Effects of intraoperative irradiation and intraoperative hyperthermia on canine sciatic nerve: Neurologic and electrophysiologic study (original) (raw)

1996, International Journal of Radiation Oncology*Biology*Physics

Pupuse: Late radiation lqjnry to perIpberal nerve may be the limitjng factor in the cWcai applicat$on of intraoperative radiation therapy (IORT). The combhation of IORT with intraoperatlve hyperWn& (IOHT) ~specificconcentsregardingtbeeffectsoncertainnormaltiarmessuchas~~e~nwve,which~t be included in the treatment iield. The objective of this study was to compare the effect of IORT alone to the effect of IORT comW with IOIIT on peripheral nerve in normal beagle dogs. Methods and Materialsz Young adult beagle dogs were randomized into five groups of three to five dogs each toreceiveIORTdosesof16,2O,24,2S,or32Gyto5anofsmgicaUyexposedrightsciaticnerveusing6MeV el~~amlsixgroupsoffourtofivedogseachreceivedIORTdasesof0,12,16,~,~,or28Gy~ with 44°C of IOHT for 60 min. IOHT was performed using a water circ&t& hyperthermia devlcewlth~ multi&umel thermometq system on the surgically exposed sciatic nerve. Nem-olo@c and eJe&rqhyslo@ic. xammahs were done before and monthly after treatment for 24 months. ElectrophysioIog& studies haduded &ctromyographIc (EMG) e xambmtions of motor tictioh as well as motor nerve conduction velnc&s studies Results Two years after treatment, the effective dose for 50% compIiadion (ED& for limb paresis in dogs exposed to IORT only was 22 Gy. The EDs for paresis in dogs exposed to IORT combii with IOEIT weds 15 Gy. Tbe thermal enhancement ratio (TER) was 1.5. Electrophysiologic studies showed more promhx& changes suchasEMGabnormalities,decreaseinconductionvelocityandamplitudeoftheactionpdential,andcomplete amduction bIo& in dw that received the combiin of IORT and IOHT. The latency to development of pedpbed neuropathies was shorter for dogs exposed to the combined treatment. Conclusion: The lHobebility of developing peripheral nem-opathies in a large anhnal model was higher for. ORT combmed with IOHT, than for IORT alone. The dose req&ed to produce the same level of h&e mdiation &my to the sciatic nerve was reduced by a factor of 1.5 (TER) if IORT was combined with 44°C of IOHT for 60 min. Intraoperatlve irrsdiation, Intraoperatlve hyperthermia, Peripheral nerve.