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Case Study 4

For each question, choose the answer you think is correct. See the end of this page for the answers.

L.Y. is a 42-year-old woman diagnosed with stage IIIc epithelial ovarian cancer. The oncologist has suggested she receive PACLitaxel and CARBOplatin, as per the GOOVCATX protocol.

Lab results

  • ANC 15.7
  • Platelets 498
  • Creatinine 79

Weight: 73.4 kg; Height: 150 cm; GFR = 110 mL/min (by renogram)

1. What special precautions must be observed when preparing the PACLitaxel dose?
  1. None required 
  2. PACLitaxel can react with DEHP in plasticized PVC equipment, so must be prepared using non-DEHP equipment 
  3. PACLitaxel can react with latex gloves 
  4. PACLitaxel requires a special diluent from the manufacturer 
2. Based on L.Y.’s serum creatinine and weight, how does the calculated GFR estimate compare to the renogram results, and which should be used for determining the initial CARBOplatin dose?
  1. The calculated GFR is less than the renogram GFR; the renogram is considered a more accurate reflection of renal function and should be used to determine the CARBOplatin dose 
  2. The calculated GFR is more than the renogram GFR; the calculated GFR is considered a more accurate reflection of renal function and should be used to determine the initial CARBOplatin dose 
  3. The calculated GFR is less than the renogram GFR and the calculated GFR is considered a more accurate reflection of renal function because it takes into account the most recent weight and serum creatinine levels 
  4. The calculated GFR is more than the renogram GFR and the renogram is only used to verify the accuracy of the calculated creatinine clearance 
3. Based on a starting AUC = 6, what dose of each drug can you expect for her first cycle of GOOVCATX?
  1. PACLitaxel 306 mg and CARBOplatin 718 mg 
  2. PACLitaxel 219 mg and CARBOplatin 718 mg 
  3. PACLitaxel 306 mg and CARBOplatin 810 mg 
  4. PACLitaxel 219 mg and CARBOplatin 810 mg 
4. L.Y. returns for her second cycle of CARBOplatin. Her weight is 65.4 kg, and her labs are: ANC = 9.3, platelets = 528, and creatinine = 74. The week prior to her second cycle, her platelets = 382 and ANC = 2.1. The doctor re-writes the orders with the following doses: PACLitaxel 306 mg and CARBOplatin 945 mg. Are these doses appropriate?
  1. No, he has mistakenly increased the CARBOplatin dose and not the PACLitaxel dose 
  2. No, the patient has lost more than 5% of her body weight, enough that the doses for both drugs need to be modified 
  3. Yes, the dose of PACLitaxel is still correct despite the weight decrease, and the CARBOplatin dose may be increased when there are good platelet counts at the nadir 
  4. Yes, the dose of PACLitaxel is still correct despite the weight decrease, and the CARBOplatin dose is automatically increased from the second cycle onwards 

 

The correct answer is 2.


Rationale: Some drug solutions have the capacity to leach DEHP ifrom PVC containers into the intravenous solution. PACLitaxel is one such drug; the Chemotherapy Preparation and Stability Chart [Cancer Drug Manual] indicates that non-DEHP bags and tubing are to be used when preparing and administering PACLitaxel. Refer to the Clinical Pharmacy Guide, Parenteral Drug Delivery, Non-DEHP Equipment section for more information.

The correct answer is 1.

 

Rationale:

Calculated GFR =

 

N x (140 – age) x weight (kg) 
Serum creatinine (micromol/L)    Where N = 1.04 for females

 

     = 1.04 (140 – 42) x 73.4
                      79

     = 94.69 mL/min


Calculated GFR (94.69 mL/min) is less than Renogram GFR (110 mL/min).


Directly measuring the GFR, using a renogram is considered more accurate than calculating an estimated GFR, based on serum creatinine and age. Refer to the Clinical Pharmacy Guide, Renal Function and Associated Laboratory Tests.

 

The correct answer is 3.

 

Rationale: Based on GOOVCATX, "Treatment" plan, doses of PACLitaxel and CARBOplatin are calculated as follows:


Mosteller equation


(BSA in metres squared) = square root of ((height x weight) over 3600) = square root of ((150cm x 73.4kg) over 3600) = 1.75 metres squared 

 

Dose of PACLitaxel: 
     = 175 mg/m2 x 1.75 m2 = 306.3 mg


Dose of CARBOplatin: 
     = AUC x (GFR + 25) 
     = 6 x (110 + 25) 
     = 810 mg

 

The correct answer is 3.

 

Rationale: Based on GOOVCATX protocol, "Dose Modification, Hematology": If ANC is greater than or equal to 1.5, and Platelets are greater than or equal to 100 at nadir, the dose of PACLitaxel is given at 100% and CARBOplatin is given at 120%. Note that this is 120% of the dose from the previous cycle that was calculated based on the renogram GFR.


As per BC Cancer Agency Policy III-10, the BSA calculated at Cycle 1 is used for subsequent cycles, so PACLitaxel dose does not change.


Calculated dose of CARBOplatin:

     120% x 810 mg = 972 mg


Dose ordered by physician = 945 mg


Difference between the 2 doses: 972 – 945 = 27

27/945 x 100% = 2.9%


There is less than 5% difference between the two  calculated doses, so the dose ordered is acceptable.

 


 


SOURCE: Case Study 4 ( )
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