Paclitaxel-induced neuropathy

Melatonin, a promising role in taxane-related neuropathy

Purpose:

Melatonin has neuroprotective effects in animal studies and has been suggested to decrease adverse reactions of chemotherapy including neuropathy. This pilot trial aimed at assessing whether melatonin, given during taxane chemotherapy for breast cancer, will decrease the incidence and/or severity of neuropathy.

Methods:

Twenty two consecutive patients beginning chemotherapy for breast cancer with paclitaxel, or docetaxel were enrolled. Patients received melatonin 21 mg daily at bedtime. Incidence and severity of neuropathy were assessed using neurological examinations, toxicity assessment per NCI-CTC 3.0 scale and FACT-Taxane quality of life questionnaire.

Results:

Neuropathy was seen in 45% (n = 10) of patients, 23% (n = 6) grade 1 and 22% (n = 5) Grade 2 neuropathy. No grade 3 neuropathies were reported. The majority (55%) of all patients reported no neuropathy. Compliance with melatonin (>60% of dose) was seen in most patients (86%) No patient reported daytime sedation. The median FACT-Taxane quality of life end of study score was 137, with only a 0.5 median decline from baseline.

Conclusion:

Patients receiving melatonin during taxane chemotherapy had a reduced incidence of neuropathy. Melatonin may be useful in the prevention or reduction of taxane-induced neuropathy and in maintaining quality of life. Larger trials are warranted to further explore the role of melatonin in neuropathy treatment and prevention.

Eribulin binds at microtubule ends to a single site on tubulin to suppress dynamic instability

Eribulin mesylate (E7389), a synthetic analogue of the marine natural product halichondrin B, is in phase III clinical trials for the treatment of cancer. Eribulin targets microtubules, suppressing dynamic instability at microtubule plus ends through an inhibition of microtubule growth with little or no effect on shortening [Jordan, M. A., et al. (2005) Mol. Cancer Ther. 4, 1086-1095]. Using [(3)H]eribulin, we found that eribulin binds soluble tubulin at a single site; however, this binding is complex with an overall K(d) of 46 microM, but also showing a real or apparent very high affinity (K(d) = 0.4 microM) for a subset of 25% of the tubulin. Eribulin also binds microtubules with a maximum stoichiometry of 14.7 +/- 1.3 molecules per microtubule (K(d) = 3.5 microM), strongly suggesting the presence of a relatively high-affinity binding site at microtubule ends. At 100 nM, the concentration that inhibits microtubule plus end growth by 50%, we found that one molecule of eribulin is bound per two microtubules, indicating that the binding of a single eribulin molecule at a microtubule end can potently inhibit its growth. Eribulin does not suppress dynamic instability at microtubule minus ends. Preincubation of microtubules with 2 or 4 microM vinblastine induced additional lower-affinity eribulin binding sites, most likely at splayed microtubule ends. Overall, our results indicate that eribulin binds with high affinity to microtubule plus ends and thereby suppresses dynamic instability.

Paclitaxel induces axonal microtubules polar reconfiguration and impaired organelle transport: implications for the pathogenesis of paclitaxel-induced polyneuropathy

In differentiated axons almost all microtubules (MTs) uniformly point their plus ends towards the axonal tip. The uniform polar pattern provides the structural substrate for efficient organelle transport along axons. It is generally believed that the mass and pattern of MTs polar orientation remain unchanged in differentiated neurons. Here we examined long-term effects of the MTs stabilizing reagent paclitaxel (taxol) over MTs polar orientation and organelle transport in cultured Aplysia neurons. Unexpectedly, we found that rather than stabilizing the MTs, paclitaxel leads to their massive polar reconfiguration, accompanied by impaired organelle transport. Washout of paclitaxel does not lead to recovery of the polar orientation indicating that the new pattern is self-maintained. Taken together the data suggest that MTs in differentiated neurons maintain the potential to be reconfigured. Such reconfiguration may serve physiological functions or lead to degeneration. In addition, our observations offer a novel mechanism that could account for the development of peripheral neuropathy in patients receiving paclitaxel as an antitumor drug.

Oxaliplatin-induced loss of phosphorylated heavy neurofilament subunit neuronal immunoreactivity in rat DRG tissue

Background

Oxaliplatin and related chemotherapeutic drugs cause painful chronic peripheral neuropathies in cancer patients. We investigated changes in neuronal size profiles and neurofilament immunoreactivity in L5 dorsal root ganglion (DRG) tissue of adult female Wistar rats after multiple-dose treatment with oxaliplatin, cisplatin, carboplatin or paclitaxel.

Results

After treatment with oxaliplatin, phosphorylated neurofilament heavy subunit (pNF-H) immunoreactivity was reduced in neuronal cell bodies, but unchanged in nerve fibres, of the L5 DRG. Morphometric analysis confirmed significant changes in the number (-75%; P < 0.0002) and size (-45%; P < 0.0001) of pNF-H-immunoreactive neurons after oxaliplatin treatment. pNF-H-immunoreactive neurons had overlapping size profiles and co-localisation with neurons displaying cell body immunoreactivity for parvalbumin, non-phospho-specific neurofilament medium subunit (NF-M) and non-phospho-specific neurofilament heavy subunit (NF-H), in control DRG. However, there were no significant changes in the numbers of neurons with immunoreactivity for parvalbumin (4.6%, P = 0.82), NF-M (-1%, P = 0.96) or NF-H (0%; P = 0.93) after oxaliplatin treatment, although the sizes of parvalbumin (-29%, P = 0.047), NF-M (-11%, P = 0.038) and NF-H (-28%; P = 0.0033) immunoreactive neurons were reduced. In an independent comparison of different chemotherapeutic agents, the number of pNF-H-immunoreactive neurons was significantly altered by oxaliplatin (-77.2%; P < 0.0001) and cisplatin (-35.2%; P = 0.03) but not by carboplatin or paclitaxel, and their mean cell body area was significantly changed by oxaliplatin (-31.1%; P = 0.008) but not by cisplatin, carboplatin or paclitaxel.

Conclusion

This study has demonstrated a specific pattern of loss of pNF-H immunoreactivity in rat DRG tissue that corresponds with the relative neurotoxicity of oxaliplatin, cisplatin and carboplatin. Loss of pNF-H may be mechanistically linked to oxaliplatin-induced neuronal atrophy, and serves as a readily measureable endpoint of its neurotoxicity in the rat model.

Recommendations for research priorities in breast cancer by the Coalition of Cancer Cooperative Groups Scientific Leadership Council: systemic therapy and therapeutic individualization

Over 9,000 women with breast cancer are enrolled annually on clinical trials sponsored by the National Cancer Institute (NCI), accounting for about one-third of all patients enrolled on NCI-sponsored trials. Thousands are also enrolled on pharmaceutical-sponsored studies. Although breast cancer mortality rates have recently declined for the first time in part due to systemic therapeutic advances, coordinated efforts will be necessary to maintain this trend. The Coalition of Cancer Cooperative Groups convened the Scientific Leadership Council in breast cancer (BC), an expert panel, to identify priorities for future research and current trials with greatest practice-changing potential. Panelists formed a consensus on research priorities for chemoprevention, development and application of molecular markers for predicting therapeutic benefit and toxicity, intermediate markers predictive of therapeutic effect, pathogenesis-based therapeutic approaches, utilization of adaptive designs requiring fewer patients to achieve objectives, special and minority populations, and effects of BC and treatment on patients and families. Panelists identified 13 ongoing studies as High Priority and identified gaps in the current trial portfolio. We propose priorities for current and future clinical breast cancer research evaluating systemic therapies that may serve to improve the efficiency of clinical trials, identify individuals most likely to derive therapeutic benefit, and prioritize therapeutic strategies.

