Alicia Eve Gittleman MD, Presenter: Nothing to Disclose

Melissa DeRouen, Abstract Co-Author: Nothing to Disclose

Tamara L Duckworth MS, Abstract Co-Author: Nothing to Disclose

Samir Taneja MD, Abstract Co-Author: Nothing to Disclose

Anurag Chandra MD, Abstract Co-Author: Nothing to Disclose

J Keith DeWyngaert PhD, Abstract Co-Author: Nothing to Disclose

Silvia Chiara Formenti MD, Abstract Co-Author: Nothing to Disclose

Nicholas J Sanfilippo MD, Abstract Co-Author: Nothing to Disclose

Purpose/Objective: The results from RTOG 9413 (Roach M, JCO, 2003) justify in specific subsets of patients with prostate cancer, the adoption of radiation therapy fields that include the whole pelvis. We elected to model on a cohort of nine consecutive patients, the effect of different techniques on dosimetry. Results of Intensity Modulated Radiation Therapy (IMRT), 3-Dimensional Conformal Radiation Therapy (3D-CRT), and 2-Dimensional Radiation Therapy (2D) for pelvic nodal irradiation (PNI) are compared. Materials/Methods: Eligibility to pelvic nodal irradiation included men with localized prostate cancer with an estimated risk of lymph node involvement of > 15%. Between November, 2004 and March, 2005, nine consecutive patients were treated with PNI, with a prescription dose of 45 Gy. CT planning was used. The CTV included the prostate gland, peri-prostatic fat, seminal vesicles, and external/internal/obturator/presacral lymph nodes, as defined by the corresponding blood vessels. The PTV was created using a 5-7 mm margin around the CTV. For each patient, the same CTV and PTV were used to compare the three techniques. IMRT plans were devised using inverse planning to deliver 95% of the dose to 95% of the PTV, with the dose delivered through seven fields. For 3D-CRT, a 4-field technique (AP/PA and laterals) was used, and an additional 7 mm around the PTV was added to account for penumbra. 2D plans were created based on standard bony landmarks for a 4-field technique. Dose volume histograms were created for each technique. Results: Among the nine patients, a mean value was obtained for each experimental variable in the three distinct techniques. The variables studied included the median dose to the small bowel, rectum, and bladder. The mean dose to the penile bulb was analyzed, as it is the parameter commonly reported in the literature. Additionally, for both CTV and PTV, the volume receiving 95% of the prescription dose (V95) was calculated. The table summarizes these results. Conclusions: The IMRT technique resulted in a dramatic reduction in dose to normal structures in all nine patients as compared to the 3D-CRT and 2D plans. IMRT and 3D-CRT resulted in similar coverage of the CTV/PTV, while the 2D technique resulted in inadequate coverage of the target volumes in all nine patients.

Gittleman, A, DeRouen, M, Duckworth, T, Taneja, S, Chandra, A, DeWyngaert, J, Formenti, S, Sanfilippo, N, Pelvic Nodal Irradiation for Prostate Carcinoma: A Dosimetric Comparison of Intensity-modulated, 3-Dimensional Conformal, and 2-Dimensional Radiation Therapy Techniques.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4420729.html