Dose Escalation Study with Two Different Hypofractionated Intensity Modulated Radiotherapy Techniques for Localized Prostate Cancer: Acute Toxicity

Abstract

To assess acute gastrointestinal (GI) and genitourinary (GU) toxicities in patients with localized prostate cancer treated with a sequential dose escalation hypofractionated intensitymodulated radiotherapy (IMRT) study using two different delivery methods. Since 2003, 88 and 48 patients were sequentially treated to 56 Gy and to 60 Gy (4 Gy/fraction twice weekly), respectively. IMRT with 6 MV beams was delivered with five fields in Geneva and with nine in Barcelona. Acute GI and GU side effects were scored weekly during treatment and 6 weeks after treatment completion using the Radiation Therapy Oncology Group (RTOG) toxicity scale. Clinical, technical, and dosimetric parameters were analyzed in order to assess for a potential correlation with toxicity.Grade 1-2, GU and GI toxicities during and 6 weeks after treatment completion were 64%, and 24%, and 35% and 12%, respectively. Only one Grade 4 GU toxicity, consisting of transitory urinary obstruction, was observed. Patients treated to 60 Gy in Geneva presented a higher rate of Grade 1-2 GU toxicity (p = 0.01), while patients treated to both 56 and 60 Gy in Barcelona presented a higher Grade 1-2 GI toxicity (p = 0.02). A lower rate of rectal toxicity was observed in the subgroup of 22 patients treated with a rectal balloon (p = 0.02). The use of androgen deprivation therapy was associated with a higher rate of Grade 1-2 GU toxicity after the end of the treatment (p = 0.02). Dose escalation with either 14 × 4 Gy or 15 × 4 Gy delivered with two different IMRT techniques is feasible and is associated with a tolerable acute toxicity.