Correlation between calculated and measured creatinine clearance in head and neck cancer patients undergoing concurrent chemoradiation

Abstract

Author(s): Joneetha Jones, Dr Arun P Narendran*, Vinin N V, Geetha M, Greeshma K E, Nabeel Yahiya, Akhil P suresh, Bindu Anilkumar and Hima Sasikumar

Background: Cisplatin based chemoradiation forms the standard treatment for locally advanced head and neck malignancies. Cisplatin is notorious for its potential nephrotoxicity. Renal function assessment is crucial in determining the eligibility or the need for dose modification of potentially nephrotoxic drugs in clinical practice. measuring Glomerular Filtration Rate (GFR) is a uniformly accepted index of renal function. Even though the most common method of GFR assessment is 24 hour urine collection for evaluation of creatinine clearance, most of the time this test is inconvenient for the patient. This test may also overestimate GFR due to renal tubular secretion of creatinine. So, attempts have been focused on formulas that estimate GFR without collecting the patient's urine. In this scenario the most common formulas used by laboratories to predict GFR are the Cockcroft and Gault (CG) formula. In high volume centers and especially in resource constrained setting it will be difficult to get 24 hour measured CCT before each cycle of chemotherapy. Also in order to ensure proper 24 hour urine sample collection the ideal choice would be to do it in an inpatient setting. But it is impractical in a busy department and with limited resources. In our center we do 24 hour urine CCT as baseline before the start of cisplatin chemotherapy. The aim of this study was to find out the correlation between measured creatinine clearance and calculated creatinine clearance in patients with head and neck malignancy treated with cisplatin chemo radiation for locally advanced head and neck malignancy treated 1st January 2015 to 31st December 2019 at a tertiary cancer center in South India.

Methods: This was a retrospective study done in head and neck cancer patients being planned for concurrent chemoradiation. Medical records were reviewed and necessary data was collected. Demographic det ails,stage,site,histology,serum creatinine,body weight and measured creatinine clearance was recorded from the medical records and lab reports. Calculated Creatinine clearance was obtained from the Cockcroft and Gault formula. Pearson correlation test was used to find out the correlation between the two variables and Bland Altman plot was used to find out the level of agreement.

Result: A total of 104 patients were analyzed. The mean age of the study population was 56 years. 92 (88%) were males and 12 (12%) were females. Oral cavity (42%) was the most common site followed by oropharynx. Majority of the patients had stage IV B (44%) disease. Moderately differentiated squamous cell carcinoma (66%) was the most common histopathological subtype. The mean creatinine value was 0.79. he mean Body Mass Index was 20.50. he mean creatinine clearance that was calculated by Cockcroft & Gault equation was 81.1 (SD=23.03) ml/min compared to 102.56 (SD=38.91) ml/min estimated by 24-hour urine collection. The measured creatinine clearance and the calculated creatinine clearance showed a moderate level of correlation(r=0.561 and p<0.0001). he Bland Altman plot showed that there is good level of agreement between two measurements.

Conclusion: This study showed moderate correlation between creatinine clearance calculated by Cockcroft & Gault equation and 24-hour urine collection in head and neck cancer patients. If the calculated creatinine clearance is less than the cutoff, then a measured adequate creatinine clearance should be obtained before deciding on the chemotherapy. ince our study showed good correlation between measured and calculated CCT we plan to get a measured CCT before the start of chemotherapy and to get calculated CCT before each subsequent cycles.

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