Lawrence R Solomon1. 1. Section of Palliative Care, Department of Medicine, Yale University School of Medicine and Smilow Cancer Hospital, 333 Cedar Street WWW-403, P.O. Box 208021, New Haven, CT, 06520-8021, USA. lawrence.solomon@yale.edu.
Abstract
BACKGROUND AND AIM: Treatment of neuropathic pain and chemotherapy-induced peripheral neuropathy (CIPN) in patients with malignancy is often unsuccessful. Functional vitamin B12 deficiency, defined by elevated levels of the B12-dependent metabolites, methylmalonic acid (MMA), and/or homocysteine, despite normal B12 values, may cause neuropathy and is associated with disorders linked to increased oxidative stress. Since both cancer and neurotoxic antineoplastic agents increase oxidative stress, a role for functional B12 deficiency in CIPN was considered. METHODS: A retrospective record review of 241 cancer subjects evaluated by the adult palliative care service for B12 deficiency in a university-based cancer center between October 2008 and September 2012 with measurement of B12, MMA, and/or homocysteine levels was performed. RESULTS: B12 values were elevated (>900 pg/ml) in 30 % and low (≤300 pg/ml) in 17 % of subjects tested. Elevated MMA (>250 nmol/l) and homocysteine (>12.1 μmol/l) levels occurred in 38 and 23 % of subjects respectively and at least one metabolite was increased in 54 % of evaluable subjects. Even when B12 values were ≥1500 pg/ml (n = 36), increased MMA and homocysteine values occurred in 31 and 23 % of subjects, respectively. B12 therapy decreased MMA values in all four subjects studied and improved neurologic findings in the three subjects tested. CONCLUSIONS: Functional vitamin B12 deficiency is common in subjects with advanced malignancy. Further studies are needed to determine if this disorder is a risk factor for CIPN and if B12 therapy has a role in the management and/or prevention of neuropathy and neuropathic pain in this population.
BACKGROUND AND AIM: Treatment of neuropathic pain and chemotherapy-induced peripheral neuropathy (CIPN) in patients with malignancy is often unsuccessful. Functional vitamin B12 deficiency, defined by elevated levels of the B12-dependent metabolites, methylmalonic acid (MMA), and/or homocysteine, despite normal B12 values, may cause neuropathy and is associated with disorders linked to increased oxidative stress. Since both cancer and neurotoxic antineoplastic agents increase oxidative stress, a role for functional B12 deficiency in CIPN was considered. METHODS: A retrospective record review of 241 cancer subjects evaluated by the adult palliative care service for B12 deficiency in a university-based cancer center between October 2008 and September 2012 with measurement of B12, MMA, and/or homocysteine levels was performed. RESULTS:B12 values were elevated (>900 pg/ml) in 30 % and low (≤300 pg/ml) in 17 % of subjects tested. Elevated MMA (>250 nmol/l) and homocysteine (>12.1 μmol/l) levels occurred in 38 and 23 % of subjects respectively and at least one metabolite was increased in 54 % of evaluable subjects. Even when B12 values were ≥1500 pg/ml (n = 36), increased MMA and homocysteine values occurred in 31 and 23 % of subjects, respectively. B12 therapy decreased MMA values in all four subjects studied and improved neurologic findings in the three subjects tested. CONCLUSIONS: Functional vitamin B12 deficiency is common in subjects with advanced malignancy. Further studies are needed to determine if this disorder is a risk factor for CIPN and if B12 therapy has a role in the management and/or prevention of neuropathy and neuropathic pain in this population.
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