544 Background: Neurotoxicity is the most frequent dose-limiting toxicity of oxaliplatin. Cumulative sensory peripheral neurotoxicity results in discontinuation of chemotherapy for cancer and impairs neurological function irreversibly. To develop new strategies to continue chemotherapy according to the treatment plan without more severe neurotoxicity, objective assessment tools for oxaliplatin-induced peripheral neuropathy (OIPN) are needed. The clanging tuning fork test (CTFT) and the nerve conduction velocity test (NCVT) are widely used forbenign neuropathies. However, little is known about their clinical usefulness for OIPN. Methods: Colorectal cancer patients were prospectively monitored at baseline and during chemotherapy with modified FOLFOX6. The incidence and severity of OIPN were recorded using NCI-CTC grading (ver. 4.0). CTFT was conducted every 2 weeks and NCVT every 8 weeks. A generalized estimating equation model was used to examine the correlations between NCI-CTC grade and CTFT/NCVT. The accuracy of the assessment was evaluated using receiver operating characteristic (ROC) curve analysis. Results: Twenty-one patients without peripheral sensory neuropathy (PSN) were enrolled. Mean CTFT values were 13.4 ± 0.7 sec at baseline, 14.1 ± 0.4 sec with grade 0 PSN, 14.0 ± 0.4 sec with grade 1 PSN, 12.5 ± 0.7 sec with grade 2 PSN, and 7.5 ± 0.9 sec with grade 3 PSN. The mean CTFT value with grade 3 PSN was significantly shorter than with the other grades (p<.001, all). ROC curve analysis showed that variation in CTFT provides a high-accuracy assessment of grade 3 PSN (AUC=0.898, 95% CI: 0.764-1.000, p=.004), and its optimal cut-off value was -3.5 sec (sensitivity and specificity for grade 3 PSN were 86% and 79%, respectively). Unlike CTFT, NCVT showed little association with OIPN. Conclusions: CTFT was found to be very effective for assessing grade 3 OIPN. The present results suggest that CTFT, a simple, quick, and non-invasive examination, is a promising assessment tool for OIPN. Clinical trial information: 000004305.