International Journal of Radiation Oncology*Biology*Physics
ICTR 2000Intensity modulated radiation therapy (IMRT) following prostatectomy: more favorable acute genitourinary toxicity profile compared to primary IMRT for prostate cancer
Introduction
The advances of radiation oncology technology have led to the implementation of three-dimensional conformal radiotherapy (3D-CRT) in the clinics. 3D-CRT has been shown to reduce treatment-related toxicity and to improve biochemical control (1). Intensity modulated radiation therapy (IMRT) combines two advanced concepts to deliver 3D-CRT: (1) Inverse treatment planning with optimization by computer, and (2) Computer-controlled intensity modulation of the radiation beam during treatment 2, 3.
There are many studies (randomized and nonrandomized) addressing acute toxicity following primary 3D-CRT for prostate cancer 1, 4. However, acute toxicity related to postprostatectomy radiotherapy is not as well studied, especially in the 3D-CRT era. To date, there are no data on postprostatectomy IMRT (PPI). We report our initial experience on PPI addressing acute genitourinary (GU) toxicity and treatment planning dosimetric parameters in comparison to primary IMRT (PI) for prostate cancer.
Section snippets
Patient characteristics
From April 1998 to December 1999, 40 patients were treated with IMRT using a commercially available inverse planning system (Peacock, NOMOS Corporation, Sewickley, PA) following initial radical prostatectomy. Patient characteristics are shown in Table 1. Twenty patients had established extracapsular extension, while 19 had positive surgical margin. Five patients had involvement of seminal vesicles. The patients could be broadly divided into two groups:
- 1.
Adjuvant radiotherapy: 9 patients (22.5%)
Treatment planning dosimetry
Fig. 1, Fig. 2, Fig. 3 show axial (two separate levels) and sagittal images of dose distribution for PPI. Dose coverage of the prostatic fossa and doses delivered to the surrounding normal structures, especially bladder and rectum, are depicted. Please note that the patient was treated in the prone position with an air-filled rectal balloon in place. A comparison of target volumes (prostatic fossa vs. prostate with or without seminal vesicles) is shown in Table 3. The target volume was
Discussion
This report is the first to demonstrate the clinical implementation of IMRT with inverse treatment planning in patients following radical prostatectomy. We have previously shown that PI with prostate immobilization using a rectal balloon has significantly reduced acute toxicity when compared to conventional and six-field conformal radiotherapy (5). Before implementing this technique in the postprostatectomy setting, we noted two inherent problems. First, it is more difficult to define the
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