Targeted delivery of albumin bound paclitaxel in the treatment of advanced breast cancer

Taxanes are chemotherapeutic agents with a large spectrum of antitumor activity when used as monotherapy or in combination regimens. Paclitaxel and docetaxel have poor solubility and require a complex solvent system for their commercial formulation, Cremophor EL(R) (CrEL) and Tween 80(R) respectively. Both these biological surfactants have recently been implicated as contributing not only to the hypersensitivity reactions, but also to the degree of peripheral neurotoxicity and myelosuppression, and may antagonize the cytotoxicity. Nab-paclitaxel, or nanoparticle albumin-bound paclitaxel (ABI-007; Abraxane(R)), is a novel formulation of paclitaxel that does not employ the CrEL solvent system. Nab-paclitaxel demonstrates greater efficacy and a favorable safety profile compared with standard paclitaxel in patients with advanced disease (breast cancer, non-small cell lung cancer, melanoma, ovarian cancer). Clinical studies in breast cancer have shown that nab-paclitaxel is significantly more effective than standard paclitaxel in terms of overall objective response rate (ORR) and time to progression. Nab-paclitaxel in combination with gemcitabine, capecitabine or bevacizumab has been shown to be very active in patients with advanced breast cancer. An economic analysis showed that nab-paclitaxel would be an economically reasonable alternative to docetaxel or standard paclitaxel in metastatic breast cancer. Favorable tumor ORR and manageable toxicities have been reported for nab-paclitaxel as monotherapy or in combination treatment in advanced breast cancer.

Chemotherapy-induced neuropathy

Neurotoxic side effects of cancer therapy are second in frequency to hematological toxicity. Unlike hematological side effects that can be treated with hematopoietic growth factors, neuropathies cannot be treated and protective treatment strategies have not been effective. For the neurologist, the diagnosis of a toxic neuropathy is primarily based on the case history, the clinical and electrophysiological findings, and knowledge of the pattern of neuropathy associated with specific agents. In most cases, toxic neuropathies are length-dependent, sensory, or sensorimotor neuropathies often associated with pain. The platinum compounds are unique in producing a sensory ganglionopathy. Neurotoxicity is usually dependent on cumulative dose. Severity of neuropathy increases with duration of treatment and progression stops once drug treatment is completed. The platinum compounds are an exception where sensory loss may progress for several months after cessation of treatment ("coasting"). As more effective multiple drug combinations are used, patients will be treated with several neurotoxic drugs. Synergistic neurotoxicity has not been extensively investigated. Pre-existent neuropathy may influence the development of a toxic neuropathy. Underlying inherited or inflammatory neuropathies may predispose patients to developing very severe toxic neuropathies. Other factors such as focal radiotherapy or intrathecal administration may enhance neurotoxicity. The neurologist managing the cancer patient who develops neuropathy must answer a series of important questions as follows: (1) Are the symptoms due to peripheral neuropathy? (2) Is the neuropathy due to the underlying disease or the treatment? (3) Should treatment be modified or stopped because of the neuropathy? (4) What is the best supportive care in terms of pain management or physical therapy for each patient? Prevention of toxic neuropathies is most important. In patients with neuropathy, restorative approaches have not been well established. Symptomatic and other management are necessary to maintain and improve quality of life.

An evolving cellular pathology occurs in dorsal root ganglia, peripheral nerve and spinal cord following intravenous administration of paclitaxel in the rat

Paclitaxel (Taxol) is a frontline antineoplastic agent used to treat a variety of solid tumors including breast, ovarian, or lung cancer. The major dose limiting side effect of paclitaxel is a peripheral sensory neuropathy that can last days to a lifetime. To begin to understand the cellular events that contribute to this neuropathy, we examined a marker of cell injury/regeneration (activating transcription factor 3; ATF3), macrophage hyperplasia/hypertrophy; satellite cell hypertrophy in the dorsal root ganglia (DRG) and sciatic nerve as well as astrocyte and microglial activation within the spinal cord at 1, 4, 6 and 10 days following intravenous infusion of therapeutically relevant doses of paclitaxel. At day 1 post-infusion, there was an up-regulation of ATF3 in a subpopulation of large and small DRG neurons and this up-regulation was present through day 10. In contrast, hypertrophy of DRG satellite cells, hypertrophy and hyperplasia of CD68(+) macrophages in the DRG and sciatic nerve, ATF3 expression in S100beta(+) Schwann cells and increased expression of the microglial marker (CD11b) and the astrocyte marker glial fibrillary acidic protein (GFAP) in the spinal cord were not observed until day 6 post-infusion. The present results demonstrate that using the time points and markers examined, DRG neurons show the first sign of injury which is followed days later by other neuropathological changes in the DRG, peripheral nerve and dorsal horn of the spinal cord. Understanding the cellular changes that generate and maintain this neuropathy may allow the development of mechanism-based therapies to attenuate or block this frequently painful and debilitating condition.

Peripheral neuropathy due to paclitaxel: study of the temporal relationships between the therapeutic schedule and the clinical quantitative score (QST) and comparison with neurophysiological findings

Peripheral neuropathy (PN) is one of the most common and dose-limiting side effects of paclitaxel, a chemiotherapeutic drug of proven efficacy in various tumours. We investigated the pathophysiological features of the PN and the temporal relationships between the development of the symptoms and signs associated with paclitaxel administration in two groups of patients with breast cancer: group A received paclitaxel alone (total cumulative dose range: 950-2,475 mg/m2), and group B paclitaxel and adriamycin (total cumulative dose range: 700-2,800 mg/m2). A codified assessment scoring clinical sensory and motor functions according to the Common Toxicity Scale and neurophysiological measurements were made before treatment, after the third and sixth cycles, and at the end of therapy. A total neuropathy score (TNS) included selected clinical and neurophysiological parameters. Both positive and negative sensory and motor symptoms and signs of PN developed during therapy, the most common being painful paresthesias, global areflexia and distal weakness. The neurophysiological study showed an early onset, length-independent and progressive sensory defect, and delayed, distal and length-dependent motor deficits. The neuropathy progressed faster in group A than in group B but, after therapy, most of the patients were TNS grade 2 regardless of their group. The temporal relationships between the PN and paclitaxel were robustly characterised, and thus provide reference data and a model for testing the efficacy of drugs designed to provide neuroprotection.

