A prospective evaluation of helical tomotherapy.

PURPOSE: To report results from two clinical trials evaluating helical tomotherapy (HT). METHODS AND MATERIALS: Patients were enrolled in one of two prospective trials of HT (one for palliative and one for radical treatment). Both an HT plan and a companion three-dimensional conformal radiotherapy (3D-CRT) plan were generated. Pretreatment megavoltage computed tomography was used for daily image guidance. RESULTS: From September 2004 to January 2006, a total of 61 sites in 60 patients were treated. In all but one case, a clinically acceptable tomotherapy plan for treatment was generated. Helical tomotherapy plans were subjectively equivalent or superior to 3D-CRT in 95% of plans. Helical tomotherapy was deemed equivalent or superior in two thirds of dose-volume point comparisons. In cases of inferiority, differences were either clinically insignificant and/or reflected deliberate tradeoffs to optimize the HT plan. Overall imaging and treatment time (median) was 27 min (range, 16-91 min). According to a patient questionnaire, 78% of patients were satisfied to very satisfied with the treatment process. CONCLUSIONS: Helical tomotherapy demonstrated clear advantages over conventional 3D-CRT in this diverse patient group. The prospective trials were helpful in deploying this technology in a busy clinical setting.

Intensity-modulated arc therapy for treatment of high-risk endometrial malignancies.

PURPOSE: We developed an intensity-modulated arc therapy (IMAT) technique for the treatment of women with high-risk endometrial malignancies. In the context of multimodality therapy, nodal and tumor bed irradiation was delivered while respecting tolerance doses for critical structures. METHODS AND MATERIALS: Five patients were planned and treated with the IMAT technique after hysterectomy. Computed tomographic (CT) scans for treatment planning were acquired with the tumor bed contoured as the clinical target volume (CTV(tumor_bed)) and the iliac and presacral vessels contoured as the gross tumor volume (GTV). In 2 patients the lower para-aortic nodes were included into the GTV. The small bowel, iliac crests, femoral heads, bladder, and rectum were contoured as critical organs. For the nodes, a CTV(nodes) was generated with a 7-10-mm margin around the vessels, and the planning target volume (PTV(nodes)) was generated by a further 5-mm expansion. For the tumor bed, the PTV(tumor_bed) was generated with a margin of 7-10 mm around CTV(tumor_bed). Planning constraints included adequate coverage of the tumor bed (>95% receiving > or =45 Gy) and nodes (> or =95% receiving > or =40 Gy). Arc combinations with different extents were tested, and the final plan was generated based on the balance between complexity (number of arcs), PTV coverage, and critical structure sparing. Conventional and 8-field intensity-modulated radiation therapy (IMRT) plans were generated for each patient for comparison purposes. All patients were treated with IMAT. RESULTS: We found that two anterior intensity-modulated arcs (300 degrees to 30 degrees and 330 degrees to 60 degrees ) adequately treated the PTVs. Furthermore, this IMAT technique allowed sparing of small bowel and the iliac crests (marrow space) to a similar degree as the 8-field IMRT. The 8-field IMRT yielded better dose uniformity than IMAT in the target volumes; however, neither technique was as uniform as the conventional plan. In the 5 patients, IMAT treatment was well tolerated and completed as planned. CONCLUSIONS: We successfully piloted an optimized intensity-modulated arc technique to treat 5 high-risk endometrial cancer patients undergoing multimodality treatment. This allowed a significant reduction in dose to bone marrow and small bowel compared with conventional techniques and was simpler to deliver than multifield IMRT.

Planning evaluation of radiotherapy for complex lung cancer cases using helical tomotherapy.

Lung cancer treatment is one of the most challenging fields in radiotherapy. The aim of the present study was to investigate what role helical tomotherapy (HT), a novel approach to the delivery of highly conformal dose distributions using intensity-modulated radiation fan beams, can play in difficult cases with large target volumes typical for many of these patients. Tomotherapy plans were developed for 15 patients with stage III inoperable non-small-cell lung cancer. While not necessarily clinically indicated, elective nodal irradiation was included for all cases to create the most challenging scenarios with large target volumes. A 2 cm margin was used around the gross tumour volume (GTV) to generate primary planning target volume (PTV2) and 1 cm margin around elective nodes for secondary planning target volume (PTV1) resulting in PTV1 volumes larger than 1000 cm3 in 13 of the 15 patients. Tomotherapy plans were created using an inverse treatment planning system (TomoTherapy Inc.) based on superposition/convolution dose calculation for a fan beam thickness of 25 mm and a pitch factor between 0.3 and 0.8. For comparison, plans were created using an intensity-modulated radiation therapy (IMRT) approach planned on a commercial treatment planning system (TheraplanPlus, Nucletron). Tomotherapy delivery times for the large target volumes were estimated to be between 4 and 19 min. Using a prescribed dose of 60 Gy to PTV2 and 46 Gy to PTV1, the mean lung dose was 23.8+/-4.6 Gy. A 'dose quality factor' was introduced to correlate the plan outcome with patient specific parameters. A good correlation was found between the quality of the HT plans and the IMRT plans with HT being slightly better in most cases. The overlap between lung and PTV was found to be a good indicator of plan quality for HT. The mean lung dose was found to increase by approximately 0.9 Gy per percent overlap volume. Helical tomotherapy planning resulted in highly conformal dose distributions. It allowed easy achievement of two different dose levels in the target simultaneously. As the overlap between PTV and lung volume is a major predictor of mean lung dose, future work will be directed to control of margins. Work is underway to investigate the possibility of breath-hold techniques for tomotherapy delivery to facilitate this aim.