| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2160804 | Radiotherapy and Oncology | 2007 | 7 Pages |
Background and PurposeTo investigate the effects of starting gantry angle and number of equiangular-spaced beams for prostate cancer radiotherapy on the Radiation Therapy Oncology Group (RTOG) 0126 protocol using intensity-modulated radiation therapy (IMRT).Materials and methodsTen localized prostate cancer patients were prescribed to 79.2 Gy in 44 fractions. Static IMRT plans using five and seven equiangular-spaced beams were generated. The starting gantry angles were incremented by 5° resulting in 15 (5 beams) and 11 (7 beams) plans per patient. Constant target coverage was ensured for all plans in order to isolate the variation in the rectal and bladder metrics as a function of starting gantry angle.ResultsThe variation with starting gantry angle in rectal metrics using 5 beams was statistically significant (p < 0.001) with dosimetric importance. The 5-beam rectal V 75 Gy and V 70 Gy demonstrated a class solution with a characteristic ‘W’ pattern and two optimal starting gantry angles near 20° and 50°. Statistically insignificant differences were observed for the bladder metrics using 5 beams. There was little dosimetric variation in the rectal and bladder metrics with 7 beams. Nearly equivalent rectal V 75 Gy was achieved between 5 optimal equiangular-spaced beams starting at 20° (class solution) and 7 equiangular-spaced beams starting at 0° for most patients.ConclusionsThe use of an optimal starting gantry angle for 5 equiangular-spaced beams, as indicated by a class solution in this study, will facilitate rectal sparing and can produce plans that are equivalent to those employing 7 equiangular-spaced beams.