Intrathecal interleukin-10 gene therapy attenuates paclitaxel-induced mechanical allodynia and proinflammatory cytokine expression in dorsal root ganglia in rats

Paclitaxel is a commonly used cancer chemotherapy drug that frequently causes painful peripheral neuropathies. The mechanisms underlying this dose-limiting side effect are poorly understood. Growing evidence supports that proinflammatory cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor (TNF), released by activated spinal glial cells and within the dorsal root ganglia (DRG) are critical in enhancing pain in various animal models of neuropathic pain. Whether these cytokines are involved in paclitaxel-induced neuropathy is unknown. Here, using a rat neuropathic pain model induced by repeated systemic paclitaxel injections, we examined whether paclitaxel upregulates proinflammatory cytokine gene expression, and whether these changes and paclitaxel-induced mechanical allodynia can be attenuated by intrathecal IL-1 receptor antagonist (IL-1ra) or intrathecal delivery of plasmid DNA encoding the anti-inflammatory cytokine, interleukin-10 (IL-10). The data show that paclitaxel treatment induces mRNA expression of IL-1, TNF, and immune cell markers in lumbar DRG. Intrathecal IL-1ra reversed paclitaxel-induced allodynia and intrathecal IL-10 gene therapy both prevented, and progressively reversed, this allodynic state. Moreover, IL-10 gene therapy resulted in increased IL-10 mRNA levels in lumbar DRG and meninges, measured 2 weeks after initiation of therapy, whereas paclitaxel-induced expression of IL-1, TNF, and CD11b mRNA in lumbar DRG was markedly decreased. Taken together, these data support that paclitaxel-induced neuropathic pain is mediated by proinflammatory cytokines, possibly released by activated immune cells in the DRG. We propose that targeting the production of proinflammatory cytokines by intrathecal IL-10 gene therapy may be a promising therapeutic strategy for the relief of paclitaxel-induced neuropathic pain.

Stabilization of hyperdynamic microtubules is neuroprotective in amyotrophic lateral sclerosis

Mutations in copper/zinc superoxide dismutase 1 (SOD1), a genetic cause of human amyotrophic lateral sclerosis, trigger motoneuron death through unknown toxic mechanisms. We report that transgenic SOD1G93A mice exhibit striking and progressive changes in neuronal microtubule dynamics from an early age, associated with impaired axonal transport. Pharmacologic administration of a microtubule-modulating agent alone or in combination with a neuroprotective drug to symptomatic SOD1G93A mice reduced microtubule turnover, preserved spinal cord neurons, normalized axonal transport kinetics, and delayed the onset of symptoms, while prolonging life by up to 26%. The degree of reduction of microtubule turnover was highly predictive of clinical responses to different treatments. These data are consistent with the hypothesis that hyperdynamic microtubules impair axonal transport and accelerate motor neuron degeneration in amyotrophic lateral sclerosis. Measurement of microtubule dynamics in vivo provides a sensitive biomarker of disease activity and therapeutic response and represents a new pharmacologic target in neurodegenerative disorders.

Quantitative Sensory Findings in Patients With Bortezomib-Induced Pain

Bortezomib (PS-341) is a newly developed proteosome inhibitor that shows extremely promising antineoplastic effects against a variety of neoplasias. Neuropathic pain is emerging as a major complication of bortezomib. Although clinical reports have appeared in the literature describing the general symptoms of bortezomib chemoneuropathy, specific quantitative sensory data that detail the sensory deficits that might yield insight to the primary afferent dysfunction contributing to this pain is lacking. In this report, it is shown that patients with bortezomib-induced neuropathic pain have significantly elevated touch detection threshold and slotted peg board time, impaired sharpness detection, and elevated thresholds for the detection of skin warming and heat pain. Patients also had increased reports of cold pain. These data indicate that bortezomib-induced neuropathy is associated with deficits in Abeta, Adelta, and C caliber primary afferent fibers.

PERSPECTIVE

This work demonstrates that pain induced by the chemotherapy drug bortezomib is accompanied by dysfunction in all fiber types in sensory nerves. Impaired Abeta and C sensory function also extends into areas of skin that are not perceived as affected by pain.

Validation and reduction of FACT/GOG-Ntx subscale for platinum/paclitaxel-induced neurologic symptoms: a gynecologic oncology group study

The FACT/GOG (Gynecologic Oncology Group) Neurotoxicity (Ntx) subscale for assessing platinum/paclitaxel-induced neurologic symptoms was evaluated. The 11-item questionnaire was administered to patients with advanced endometrial cancer treated with doxorubicin/cisplatin (AP) or doxorubicin/cisplatin/paclitaxel (TAP) prior to 1-7 cycles of treatment in GOG 177. The subscale was evaluated in 134 patients in the TAP group for internal reliability, construct validity, criteria validity, sensitivity to treatment differences, and change over time. Cronbach coefficients for internal consistency prior to cycles 1-7 were 0.85, 0.80, 0.84, 0.82, 0.82, 0.85, and 0.84, respectively. The area under the receiver operating characteristic curve was 0.81 for the Ntx score prior to cycle 3. The TAP arm Ntx scores increased significantly from 3.67 at baseline to 8.13 prior to cycle 7; these were higher than the AP arm Ntx scores, which increased from 3.54 at baseline to 4.72 prior to cycle 7. The four sensory items accounted for 80% of treatment differences and 63% of longitudinal changes in the observed subscale score. The 11-item Ntx subscale reliably and validly assesses platinum/paclitaxel-induced peripheral neuropathy. A reduced four-item version is an efficient alternative in measuring this toxicity in clinical trials without compromising its performance.

Intravenous paclitaxel administration in the rat induces a peripheral sensory neuropathy characterized by macrophage infiltration and injury to sensory neurons and their supporting cells

Paclitaxel-induced peripheral neuropathy (PN) can be a significant problem for patients receiving chemotherapeutic regimens for the treatment of breast, ovarian, and lung cancer as PN can influence the quality of life and survivorship in these patients. To begin to understand the cellular changes that occur within the peripheral and central nervous system as PN develops, we intravenously infused rats with clinically relevant doses of paclitaxel. Ten days later, behavioral changes indicative of PN became evident that included mechanical allodynia, cold hyperalgesia, and deficits in ambulation/coordination. These behaviors were accompanied by increased expression of activating transcription factor 3 (ATF3; a marker of cellular injury) in a population of large>medium>small diameter sensory neurons, a population of satellite cells in the lumbar dorsal root ganglia (DRG) and in myelinating Schwann cells in the sciatic nerve. In addition, there was an increase in the expression of glial fibrillary acidic protein (GFAP) in DRG satellite cells and an increase in the number of CD68 positive activated macrophages within the DRG and peripheral nerve. Within lamina III-IV of the lumbar spinal cord, there was an increase in OX42 positive microglia. These data suggest that intravenous infusion of paclitaxel induces a peripheral neuropathy characterized by injury of neuronal and non-neuronal cells in the peripheral nervous system, macrophage activation in both the DRG and peripheral nerve, and microglial activation within the spinal cord. An understanding of the factors involved in the development and maintenance of PN may lead to mechanism based therapies that prevent/treat PN and thus improve the survival and quality of life of patients receiving chemotherapy.

Using nanotechnology to improve the characteristics of antineoplastic drugs: Improved characteristics of nab-paclitaxel compared with solvent-based paclitaxel

Nanotechnology refers to the use of very small pieces of matter, typically < or =200 nm in diameter. Nanoparticle albumin-bound (nab) paclitaxel, a soluble form of the cytotoxin paclitaxel that has demonstrated utility in the setting of cancer chemotherapy, is produced by nab technology using the protein albumin. nab-Paclitaxel targets tumors, enhances tumor penetration by the novel mechanism of albumin receptor-mediated (gp60) endothelial transcytosis, and avoids the use of surfactants and solvents such as Cremophor and Tween. nab-Paclitaxel minimizes the toxicities associated with Cremophor and eliminates the need for premedication for hypersensitivity reactions caused by Cremophor. The albumin coating that surrounds the active drug assists in the transport of the nanoparticles to the interior of the tumor cell that preferentially takes in albumin as a nutrient through the gp60 pathway. In nonclinical studies, nab-paclitaxel achieved higher intratumoral concentrations compared with solvent-based paclitaxel and increased the bioavailability of paclitaxel by eliminating the entrapment of paclitaxel in the plasma. Compared with solvent-based paclitaxel, at equitoxic doses, the nab-paclitaxel produced more complete regressions, longer time to recurrence, longer doubling times, and prolonged survival. nab-Paclitaxel has been shown to have superior efficacy compared with solvent-based paclitaxel without the need for premedication in clinical trials of patients with advanced solid tumors. nab-Paclitaxel has been effective in patients for whom previous chemotherapy has not been helpful. nab Technology has the potential to be applied to other insoluble drugs.

