Randomized, Placebo-Controlled Clinical Trial Combining Pentoxifylline-Tocopherol and Clodronate in the Treatment of Radiation-Induced Plexopathy

PURPOSE

Radiation-induced (RI) plexopathy is a rare peripheral nerve injury after radiation therapy for cancer. No treatment has been shown to slow its progression. A pentoxifylline-vitamin E combination significantly reduced RI fibrosis, and its association with clodronate (PENTOCLO) allowed healing of osteoradionecrosis and reduction of neurologic symptoms in phase 2 trials.

METHODS AND MATERIALS

A placebo-controlled, double-blind trial conducted in adults with RI limb plexopathy without cancer recurrence, randomized in 2 arms to PENTOCLO (pentoxifylline 800 mg, tocopherol 1000 mg, clodronate 1600 mg 5 days per week) or triple placebo. The primary outcome measure after 18 months of treatment was the neurologic Subjective Objective Management Analytic (SOMA) score evaluating pain, paresthesia, and motor disability.

RESULTS

Between 2011 and 2015, 59 patients were included: 1 false inclusion (neoplastic plexopathy), 29 treated with placebo (group P), and 29 treated with the active drugs (group A); 46 patients presented an upper-limb and 12 a lower-limb plexopathy. The mean delay after irradiation was 26 ± 8 years, for patients with neurologic symptoms for 5 ± 5 years. The median global SOMA scores in the P and A groups, respectively, were 9 (range, 6-11) versus 9 (range, 8-11) at M₀ and 9 (range, 5-12) versus 10 (range, 6-11) at M₁₈ without any significant difference. Analysis of the secondary outcomes showed that SOMA score subdomains for pain and paresthesia were more affected in group A (not significant). The frequency of adverse events was similar in the 2 groups (81% of patients): slight expected vascular-gastrointestinal symptoms in A, but a large excess of RI complications (arterial stenosis).

CONCLUSIONS

This first randomized drug trial in RI plexopathy failed to show a beneficial effect. More studies are needed in patients with less advanced disease and fewer confounding comorbidities and with a more sensitive measure to detect a therapeutic effect.

Lumbosacral plexopathy: A rare long term complication of concomitant chemo-radiation for cervical cancer

Radiation induced Lumbosacral plexophaty (RILP) is a rare but severe complication that has a considerable impact on quality of life. Its occurrence is rare but increasing with improved long-term cancer survival. This entity commonly results in different degrees of sensory and motor deficits. The pathophysiological mechanisms are not yet fully understood. Diagnosis of radiation myelopathy in women with gynecologic malignancies may increase with the use of concomitant chemo-radiation. This report describes the effect of this combination therapy in a 64-year-old woman with cervical carcinoma.

Radiation-induced neuropathy in cancer survivors

Radiation-induced peripheral neuropathy is a chronic handicap, frightening because progressive and usually irreversible, usually appearing several years after radiotherapy. Its occurrence is rare but increasing with improved long-term cancer survival. The pathophysiological mechanisms are not yet fully understood. Nerve compression by indirect extensive radiation-induced fibrosis plays a central role, in addition to direct injury to nerves through axonal damage and demyelination and injury to blood vessels by ischaemia following capillary network failure. There is great clinical heterogeneity in neurological presentation since various anatomic sites are irradiated. The well-known frequent form is radiation-induced brachial plexopathy (RIBP) following breast cancer irradiation, while tumour recurrence is easier to discount today with the help of magnetic resonance imaging and positron emission tomography. RIBP incidence is in accordance with the irradiation technique, and ranges from 66% RIBP with 60Gy in 5Gy fractions in the 1960s to less than 1% with 50Gy in 2Gy fractions today. Whereas a link with previous radiotherapy is forgotten or difficult to establish, this has recently been facilitated by a posteriori conformal radiotherapy with 3D-dosimetric reconstitution: lumbosacral radiculo-plexopathy following testicular seminoma or Hodgkin's disease misdiagnosed as amyotrophic lateral sclerosis. Promising treatments via the antioxidant pathway for radiation-induced fibrosis suggest a way to improve the everyday quality of life of these long-term cancer survivors.

Late radiation injury to peripheral nerves

Although the peripheral nerve has often been considered as radioresistant, clinical practice demonstrates the occurrence of radiation-induced peripheral neuropathies. Because these complications appear late, usually several years after the course of radiotherapy, their occurrence is explained by improvement in the prognosis of several cancers. Their physiopathology is not fully understood. Compression by radio-induced fibrosis probably plays a central role but direct injury to nerves and blood vessels is probably also involved. The most frequent and best known form of postradiation neuropathy is brachial plexopathy, which may follow irradiation for breast cancer. Recent reports demonstrate that postradiation neuropathies show a great heterogeneity, particularly in the anatomical sites, but also in the clinical, electrophysiological, and neuroimaging features. The link with radiotherapy may be difficult for the clinician to establish. Patients with radiation-induced lumbosacral radiculoplexopathy may be misdiagnosed with amyotrophic lateral sclerosis as they often present with pure lower motor neuron syndrome, or with leptomeningeal metastases since nodular MRI enhancement of the nerve roots of the cauda equina and increased CSF protein content can be observed. From a pathophysiological perspective, radiation-induced neuropathy offers an interesting model for deciphering the mechanisms of peripheral neuropathies due to environmental factors. Recent developments show promising strategies for the prevention and treatment of these complications, which have a considerable impact on a patient's quality of life.

[Radiation-induced neuropathies: collateral damage of improved cancer prognosis]

INTRODUCTION

Because of the improvement of cancer prognosis, long-term damages of treatments become a medical and public health problem. Among the iatrogenic complications, neurological impairment is crucial to consider since motor disability and pain have a considerable impact on quality of life of long cancer survivors. However, radiation-induced neuropathies have not been the focus of great attention. The objective of this paper is to provide an updated review about the radiation-induced lesions of the peripheral nerve system.

STATE OF THE ART

Radiation-induced neuropathies are characterized by their heterogeneity in both symptoms and disease course. Signs and symptoms depend on the affected structures of the peripheral nerve system (nerve roots, nerve plexus or nerve trunks). Early-onset complications are often transient and late complications are usually progressive and associated with a poor prognosis. The most frequent and well known is delayed radiation-induced brachial plexopathy, which may follow breast cancer irradiation. Radiation-induced lumbosacral radiculoplexopathy is characterized by pure or predominant lower motor neuron signs. They can be misdiagnosed, confused with amyotrophic lateral sclerosis (ALS) or with leptomeningeal metastases since nodular MRI enhancement of the nerve roots of the cauda equina and increased cerebrospinal fluid protein content can be observed. In the absence of specific markers of the link with radiotherapy, the diagnosis of post-radiation neuropathy may be difficult. Recently, a posteriori conformal radiotherapy with 3D dosimetric reconstitution has been developed to link a precise anatomical site to unexpected excess irradiation.

PERSPECTIVES AND CONCLUSION

The importance of early diagnosis of radiation-induced neuropathies is underscored by the emergence of new disease-modifying treatments. Although the pathophysiology is not fully understood, it is already possible to target radiation-induced fibrosis but also associated factors such as ischemia, oxidative stress and inflammation. A phase III trial evaluating the association of pentoxifylline, tocopherol and clodronate (PENTOCLO, NCT01291433) in radiation-induced neuropathies is now recruiting.