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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. Her oncologist has suggested she receive PACLitaxel and CARBOplatin, as per the GOOVCATX protocol.

Lab results

  • ANC 10.7
  • Platelets 398
  • 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 initial 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; 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 and should be used to determine initial CARBOplatin dose
  4. The calculated GFR is more than the renogram GFR; 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 GOOVCATX. Her weight is 67.3 kg, and her labs are: ANC = 3.9, platelets = 128, and creatinine = 87. The week prior to her second cycle, her platelets = 88 and ANC = 0.9. The physician has re-ordered the same doses as in Cycle 1. Are these doses appropriate?
  1. No, according to the nadir taken the week prior, doses should be 80% of the previous cycle's 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, both doses are still correct despite the weight decrease and creatinine increase
  4. No, the CARBOplatin dose needs to be recalculated since creatinine has increased by more than 10% 

 

The correct answer is 2.


Rationale: Some drug solutions have the capacity to leach DEHP from 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 Non-DEHP Equipment [Clinical Pharmacy Guide - Module 4 - Parenteral Drug Delivery] 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 CARBOplatin Dosing [Clinical Pharmacy Guide - Module 3 - Renal Function Tests] for more information. 

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 the GOOVCATX protocol "Dose Modifications, Hematology" section: if ANC is greater than or equal to 1.0, and Platelets are greater than or equal to 100, treat as per nadir. At nadir, ANC was 0.9 and platelets were 88 which means both PACLitaxel and CARBOplatin may be given at 100%. Note that this is 100% of the dose from the previous cycle that was calculated based on the previous GFR.


As per BC Cancer Policy III-10, the BSA calculated at Cycle 1 can be used for subsequent cycles. BSA recalculation for weight changes is warranted when weight changes are greater than 10%. In this case, the weight only decreased by 8.3% so the PACLitaxel dose does not have to change as it was otherwise well tolerated.


As per the GOOVCATX protocol "Treatment" section: GFR should be recalculated if creatinine increases by greater than 20% or rises above the upper limit of normal. In this case, the small creatinine increase does not warrant a recalculation.

 


SOURCE: Case Study 4 ( )
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