "no new growth".

Jane

[jamie]

Elaine,

Guess its my turn to add to the mass confusion.... I think a 10% response rate means in tumor its shrinkage, and in meds its people who have a response to it. Im no doctor, and not sure which it could be

Jamie

[Elaine]

Well I think that JaneC is right, but I got myself confused last night reading something. But it has been my understanding that if a chemo has a response rate of 13 per cent (which is about average for most chemos I have read about) that means only 13 out of 100 will have ANY benefit from the drug??? Oh John, pls let us know what the right answer is.

thanks

elaine

[mhutch1366]

Elaine,

A thirteen percent response rate would be a "significant response" by 13% of the participants or of the group of people participating.

Note: Trials are often very narrow in who they accept, because they want to be able to clearly see if there is a response solely due to treatment, not maybe something else too. So this may not be a general population, but a smaller subset.

"significant response" is one deemed to be statistically significant, which depends on the size of changes being measured as well as the number of people in the study. The more measurements, the higher the confidence level, which means the more accurate "significant" is considered to be.

Reading medical research is loaded with assumptions and caveats.

Hope that helps.

MaryAnn

[john]

12 STATISTICAL CONSIDERATIONS

12.1 Survival

Survival is defined as the time from date of randomization to date of death. In the absence of confirmation of death, survival time will be censored at the last date of follow-up.

12.2 Objective Tumor Response Rate

Objective response rate is defined as the proportion of patients who have any evidence of objective CR or PR.

Confirmed objective response rate is defined as the proportion of patients who have evidence of objective CR or PR that is confirmed by follow-up tumor assessment greater than or equal to 4 weeks from the tumor assessment documenting the initial response.

12.3 Time to Objective Tumor Response

Time to response is defined as the time from date of randomization to first objective documentation of response.

12.4 Duration of Objective Tumor Response

Duration of response is defined as the date of first objective documentation of response until the first objective documentation of tumor progression or death due to tumor progression in the absence of previous documentation of tumor progression. For patients with responding tumors who do not have objective evidence of tumor progression and who are removed from study, who die of causes not related to pancreatic cancer, or who are given antitumor treatment other than the study treatment, duration of response will be censored. Patients who die of unknown causes will be considered to have experienced tumor progression.

12.5 Time to Objective Tumor Progression

Time to objective tumor progression is defined as the time from date of randomization to first objective documentation of tumor progression or death due to tumor progression in the absence of previous documentation of tumor progression. For patients who do not have objective evidence of tumor progression and who are removed from study, who die of causes not related to pancreatic cancer, or who are given antitumor treatment other than the study treatment, time to tumor progression will be censored. Patients who die of unknown causes will be considered to have experienced tumor progression. A CA19-9 increase meeting criteria for tumor marker progression does not constitute adequate objective evidence of tumor progression. However, such a CA 19-9 increase should prompt a repeat radiographic evaluation to document whether or not objective tumor progression has occurred.

12.6 Time to Treatment Failure

Time to treatment failure is defined as the time from date of randomization to first objective documentation of tumor progression, or off-treatment date, or death, whichever comes first. Patients who are still on treatment at the time of the analysis and patients who are removed from therapy by their physicians during an objective response and who, at the off-treatment date, have no evidence of objective tumor progression will not be considered to have experienced treatment failure, unless the withdrawal is due to the occurrence of a medical event. For these patients, time to treatment failure will be censored at the off-study date. Censoring for time to treatment failure will also be performed in those patients who are given antitumor treatment other than the study treatment before the first objective tumor progression, off-study date, or death. A CA19-9 increase meeting criteria for tumor marker progression does not constitute adequate objective evidence of treatment failure. However, such a CA19-9 increase should prompt a repeat radiographic evaluation to document whether or not objective tumor progression (and thus treatment failure) has occurred.

[Elaine]

Cr equals what?

PR equals progression?

Is 13 per cent considered good response for lc?

Thanks for this invaluable resourse John.

[mhutch1366]

Elaine,

CR is complete response, PR is partial response.

The example john gave is from a protocol on pancreatic cancer.

Response rate depends...... on a lot of things. It's all relative. I do know that when phase ii trials show a response rate of 5-10%, it is not considered encouraging to the industry...generally.... for that treatment....

For example, in my case...

The original protocol/ clinical trial phase II I benefitted by showed a response rate of about 50%, defined as 50% unresectable tumor after surgery (=dead cells) with 50% metastases-free liver after 12 months.

These results were considered good enough to STOP the phase II trials, skip the phase III trials altogether, and allow immediate implementation of this protocol ( chemo/radiation, then surgery, then chemo) for pancoast tumors, which are considered rare.

[JaneC]

Elaine,

With all of these variations in definitions for response rate, this doesn't seem like a dumb question at all .

Jane