Once again - 2 infusions vs 4 - Rituxan

A multi-centre, single-arm, open-label study evaluating the safety and efficacy of fixed dose rituximab in patients with refractory, relapsed or chronic idiopathic thrombocytopenic purpura (R-ITP1000 study).

Abstract

The efficacy of a fixed-dose rituximab schedule was prospectively explored in primary/acute refractory, relapsed or chronic (platelet count >10 × 109 /l and ≤50 × 109 /l) idiopathic thrombocytopenic purpura (ITP). Patients received two doses of rituximab (1000 mg) on days 1 and 15 and were followed-up on weeks 1-8, 12, 26, 39 and 52. A total of 122 patients were included in the safety population; efficacy was analysed in 108 patients. Overall response rate (ORR) at week 8, defined as the proportion of patients achieving complete response (CR; platelet count >150 × 109 /l) or partial response (PR; platelet count >50 × 109 /l) was 44%. Therapeutic response, defined as achieving a response at week 8, with at least a minor response (MR; platelet count >30 × 109 /l), sustained up to weeks 26 and 52 and accompanied by a reduction in ITP medications, was achieved in 44% (week 26) and 35% (week 52) of patients, respectively. Treatment was well tolerated with no safety concerns. While this study failed to meet its primary endpoint of an ORR of 50%, the efficacy of two fixed doses of rituximab appear to provide similar efficacy to the standard 375 mg/m2 four-dose schedule in relapsed/chronic ITP.

© 2014 John Wiley & Sons Ltd.


www.ncbi.nlm.nih.gov/pubmed/25041261

I'm still learning how to read study results.

So what I'm getting is ... Patients got a total of 2000 mg in two infusions vs. the 1500 they would get in four? To what benefit?

To the exact same benefit as the higher dose for 4 infusions. So, why use more when you can use less.
Erica

No, apparently 375mg/m2 is: This chosen protocol calls for 375 mg/m2. That should be read as 375 milligrams of Rituxan per square meter. If you are 5' 10" tall, and you weigh 170 lbs, the BSA calculator above gives you a BSA of 1.95 square meters. That is the surface area of your entire body. To get the drug dosage customized for you, simply multiply the 375 milligrams by 1.95 square meters, and you come up with 731 milligrams of Rituxan. So, a person of that size (5' 10", 170 lbs. would get 2,924 mg's of Rituxan overall as opposed to 2,000 mg's with the 2 infusion version.

The benefit: similar result, less infusions, less toxicity, less expense.

**Disclaimer* I am not a math whiz, so if I am incorrect, please speak up!

I suck at math so I won't challenge what you said!

What my doctor said about this subject was: the 2 infusions had more rituxan per infusion than the 4 infusions but that the over all amount given was less in the 2 infusions.

Okay, I got it. Thanks for the explanation.
I would still choose the low-dose option over this one, for even less cost and toxicity, but that's me.

Julia - exactly.

Janet - me too.

I am 4'11" and weight 110 lbs. I asked my hemo to put me on the 100 dosage and he said no, it was too low and I needed to have the 375 x 4 treatments to have it be effective. I thought size was a factor but apparently he didn't agree. Am I wrong? Is size a factor in dosage?

Renee, your body surface area works out at 1.44 by my calculations so multiplied by the 375 would give 540mg which would be your weekly dose under the usual regime. However, if you want lower just stick to his 375mg. You could also do the first one or two and then refuse more as you'll have probably had enough by then.

Renee:

Print out the articles and show him. Many doctors are not aware of new literature. They get stuck in their ways. It's a new world these days where patients sometimes educate their doctors. Some are receptive to that and others are not, but you won't know unless you try.

My doctor today talked and Yes Please print it off. Because they tend to not believe us when we speak of it without proof!

Renee, most of the low-dose rituximab studies are summarized here:

pdsa.org/forum-sp-534/7-treatment-general/27993-low-dose-rituximab-rituxan-research.html?limitstart=0#40513

My wife, Ellen, will be going the low-dose route, and her hematologist at Emory agreed to it.