Why does TX-history matter? Why does TX-duration matter? Why does cirrhosis?

[sickpuppy]

Basically I don't understand why having an interferon TX-history matters when the new drugs are acting through a different mechanism. Does anyone have any articles that can shed some light on this?

Also, why does the TX duration matter if in most cases the virus becomes undetectable (so it's gone) at week 4? Why do we need to keep it up for another 8 or 20 weeks?

Why does having cirrhosis matter? I mean - if a person without cirrhosis becomes undetectable, and a person with cirrhosis also becomes undetectable at the same time, then why does the one without cirrhosis has a better chance of SVR in the end?

[KimInTheForest]

Also, why does the TX duration matter if in most cases the virus becomes undetectable (so it's gone) at week 4? Why do we need to keep it up for another 8 or 20 weeks?

The "undetected" results we get from our blood work (which commonly happens at 4 weeks with the new drugs) only means there is no virus found in a tiny amount of our circulating blood collected in a vial. It gives no insight into virus still remaining in the liver itself or in lymphatic tissue, which Hep C virus also has an affinity for. So we keep taking the drugs for a set duration on the assumption that after that point there is no live virus left. And the treatment duration seems to be a fairly accurate estimate, since the large majority of people on the new drugs do end up achieving SVR12.

best,
kim

[sickpuppy]

That's a great answer. Thank you. Now for the other two! Anyone?

[inaglasshouse]

I think, just my opinion, this is because the immune system is crucial during the therapy process, even with the new DAAs.
Getting rid of the virus means the drugs interfering the virus replication enough to help the immune system to work in a easier way, but you still need a somehow healthy immune system.
Probably this is the reason because some of us experience flu-like symptoms during the therapy, they might be signs of a inner fight.
And how the immune system "understands" this opportunity calls for interesting speculations.
So, when you have cirrhosis your body is weaker, so the immune system.
If you failed previously this can be a sign that the immune system is not strong/expert enough to kill the virus.