Follow-up care of patients with breast cancer

In the US, over 200,000 new cases of invasive breast cancer are diagnosed each year, with an additional 60,000 cases of ductal carcinoma in situ. The majority of these women will never experience a recurrence of their disease, and most will survive more than 5 years. Follow-up care for these women is focused on addressing long-term complications of therapy, and early detection of new primary cancers and locoregional recurrences. There is no evidence that early detection of distant metastases will lead to an increase in survival, and currently routine imaging studies are not recommended. With the growing number of breast cancer survivors, further studies should be undertaken to study the cost-effectiveness of surveillance strategies.

Cancer pain and its impact on diagnosis, survival and quality of life

Cancer pain significantly affects the diagnosis, quality of life and survival of patients with cancer. During the past decade, preclinical and clinical data has begun to provide insight into the mechanisms that drive and mask cancer pain and the mechanisms by which anti-neoplastic agents induce peripheral neuropathy. Developing a mechanism-based understanding and mechanism-based therapies to treat cancer-associated pain and sensory neuropathy, and incorporating these into mainstream cancer research and therapy, will be crucial to improving the quality of life and survival of patients with cancer.

Upper-extremity pain disorders in breast cancer

Upper-extremity pain is a common and debilitating problem for patients with breast cancer. Although there is considerable literature describing symptoms, little is available on the specific disorders responsible for pain and debility in these patients. Cervical radiculopathy, brachial plexopathy, neuropathy, rotator cuff tendonitis, adhesive capsulitis, epicondylitis, postmastectomy syndrome, swelling, and bone metastases are among the common disorders responsible for upper-extremity pain in breast cancer patients.

OVERALL ARTICLE OBJECTIVE

To discuss common upper-extremity pain disorders in patients with breast cancer.

Peripheral neuropathy induced by microtubule-stabilizing agents

Microtubule-stabilizing agents (MTSAs), including the taxanes and epothilones, are effective chemotherapeutic agents for the treatment of many cancers. Neuropathy is a major adverse effect of MTSA-based chemotherapy, with severe peripheral neuropathy (grade 3 or 4) occurring in as many as 30% of patients treated with a MTSA. MTSA-induced neuropathy usually resolves gradually after cessation of the treatment. The most reliable method to accurately assess MTSA-induced neuropathy is by clinical evaluation, although additional techniques are being developed and evaluated. Among MTSA-induced neuropathy, the most extensively studied is that induced by taxanes; such a neuropathy usually presents as sensory neuropathy and is more common with paclitaxel than docetaxel. The incidence of MTSA-induced neuropathy seems to depend on the MTSA dose per treatment cycle, the schedule of treatment, and the duration of the infusion. Although there have been several small clinical trials with neuroprotective agents, early recognition and supportive care are the best approaches for prevention and management of MTSA-induced neuropathy. In the future, research should focus on elucidating the mechanism of MTSA-induced neuropathy, developing reliable in vivo and in vitro preclinical models to study MTSA-induced neuropathy, developing a more reliable grading system for MTSA-induced neuropathy, developing more reliable methods for evaluating MTSA-induced neuropathy, and evaluating the efficacy of potential neuroprotective agents in clinical trials.

Peripheral neuropathy induced by paclitaxel: recent insights and future perspectives

Paclitaxel is an antineoplastic agent derived from the bark of the western yew, Taxus brevifolia, with a broad spectrum of activity. Because paclitaxel promotes microtubule assembly, neurotoxicity is one of its side effects. Clinical use of paclitaxel has led to peripheral neuropathy and this has been demonstrated to be dependent upon the dose administered, the duration of the infusion, and the schedule of administration. Vehicles in the drug formulation, for example Cremophor in Taxol, have been investigated for their potential to induce peripheral neuropathy. A variety of neuroprotective agents have been tested in animal and clinical studies to prevent paclitaxel neurotoxicity. Recently, novel paclitaxel formulations have been developed to minimize toxicities. This review focuses on recent advances in the etiology of paclitaxel-mediated peripheral neurotoxicity, and discusses current and ongoing strategies for amelioration of this side effect.

Phase I Trial with BMS-275183, a Novel Oral Taxane with Promising Antitumor Activity

PURPOSE

BMS-275183 is an orally administered C-4 methyl carbonate analogue of paclitaxel. We did a dose-escalating phase I study to investigate its safety, tolerability, pharmacokinetics, and possible antitumor activity.

EXPERIMENTAL DESIGN

A cycle consisted of four weekly doses of BMS-275183. The starting dose was 5 mg, which was increased by 100% increments (i.e., 5, 10, 20 mg/m2, etc.) in each new cohort consisting of one patient. Cohorts were expanded when toxicity was encountered, and 20 patients were treated at the maximum tolerated dose (MTD). Plasma pharmacokinetics were done on days 1 and 15.

RESULTS

A total of 48 patients were enrolled in this trial. Dose-limiting toxicities consisted of neuropathy, fatigue, diarrhea, and neutropenia. First cycle severe neuropathy was reported in four patients treated at 320 (n = 1), 240 (n = 2), and 160 mg/m2 (n = 1), whereas eight patients treated at dose levels ranging from 160 to 320 mg/m2 experienced grade 2 neuropathy in cycle one. The MTD was 200 mg/m2, as 3 of 20 patients experienced grade 3 or 4 toxicity in cycle one [fatigue (n = 2), and neutropenia/diarrhea (n = 1)]. BMS-275183 was rapidly absorbed with a mean plasma half-life of 22 hours. We observed a significant correlation between drug-exposure and toxicity. Tumor responses were observed in 9 of 38 evaluable patients with non-small cell lung cancer, prostate carcinoma, and other tumor types.

CONCLUSIONS

BMS-275183 is generally well tolerated on a weekly schedule. The main toxicity is peripheral neuropathy, and the MTD is 200 mg/m2. Promising activity was observed in several tumor types, and a phase II trial in non-small cell lung cancer has been initiated.

