IMRT versus conventional 3DCRT on prostate and normal tissue dosimetry using an endorectal balloon for prostate immobilization.

This study was undertaken to compare prostate and normal tissue dosimetry in prostate cancer patients treated with intensity-modulated radiation therapy (IMRT) and conventional 3-dimensional conformal radiotherapy (3DCRT) using an endorectal balloon for prostate immobilization. Ten prostate cancer patients were studied using both IMRT and conventional 3DCRT at Houston Veterans Affairs Medical Center. For IMRT, the prescription was 70 Gy at 2 Gy/fraction at the 83.4% isodose line, allowing no more than 15% of the rectum and 33% of the bladder to receive above 68 and 65 Gy, respectively. For conventional 3DCRT, a 6-field arrangement with lateral and oblique fields was used to deliver 76 Gy at 2Gy/fraction, ensuring complete tumor coverage by the 72-Gy isodose line. Mean doses for prostate and seminal vesicles were 75.10 and 75.11 Gy, respectively, for IMRT and 75.40 and 75.02 Gy, respectively, for 3DCRT (p > 0.218). 3DCRT delivered significantly higher doses to 33%, 50%, and 66% volumes of rectum by 3.55, 6.64, and 10.18 Gy, respectively (p < 0.002), and upper rectum by 7.26, 9.86, and 9.16 Gy, respectively (p < 0.007). 3DCRT also delivered higher doses to femur volumes of 33% and 50% by 9.38 and 10.19 Gy, respectively, (p < 0.001). Insignificant differences in tumor control probability (TCP) values between IMRT and 3DCRT were calculated for prostate (p = 0.320) and seminal vesicles (p = 0.289). Compared to 3DCRT, IMRT resulted in significantly reduced normal tissue complication probability (NTCP) only for upper rectum (p = 0.025) and femurs (p = 0.021). This study demonstrates that IMRT achieves superior normal tissue avoidance, especially for rectum and femurs compared to 3DCRT, with comparable target dose escalation.

Intensity-modulated radiation therapy (IMRT) for meningioma.

PURPOSE: To assess the safety and efficacy of intensity-modulated radiation therapy (IMRT) in the treatment of intracranial meningioma. METHODS AND MATERIALS: Forty patients with intracranial meningioma (excluding optic nerve sheath meningiomas) were treated using IMRT with the NOMOS Peacock system between 1994 and 1999. Twenty-five patients received IMRT after surgery either as adjuvant therapy for incomplete resection or for recurrence, and 15 patients received definitive IMRT after presumptive diagnosis based on imaging. Thirty-two patients had skull base lesions, and 8 had nonskull base lesions. The prescribed dose ranged from 40 to 56 Gy (median 50.4 Gy) at 1.71 to 2 Gy per fraction, and the volume of the primary target ranged from 1.55 to 324.57 cc (median 20.22 cc). The mean dose to the target ranged from 44 to 60 Gy (median 53 Gy). Follow-up ranged from 6 to 71 months (median 30 months). Acute and chronic toxicity were assessed using Radiation Therapy Oncology Group (RTOG) morbidity criteria and tumor response was assessed by patient report, examination, and imaging. Overall survival, progression-free survival, and local control were calculated using the Kaplan-Meier method. RESULTS: Cumulative 5-year local control, progression-free survival, and overall survival were 93%, 88%, and 89%, respectively. Two patients progressed after IMRT, one locally and one distantly. Each was treated with IMRT after multiple recurrences of benign meningioma over many years. Both were found to have malignant meningioma at the time of relapse after IMRT, and it is likely their tumors had already undergone malignant change by the time IMRT was given. Defined normal structures generally received a significantly lower dose than the target. The most common acute central nervous system (CNS) toxicity was mild headache, usually relieved with steroids. One patient experienced RTOG Grade 3 acute CNS toxicity, and 2 experienced Grade 3 or higher late CNS toxicity, with one possible treatment-related death. No toxicity was observed with mean doses to the optic nerve/chiasm up to 47 Gy and maximum doses up to 55 Gy. CONCLUSION: IMRT is a promising new technology that is safe and efficacious in the primary and adjuvant treatment of intracranial meningiomas. A history of local aggression may indicate malignant degeneration and predict a poorer outcome. Toxicity data are encouraging, but the potential for serious side effects exists, as demonstrated by one possible treatment-related death. Larger cohort and longer follow-up are needed to better define efficacy and late toxicity of IMRT.