First chemotherapy

Chemotherapy comes in all sorts of guises. The sort you get for abdominal cancer is very different from what you get for CLL.

The ‘chlorambucil’ of GI malignancies is 5-fluorouracil. How it works is this: DNA has four bases – adenine, cytosine, guanine and thymidine, RNA is very similar but instead of thymidine it has uracil. The body’s only source of thymidine in to make it from uracil. The idea is to feed the body modified uracil, with a fluorine atom stuck on so that when it is converted to thymidine, the stuck on fluorine prevents the DNA from replicating and therefore the cancer cell cannot divide.

The enzyme that does the conversion is called thymidine synthetase and the co-enzyme for the reaction is folinic acid. The idea is that giving excess folinic acid forces the reaction down this pathway and enhances the effect. Clinical trials have shown that this cheap vitamin greatly improves the performance of the drug.

The second drug is oxaliplatin which is one of a series of platinum compounds discovered when researchers tried passing an electric current through cancer cells in tissue culture. They found that the cancer cells died around the platinum electrodes. One of these drugs was developed by a boy in my class at school when he was doing his PhD. He is now a professor at Princeton. He was always cleverer than I.

This combination has some strange side effects. As well as marrow suppression, which is very common with all chemotherapy it can cause diarrhea and vomiting, but there are medicines to prevent these. The really strange thing is cold induced pins and needles. This means no cold drinks or going to the fridge. Even getting a clean shirt from the drawer can trigger it – put it in the airing cupboard first.

This in fact is the only side effect that I have had – it is disconcerting rather than unpleasant.

The other interesting thing is how the 5-fluorouracil is delivered. It is pumped in at a constant rate over 46 hours by a pump with no moving parts. The drug is contained in a thick walled balloon with a slow puncture, which deflates in exactly 46 hours. Very clever these Americans.

The pump is disconnected tomorrow and restarts in two weeks. The other noticeable change in me is the effect of one of the anti-sickness pills. Dexamethasone is a very strong steroid drug used for all sorts of anti-cancer effects, but also to prevent vomiting. It made me as high as a kite. I didn’t dare blog yesterday when under its full influence. Goodness knows what I said to my pastor when he came to visit, Garrulous isn’t in it.