Studies of peripheral sensory nerves in paclitaxel-induced painful peripheral neuropathy: evidence for mitochondrial dysfunction

Paclitaxel chemotherapy frequently induces neuropathic pain during and often persisting after therapy. The mechanisms responsible for this pain are unknown. Using a rat model of paclitaxel-induced painful peripheral neuropathy, we have performed studies to search for peripheral nerve pathology. Paclitaxel-induced mechano-allodynia and mechano-hyperalgesia were evident after a short delay, peaked at day 27 and finally resolved on day 155. Paclitaxel- and vehicle-treated rats were perfused on days 7, 27 and 160. Portions of saphenous nerves were processed for electron microscopy. There was no evidence of paclitaxel-induced degeneration or regeneration as myelin structure was normal and the number/density of myelinated axons and C-fibres was unaltered by paclitaxel treatment at any time point. In addition, the prevalence of ATF3-positive dorsal root ganglia cells was normal in paclitaxel-treated animals. With one exception, at day 160 in myelinated axons, total microtubule densities were also unaffected by paclitaxel both in C-fibres and myelinated axons. C-fibres were significantly swollen following paclitaxel at days 7 and 27 compared to vehicle. The most striking finding was significant increases in the prevalence of atypical (swollen and vacuolated) mitochondria in both C-fibres (1.6- to 2.3-fold) and myelinated axons (2.4- to 2.6-fold) of paclitaxel-treated nerves at days 7 and 27. Comparable to the pain behaviour, these mitochondrial changes had resolved by day 160. Our data do not support a causal role for axonal degeneration or dysfunction of axonal microtubules in paclitaxel-induced pain. Instead, our data suggest that a paclitaxel-induced abnormality in axonal mitochondria of sensory nerves contributes to paclitaxel-induced pain.

Mild cognitive impairment after adjuvant chemotherapy in breast cancer patients--evaluation of appropriate research design and methodology to measure symptoms

The development of new chemotherapeutic agents and regimens has contributed to reduced risk of cancer recurrence and prolonged patient survival. However, mild cognitive impairment (MCI), also known as ''chemofog'' or ''chemobrain'' following adjuvant chemotherapy for breast cancer has been reported since the late 1980s. Unfortunately, little is known about it's mechanism, type, severity, and episode length. This article reviewed related studies on the subject, and found that chemotherapy-induced MCI appears to occur in 10-40% of patients, and memory loss and lack of concentration are the most frequent symptoms. The symptoms are apparently transient, but take at least several years to disappear. Reviewed studies show a lack of clear understanding of what causes MCI directly. There is also a lack of consistency in symptom measurement. We point to the need to conduct well-designed studies which begin with a proper hypothesis. Future research needs to be randomized and longitudinal with a base measurement point before the chemotherapy cycle starts. Future studies must adopt an effective and sensitive method to measure MCI. The latest imaging technique, positron emission tomography (PET) may be a powerful tool. Also, all confounding factors, such as age, education, intelligence quotient (IQ), fatigue and depression, hormonal therapy and other treatments should be controlled within the study design. It is hoped that the results of such future studies will allow medical professionals to contemplate effective prevention, treatment and rehabilitation for MCI.

Peripheral neuropathy: A persisting challenge in paclitaxel-based regimes

Cumulative peripheral neuropathy (PNP) still remains a limitation to optimal treatment with paclitaxel (PAC), especially in more dose-dense schedules. This primary sensory PNP may affect the majority of patients after administration of certain cumulative dosages of PAC, while the exact mechanisms of PAC-induced PNP are not known. While a number of preclinical models revealed its vehicle Cremophor EL (CrEL) to be mainly responsible for ganglionopathy, axonopathy and demyelination, clinical data also supports a strong and independent effect of PAC itself, which is most likely based on disturbances in the microtubules in perikaryons, axons and glia cells. Indeed, clinical trials of CrEL-free formulations of PAC still report grade III neurotoxicity as dose-limiting. As treatment options of PAC-induced PNP are rare the use of specific scoring systems for screening purposes is strongly encouraged. In this report we review and discuss the pathogenesis, incidence, risk factors, diagnosis, pharmacodynamics and treatment options for PAC-induced PNP.

Symptomatic and neurophysiological responses of paclitaxel- or cisplatin-induced neuropathy to oral acetyl-L-carnitine

Acetyl-L-carnitine (ALC) improves non-oncological neuropathies. We tested oral ALC (1 g tid) for 8 weeks in 25 patients with neuropathy grade 3 (common toxicity criteria--CTC) during paclitaxel or cisplatin therapy, or grade 2 persisting for at least three months after discontinuing the drugs. An independent neurologist assessed patients before and after ALC. All patients except one reported symptomatic relief, and only two described grade 1 nausea. The sensory neuropathy grade improved in 15 of 25 (60%), and motor neuropathy in 11 of 14 patients (79%). Total neuropathy score (TNS) that included neurophysiological measures improved in 23 (92%). Amelioration of sensory amplitude and conduction velocity (sural and peroneal nerves) was measured in 22 and 21 patients, respectively. Symptomatic improvement persisted in 12 of 13 evaluable patients at median 13 months after ALC. In view of its effect in improving established paclitaxel- and cisplatin-neuropathy, we recommend ALC testing in preventing progression or revert symptoms during neurotoxic chemotherapy.

Phase III trial of nanoparticle albumin-bound paclitaxel compared with polyethylated castor oil-based paclitaxel in women with breast cancer

PURPOSE

ABI-007, the first biologically interactive albumin-bound paclitaxel in a nanameter particle, free of solvents, was compared with polyethylated castor oil-based standard paclitaxel in patients with metastatic breast cancer (MBC). This phase III study was performed to confirm preclinical studies demonstrating superior efficacy and reduced toxicity of ABI-007 compared with standard paclitaxel.

PATIENTS AND METHODS

Patients were randomly assigned to 3-week cycles of either ABI-007 260 mg/m(2) intravenously without premedication (n = 229) or standard paclitaxel 175 mg/m(2) intravenously with premedication (n = 225).

RESULTS

ABI-007 demonstrated significantly higher response rates compared with standard paclitaxel (33% v 19%, respectively; P = .001) and significantly longer time to tumor progression (23.0 v 16.9 weeks, respectively; hazard ratio = 0.75; P = .006). The incidence of grade 4 neutropenia was significantly lower for ABI-007 compared with standard paclitaxel (9% v 22%, respectively; P < .001) despite a 49% higher paclitaxel dose. Febrile neutropenia was uncommon (< 2%), and the incidence did not differ between the two study arms. Grade 3 sensory neuropathy was more common in the ABI-007 arm than in the standard paclitaxel arm (10% v 2%, respectively; P < .001) but was easily managed and improved rapidly (median, 22 days). No hypersensitivity reactions occurred with ABI-007 despite the absence of premedication and shorter administration time.

CONCLUSION

ABI-007 demonstrated greater efficacy and a favorable safety profile compared with standard paclitaxel in this patient population. The improved therapeutic index and elimination of corticosteroid premedication required for solvent-based taxanes make the novel albumin-bound paclitaxel ABI-007 an important advance in the treatment of MBC.

A phase I combination chemotherapy study of biweekly paclitaxel and S-1 administration in patients with advanced gastric cancer

The aim of the current study was to determine the maximum tolerated dose (MTD) and the dose limiting toxicity (DLT) of a combination of paclitaxel and S-1 in patients with advanced gastric cancer. Fifteen patients were enrolled. The dose for S-1 was set at 80 mg/m2/day (days 1-14), while the dose for paclitaxel increased by 10 mg/m2 for every three patients, with a starting dose of 100 mg/m2 and was given biweekly on day 1 and 15. There was no severe toxicity (grade 4) recorded in patients receiving up to 120 mg/m2 of paclitaxel. Leukopenia/neutrophilia with grade 1 to 3 occurred in six patients up to level 3. At 130 mg/m2 of paclitaxel, grade 4 leukocytopenia and neutropenia events and grade 3 diarrhea developed in one out of three patients. One patient in another group of three patients that were enrolled at level 3, developed grade 4 granulocytopenia with fever (a body temperature higher than 38 degrees C) and grade 3 leukocytopenia. Eight patients, out of a total of 15, showed a partial response, resulting in an objective response rate of 53%. Five patients received gastrectomy. Median survival time was 428 days and the 1 year survival rate was 53%. Biweekly paclitaxel/S-1 combination chemotherapy could be safely used for the treatment of advanced gastric cancer. The recommended doses for a phase II study with paclitaxel and S-1 are 120 mg/m2 and 80 mg/m2, respectively.

