IMPACT OF CRADLE IMMOBILIZATION ON SETUP REPRODUCIBILITY DURING EXTERNAL-BEAM RADIATION-THERAPY FOR LUNG-CANCER

Purpose: To compare the setup accuracy during fractionated radiation t herapy for two patient groups with lung cancer treated with and withou t an immobilization cradle. Methods: Three hundred ninety-seven port f ilms from 30 patients immobilized in the Alpha Cradle(TM)(1) were comp ared with 329 port films from 30 patients who were not immobilized wit h the cradle, All patients were treated with curative intent for nonme tastatic lung cancer, The frequency of physician-requested isocenter s hifts were compared in the two groups using a two-tailed chi-square te st, Initial port films taken on the first day of treatment, routine fi lms taken usually weekly during radiation therapy, and requested films taken after a requested shift were considered separately, The immobil ization device consisted of a custom-made foam cradle that extended fr om above the head to the knees, Patients were generally treated with t heir arms above their heads, and treatment setup marks in the immobili zed patients were placed on both the patients' skin and the immobiliza tion cradle, For the noncradle patients, setup marks were placed only on the patients' skin. Results: For the routine films, the frequency o f physician-requested isocenter shifts was lower in immobilized patien ts than in the nonimmobilized group (p = 0.139). Most of this reductio n was seen on oblique fields (p = 0.038), No benefits were seen among initial or requested films, The two groups were well balanced with reg ard to stage, age, field size, and total dose. Conclusions: The use of aggressive immobilization improves the setup reproducibility in patie nts receiving external beam radiation therapy for lung cancer, especia lly during treatment with oblique fields, This improvement in treatmen t accuracy might improve the therapeutic ratio. (C) 1997 Elsevier Scie nce Inc.