Acute Toxicity in Definitive Versus Postprostatectomy Image-Guided Radiotherapy for Prostate Cancer
Received 24 August 2007; received in revised form 13 September 2007; accepted 27 September 2007. published online 03 January 2008.
Purpose
To assess the incidence of acute gastrointestinal (GI) and genitourinary (GU) injury and the dose–volume response in patients with clinically localized prostate cancer treated with image-guided radiotherapy using helical tomotherapy.
Methods and Materials
Between November 2004 and March 2007, 146 consecutive patients with localized prostate cancer were treated with helical tomotherapy at the City of Hope Medical Center. Of the 146 patients, 70 had undergone prostatectomy. Acute GI and GU toxicities were evaluated using the Radiation Therapy Oncology Group/European Organization for Research and Cancer of Medical scoring system. Events were scored for patients developing Grade 2 or greater morbidity within 90 days after the end of radiotherapy (RT). The dosimetric parameters included the minimal dose received by the highest 10%, 20%, 50%, 80%, and 90% of the target volume, the mean rectal dose, minimal rectal dose, maximal rectal dose, and the volume receiving ≥45, ≥65, and ≥70 Gy. These variables, plus the status of radical prostatectomy, hormonal therapy, RT techniques, and medical conditions, were included in a multivariate logistic regression analysis. A goodness-of-fit evaluation was done using the Hosmer-Lemeshow statistic.
Results
A dose–response function for acute GI toxicity was elicited. The acute GI Grade 2 or greater toxicity was lower in the definitive RT group than in the postoperative RT group (25% vs. 41%, p <0.05). Acute GU Grade 2 or greater toxicity was comparable between the two groups. No grade 3 or greater complications were observed. No dosimetric variable was significant for GU toxicity. For acute GI toxicity, the significant dosimetric parameters were the minimal dose received by 10%, 20%, and 50% of the target volume and the mean rectal dose; the most predictive parameter was the minimal dose received by 10% of the target volume. The dose-modifying factor was 1.2 for radical prostatectomy.
Conclusion
The results of our study have shown that acute rectal symptoms are dose-volume related. Postprostatectomy RT resulted in a greater incidence of acute GI toxicity than did definitive RT. For postoperative RT, it would be prudent to use different dose–volume limits.
∗Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA
†Department of Radiation Oncology, University of California at Irvine Medical Center, Orange, CA
Reprint requests to: Timothy E. Schultheiss, Ph.D., Department of Radiation Physics, City of Hope Medical Center, 1500 E. Duarte Rd., Duarte, CA 91010-3000. Tel: (626) 301-8247; Fax: (626) 930-5334
These data were presented at the 49th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), October 28–November 1, 2007, Los Angeles, CA.
ABSTRACT