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S. Conijn

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    MO23 - Radiotherapy II: Lung Toxicity, Target Definition and Quality Assurance (ID 107)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      MO23.09 - Intra Thoracic Anatomical Changes (ITAC) in lung cancer patients during the course of radiotherapy (ID 2699)

      10:30 - 12:00  |  Author(s): S. Conijn

      • Abstract
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      Cone beam-CT (CBCT) guidance is routinely used for setup verification of lung cancer patients treated with radiotherapy. CBCT’s frequently show intra-thoracic anatomical changes (ITAC) during treatment. We developed a protocol as a decision support system to guide the radiation technologist in prioritizing these changes. The purpose of this study was to quantify these ITAC during the radiotherapy course and evaluate the current decision protocol.

      The CBCT-scans (made the first 3 fractions and weekly thereafter) of all lung cancer patients treated in 2010 in our institute with radical radiotherapy were evaluated. Each CBCT-scan was visually compared with the planning-CT and all visible ITAC were scored. Additionally, our decision protocol called “traffic-light protocol” was retrospectively applied to all CBCT-scans. The traffic-light protocol has three urgency levels: 1) red: ITAC that likely have a considerable impact on the delivered dose to the primary tumor and/or involved lymph-nodes such as tumor shifts outside the high dose region, large in- or decrease of atelectasis; 2) orange: ITAC with likely moderate impact on the dose distribution such as tumor progression, minor in- or decrease of atelectasis, pleural effusion and post obstructive pneumonia; 3) green: ITAC with likely negligible impact on the dose distribution such as tumor regression without considerable centre of mass displacement or other anatomical changes. For level red changes, the radiation oncologist needs to be consulted immediately before the treatment fraction is delivered. For level orange, the radiation oncologist will be informed by email and a response is required before the next fraction. For level green, the radiation oncologist is informed but no response is required.

      In total 1500 CBCT-scans of 177 patients were evaluated. All patients received radical radiotherapy (≥50 Gy); 97 patients with concurrent chemoradiation, 23 with sequential chemoradiation and 57 with radiotherapy only. In 128 patients (72%) ITAC were observed with maximum level red, orange and green in 12%, 36% and 24% respectively. Fourteen patients (10%) required a new CT and treatment plan to account for the changed anatomy. Most ITAC occurred in the first week (55%). Of all patients with ITAC during treatment, 45%, 36% and 17% had 1, 2, and ≥3 ITAC respectively. Types of observed ITAC were evident regression (36%), considerable tumor baseline shift (28%), changes in atelectasis (15%), tumor progression (11%), pleural effusion (7%) and pneumonia (3%). Progression seen on the CBCT had a significant correlation with changes in week 1 (p<1e3), and level red changes (p=0.01).

      ITAC have been observed in 72% of all lung cancer patients during radical radiotherapy. In 12% of the patients the radiation oncologist needed to respond immediately and in 10% of the patients a new planning-CT was made to mitigate the risk of tumor under dosing. Volumetric image guided radiotherapy in combination with a decision protocol is recommended for lung cancer patients treated with radical radiotherapy. In our institute we implemented daily CBCT guidance for accurate patient alignment and simultaneously capture ITAC as soon as possible.

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