Siginificance of platinum concentration in blood and red blood cell in patients with oxaliplatin-based chemotherapy [UMIN000009128]

620 Background: Oxaliplatin(Ox) based regimen is widely used in colorectal cancer patients.One of the major adverse effects of Ox is a neuropathy. There is no useful biomarker predicting such adverse effect. The aim of this study is to evaluate platinum concentration as a biomarker predicting the adverse effect. Methods: Ten patients who underwent curative colectomy were included in this study. Final stage of all patients was UICC stage III. All patients underwent adjuvant chemotherapy by CapeOX regimen for eight cycles (or six months). Blood samples were collected after fourth cycle and last cycle. Ox concentration was measured in red blood cells (RBC) and serum, and evaluated the kinetics of platinum (PL) in blood. In addition, we investigated relationship between Ox concentration and adverse effects. Results: 1) Kinetics of PL concentration: PL concentration in RBC tended to be correlated with the difference of RBC numbers between pre- and post-chemotherapy (R2=0.358, p=0.068). The PL concentration in RBC siginificantly correlated with the difference of mean corpuscular volume (MCV) between pre- and post-chemotherapy (R2=0.661, p=0.004). After four cycle, the platinum concentration in RBC siginificantly correlated with the hemoglobin and hematocrit (R2=0.447, p=0.004 and R2=0.425, p=0.041). There was no siginificant difference in PL concentration in both RBC and serum between the points after four cycle and last cycle points (RBC: 1380.5±495.2 ng/ml vs. 1107.0±699.2 ng/ml Aserum: 210.1±38.9 ng/ml vs. 221.2±99.2 ng/ml). 2) PL concentration and adverse effects: PL concentration did not elevate depending on cycle number. There was no siginificant correlations between PL concentrations in RBC or serum and the grade of neuropathy. Conclusions: The PL concentration was significantly related with the difference of RBC numbers and MCV between pre- and post-chemotherapy. However, there was no siginificant relationship between Ox concentration in blood and side effects including neuropathy. So Ox concentration in blood could not be a reliable biomarker for predicting the grade of neuropathy. Clinical trial information: 000009128.