Analysis of O6-Methylguanine in Cancer Patient Blood during Administration of Cyclophosphamide Using Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry

Aims: To determine O6-Methylguanine in Cancer Patient Blood during Administration of Cyclophosphamide using Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry.

Place and Duration of Study: Dharmais Cancer Hospital and Bioavailability/Bioequivalence Laboratory, Faculty of Pharmacy, University of Indonesia. Duration: Dec 2012 until May 2013.

Methodology Study Design: This study was approved by the Ethics Committee of Medical Faculty, University of Indonesia. Cross sectional design was conducted for this study, blood samples were collected from 72 cancer patients receiving four or more cycles of chemotherapy with regiment which contains cyclophosphamide. DNA adduct was analysed from isolated DNA after the fourth cycle chemotherapy or more by UPLC-MS/MS ESI+ and the analysis mode on value of m/z 166.10>149.10 and 166.10>134.10.

Results: The method was validated using a calibration curve with good linearity (r>0.999); the coefficient of variance was <6.54%; the recovery was in the range of 90.52-109.65% Among 72 analyzed samples, O6-methylguanine was detected in 17 samples and could be quantified in 1 sample at a concentration of 5.87 ng/mL.

Conclusion: The results of this study showed that O6-methylguanine is not always found in cancer patients treated with cyclophosphamide. The detected and quantified O6-methylguanine can be a predictor of secondary cancer risk therefore, the dose administered should be monitored and set to the appropriate and safe levels, in order to reduce the risk of secondary cancer.