Sweeping up

Twenty days in the hospital and twenty infusions, the last of which was today. The last three infusions have been a dose of Rituxan weekly. The first dose was at the end of my trip at sea while I was still aboard the ship. Rituxan is a chimeric - part human part mouse - antibody that binds to B cells bearing the cell surface marker CD 20 in the blood, lymph and bone. The antibody bound B cells then begin to die off, through a process directed by the immune system. Rituxan does not bind to the progenitors of those B cells, the hematapoetic stem cells.

 

Although Rituxan is cytotoxic ( kills cells) to B cells with CD 20 surface proteins, it is not "chemotherapy". The antibody- antigen binding is highly specific targeting B cells. Chemotherapy targets actively growing cells of the body. The collateral damage of chemotherapy is that non- malignant cells are also damaged. You lose your hair. Your mouth, esophagus, and gut hurt because these rapidly dividing cells are also taken out by the chemotherapy. Most chemotherapies do not cross the blood brain barrier. There is experimental evidence that Rituxan plus CHOP crosses the barrier into the cereborspinal fluid, significantly reducing the incidence of CSF cancers (http://www.rituxan.com/hem/hcp/mechanism-action/index.htm). When I was diagnosed 10 years ago, Rituxan was still in clinical trials. The first antibody to be approved in cancer therapy, in combination with traditional chemotherapies it prolongs overall survival, the gold standard for therapy. Rituxan does have a dark side. It can produce such a rapid die off of tumour cells that the blood floods with the toxic contents of millions of cells disrupting blood chemistry, 'tumor lysis syndrome'. Patients can also have a strong allergic like reaction to the murine portion of the antibody. Rituxan can also re- activate dormant hepatitis B. Not surprising as it reduces an important component of your immune system - B cells those that are malignant and those providing immune protection. Most people react to Rituxan on the first infusion; administration of pre-meds that rein in the infusion rate, gradual increase of infusion rate, and close monitoring of vitals during infusion make clinical management of reactions possible.

Doctors administer Rituxan with chemotherapy, use it as a in vivo purge when "priming" the body for transplant, use it on the first day of hi dose chemotherapy, and then use it to sweep up the blood of any residual malignancy post transplant.

Shortly after 1 PM, both Dr. T and Richard (remember Cerberus) surprised D and I with a visit in the infusion room. After asking if I was doing OK, he said the nurses called and said my body surface area - the metric used to determine all infusion mixes - had changed due to weight loss.

" You loosing weight?"

" At my lowest last week, back up to 170" .

" The nurses wanted to know if I wanted to change the rate. I told them full strentgh because a life half lived leaves room for regret. Want none of that around here".

He left the room laughing.

Those interested in the proposed mechanisms of how Rituxan works should take a look at http://www.rituxan.com/hem/hcp/mechanism-action/index.htm.