Selective killing of adriamycin-resistant (G2 checkpoint-deficient and MRP1-expressing) cancer cells by docetaxel

Chemotherapy of cancer is limited by toxicity to normal cells. Drug resistance further limits the therapy. Here, we investigated selective killing of drug-resistant cancer cells by antagonistic drug combinations, which can spare (because of drug antagonism) normal cells. We used paired cell lines that are resistant to Adriamycin due to either expression of MRP1 or lack of G2 checkpoints. The goal was to selectively kill Adriamycin-resistant cancer cells with Docetaxel (Taxotere), while protecting parental (Adriamycin-sensitive) cells, using cytostatic concentrations of Adriamycin. Taxotere kills cells in mitosis. Therefore, by arresting parental cells in G2, 20 to 40 ng/mL of Adriamycin prevented cell death caused by Taxotere. Also, Adriamycin prevented the effects of Taxotere in normal human lymphocytes. In contrast, Taxotere selectively killed MRP1-expressing leukemia cells, which did not undergo G2 arrest in the presence of Adriamycin. Also, in the presence of Adriamycin, HCT116-p21-/- cancer cells with a defective G2 checkpoint entered mitosis and were selectively killed by Taxotere. Finally, 20 ng/mL of Adriamycin protected normal FDC-P1 hematopoietic cells from Taxotere. Whereas parental cells were protected by Adriamycin, the mitogen-activated protein/extracellular signal-regulated kinase inhibitor PD90598 potentiated the cytotoxic effect of Taxotere selectively in Raf-1-transformed FDC-P1 leukemia cells. We propose a therapeutic strategy to prevent normal cells from entering mitosis while increasing apoptosis selectively in mitotic cancer cells.

Association of Paclitaxel Pharmacokinetics with the Development of Peripheral Neuropathy in Patients with Advanced Cancer

Purpose: The shortening of infusion time from 3 to 1 hour decreases the systemic exposure (area under the curve, AUC) of total and unbound paclitaxel but increases the AUC of its vehicle Cremophor EL, whereas the time above total paclitaxel concentrations of 0.05 μmol/L (T&gt;0.05) remains almost constant. As both Cremophor EL and paclitaxel are neurotoxic, we evaluated their pharmacodynamic effects on the development of peripheral neuropathy as the most important nonhematologic toxicity.

Experimental Design: Patients with advanced cancer of different origin were randomized to receive a maximum of 12 weekly-given 1- or 3-hour infusions of 100 mg/m2 paclitaxel (Taxol). Twenty-four patients were assessable for both pharmacokinetics and peripheral neuropathy development evaluated by a clinical scoring system including sensory symptoms, strength, tendon reflexes, and vibratory sense.

Results: Patients with peripheral neuropathy development (n = 14) received more weeks of therapy (P = 0.056) and showed significantly higher T&gt;0.05 (P = 0.022) and overall systemic drug exposures (weeks of therapy × AUC) for total paclitaxel (P = 0.002) and unbound paclitaxel (P = 0.003) than those without peripheral neuropathy. In Kaplan-Meier analyses, T&gt;0.05 ≥ 10.6 hours (P = 0.023), AUC of total paclitaxel ≥ 4.7 μg/mL × hour (P = 0.047), and AUC of unbound paclitaxel ≥ 0.375 μg/mL × hour (P = 0.095) were identified as being potential factors for peripheral neuropathy development. In a Cox regression analysis, only T&gt;0.05 ≥ 10.6 hours remained as an independent risk factor (relative risk, 18.43; P = 0.036) after adjusting for prior vincamycin (relative risk, 11.28; P = 0.038).

Conclusions: From the results obtained in this study, it is concluded that exposure to paclitaxel but not Cremophor EL is associated with peripheral neuropathy development.

Phase II study of weekly vinorelbine and 24-h infusion of high-dose 5-fluorouracil plus leucovorin as first-line treatment of advanced breast cancer

We prospectively investigated the efficacy and safety of combining weekly vinorelbine (VNB) with weekly 24-h infusion of high-dose 5-fluorouracil (5-FU) and leucovorin (LV) in the treatment of patients with advanced breast cancer (ABC). Vinorelbine 25 mg m⁻² 30-min intravenous infusion, and high-dose 5-FU 2600 mg m⁻² plus LV 300 mg m⁻² 24-h intravenous infusion (HDFL regimen) were given on days 1 and 8 every 3 weeks. Between June 1999 and April 2003, 40 patients with histologically confirmed recurrent or metastatic breast cancer were enrolled with a median age of 49 years (range: 36–68). A total of 25 patients had recurrent ABC, and 15 patients had primary metastatic diseases. The overall response rate for the intent-to-treat group was 70.0% (95% CI: 54–84%) with eight complete responses and 20 partial responses. All 40 patients were evaluated for survival and toxicities. Among a total of 316 cycles of VNB–HDFL given (average: 7.9: range: 4–14 cycles per patient), the main toxicity was Gr3/4 leucopenia and Gr3/4 neutropenia in 57 (18.0%) and 120 (38.0%) cycles, respectively. Gr1/2 infection and Gr1/2 stomatitis were noted in five (1.6%) and 59 (18.7%) cycles, respectively. None of the patients developed Gr3/4 stomatitis or Gr3/4 infection. Gr2/3 and Gr1 hand–foot syndrome was noted in two (5.0%) and 23 (57.5%) patients, respectively. Gr1 sensory neuropathy developed in three patients. The median time to progression was 8.0 months (range: 3–25.5 months), and the median overall survival was 25.0 months with a follow-up of 5.5 to 45+ months. This VNB–HDFL regimen is a highly active yet well-tolerated first-line treatment for ABC.

[Ca2+]i signaling between mitochondria and endoplasmic reticulum in neurons is regulated by microtubules. From mitochondrial permeability transition pore to Ca2+-induced Ca2+ release

The positioning and dynamics of organelles depend on membrane-cytoskeleton interactions. Mitochondria relocate along microtubules (MT), but it is not clear whether MT have direct effects on mitochondrial function. Using two-photon microscopy and the mitochondrial fluorescent dyes rhodamine 123 and Rhod-2, we showed that Taxol and nocodazole, which correspondingly stabilize and disrupt MT, decreased potential and Ca(2+) in the mitochondria of brain stem pre-Botzinger complex neurons. Without changing basal cytoplasmic Ca(2+) ([Ca(2+)](i)), Taxol promoted the generation of [Ca(2+)](i) spikes in dendrites. These spikes were abolished after blockade of Ca(2+) influx and after depletion of internal Ca(2+) stores, indicating the involvement of Ca(2+)-induced Ca(2+) release. Nocodazole decreased mitochondrial potential and [Ca(2+)](m) and produced a long lasting increase in [Ca(2+)](i). MT-acting drugs depolarized single immobilized mitochondria and released previously stored Ca(2+). All of these effects were inhibited by pretreatment with blockers of mitochondrial permeability transition pore (mPTP), cyclosporin A, and 2-aminoethoxydiphenyl borate. Induction of mPTP by Taxol and nocodazole was confirmed by using a calcein/Co(2+) imaging technique. Electron and optical microscopy revealed tubulin bound to mitochondria. Mitochondria, MT, and endoplasmic reticulum (ER) showed strong co-localization, the degree of which decreased after MT were disrupted. We propose that changes in the structure of MT by Taxol and nocodazole promote the induction of mPTP. Subsequent Ca(2+) efflux stimulates the Ca(2+) release from the ER that drives spontaneous [Ca(2+)](i) transients. Thus, close positioning of mitochondria to the ER as determined by MT can be essential for the local [Ca](i) signaling in neurons.

