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Helical tomotherapy for anal cancer: Initial clinical outcomes and organ motion. J Clin Oncol 2011 Feb;29(4_suppl):530

Date

02/01/2011

Pubmed ID

27985784

Abstract

: 530 Background: Helical tomotherapy (HT) delivers rotational IMRT with megavoltage CT (MVCT) guidance for patient positioning, offering improved dose conformality and accuracy. We report preliminary clinical outcomes using HT in patients with anal cancer with estimated organ motion and delivered doses.

METHODS: From 9/2005-8/2009, 15 patients with anal cancer were treated with HT and concurrent chemotherapy (MMC 10 mg/m(2) IV bolus d1 and 29; 5FU 1,000 mg/m(2)/day CI d1-4 and 29-32). Median doses for primary tumor, involved lymph nodes and uninvolved lymph nodes were 50.5, 50.4 and 45 Gy. Dose specifications and target definitions were per RTOG 0529 for the majority. Treatment plans, daily MVCT, and initial clinical outcomes and toxicity were retrospectively analyzed. Center-of-mass (COM) locations and volumes of the targets and OAR with daily shifts were analyzed on selected patients. Doses actually delivered daily were reconstructed.

RESULTS: At median follow-up of 15 months, all patients were alive without any evidence of recurrence. There were 40% male, 27% HIV+, 13% T3/4, and 47% lymph node positive. Four patients required treatment break of ≤ 1 week. There were no non-hematologic grade 4/5 toxicities. Overall non-hematologic grade 3 toxicity was 33.3% (GI and skin). All other patients had ≤ grade 2 GI or skin toxicity that completely resolved with aggressive supportive care. There was 40% overall hematologic grade 4 toxicity. Overall hematologic grade 3 toxicity was 60%. Daily shifts were 0.6 ± 3.3, 0.4 ± 3.0, and 0.5 ± 2.2 (SD) mm in lateral, longitudinal and vertical directions. Average daily displacements of the COM from their locations on the planning CT were 9 ± 3, 7 ± 4, 9 ± 2, and 7 ± 2 (SD) mm, for anus, rectum, bladder and vulva. Interfractional organ motion and deformation resulted in variations in the dose delivered in each fraction.For example, daily dose covering 95% of PTV varied by 4%, and vulva volume covered by 50 Gy changed by 23% daily.

CONCLUSIONS: HT with concurrent chemotherapy is well-tolerated compared to historical reports. Interfractional organ motion is significant and can result in deviations in dose delivery to the target and OAR. Such deviations should be considered in analyzing dose response outcome. No significant financial relationships to disclose.

Author List

Siker ML, Qi XS, Hu B, Wong SJ, Li XA, Erickson B

Author

Beth A. Erickson MD Professor in the Radiation Oncology department at Medical College of Wisconsin




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