Author of

• 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

  • 11669

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    P2.08-024 - A new dose constraint reduce the incidence and severity of radiation-induced pneumonitis in locally advanced NSCLC treated with Intensity-Modulated Radiotherapy (ID 2913)

    09:30 - 09:30  |  Author(s): M.M. Knap
    • Abstract

    Background
    Applying Intensity-Modulated Radiotherapy (IMRT) techniques to patients with stage III NSCLC allows treating large tumour volumes and bulky mediastinal lymph nodes while respecting the usual normal tissue constraints to the lungs and organs at risks. IMRT techniques lead to irradiating a large lung volume with low doses (lung bath). The volume of lung receiving doses of 5 Gy or more (V5) may estimate the toxicity related to low dose irradiation. In the current study, an analysis was performed to test whether the introduction of IMRT was associated with increased incidence of severe radiation pneumonitis (RP) compared to three-dimensional conformal radiotherapy (3D-CRT) and whether introducing a new dose constraints to the V5 (V5 = 60%) would reduce the incidence and/or severity of radiation pneumonitis.

    Methods
    The control group included 105 patients with pathologically confirmed inoperable stage III NSCLC receiving radical radiotherapy (60-66Gy in 2Gy/fraction) between 2007 and 2009, at our department using 3D-CRT. The Study group included ninety consecutive matching patients receiving the same radical dose of radiotherapy using IMRT in the period January 2011 to June 2012. The first 35 patients (group I) were treated with standard dose constrains on MLD (maximum 20 Gy) and V20 (Maximum 40%). In group II including 55 patients, a new dose constraint to V5 was introduced (maximum 60%). All patients were seen weekly under radiotherapy, 6 weeks after, and then with 3 months intervals. Radiation Pneumonitis was graded using CTC 3.3. The clinical and dosimetric parameters related to RP were analysed using SPSS.

    Results
    IMRT was delivered using 4 to 8 beam arrangements. The incidence of grade 3 or more RP in the control group reciving 3D conformal radiotherapy was 16.3% (2% lethal). This was increased to 33% (14% lethal) in group I. Introducing a new dose constrain for the volume receiving low dose (V5) reduced the incidence of severe radiation pneumonitis to less than 10% (0% lethal) in group II. Neither the Mean Lung Dose nor the volume receiving 20 Gy (V20) values were significantly different in the 3 groups.

    Conclusion
    Irradiating large lung volumes with low radiation doses of 5 Gy or more is associated with higher incidence of severe pneumonitis that is potentially lethal despite respecting the V20 and MLD constraints. Using IMRT in patients with large tumours especially if receiving concurrent chemotherapy should be performed with caution. The cut level of V5 of 60% was applied in our department and was found feasible.