First of all THANK YOU for being here. Your mission meets a need quite precisely.
My question is a request for a discussion of the variation within cancer cells, in particular EGFR mutations and cancer stem cells as it relates to treatment. I hope this is focused enough to be considered one question.
In general how much variation is there between cancer cells by individual? between individuals? Does this vary by type (I'm most interested in NSCLC) or stage? Does the organization or lack thereof create differentiation between cancer cells?
My dad has the EGFR19 mutation, does that mean all of his cancer cells have that marker? If not, does the test measure proportions and does this change over time or as a result of treatment?
I've found very few mentions of cancer stem cells. Is it known what proportion of tumors are stem cells? What kills them or makes them harmless? I understand that stem cells do not divide rapidly therefor not affected by the chemo/radiation. Are they also not impacted by the new TKI class of drugs? Do stem cells spread through the lymphatic system? Are stem cells the only ones present when a cancer is said to be stable?
Summary of experience behind my question:
My father recently completed chemo/radiation for stage 3B NSCLC and the mass (originally measured as 9x7x11cm) is still there. Also the rate of response to the combined treatment dropped over time. The radiologist told him not to expect the initial 75% shrinkage to continue. Dad was thinking that the remaining cells of the mass might be closer to blood flow and therefor stronger, but at the final appointment the Dr referred to them as cancer stem cells which do not divide rapidly and are therefor not affected by the chemo/radiation.
Reply # - October 18, 2015, 07:42 AM
Hi Amy,
Hi Amy,
Welcome to GRACE. You have asked some interesting questions, and I'll try to provide a summary of what is currently known.
Since cancer is not a specific disease but a word to generally describe a group of many diseases that share one important factor - mutated cells which grow and divide in an uncontrolled way, unlike normal cells which have a specific life cycle. A wide range of influences can cause normal cells to mutate, such as exposure to tobacco and other carcinogenic substances, and although there are similarities between the cancer cells of patients with a particular EGFR mutation, for example, everyone's cancer is to a certain extent unique.
Adding to the complexity and treatment challenge is the fact that each person's cancer may have varied causes and mutations, such that even in the presence of an activating EGFR mutation such as exon 19, some of the cells may not harbor this mutation and may not respond to treatment. In addition, for some patients even the EGFR-mutated cells don't respond to an EGFR TKI, and the cause of that is not fully understood. Also, treatment with targeted therapy can lead to further, resistant mutations such as T790M.
The role of cancer stem cells is not yet well-understood, and I don't think you can necessarily say that your father's remaining cancer cells are stem cells. Some cancer cells, for whatever reason, do not respond to treatment. Although it is in the context of head and neck cancer, this post by Dr. Jimeno may help provide insight into the current state of knowledge about cancer stem cells.
JimC
Forum moderator