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Showing posts from March, 2012

RB genetics ... What would happen in Ethiopia?

Retinoblastoma is a complicated business. It’s not uncommon for us to ask a question of a doctor, only to be told, "Ah, that's a question for Dr X."
The team that manages Asa’s treatment includes ophthalmologists, oncologists, and geneticists – each of whom contributes a piece of the puzzle.
As it turns out, some of our questions about the causes of Rb and its long-term implications are questions for geneticists.
Genetics is relevant here because, given that both Asa's eyes are affected, there's a very high likelihood that it’s due to a mutation in a gene known as RB1. 
Dr Rosser, a geneticist at Great Ormond Street Hospital, helped us understand how this mutation might have arisen, and what its implications are.
Since neither Selam nor I have relatives with Rb, the most likely way Asa got the mutation is through a random change in the sperm or egg that made him.
As Dr Rosser explained: "Every time a cell divides, 40,000 genes get copied.”
“All of us have 20-50 …

"What's the prognosis?"

The examination under anaesthetic last week revealed that the tumours in Asa’s eyes have halved in size in the left eye and more than halved in the right eye since he began chemo.

The retcam images show how the tumours have shrunk, and also changes in texture from diffuse blobs to gnarly, calcified masses.
This is encouraging, but there’s still a lot of cause for concern.
For one thing, systemic chemo has its greatest effects in the first cycles.So unfortunately we can’t expect this rate of shrinkage to continue through the remaining 4 cycles of chemo. As the ophthalmologist told us, the remaining chemotherapy is to prevent relapse.
The other cause for concern is seeding.
In the images, the constellations of little spots around the tumours are “seeds”: tumours-in-the-making that, if they’re not attacked, will grow bigger.These are a worry because (a) they’re so many of them and (b) they’re not well supplied by blood vessels, the way the big tumours were, so they won’t respond as well to s…
Last week Asa's blood counts -- specifically, his neutrophil count -- didn't return to normal in time for him to undergo his eye exam and begin the 3rd round of chemo. Our medical appointments were pushed back a week, and in the meantime we've enjoyed a lull, waiting things out, and hoping the neutrophils are climbing, but also getting more time and space to reflect on life than we've had for the last couple of months.
The first time Asa’s neutrophils fell below 1.0, during the first cycle of chemo, we were thrown into a panic, and half expected him to break out in spots or immediately develop a fever.Since then we’ve learned that the danger is manageable.
Neutrophils are one component of white blood cells, which indicate your body's ability to withstand infections.The chemo drugs Asa is taking inhibit his ability to produce white blood cells, and consequently his immune system is seriously depressed for a while after each dose.During the first cycle they plunged aft…