Forward- and Inverse-Planned Intensity-Modulated Radiotherapy in the CHHiP Trial: A Comparison of Dosimetry and Normal Tissue Toxicity.

AIMS: The CHHiP (Conventional or Hypofractionated High-dose Intensity Modulated Radiotherapy In Prostate Cancer; CRUK/06/016) trial investigated hypofractionated radiotherapy for localised prostate cancer. Forward- (FP) or inverse-planned (IP) intensity-modulated techniques were permitted. Dose-volume histogram and toxicity data were compared to explore the effects of planning method. MATERIALS AND METHODS: In total, 337 participants with intermediate-risk disease and prospectively collected toxicity data were included. Patients were matched on prostate and rectum/bladder volumes and on radiotherapy dose for toxicity comparisons. The primary outcome was grade 2 or higher Radiation Therapy Oncology Group (RTOG) bowel or bladder toxicity at 2 years. RESULTS: IP patients had smaller volumes of rectum irradiated to 50-70 Gy (P < 0.001); FP patients had smaller volumes of bladder irradiated to 74 Gy (P = 0.001). Acute grade 2 + bowel toxicity was worse with FP (27/53 [52%]; 11/53 [21%] IP; P = 0.0002); with no significant differences in acute urinary toxicity. At 2 years, RTOG grade 2 + bowel toxicity rates were FP 0/53 and IP 2/53 and RTOG grade 2 + bladder rates were FP 0/54 and IP 1/57. CONCLUSIONS: Significant differences were found between dose-volume histograms from FP and IP methods. IP may result in small reductions in acute bowel toxicity but both techniques were associated with low rates of late radiotherapy side-effects.

Interobserver variation in clinical target volume and organs at risk segmentation in post-parotidectomy radiotherapy: can segmentation protocols help?

OBJECTIVE: A study of interobserver variation in the segmentation of the post-operative clinical target volume (CTV) and organs at risk (OARs) for parotid tumours was undertaken. The segmentation exercise was performed as a baseline, and repeated after 3 months using a segmentation protocol to assess whether CTV conformity improved. METHODS: Four head and neck oncologists independently segmented CTVs and OARs (contralateral parotid, spinal cord and brain stem) on CT data sets of five patients post parotidectomy. For each CTV or OAR delineation, total volume was calculated. The conformity level (CL) between different clinicians' outlines was measured using a validated outline analysis tool. The data for CTVs were re-analysed after using the cochlear sparing therapy and conventional radiation segmentation protocol. RESULTS: Significant differences in CTV morphology were observed at baseline, yielding a mean CL of 30% (range 25-39%). The CL improved after using the segmentation protocol with a mean CL of 54% (range 50-65%). For OARs, the mean CL was 60% (range 53-68%) for the contralateral parotid gland, 23% (range 13-27%) for the brain stem and 25% (range 22-31%) for the spinal cord. CONCLUSIONS: There was low conformity for CTVs and OARs between different clinicians. The CL for CTVs improved with use of a segmentation protocol, but the CLs remained lower than expected. This study supports the need for clear guidelines for segmentation of target and OARs to compare and interpret the results of head and neck cancer radiation studies.

Practical experience with intensity-modulated radiotherapy.

At the Ipswich Hospital implementation of intensity-modulated radiotherapy (IMRT) commenced in February 2001 based on an established 3D conformal radiotherapy (3D CRT) service. This paper describes our experiences as we commissioned a fully-integrated IMRT planning and delivery system, and established IMRT within the department. Commissioning measurements incorporated a series of tests to ensure the integrity of the system and form the basis of routine quality assurance (QA) procedures. Potential IMRT patients proceeded through pre-treatment in the same way as standard 3D CRT patients. All were dual-planned for IMRT and 3D CRT with no change in established fractionation regimen, and the resulting plans evaluated. IMRT was selected for treatment where it offered a significant advantage by improving dose homogeneity and conformity within the target volume and/or reducing dose to organs at risk. Extensive pre-treatment verification was undertaken on all plans to check dynamic multileaf collimator (MLC) delivery and monitor unit calculation. Patients were monitored throughout treatment with amorphous silicon electronic portal imaging to ensure reproducibility of set-up. Between June 2001 and June 2003 21 patients were treated with inverse-planned IMRT to sites within the head and neck and lung. IMRT has enabled precise delivery to irregular shaped target volumes, avoiding organs at risk and enabling doses to be increased to radical levels in some cases. Additionally over 200 CT scanned breast patients were treated with forward-planned electronic compensation delivered by dynamic MLC, improving dose homogeneity within the breast volume compared with standard wedged plans. The IMRT programme will continue at the Ipswich Hospital with the introduction of further clinical sites and adoption of more aggressive fractionation regimens within the confines of multicentre clinical trials.