ABC-Transporter Expression Does Not Correlate with Response to Irinotecan in Patients with Metastatic Colorectal Cancer

BACKGROUND

Active efflux of irinotecan by ATP-binding cassette (ABC)-transporters, in particular ABCB1 and ABCG2, is a well-established drug resistance mechanism in vitro and in pre-clinical mouse models, but its relevance in colorectal cancer (CRC) patients is unknown. Therefore, we assessed the association between ABC-transporter expression and tumour response to irinotecan in patients with metastatic CRC.

METHODS

Tissue microarrays of a large cohort of metastatic CRC patients treated with irinotecan in a prospective study (CAIRO study; n=566) were analysed for expression of ABCB1 and ABCG2 by immunohistochemistry. Kaplan-Meier and Cox proportional hazard regression analyses were performed to assess the association of ABC transporter expression with irinotecan response. Gene expression profiles of 17 paired tumours were used to assess the concordance of ABCB1/ABCG2 expression in primary CRC and corresponding metastases.

RESULTS

The response to irinotecan was not significantly different between primary tumours with positive versus negative expression of ABCB1 (5.8 vs 5.7 months, p=0.696) or ABCG2 (5.7 vs 6.1 months, p=0.811). Multivariate analysis showed neither ABCB1 nor ABCG2 were independent predictors for progression free survival. There was a mediocre to poor concordance between ABC-transporter expression in paired tumours.

CONCLUSION

In metastatic CRC, ABC-transporter expression in the primary tumour does not predict irinotecan response.

An fMRI study of prefrontal dysfunction and symptomatic recovery in schizophrenia

OBJECTIVE

Prefrontal cortical dysfunction has been implicated in the pathophysiology of schizophrenia but it is unclear to what extent these are related to changes in symptomatology as well as task demand.

METHOD

We examined the neural correlates of symptom change and task demand during a longitudinal functional magnetic resonance imaging (fMRI) study using a verbal fluency task with differential task demands in patients with schizophrenia and matched healthy control subjects. The fMRI data were acquired using clustered acquisition technique, enabling ongoing monitoring of behavioural responses, in the patient group on two occasions separated by 6-8 weeks, and the control group at baseline.

RESULTS

Positive psychotic symptoms were significantly reduced over the 6-8-week duration of the study. This change was associated with increased activation within the left middle frontal gyrus and decreased activation of the left precuneus. An interaction between symptom change and task demand was evident in the activation of the left middle frontal gyrus. The decrease in positive symptoms was associated with normalisation of activation in the dorsolateral prefrontal cortex and a decrease in parietal activation during the verbal fluency task.

CONCLUSION

The data supports the role of dysfunctional prefronto-parietal relationships in the genesis of positive psychotic symptoms.

Follow-up of GFR estimated from plasma creatinine after cimetidine administration in patients with diabetes mellitus type 2

BACKGROUND

The glomerular filtration rate (GFR) can be estimated from plasma creatinine according to the formula of Cockcroft and Gault (CG). When tubular secretion of creatinine is inhibited by cimetidine the mean difference between the Cockcroft-Gault clearance (CG(Cim) and GFR approximates zero, but there is still some interindividual difference, especially in type-2-diabetic patients. We studied during longitudinal follow-up, whether the discrepancies between CG(Cim) and GFR per patient are consistent in time in type-2-diabetic patients.

PATIENTS AND METHODS

In 1996 and 1998 (interval 20-26 months) GFR was measured in 21 patients as the urinary clearance of continuously infused 125I-iothalamate. Plasma creatinine was analyzed with an enzymatic assay before and after oral cimetidine 800 mg t.i.d. during 24 hours. GFR estimations were calculated with the Cockcroft-Gault formula before (CG) and after cimetidine (CG(Cim)) and expressed as means +/- SEM.

RESULTS

GFR deteriorated from 89.7 +/- 5.7 to 81.3 + 5.8 ml/min/1.73 m2 and CG(Cim) from 85.3 +/- 5.7 to 81.1 +/- 6.6 ml/min/1.73 m2, whereas CG decreased from 102.4 +/- 6.8 to 98.4 +/- 7.0 ml/min/1.73 m2. Changes in GFR and changes in CG(Cim) were correlated (r = 0.72, p < 0.001) and were not significantly different from each other. The discrepancy between CG(Cim) and GFR per patient in 1996 also correlated with the discrepancy between CG(Cim) and GFR in 1998 (r = 0.85, p < 0.001 ).

CONCLUSIONS

In individual patients the discrepancies between the CG(Cim) and GFR are consistent in time and the change in GFR is reflected by the change in CG(Cim). This small variability means that CG(Cim), based on an enzymatic plasma creatinine assay, would be suitable for follow-up of GFR in type-2-diabetic patients, independent of albuminuria.

Estimation of the glomerular filtration rate in NIDDM patients from plasma creatinine concentration after cimetidine administration

OBJECTIVE

Glomerular filtration rate (GFR) can be estimated in patients with renal disease from plasma creatinine concentration, age, sex, and body weight according to the formula of Cockcroft and Gault. The hypothesis that this method can be improved when tubular secretion of creatinine is inhibited by cimetidine was studied in NIDDM patients.

RESEARCH DESIGN AND METHODS

In 30 outpatients with NIDDM and normo- (n = 10), micro- (n = 9), or macroalbuminuria (n = 11), GFR was measured as the urinary clearance during continuous infusion of 125I-labeled iothalamate. Plasma creatinine concentration was analyzed with an enzymatic assay before and after 800 mg t.i.d. oral cimetidine was given during a 24-h period.

RESULTS

Plasma creatinine rose in all patients after cimetidine administration and, as a consequence, the clearance calculated with the Cockcroft-Gault formula fell. The ratio of this formula and GFR decreased from 1.16 +/- 0.20 to 0.97 +/- 0.16 (means +/- SD). This ratio tended to be smaller in the normo- (0.93) than in the micro- (0.98) and macroalbuminuric (1.00) groups. Also, 20 patients with a BMI < 30 kg/m2 had a smaller ratio than those with a BMI > 30 kg/m2 (0.92 vs. 1.07; P < 0.05). Bland and Altman analysis showed a difference of the Cockcroft-Gault formula and GFR of 12.0 +/- 17.4 ml.min-1 (1.73 m2)-1, which decreased to -3.8 +/- 14.8 ml.min-1.(1.73 m2)-1. The same analysis of 24-h creatinine clearance with urine collection and GFR showed larger standard deviations.

CONCLUSIONS

GFR can be estimated in an acceptable way from plasma creatinine concentration after cimetidine administration in outpatients with NIDDM. Despite a nonsignificant underestimation in normoalbuminuric and overestimation in overweighted patients, this method is superior to 24-h creatinine clearance with outpatient urine collection.

[Serious psychological side effect in children taking high doses of deptropine]

Since 1986 the Netherlands Centre for Monitoring of Adverse Reactions to Drugs has received 16 reports concerning psychic effects attributed to the use of deptropine citrate (Brontine) in children ranging from one to ten years of age. Within 1 to 3 days after starting treatment with a daily dose of 0.6-3 mg, hallucinations appeared in 7 children, aggressive behaviour and/or agitation in 6 children, ataxia in 2 children, and anxiety in 1 child. In none of these cases could another cause be found. In one patient symptoms persisted during the whole 15-month period of treatment. All patients recovered rapidly after discontinuation of deptropine citrate. As it probably concerns a dose-dependent effect and because most patients had been prescribed a daily dose of 0.06 mg/kg body weight, it is strongly advised to exceed the recommended daily dose of 0.03 mg/kg body weight as little as possible.