Treatment of lung, bladder and ovarian cancer is performed using the chemotherapeutic agent, carboplatin. Carboplatin is eliminated from the body by clearance via the kidneys (glomerular filtration) and there is a high correlation of Glomerular Filtration Rate (GFR) with renal clearance of carboplatin. Consequently there is a requirement to individualise patients' chemotherapy dosages to their underlying renal function in order to optimise treatment of the tumour; that is to avoid the potential for sub-maximal chemotherapy dosages in patients with high renal clearance of carboplatin, but also to prevent the overdosing of those patients with impaired renal function.
On Teesside three nuclear medicine departments provide the GFR measurements essential for accurate carboplatin dosage calculation for patients referred to the Middlesbrough Cancer Centre and its satellite clinics.
The current GFR calculation method ("NIRAS") uses the Chantler method of Slope-Intercept correction. In response to the publication of British Nuclear Medicine Society's GFR guidelines [1], the need to replace dated software and the desirability of a common network-wide approach to GFR technique, a new package, the Excel Spreadsheet for Calculation of GFR ("The Cosgriff Spreadsheet") [2] was purchased by all three centres. This software utilises Brochner-Mortensen (1972) first exponential correction in accordance with the BNMS guidelines.
For a three month period all GFR referrals for chemotherapy prescribing were calculated using the existing method and Cosgriff's Spreadsheet (n=134). This allowed a direct comparison of the two methods on measured GFR and their subsequent impact on prescribed carboplatin dose for this patient population.
The mean percentage difference between the NIRAS and Cosgriff methods was 0.32 ± 0.45 (mean ± S.E.) for absolute GFR but with a range of over 33% (-23.45% to 9.68%). Most importantly 90% of the audited patient group would receive only a + 5% difference in chemotherapy dose, depending on their GFR. This is not regarded as a clinically significant impact on patient management. Relative overdosing of chemotherapy is not seen and significant under-dosing (>20% reduction) is only likely at very high GFR's (>140 ml/min) which are very uncommon in our practice in oncology (n=1).
Adoption of the new method of GFR calculation into routine clinical practice by the Cancer Care Alliance's clinicians and the Nuclear Medicine Departments at James Cook, Hartlepool and Darlington has improved the consistency of care for patients across the alliance.
References:
1. Fleming, J.S., Zivanovic, M.A., Blake, G.M., Burniston, M. and Cosgriff, P.S. (2004) Guidelines for the Measurement of Glomerular Filtration Rate using Plasma Sampling. www.bnms.org
2. www,nuclearmedicine.org.uk (version 4.6); Cosgriff P.S.
Richardson MA, Phillips D, Ardley RG, Chandler ST. The Impact of Glomerular Filtration Rate (GFR) Calculation Methodology on Chemotherapy Dose Prescription in Oncology. Annual Research and Development Day, James Cook University Hospital, Middlesbrough, 30th March 2007.
Mark Richardson, Cleveland Unit, Middlebrough. Tel: +44 (0)1642-850-850
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