INTERSTITIAL THERMORADIOTHERAPY WITH FERROMAGNETIC IMPLANTS FOR LOCALLY ADVANCED AND RECURRENT NEOPLASMS

Purpose: The University of Arizona, University of California at San Fr ancisco, City of Hope Medical Center, and University of Wisconsin part icipated in a Phase I/II protocol to assess the heating ability and th e toxicity of interstitial thermoradiotherapy using ferromagnetic impl antation. Methods and Materials: Forty-four patients with advanced pri mary or recurrent extra-cranial solid malignancies were enrolled in th is study. Fourteen gauge catheters were implanted into tumors and, onc e in the department of Radiation Oncology, loaded with ferromagnetic s eeds to deliver a 60 min hyperthermia treatment. Multi-point thermomet ry was continuously used throughout the heating sessions for all patie nts, sampling the periphery as well as the core of the tumor. After Ir idium-192 brachytherapy, 18 patients then had an additional treatment. The mean radiation dose while on protocol was 50.0 Gy, with total dos es (including prior radiotherapy) ranging from 20.3-151.8 Gy (median = 88.7 Gy). Response and toxicity were assessed by inspection, palpatio n, and/or radiologic studies. Forty-one patients were evaluable for re sponse, and there were 55 analyzable hyperthermia treatment sessions. Results: The complete response rate was 61% (25/41). The partial respo nse rate was 31.7% and only 7.3% failed to respond. Median duration of local control has not yet been reached. The mean maximum, minimum, an d mean time-averaged temperatures for all in-tissue sensors were 43.7- degrees-C, 38.7-degrees-C, and 41.0-degrees-C, respectively. Tumor siz e was the only factor significantly correlated with temperatures or wi th complete response rate; larger tumors attained higher temperatures but smaller tumors had a higher response probability. Nineteen patient s (43%) experienced toxicities, however there was only a 7% (3/44) rat e of serious complications (Grade 3 or 4). Prior treatment with hypert hermia was the only factor significantly correlated with serious toxic ity. Conclusion: These results, a 93% total response with only 7% seri ous toxicity, are encouraging especially in the context of the patient population treated. Phase II/III studies involving ferromagnetic impl antation are warranted.