Weekly paclitaxel combined with pegylated liposomal doxorubicin (Caelyx™) given every 4 weeks: dose-finding and pharmacokinetic study in patients with advanced solid tumors

BACKGROUND

We aimed to define the maximum tolerated dose (MTD) and characterize the toxicity of the combination of pegylated liposomal doxorubicin (PLD; Caelyx trade mark ) and weekly paclitaxel (wPTX), and to investigate pharmacokinetics of PLD in this combination.

METHODS

A phase I study was performed with an initial dose of 50 mg/m(2) wPTX and 30 mg/m(2) PLD. The paclitaxel dose was escalated in increments of 10 mg/m(2) and PLD in increments of 5 mg/m(2) until the MTD was reached. The pharmacokinetics of PLD were studied at the highest achieved dose levels.

RESULTS

Forty-four cancer patients were enrolled. The MTD was 30/90 and 35/80 mg/m(2) for PLD/wPTX. Dose-limiting toxicities included treatment delay for neutropenia grade 3, febrile neutropenia, palmar-plantar erythrodysesthesia and deep venous thrombosis. Toxicity below the MTD was mild: skin toxicity grade 1-2 developed at high cumulative doses and vascular thrombotic events occurred in two patients with predisposing factors. No cardiotoxicity or clinically relevant peripheral neuropathy was seen. Nausea/vomiting and alopecia were negligible. Three complete responses and nine partial responses were documented among 34 evaluable cases. PLD plasma concentrations were evaluated in seven patients treated at subMTD. Paclitaxel produced a median 53.5% increase of PLD area under the concentration curve (range 4.4%-219%).

CONCLUSIONS

The combination of PLD/wPTX constitutes an active chemotherapy regimen with mild toxicity that merits investigation in phase II at 30/80 or 35/70 mg/m(2). Patients should be monitored for a potentially increased risk of thromboembolic events.

Taxol-induced sensory disturbance is characterized by preferential impairment of myelinated fiber function in cancer patients

Taxol produces neuropathic pain with three distinct zones of involvement in the extremities. Most distally is an area of on-going pain and proximal to this is a zone of sensory disturbance but not overt pain. These two areas were confined in all but one case to the glabrous skin of the hands and/or feet. More proximal is an area not recognized by the patients as involved with pain or sensory disturbance yet wherein quantitative sensory tests nevertheless reveal altered sensibility. Impairment of perception to light touch, normally conveyed by myelinated fibers, was dramatically altered in all three areas, being approximately 50-fold greater than normal in areas of pain and sensory disturbance as well as in areas of skin perceived by the patients as not affected. Impairment of perception to sharpness, normally conveyed by small myelinated fibers, was most pronounced in areas of on-going pain, intermediate in areas of sensory disturbance and near baseline in more proximal skin of chemotherapy patients. In contrast to mechanical sensibility, thermal thresholds for warm and heat pain detection were normal throughout. Finally, chemotherapy patients showed paradoxical burning pain to skin cooling that was most pronounced in proximal areas of skin thought to be unaffected by the patients, intermediate in the border zone of altered sensibility and least pronounced in areas of on-going pain. These data suggest that taxol produces a neuropathy characterized by pronounced impairment of function in A-beta myelinated fibers, intermediate impairment of A-delta myelinated fibers, and a relative sparing of C-fibers.

Ethosuximide reverses paclitaxel- and vincristine-induced painful peripheral neuropathy

Paclitaxel (Taxol) is one of the most effective and frequently used chemotherapeutics for the treatment of solid tumours. However, paclitaxel produces peripheral neurotoxicity with patients reporting sensory abnormalities and neuropathic pain during and often persisting after paclitaxel therapy. The mechanisms underlying this dose-limiting side effect are currently unknown and there are no validated drugs for its prevention or control. Male Sprague-Dawley rats received four intraperitoneal (i.p.) injections on alternate days of 2 mg/kg paclitaxel. Behavioural assessment using von Frey filaments and acetone showed that such paclitaxel treatment induced a pronounced mechanical and cold allodynia/hyperalgesia. Thus these studies aim to test potential analgesics on established paclitaxel-induced pain. Paclitaxel-induced pain appears to be relatively resistant to opioid therapy i.p. 4 mg/kg morphine was ineffective and i.p. 8 mg/kg morphine only elicited up to a 50% reversal of mechanical allodynia/hyperalgesia. Interestingly, a maximally tolerated dose (i.p. 0.2 mg/kg) of the potent NMDA receptor antagonist MK-801 produced no significant reversal of the mechanical allodynia/hyperalgesia suggesting that NMDA receptors have little role in paclitaxel-induced pain. Ethosuximide (i.p. 450 mg/kg) an anti-epileptic and relatively selective T-type calcium channel blocker elicited a near complete reversal of mechanical allodynia/hyperalgesia. Repetitive dosing with ethosuximide (i.p. 100 or 300 mg/kg daily for 3 days) showed a dose-related consistent reversal of mechanical allodynia/hyperalgesia with no evidence of tolerance. Ethosuximide (i.p. 300 mg/kg) also reversed paclitaxel-induced cold allodynia and vincristine-induced mechanical allodynia/hyperalgesia. These data suggest that T-type calcium channels may play a role in chemotherapy-induced neuropathy and moreover identify ethosuximide as a new potential treatment for chemotherapy-induced pain.

Neurotoxicity of taxanes: symptoms and quality of life assessment

Paclitaxel (TXL) and docetaxel (TXT), especially TXL, cause neurotoxicity manifested as polyneuropathy. In clinical practice, detailed knowledge of the symptoms and effect on quality of life (QOL) of neurotoxicity is crucially important both for diagnosis of neuropathy and for management of patients treated with taxanes. In this review, we summarize the symptoms of neurotoxicity caused by taxanes, and highlight the importance of QOL assessment in breast cancer patients treated with taxanes. The most common feature of taxane neurotoxicity is a predominant sensory distal neuropathy, and the incidence and severity of the neuropathic manifestations appear to be related to dose level and cumulative dose. A mixture of paresthesias and dysesthesias is often prominent, and the complaints include burning dysesthesia, numbness, tingling, and shooting pains, typically in a stocking-glove distribution. In contrast to sensory disturbances, motor neuropathy is not well recognized, and is believed to be much less common than sensory neuropathy. Weakness is usually mild, and distal motor neuropathy caused by taxanes rarely affects patients' activities of daily living. The effect of neurotoxicity on QOL is not fully understood, as no study has specifically assessed QOL in terms of neurotoxicity. There is therefore a clear need to collect more detailed data about QOL using well validated, reliable instruments. This will enable us to provide the information that patients require when treatment decisions are being made, and will help in the pursuit of the ameliorative interventions.

