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Letter To The Editor

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In Reply

^aNational Yang-Ming University School of Medicine, Taipei, Taiwan, Republic of China; ^bDivision of Oncology & Hematology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China; ^cDivision of Colorectal Surgery, Department of Surgery, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China

Correspondence: Po-Min Chen, M.D., Ph.D., Division of Oncology & Hematology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China. Telephone: 886-2-2875-7528; Fax: 886-2-2873-2184; e-mail: pmchen{at}vghtpe.gov.tw

Received August 27, 2007; accepted for publication September 25, 2007.

Disclosure: No potential conflicts of interest were reported by the authors, planners, reviewers, or staff managers of this article.

Indeed, electrophysiological examinations, including nerve conduction velocity (NCV), are useful tools in assessing oxaliplatin-induced peripheral sensory neuropathy [1–4]. It has been shown that damage to the nucleolus of ganglionic sensory neurons of rats treated with various platinum drugs is closely linked to the alteration of sensory NCV [1]. Interestingly, oxaliplatin reduced NCV mainly in peripheral and sensory nerves, without affecting central or motor nerve conductions [3], which was compatible with the clinical manifestations of patients who have been treated with oxaliplatin. And the severity of neurological symptoms correlated well with electrophysiological findings [4].

Because the symptoms of peripheral sensory neuropathy are, on occasion, subjective, a precise clinical evaluation, including a detailed history-taking as well as physical examination, is crucial for detecting the occurrence of peripheral neuropathy during chemotherapy. In fact, the grading systems we commonly use in daily practice and clinical trials for evaluating chemotherapy-induced peripheral neuropathy do not include electrophysiological studies. For example, the grading scales designed by the World Health Organization, Eastern Cooperative Oncology Group, and National Cancer Institute Common Toxicity Criteria, or the oxaliplatin-specific neuropathy scale designed for the Multicenter International Study of Oxaliplatin/5-Fluorouracil/Leucovorin in the Adjuvant Treatment of Colorectal Cancer trial [5], consist of subjective sensory loss, paresthesias, loss of deep tendon reflexes, constipation, bladder dysfunction, paralysis, etc., without abnormalities in electrophysiological studies.

It is obvious that the evaluation of patients' neurological symptoms during chemotherapy is very practical and easier to perform than electrophysiological examination, because the latter is not always available in the general oncology practice. In addition, the findings of nerve conduction studies do not always correlate with the severity of sensory neuropathy. For example, it has been shown that the abnormalities of sensory NCV may persist even though the symptoms of oxaliplatin-induced neuropathy have been remarkably reduced after discontinuation of oxaliplatin treatment [6].

Occasionally, the development of severe neurological symptoms after oxaliplatin treatment is not always accompanied by remarkable change in NCV. In our previous study, we noticed no significant between-group differences in electrophysiological studies of patients receiving glutamine supplements or not [7]. In this study, electrophysiological examinations were performed in 28 patients. Twenty of them showed reduced NCV and the remainder had normal NCV. A significant correlation was identified between NCV abnormalities and the severity of neurological symptoms (p = .006), including 16 patients with reduced NCV accompanied by severe (grade 3 or 4) neuropathy and six patients with normal NCV without development of severe neurological symptoms. However, two patients with normal NCV developed severe neuropathies. We did not show these data because, in this study, we did not focus on the efficacy of electrophysiological examination in predicting oxaliplatin-induced neuropathy, and the sample size was quite small. Furthermore, we believe that it is the "clinical symptoms" of neuropathy that really bother patients, not nerve conduction data themselves.

We agree with Dr. Argyriou's viewpoint that nerve conduction studies correlate well with the severity of neurological symptoms and may serve as a useful tool in objectively assessing the severity of chemotherapy-induced peripheral neuropathy. The addition of a detailed electrophysiological examination to a precise physical examination may provide more valuable data regarding the characteristics of chemotherapy-induced peripheral neuropathy.

	REFERENCES

Top References

 

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3. Jamieson SM, Liu J, Connor B et al. Oxaliplatin causes selective atrophy of a subpopulation of dorsal root ganglion neurons without inducing cell loss. Cancer Chemother Pharmacol 2005;56:391–399.[CrossRef][Medline]
4. Argyriou AA, Chroni E, Polychronopoulos P et al. Efficacy of oxcarbazepine for prophylaxis against cumulative oxaliplatin-induced neuropathy. Neurology 2006;67:2253–2255.[Abstract/Free Full Text]
5. Andre T, Boni C, Mounedji-Boudiaf L et al. Oxaliplatin, fluorouracil, and leucovorin as adjuvant treatment for colon cancer. N Engl J Med 2004;350:2343–2351.[Abstract/Free Full Text]
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7. Wang WS, Lin JK, Lin TC et al. Oral glutamine is effective for preventing oxaliplatin-induced neuropathy in colorectal cancer patients. The Oncologist 2007;12:312–319.[Abstract/Free Full Text]

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