Does treatment of the pelvic nodes with IMRT increase late rectal toxicity over conformal prostate-only radiotherapy to 76 Gy?

PURPOSE: To compare late rectal toxicity rates after three-dimensional conformal radiotherapy to the prostate alone (P-3D-CRT) and whole-pelvis intensity-modulated radiotherapy along with a prostate boost (WP-IMRT/PB) to the same nominal total dose to the prostate. PATIENTS AND METHODS: 68 patients treated with conformal radiotherapy to the prostate only to 76 Gy at the National Institute for Cancer Research, Genoa, Italy, represented the first group (P-3D-CRT). The second group consisted of 45 patients treated at the University of Texas Medical Branch (UTMB), Galveston, TX, USA, with IMRT covering the pelvic nodes and seminal vesicles to 54 Gy at 1.8 Gy per fraction and the prostate to 60 Gy in the same 30 fractions. A separate phase boosted the prostate to 76 Gy (WP-IMRT/PB). Major aspects of planning were remarkably similar at both institutions leaving the inclusion or not of pelvic nodes as the main treatment-related difference between the two groups. Late rectal toxicity was prospectively scored according to the RTOG scale. All patients have a 12-month minimum follow-up, and mean follow-up, similar in both groups, is 25.9 months (SD [standard deviation]: 8.4 months). RESULTS: At 2 years, the estimated cumulative incidence of grade 2 late rectal toxicity is 6%+/-4% for WP-IMRT/PB and 21.2%+/-6% for P-3D-CRT (p=0.06). The difference became significant (HR [hazard ratio]=0.1, 95% CI [confidence interval]: 0.0-0.6; p=0.01) at multivariate analysis. None of the patients developed grade 3+ toxicity. CONCLUSION: Despite the larger treated volume, WP-IMRT/PB allows more rectal sparing than P-3D-CRT.

IMRT to escalate the dose to the prostate while treating the pelvic nodes.

BACKGROUND AND PURPOSE: To assess and quantify the benefit of introducing intensity-modulated radiotherapy (IMRT) over conventional approaches to cover the pelvic nodes while escalating the dose to the prostate gland. MATERIAL AND METHODS: The pelvic lymphatics were planned to receive 50 Gy at 2 Gy per fraction by four-field box (4FB) technique and standard field blocks drawn on digitally reconstructed radiographs (DRR), 4FB with field blocks according to the position of pelvic nodes as contoured on serial planning CT slices, or IMRT. The lateral fields included three different variations of field blocks to assess the role of various degrees of rectal shielding. The boost consisted in 26 Gy in 13 fractions delivered via six-field three-dimensional conformal radiotherapy (3DCRT) or IMRT. By the combination of a pelvic treatment and boost, several plans were obtained for each patient, all normalized to be isoeffective with regard to prostate-planning target volume (PTV-P) coverage. Plans were compared with respect to dose-volume histogram (DVH) of pelvic nodes/seminal vesicles-PTV (PTV-PN/SV), rectum, bladder and intestinal cavity. Reported are the results obtained in eight patients. RESULTS: Pelvic IMRT with a conformal boost provided superior sparing of both bladder and rectum over any of the 4FB plans with the same boost. For the rectum the advantage was around 10% at V70 and even larger for lower doses. Coverage of the pelvic nodes was adequate with initial IMRT with about 98% of the volume receiving 100% of the prescribed dose. An IMRT boost provided a gain in rectal sparing as compared to a conformal boost. However, the benefit was always greater with pelvic IMRT followed by a conformal boost as compared to 4FB with IMRT boost. Finally, the effect of utilizing an IMRT boost with initial pelvic IMRT was greater for the bladder than for the rectum (at V70, about 9% and 3% for the bladder and rectum, respectively). CONCLUSION: IMRT to pelvic nodes with a conformal boost allows dose escalation to the prostate while respecting current dose objectives in the majority of patients and it is dosimetrically superior to 4FB. An IMRT boost should be considered for patients who fail to meet bladder dose objectives.

Dosimetric comparison of conventional and forward-planned intensity-modulated techniques for comprehensive locoregional irradiation of post-mastectomy left breast cancers.

Three recently published randomized trials have shown a survival benefit to postoperative radiation therapy when the internal mammary chain (IMC), supraclavicular (SCV), and axillary lymphatics are treated. When treating the IMC, techniques that minimize dose to the heart and lungs may be utilized to prevent excess morbidity and mortality and achieve the survival benefit reported. The purpose of this study was to dosimetrically compare forward-planned intensity-modulated radiation therapy (fIMRT) with conventional techniques for comprehensive irradiation of the chest wall and regional lymphatics. For irradiation of the chest wall and IMC, 3 treatment plans, (1) fIMRT, (2) partially-wide tangent (PWT) fields, and (3) a photon-electron (PE) technique, were compared for 12 patients previously treated at our institution with fIMRT to the left chest wall and regional lymphatics. Additionally, the SCV and infraclavicular lymphatics were irradiated and 4 methods were compared: 2 with anterior fields only (dose prescribed to 3 and 5 cm [SC3cm, SC5cm]) and 2 with anterior and posterior fields (fIMRT, 3DCRT). Each patient was planned to receive 50 Gy in 25 fractions. Regions of interest (ROIs) created for each patient included chest wall (CW) planning target volume (PTV), IMC PTV, and SCV PTV. Additionally, the following organs at risk (OAR) volumes were created: contralateral breast, heart, and lungs. For each plan and ROI, target volume coverage (V(95-107)) and dose homogeneity (D(95-5)) were evaluated. Additionally, the mean OAR dose and normal tissue complication probability (NTCP) were computed. For irradiation of the CW, target volume coverage and dose homogeneity were improved for the fIMRT technique as compared to PE (p < 0.001, p = 0.023, respectively). Similar improvements were seen with respect to IMC PTV (p = 0.012, p = 0.064). These dosimetric parameters were also improved as compared to PWT, but not to the same extent (p = 0.011, p = 0.095 for CW PTV, and p = 0.164, p > 0.2 for IMC PTV). The PE technique resulted in the lowest heart V30, although this difference was not significant (p > 0.2). The NTCP values for excess cardiac mortality for fIMRT and PE were equivalent (1.9%) and lower than with PWT (2.8%, p > 0.2). The fIMRT technique was able to reduce heart dose and NTCP for each patient as compared to PWT. When comparing the anterior field techniques of treating SCV PTV, prescribing dose to 5 cm resulted in a improved V50 (p = 0.089). However, when compared to fIMRT, the SC3cm and SC5cm had inferior target volume coverage (p = 0.055, p = 0.014) and significantly greater dose heterogeneity (p = 0.031, p = 0.043). The addition of a posterior field increased the volume of lung receiving 40 and 50 Gy, but not significantly (p > 0.2). For complex breast treatments that irradiate the chest wall, IMC, and SCV, fIMRT resulted in improved dose homogeneity and target volume coverage as compared to conventional techniques. Furthermore, the dosimetric gains in target volume coverage with fIMRT came at no significant increase in dose to OAR. The fIMRT technique demonstrated the ability to maintain the advantage of each of the other 2 techniques: reducing the dose to OARs, as with PE, and providing superior target volume coverage, as with PWT.