Author of

• 10692

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  P1.08 - Poster Session 1 - Radiotherapy (ID 195)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/28/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 10697

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    P1.08-005 - Active Breathing Coordination to measure tumour motion in lung cancer patients: A feasibility study (ID 672)

    09:30 - 09:30  |  Author(s): P.D.T. Phan
    • Abstract

    Background
    Lung tumour motion poses a significant challenge in accurate delivery of radiotherapy. To prevent geographical miss, a generic margin is often added to the CTV to create an internal target volume (ITV). Studies have shown the effectiveness of Active Breathing Coordinator (ABC) (Elekta, Crawley, UK) in reducing this internal margin. For the purpose of this study we wanted to evaluate the feasibility of utilising ABC for our patient population and of defining ITV margin based on breath-hold scans.

    Methods
    13 patients receiving radical radiotherapy were prospectively recruited. Each patient received a 1 hour training session prior to CT simulation to determine eligibility for the study and provide training for the breath hold procedure. A minimum of fourteen seconds breath-hold was required for patients to be eligible. If eligible, patients were positioned on the CT simulator as per department protocol with the addition of ABC. Standard departmental CT protocol for lung treatment was first performed with contrast. This scan was used to identify the tumour region. A breath-hold scan at normal inspiration and expiration was done in the region of visible tumour volume with the aid of ABC. A radiation oncologist defined ITV based on current departmental protocol and using the ABC scans. To verify accuracy of ABC volume, a 4D Cone Beam CT (4D CBCT) scan was done during week 1 of treatment. To verify the reproducibility of ITV and breath-hold position, a second ABC scan and 4DCBCT were performed mid-way through treatment. The planning ITV and ABC ITV were compared. Variation in tumour position and volume were quantified and compared.

    Results
    From the 13 patients recruited, only 5 patients were able to tolerate ABC. On average, eligible patients were able to maintain a 20 second breath-hold. The generic ITV margin was larger than the patient specific ABC ITV margin in all cases. A change in centre of volume was noted between simulation ABC GTV and mid treatment ABC GTV. There was an average overall difference of 0.8cm for the 3 dimensional vectors for two eligible patients. There was no correlation between breath hold ability and the patient’s pulmonary function.

    Conclusion
    ABC was not feasible for the cohort of patients recruited for this study. For the patients who could tolerate ABC scans, the ITV could be individualized and reduced from that based on generic population data.

• 11645

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  P2.08 - Poster Session 2 - Radiotherapy (ID 198)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 11667

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    P2.08-022 - Non-Small Cell Lung Cancer (NSCLC): Changes in volume during radiotherapy and potential adaptive radiotherapy planning (ID 2511)

    09:30 - 09:30  |  Author(s): P.D.T. Phan
    • Abstract

    Background
    Curative radiotherapy for non-small cell lung cancer (NSCLC) is usually delivered over a time period of 5-7 weeks. Tumour regression has been observed over the course of curative radiotherapy. Currently, the entire radiotherapy treatment is delivered based on the original tumour volume. An evolving approach is adaptive radiotherapy planning whereby the radiotherapy plan is modified during a course of treatment to account for tumour and patient changes. This has the potential to reduce the size of radiotherapy fields, allowing dose escalation and normal tissue sparing.

    Methods
    A cohort of 20 consecutive NSCLC patients receiving a curative course of radiotherapy and who had weekly kV cone beam computer tomography (CBCT) images was identified. The gross tumour volume (GTV) and anatomical reference points were delineated on all CBCT scans. Volume and positional changes were recorded and analyzed.

    Results
    Six patients with non-small cell lung cancer who received curative radiotherapy were assessed so far. Five patients had sufficient image quality for contouring. There was a mean percent decrease of 24.8% by fraction 16 and 37.2% by fraction 26. Average tumour migration was 0.4cm. Progressive anatomical changes were more prominent where there was tumour associated with atelectasis. Updated results for the whole cohort will be presented.

    Conclusion
    Tumour regression was observed in all patients and a proportion showed significant reduction. Adaptive planning was a feasible option in selected patients.