Many questions arise when dealing with cancer. None of them easy. Some without an answer. Others, answered in a way you wish was different. Never a shortage of questions but always a lack of answers. I myself have asked this question ” How long does chemotherapy take to work?”. Just like always this question probably doesn’t have the answer you really want. But when do questions about cancer really do anyways? That’s what research is all about. Finding the truth. Finding answers, including the good and the bad.
How Long Does Chemotherapy Take to Work?
The question is a very complicated one due to all the variables involved. Many things can change this answer drastically from one person to another. Things like, type of cancer, cancer stage, type of chemotherapy, cancer aggression, etc. The list goes on and on. Not enough research has been done to be able to take every variable into consideration to predict timing. Which is why answering the question “How long does chemotherapy take to work?’ is so hard. The standard amount of time used to evaluate Chemotherapy response is anywhere from 1 to 3 cycles. Every chemotherapy has a different duration of cycles. Each cycle can be anywhere from days to weeks. The most common being every 3 weeks or monthly. This equates to checking response every 3 months or so as the standard. But remember this highly depends on the type of chemotherapy and cancer you have. This is just the standard time to CHECK for response, not the time it actually takes Chemotherapy to start working.
Size Response Vs Actual Response.
The most common method used to check cancer response is RECIST. It stands for Response Evaluation Criteria In Solid Tumors. This method uses size to evaluate chemotherapy response. But size is not a guarantee that the chemotherapy was effective or not. Tumors in very rare circumstances can get larger for a limited amount of time before they get smaller. Also a small decrease in size might not be noticeable. An Advanced non-small cell lung cancer study of 362 patients showed early response after the second cycle. Another Lung cancer clinical study with 25 patients mostly observed a chemotherapy response after 2 cycles based on tumor size as well. But this only partially answers the question”How long does chemotherapy take to work?”. If we want to get anymore specific then that we have to look at non-human studies.
A Xenograft Study using human breast cancer tested response with contrast enhanced ultrasound. Study was able to see chemotherapy effectiveness as early as day 2 even though size did not change until day 6. This reinforces the notion that size is not a full proof indication of chemotherapy effectiveness. At least not at the early stages of treatment. So how does this effect the question ” How long does chemotherapy take to work?”. It actually transforms one question into two.
How long does chemotherapy take to work in respect to tumor size? Even though no definitive answer can be found we can see that 2 cycles is a common time period. This lines up pretty well with the standard method of 2-3 cycles before you evaluate chemotherapy effectiveness. Doing tests any sooner might not be effective since most test looks for tumor dimensions to gauge response. Of course this is far from a perfect estimate, but its as close as we can get with the information available today. Future studies will be able to provide a deeper look with more accurate data so a better conclusion can be reached.
How long does Chemotherapy take to work regardless of tumor size? The only thing we know for sure is that many changes happen inside the tumor before changes in size are noticeable. The Xenograft study showed a chemotherapy response about 33% earlier then what standard methods would show. So that potentially means chemotherapy can be working 33% earlier then we can notice by size alone. So really the question is not if, but when, and how early do these changes happen. Unfortunately this will not be pursued until more studies can prove that RECIST is outdated and is no longer accurate enough for cancer patients. Until then, that’s the best answer we have.