Question for oncology experienced pharmacists

[mustang sally]

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The visiting oncologists here will write carboplatin orders for a target AUC a month ahead of time (or whatever) based on the pt's renal function that day. Then the next month the patient comes in and gets their labs done right before their chemo.

My question is, at what point does a change in creatinine necessitate a change in the target auc dose? Is it necessary to change the dose for any change in creatinine? It seems like most people have slight fluctuations in renal function from day to day.

 

[spacecowgirl]

We calculate a new dose every time they get treatment using their weight and SCr that day (and also age if they have just had a birthday).

 

[xiphoid2010]

Same at my residency site, dose calculated using latest lab drawn the same day or the day before chemo. Weight is what the actual body weight infusion clinic document that day (although there was some talk going on of that vs. ideal. vs adj body weight).

Target AUC is not dependent on renal function. Usually starts out at 5 or 6, but gets lowered if the patient couldn't tolerate it due to severe neutropenia or thrombocytopenia.

 

[Praziquantel86]

We used labs from within the last 72 hours as valid for calculations.

 

[ucrx]

Same at my residency site, dose calculated using latest lab drawn the same day or the day before chemo. Weight is what the actual body weight infusion clinic document that day (although there was some talk going on of that vs. ideal. vs adj body weight).

Target AUC is not dependent on renal function. Usually starts out at 5 or 6, but gets lowered if the patient couldn't tolerate it due to severe neutropenia or thrombocytopenia.

I'm sure part of it is just the wording of the OP, but it is important to be clear the target AUC doesn't change based on change in creatinine as is explained above. Also, target AUC varies with the regimen and indication. AUC 1-2 is common dosing with concurrent radiation.

The GFR we calculate is using the most recent scr (within 7 days) and actual body weight (except maybe gyn, I don't cover that service). We do ask for orders ahead of time and get some changes in both scr and weight. Our policy is to make interventions if the dose changes by more than 7%. Each institution usually has a standard like that for all chemo.

The actual vs ideal vs adjusted question has been discussed in some great editorials and the HOPA listserv. I have also heard it may be a presentation at HOPA this spring.

I have a related question- do you use a minimum scr when calculating GFR?

 

[mustang sally]

Thanks for all of the advice. Especially ucrx's reference to 7% above. Maybe I didn't phrase it very well in the original post, but that was the intent of my question, i.e. how much does the dose have to change to be a significant difference to the patient?

My limited understanding of carboplatin dosing is that it is based off of GFR. Here the pharmacists would not intervene to change the target AUC for neutropenia or thrombocytopenia (though maybe we should be? That is considered to be up to the oncologist). Our main role is really just to check and see if the dose that the physician came up with makes sense for that day's renal function.

 

[ucrx]

Thanks for all of the advice. Especially ucrx's reference to 7% above. Maybe I didn't phrase it very well in the original post, but that was the intent of my question, i.e. how much does the dose have to change to be a significant difference to the patient?

My limited understanding of carboplatin dosing is that it is based off of GFR. Here the pharmacists would not intervene to change the target AUC for neutropenia or thrombocytopenia (though maybe we should be? That is considered to be up to the oncologist). Our main role is really just to check and see if the dose that the physician came up with makes sense for that day's renal function.

I have also seen institutional policies of 5% and 10%.

In reference to our role, is checking dose based on weight/renal function all we do in other specialties? I know that a lot of things may be beyond some pharmacists' knowledge and training level, but there is a lot that a pharmacist can do with chemotherapy. I know there aren't many people with oncology experience on here, but how many of you would contact an oncologist to ask about the regimen they are using because you feel it might not be the best regimen for a patient?

 

[mustang sally]

I have also seen institutional policies of 5% and 10%.

In reference to our role, is checking dose based on weight/renal function all we do in other specialties? I know that a lot of things may be beyond some pharmacists' knowledge and training level, but there is a lot that a pharmacist can do with chemotherapy. I know there aren't many people with oncology experience on here, but how many of you would contact an oncologist to ask about the regimen they are using because you feel it might not be the best regimen for a patient?

We don't evaluate the regimen at this point in time. It's probably something we will be starting up in the future. It is kind of hard sometimes because it's a couple of bspharms and me (the new grad) who work at this hospital. None of us have any particular knowledge or training in oncology. I'm mainly trying to learn right now by reading, subscribing to prn listserve, whatever.

 

[ucrx]

We don't evaluate the regimen at this point in time. It's probably something we will be starting up in the future. It is kind of hard sometimes because it's a couple of bspharms and me (the new grad) who work at this hospital. None of us have any particular knowledge or training in oncology. I'm mainly trying to learn right now by reading, subscribing to prn listserve, whatever.

That's hard. It takes a lot of reading, experience, and/or training to really be able to make those interventions. I think you're probably in the right place starting with standards for dosing and what you monitor and intervene on.

 

[wrek92]

I have also seen institutional policies of 5% and 10%.

In reference to our role, is checking dose based on weight/renal function all we do in other specialties? I know that a lot of things may be beyond some pharmacists' knowledge and training level, but there is a lot that a pharmacist can do with chemotherapy. I know there aren't many people with oncology experience on here, but how many of you would contact an oncologist to ask about the regimen they are using because you feel it might not be the best regimen for a patient?

I have been in situations where I felt a carboplatin dose was too high e.g. 900mg on a patient who had never received it before. What I suggested to the oncologist was start off at lower AUC say, 5 which was like 750mg and if the patient tolerated it then escalate the dose the next cycle to AUC 6.

So, yeah, I am comfortable discussing the doses but I don't get into choice of regimen unless it's something that's I have never seen before and kinda "out there". My institution follows NCCN guidelines so the oncologists usually prescribe according to guidelines. If a regimen is not the norm I ask the oncologist to email me the journal reference that they are basing the regimen on. Luckily, most of the clinics at my institution have pharmacists in them so hopefully, there is a meaningful regimen discussion before it ever crosses my desk.