Treatment and care of neurotoxicity from taxane anticancer agents

Taxane anticancer agents play a central role in drug therapy for breast cancer today; however, they have a dose-limiting neurotoxicity that is difficult to prevent and treat. To protect against this neurotoxicity it is important to avoid large doses greater than 200 mg/m2, and to adopt 24-hour administration regimens. Care is also needed with regard to the cumulative dose. Glutamine and amitriptyline are two of the very few drugs that have been found to be clinically effective against drug-induced peripheral neuropathy. Drugs are discontinued if neuropathy appears. If administration is to be later restarted, it is recommended that combined use of glutamine or amitriptyline be considered and that patients be given guidance for daily life.

Mechanism of taxane neurotoxicity

The two taxanes (paclitaxel and docetaxel) are widely employed in standard antineoplastic practice. Although these agents are now well established, some toxic side effects have been reported. Toxicity of these agents includes bone marrow suppression (principally neutropenia), hypersensitivity reactions, cutaneous reactions, edema and neurotoxicity. The most prominent neurotoxicity is a sensory neuropathy. Controlling neuropathy is crucial for maintaining the quality of life of patients because it is usually persistent and hard to manage. The precise mechanism for taxane-induced neuropathy is still unknown. The taxanes are known to promote aggregation of intracellular microtubules. Abnormal aggregation of microtubules in the neuronal cells may cause this neuropathy. In addition, the taxanes have been suggested to have intrinsic toxicity and directly injure the cells. A better understanding of the mechanism for this neuropathy may improve the quality of life of patients who undergo taxane antineoplastic therapy.

Peripheral neuropathy and cancer

Peripheral neuropathy has a major impact on quality of life and may limit the amount of treatment patients can receive. Neurotoxic agents are used increasingly in oncologic practice, yet clinicians are often unaware of the protean manifestations of neuropathy and find its management troubling. Recent knowledge about the mechanisms of neuropathic disease and new treatments may help to minimize the impact of neuropathy on this vulnerable patient population.

Neurotoxic complications of chemotherapy in patients with cancer: clinical signs and optimal management

Neurotoxic side effects of chemotherapy occur frequently and are often a reason to limit the dose of chemotherapy. Since bone marrow toxicity, as the major limiting factor in most chemotherapeutic regimens, can be overcome with growth factors or bone marrow transplantation, the use of higher doses of chemotherapy is possible, which increases the risk of neurotoxicity. Chemotherapy may cause both peripheral neurotoxicity, consisting mainly of a peripheral neuropathy, and central neurotoxicity, ranging from minor cognitive deficits to encephalopathy with dementia or even coma. In this article we describe the neurological adverse effects of the most commonly used chemotherapeutic agents. The vinca-alkaloids, cisplatin and the taxanes are amongst the most important drugs inducing peripheral neurotoxicity. These drugs are widely used for various malignancies such as ovarian and breast cancer, and haematological cancers. Chemotherapy-induced neuropathy is clearly related to cumulative dose or dose-intensities. Patients who already have neuropathic symptoms due to diabetes mellitus, hereditary neuropathies or earlier treatment with neurotoxic chemotherapy are thought to be more vulnerable for the development of chemotherapy-induced peripheral neuropathy. Methotrexate, cytarabine (cytosine arabinoside) and ifosfamide are primarily known for their central neurotoxic side effects. Central neurotoxicity ranges from acute toxicity such as aseptic meningitis, to delayed toxicities comprising cognitive deficits, hemiparesis, aphasia and progressive dementia. Risk factors are high doses, frequent administration and radiotherapy preceding methotrexate chemotherapy, which appears to be more neurotoxic than methotrexate as single modality. Data on management and neuroprotective agents are discussed. Management mainly consists of cumulative dose-reduction or lower dose-intensities, especially in patients who are at higher risk to develop neurotoxic side effects. None of the neuroprotective agents described in this article can be recommended for standard use in daily practise at this moment, and further studies are needed to confirm some of the beneficial effects described.

Nutritional Approaches to Late Toxicities of Adjuvant Chemotherapy in Breast Cancer Survivors

Adjuvant chemotherapy of breast cancer reduces recurrence rates and prolongs survival at the cost of both acute and chronic toxicities. Breast cancer survivors who have received adjuvant chemotherapy may suffer from late effects of chemotherapy including congestive heart failure, neuropathy, premature menopause, and osteoporosis. Nutritional approaches to these problems are distinct in their orientation and success. Study of free radical scavengers for anthracycline-induced cardiomyopathy was born from known pathogenetic mechanisms of cardiotoxicity but has been universally disappointing thus far in clinical trials. Application of agents used for diabetic neuropathy suggests that evening primrose oil, alpha-lipoic acid, and capsaicin may all play a role in the empiric options available to patients with chemotherapy-induced neuropathy. Plant-derived preparations including black cohosh (Actaea racemosa), dong quai (Angelica sinensis), evening primrose (Oenothera biennis), and red clover (Trifolium pretense) are used by patients experiencing hot flashes due to premature menopause despite a paucity of clinical trial data demonstrating either safety or efficacy. Calcium and vitamin D are widely accepted as an effective means to retard bone loss leading to osteoporosis. Nutritional approaches to late effects of breast cancer chemotherapy offer the prospect of preventing or ameliorating these sequelae of treatment. However, except for vitamin D and calcium for prevention of bone loss, current clinical evidence supporting use of nutritional agents remains sparse.

Chemotherapy-induced peripheral neuropathy

While cancer remains an important public health concern, novel and enhanced treatment modalities have increased the length of survival of individuals diagnosed with the disease. The treatment of most cancers requires the use of chemotherapeutic agents to affect cure, maintain control of the disease, or provide palliation of symptoms. Although the use of chemotherapeutic agents can serve to prolong life, such agents are associated with significant side effects. Increasing clinical evidence suggests treatment of cancer with neurotoxic agents results in some degree of peripheral neuropathy. Specific drug categories implicated in the development of peripheral neuropathy are the plant alkaloids, interferons, antimitotics, taxanes, and platinum-based compounds. Drug-induced peripheral neuropathy is sensory, dose-related and cumulative and is usually delayed, appearing weeks after initiation of therapy. The number of individuals at risk for the development of chemotherapy-induced neuropathy is expected to increase proportionately with clinical protocols utilizing higher or more frequent dosing. As advanced cancer treatments and clinical trials can result in extending the lives of individuals affected by cancer, long-term functional deficits resulting from life-saving treatments must now be addressed. As such, peripheral neuropathy has emerged as an important consequence of cancer therapy.

Neuromuscular complications of cancer

Neuromuscular complications of cancer are common and can affect any component of the peripheral nervous system from peripheral nerve cell body to muscle. Perhaps the most common complication is a length-dependent symmetric axonal polyneuropathy that is often multifactorial in etiology, resulting from metabolic and treatment effects of the primary malignancy. However, neuromuscular disorders may also be the presenting complaint in many conditions, including disorders caused by malignant infiltration of nerve and disorders cause by paraneoplastic syndromes. Although many of the paraneoplastic conditions are poorly responsive to treatment, not all are, and one hopes that prompt diagnosis of the underlying malignancy will lead to improved patient outcome. Recognition of iatrogenic neuromuscular complications is also important to modify treatment protocols when possible and thus decrease the risk of long-term neurologic disability.