May 12, 2005
Role of pentoxifylline and vitamin E in attenuation of radiation-induced fibrosis.Topics: Medicine
Here is a topic of great interest to many patients that have received radiation therapy as treatment for cancer, particularly patients that have suffered from head and neck cancer. Radiation-induced fibrosis, although relatively rare, can be extremely painful and disabilitating.
The following abstract review focuses on a study to evaluate the use of pentoxifylline and vitamin E as monotherapy and in combination for the treatment of radiation-induced fibrosis (RIF).
Radiation-induced fibrosis (RIF) is a rare morbid complication of radiotherapy, without a proven and established method of management. The treatment of malignant tumors by radiation therapy is limited by the need to avoid excessive late damage to normal tissues. Although new strategies designed to improve the therapeutic ratio have reduced the incidence of radiation-induced fibrosis (RIF), it is still sometimes severe and unavoidable, and slight differences exist in its clinical presentation. Like fibrotic sequelae of any origin, RIF is mainly characterized by nonspecific changes in the connective tissue involving excessive extracellular matrix deposition and hyperactive fibroblasts. Functionally, RIF is reflected in loss of range of motion and muscle strength and the development of limb edema and pain. Tumor necrosis factor alpha and fibroblast growth factor 2 (FGF2), which are abnormally elevated in irradiated tissues, may mediate radiation fibrovascular injury. Patients treated with pentoxifylline have demonstrated improved Active and passive range of motion, and muscle strength and decreased limb edema and pain. Reversal of these delayed radiation effects was associated with a decrease in circulating FGF2.
Literature retrieval was performed through MEDLINE (1966-March 2004) using the terms vitamin E, alpha-tocopherol, pentoxifylline, radiation-induced fibrosis, and radiation injury.
Few treatments exist for managing RIF of soft tissues. Due to its antioxidant properties, vitamin E may reduce the oxidative damage induced by radiation. The precise mechanism of action for pentoxifylline in management of RIF remains unclear. Uncontrolled studies evaluating vitamin E or pentoxifylline as monotherapy in RIF have shown modest improvement in clinical regression of fibrosis. However, controlled data are needed to verify these benefits. Studies involving pentoxifylline plus vitamin E demonstrated regression in RIF. The combination was more effective than placebo and may be superior to monotherapy with either agent. Adverse effects were rarely reported in the studies and consisted mainly of gastrointestinal and nervous system effects.
Overall, pentoxifylline is well tolerated and is one of the few commercially available drugs with clinical data for management of RIF. Despite a lack of large, well-designed clinical trials, pentoxifylline plus vitamin E should be considered as an option in patients with symptomatic RIF.
Question of the day - could circulating FGF2 offer a potential target as a mechanism for amelioration or elimination of radiation-induced fibrosis? It's
Posted by Hyscience at May 12, 2005 10:20 PM
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