S48 CARO 2009

difficult to predict the end result. The free hand smoothing tool was used for this study. Materials and Methods: Twenty IMRT plans for head and neck cancer patients were used for the study. Free hand fluence smoothing was applied to these plans. The dose distribution for both smoothed and unsmoothed plans were reviewed by a radiation oncologist (RO) and a planner for target coverage and critical organ doses. The dose distribution, Monitor Units (MU), Maximum. Dose and the conformity number (CN, ideal value = 1) were compared between the smoothed and unsmoothed plans. The plan selected by a RO was used for the treatment. The viewers were composed of four ROs and seven planners. One planner and one RO reviewed one plan at a time. Results: The mean CN was 0.77 ± 0.04 with the smoothed plan and 0.76 ± 0.04 for the unsmoothed plan. All the ROs selected the smoothed plans over the non smoothed plans. The planners opted 18 smoothed plans out of twenty plans. There was a reduction of (11.0±6.2) % in total MU for the smoothed plan. The Maximum dose was reduced by (1.3+1.4-1.2) % when compared with unsmoothed plans. Since the average total MUs for these plans was as high as 1241±458, a reduction of 11% in MU was quite significant. This will reduce the probability of a secondary cancer for these patients treated with smoothed IMRT plans. We are currently using this flurence smoothing for routine IMRT planning. 150 TOMOTHERAPY IN THE TREATMENT OF ANAL CANCER: ACUTE TOXICITY DATA S. Loewen, K. Joseph, C. Small, A. Syme, H. Warkentin, E. Gaetz, K. Tankel, D. Severin, N. Usmani, C. Field, T. Nijjar Cross Cancer Institute, Edmonton, AB Purpose: Tomotherapy may provide adequate local control and increased conformality while minimizing dose and toxicity to surrounding structures. The study is to assess acute toxicity of patients with anal cancer treated radically with tomotherapy and concurrent chemotherapy. Materials and Methods: A Phase II study using tomotherapy to treat patients with anal cancer to limit acute toxicity is currently enrolling patients at the Cross Cancer Institute. All patients received 54 Gy in 30 fractions to the tumour PTV and 48 Gy in 30 fractions to the nodal PTV over 6 weeks with concomitant 5-fluorouracil/mitomycin C. Six patients have completed treatment and analysis of acute toxicity has been collected using the CTCAE v3.0 toxicity criteria. Results: Treatment was well tolerated. There were no Grade 3 or higher non-hematological toxicities to peritoneal cavity, bladder, genitalia, skin and bone marrow. Maximum hematological toxicity recorded was Grade 2. None of the patients required a treatment break and all patients received 2 cycles of chemotherapy with no dose reductions. Conclusion: Our early results indicate patients with anal cancer treated with tomotherapy report no incidences of Grade 3 or higher toxicity. 151 TREATMENT PLANNING WITH VOLUMETRIC MODULATED ARC THERAPY FOR STEREOTACTIC BODY RADIOTHERAPY (SBRT) OF SPINAL/PARASPINAL TUMOURS E.L. Marchand, A. Sahgal, B.A. Millar, J. Publicover, M. Sharpe, D. Moseley, D. Létourneau University of Toronto, Princess Margaret Hospital, Toronto, ON Purpose: Hypofractionated SBRT planned with intensity modulated radiotherapy (IMRT) is an effective treatment modality for metastatic spinal tumours. However, this technique is associated with long treatment times which may subject the patient to a greater risk of intrafractional motion. Volumetric modulated arc therapy (VMAT) allows the radiation dose to be delivered in a single gantry rotation with variable dose rate to shorten delivery time. This treatment planning

study compares delivered IMRT treatment plans to retrospectively generated VMAT plans for spinal SBRT. Materials and Methods: VMAT plans were generated for 10 patients previously treated for spinal metastases with IMRT delivering 18 Gy in one fraction or 20-30 Gy in five fractions. The following parameters were compared between IMRT and VMAT plans: maximum dose (dmax) to the spinal cord and PTV, volume of PTV receiving 95% of prescribed dose (V95), monitor units (MU) and treatment delivery time. The average difference between each specified parameter for VMAT and IMRT plans ± the standard deviation (SD) were reported. Results: All VMAT plans met treatment planning criteria for plan acceptability. In comparing VMAT to IMRT, on average superior target coverage per the V95 was observed by 3.9% ± 6.0%. However, on average a marginally higher dmax to the spinal cord of 0.1 ± 0.9 Gy, as well as a higher dmax within the PTV by 0.4 ± 1.7 Gy, was observed. Average time for fraction delivery was reduced by 7.3 ± 4.1 min with VMAT and this results in an overall 45.6% reduction in delivery time as compared to IMRT. Furthermore, less MU (986.9 ± 1662.5 MU) were required per plan with VMAT planning. Conclusion: Superior target coverage was observed with VMAT at the expense of a marginal increase in spinal cord dose. The major gain for VMAT planning is in reducing treatment delivery time which may have the added clinical benefit of less potential for intra-fraction motion. 152 AN EVALUATION OF PATTERNS OF RADIOTHERAPY PRACTICE FOR PATIENTS WITH RIB METASTASES: A SINGLE INSTITUTION STUDY L. Dalimonte, E. Sinclair, A. Lightstone Odette Cancer Centre, Toronto, ON Purpose: To describe the patterns of practice for patients with rib metastases who were treated with radiation therapy for pain relief. Can treatment burden and wait times for this patient population improve with the utilization of orthovoltage treatment machine? Materials and Methods: Cancer registry data for patients with rib disease and radiation therapy technique were collected from January 2007 to January 2009. The data was examined to establish the utilization rate of orthovoltage treatment. Results: The data demonstrated that orthovoltage treatment is an underutilized technique for the palliative treatment of rib disease. More than half of the patients were treated with high energy (6MV) photon beam with either a single direct photon field (16.2%) or a two-field photon technique (47.4%). Electron beam technique represented 35.1% of treatments while orthovoltage constituted only 1.2% of rib treatments. Conclusion: The use of orthovoltage X-ray beams has been demonstrated to be an underutilized radiotherapy treatment technique at this institution. Orthovoltage treatment is a simple radiotherapy technique with a short set-up time that may be a solution for minimizing treatment burden for an already overburdened patient population. 153 PROSPECTIVE ASSESSMENT OF AN OUTPATIENT PALLIATIVE CARE INTERVENTION IN PATIENTS WITH METASTATIC CANCER M. Follwell, D. Burman, L. Le, K. Wakimoto, D. Seccareccia, J. Bryson, G. Rodin, C. Zimmermann University of Toronto, Princess Margaret Hospital, Toronto, ON Purpose: There is increasing support for timely symptom control in patients with cancer, however few studies have assessed outpatient palliative care clinics. This study assessed prospectively the efficacy of an Oncology Palliative Care Clinic (OPCC) in improving patient symptom distress and satisfaction with care. Materials and Methods: Eligible patients were new referrals to an OPCC, had metastatic cancer with a prognosis of >1 month,