Modeling the rate of bilirubin decay after percutaneous drainage prior to chemotherapy

• Published in: Journal of vascular and interventional radiology Vol. 24; no. 4; pp. S53 - S54
• Main Authors: Mazaheri Tehrani, Y, Nieves-Cruz, D, Covey, A.M, Brody, L.A, Sofocleous, C.T, Getrajdman, G, Brown, K.T, Solomon, S.B, Thornton, R.H
• Format: Journal Article
• Language: English
• Published: 01-04-2013
• Subjects: Radiology
• ISSN: 1051-0443
• DOI: 10.1016/j.jvir.2013.01.122

Purpose To evaluate the potential of two models of bilirubin decay to predict response to drainage in patients who underwent biliary drainage to lower serum bilirubin prior to chemotherapy. Materials and Methods IRB-approved retrospective review identified 77 patients with malignant biliary obstruction who underwent a single biliary drainage to decrease bilirubin prior to chemotherapy administration and who had at least four subsequent serum bilirubin determinations (regardless of value) at 7-10 day intervals for the first 4 weeks following the procedure. Data were analyzed in both mono-exponential (ME) (bilirubin level is described in terms of pure exponential decay) and mono-exponential-static (MS) (bilirubin level is described in terms of exponential decay followed by an inflection point where the bilirubin level levels off to a constant value) models. Responders were defined as patients who achieved total serum bilirubin levels < 2 mg/dL following drainage. The R2 value from non-linear regression was used to test for goodness of fit of the models. Matched-pairs Wilcoxon signed rank test was used to test statistical significance of differences in quantitative analysis results obtained from each model. Results Across all patients, the MS model had better fit with total serum bilirubin values after drainage than the ME model (R2 0.82 vs 0.62, respectively). When patients were stratified into responders and non-responders, the MS model similarly had better fit to patient data (responders: R2 0.91 v 0.71; non-responders R2 0.66 v 0.45). Parameters extracted from both models (ME and MS) suggest that both estimated pre-drainage bilirubin (10.4 and 10.7 mg/dL, respectively) and the exponential decay rate (0.14 and 0.22 mg/dL/day) of responders was significantly different from the estimated pre-drainage bilirubin (15.0 and 15.1 mg/dL) (P=0.0003 and P<0.0001, respectively) and decay rate (0.06 and 0.12 mg/dL/day) (P=0.0003 and P=0.014, respectively) and of nonresponders. Conclusion Models of bilirubin response to percutaneous drainage may be useful to provide early clinical separation of responders from non-responders, prompting additional drainage or internalization of drainage when clinically appropriate.