Clinical experience with intensity modulated radiation therapy (IMRT) in prostate cancer

Purpose: To compare acute and late toxicities of high-dose radiation for pr ostate cancer delivered by either conventional three-dimensional conformal radiation therapy (3D-CRT) or intensity modulated radiation therapy (IMRT). Materials and methods: Between September 1992 and February 1998, 61 patient s with clinical stage T1c- T3 prostate cancer were treated with 3D-CRT and 171 with IMRT to a prescribed dose of 81 Gy. To quantitatively evaluate the differences between conventional 3D-CRT and IMRT, 20 randomly selected pat ients were planned concomitantly by both techniques and the resulting treat ment plans were compared. Acute and late radiation-induced morbidity was ev aluated in all patients and graded according to the Radiation Therapy Oncol ogy Group toxicity scale. Results: Compared with conventional SD-CRT, IMRT improved the coverage of t he clinical target volume (CTV) by the prescription dose and reduced the vo lumes of the rectal and bladder walls carried to high dose levels (P < 0.01 ), indicating improved conformality with IMRT. Acute and late urinary toxic ities were not significantly different for the two methods. However, the co mbined rates of acute grade 1 and 2 rectal toxicities and the risk of late grade 2 rectal bleeding were significantly lower in the IMRT patients. The 2-year actuarial risk of grade 2 bleeding was 2% for IMRT and 10% for conve ntional 3D-CRT (P < 0.001). Conclusions: The data demonstrate the feasibility and safety of high-dose I MRT for patients with localized prostate cancer and provide a proof-of-prin ciple that this method improves dose conformality relative to tumor coverag e and exposure to normal tissues. (C) 2000 Elsevier Science Ireland Ltd. Al l rights reserved.