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genegeek CAN

Hi. I'm genegeek (aka Catherine Anderson). Thanks for stopping by. I realized during my PostDoc that I preferred learning and explaining new results to doing science so I started a non-traditional career of teaching and outreach. I'll be using this space to explore public perception of genetics and other cool molecular biology stuff.

My posts are presented as opinion and commentary and do not represent the views of LabSpaces Productions, LLC, my employer, or my educational institution.

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Monday, October 4, 2010

This post is in honour of 007, the unbeatable secret accountant, who is getting ready to join the Terry Fox Challenge - after she finds out about options for chemo.

I have several friends around the world who are dealing with cancer diagnoses and they have had some general questions about the treatment options. None of them are science experts and instead of writing the same email to everyone, I thought I would try a general post.

Warning: this post is not advice for anyone and it is a general introduction to the topic. I won't try to explain the specifics of any particular drug because that is beyond my level of expertise.

What is chemotherapy? Why take it?

It depends who you ask. Many patients will say, 'poison'. But really, the term means 'drug therapy' although we generally use it in Canada to mean drugs to kill cancer cells. Please note that chemo is used in many diseases but I'll focus on cancer applications as that is where most of the questions have started.

In cancer treatment, chemo is usually offered when there is a concern that there might be tumour cells that were not or can not be removed with surgery or radiation. For example, my grandmother had inoperable lung cancer so she took chemotherapy to shrink her tumours and help her breathe. Another reason to take chemotherapy is to knock down any new starter tumours. You see, tumours like to grow and if they run out of space in one area, they may send out a few cells to colonize new areas. Taking chemotherapy can attack these new spots before the new growth is big enough to see through various scans.

Old school chemo

The main way that traditional chemotherapy works is to kill fast growing cells. Tumours generally grow faster than the tissue where they started (how you get a bump or tumour) so you want to stop this extra growth. But a fast growing kidney cell (not an organ that grows a lot) isn't necessarily that fast when compared to a skin cell. We shed our skin every 30 days (or so the local Science Centre tells me) and our skin divides and grows pretty fast. Other fast growing tissues are hair and gut/mouth linings. So, if you take a drug that kills fast growing cells, it can attack hair, skin, and gut linings = the common side effects seen in chemotherapy.

There are many ways that this older chemotherapy can work - including messing up the DNA of a cell. This can lead to mutations that give an increased risk of cancers in the future because some mutations stick around. But this is a long term complication and the most important thing is to survive the cancer and treatment.

Newer chemo

My field of expertise is genetics and studying tumours has not only given us ways to help predict people's risk of cancer but is leading to some therapies for specific cancers. Researchers have been comparing normal tissue to tumours and trying to develop specific drugs. One way of doing this is with monoclonal antibodies...I know, I said no mechanisms or jargon...basically, monoclonal means all the same and antibodies are neutralizing proteins. So, if you know a tumour makes something that normal tissue doesn't have, an antibody can be used to target and destroy the cancerous tissue. Monoclonal antibodies are not technically chemo but they are often discussed as chemo by patients - and the basic mechanism can be visualized - so I included them in this post.

Again, there are many different ways that this newer targeting chemo can work and one of the issues is that you need to know what targets are available. Tumours aren't static and the targets can change throughout the different stages.

So what to do?

Talk to your doctor and other members of the health care team. In Vancouver, the BC Cancer Agency has fantastic resources for patients and family members: counsellors, volunteer drivers, dentists, help with diet...please ask for help if needed. Your doctor will have a suggested treatment plan to discuss with you. My one bit of true advice: write down your questions so that you won't forget anything. Nothing is too silly to ask!

I hope this was helpful as a very brief introduction. To those who know more on the topic, please let me know if I said something incorrect.

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Prabodh Kandala
Texas Tech University Health Science Center
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Good one Catherine. I would like to add to it that Chemotherapy need not necessarily refer to treating cancer alone. Antibacterial, Antifungal etc., does come under chemotherapy. Apologies if the focus of this post is on Cancer.

Genomic Repairman
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A lot of early chemotherapeutics were based upon nitrogen mustard, a popular chemical warfare agent used in World War I.  The general principal is that they link or rather duct tape the DNA together and this is an extremely toxic form of damage to the cells because you have to be able to separate out the two strands of DNA in order to synthesize new DNA.  Nitrogen mustard is still in use today as Prabodh is right, we use it to treat skin warts, but we have developed more sophisticated chemotherapeutics, like Cisplatin.  These agents that crosslink the DNA are repaired by a pathway called Fanconi Anemia pathway.  This pathway was discovered in patients with Fanconi Anemia (FA) who have bone marrow failure, thumb abnormalities, and lastly are extremely sensitive to cross-linking agents.

Catherine does a dynamite job of bringing up  monoclonal antibodies but these are technically not chemotherapeutics but are used as an adjunct therapy in combination with chemotherapy.

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Great info and points!  I agree - I'll fix up the post to reflect your comments later today.

Chemo is definitely used in more than cancer but when the average person hears chemo, they think cancer so I wrote that post for them. Monoclonal antibodies are not technically chemo but get lumped into that class by patients and clinicians so I included them here.

Thanks for the explanations!

Washington University School of Medicine
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Thanks for the great post. I'll keep this one in my back pocket for the next time I'm asked a question about chemo.

Prabodh Kandala
Texas Tech University Health Science Center
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I agree with you Catherine. I always related Chemo to Cancer until I learnt that antibiotics etc., to come under Chemotherapy. Having said that, I would say that this post will clearly explain about Chemotherapy and Cancer to a person who is not from cancer field.

UC Davis
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Great post, and interesting discussion about what falls under the umbrella of chemotherapy. I also would always have related it to cancer.

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