Author of

• 12544

  +

  P3.08 - Poster Session 3 - Radiotherapy (ID 199)

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

  • 12550

    +

    P3.08-006 - Respiratory function changes after stereotactic ablative radiotherapy (SABR) in stage I non-surgical NSCLC: preliminary results from a single institution prospective study. (ID 1017)

    09:30 - 09:30  |  Author(s): A.R. Filippi
    • Abstract

    Background
    Stereotactic Ablative Radiotherapy (SABR) is an alternative to surgery in patients with early stage non-small cell lung cancer (NSCLC) inoperable for medical co-morbidities (mainly cardiovascular or respiratory diseases) or who refuse surgery. We performed a prospective evaluation of lung function parameters, treatment-related radiological and clinical toxicity in a cohort of patients treated with SABR.

    Methods
    We prospectively recruited 26 patients from July 2012 to May 2013. All patients had a histological or cytological diagnosis of NSCLC (n=20) or a lung lesion in dimensional growth with PET positivity (SUV>2.5) (n=6). All patients had stage IA– IB and were judged unfit for surgery or refused it. Each patient did a 4D-TC with slice of 2.5mm/2.5mm, treatment consisted of a single Volumetric Modulated Arc Therapy and the fractionation schedule was dependent on tumor location. Pulmonary toxicity was assessed through the execution of pulmonary function tests and on chest Computed Tomografy (CT). All tests were synchronously performed before treatment and at regular intervals after SABR (the first control at 45 days, then every 90 days until progression). Lung function parameters were obtained performing spirometry, body plethysmography, determination of the diffusion lung capacity of carbon monoxide (DLCO) and arterial blood gas analysis.

    Results
    Of 26 patients enrolled, 17 performed the first evaluation at 45 days, 5 at 135. At 45 days the total lung capacity (TLC) slightly decreased from 5.87±1.50 Liters (L) to 5.62±1.42 (t=1.87; NS), whereas VC, FEV~1~ and FEV~1~/VC ratio showed minimal changes. At 135 days TLC in the 5 patients who ultimate this step showed a slight recovery to 5.75±1.75 L. The pulmonary diffusion capacity for carbon monoxide (D~L~CO), corrected for hemoglobin (Hb) levels, significantly decreased from 14.4±4.9 to 12.9±5.2 (mL min[-1]·mmHg[-1]) at 45 days (p<0.019) with a slight recovery at 135 day to 13.9±2.7. When D~L~CO was corrected for the measured Alveolar Volume (D~L~CO/VA) the change was not significant. The difference between plethysmographic TLC and the dilution VA (TLC-VA) increased at 45 days from 1.24±0.7 to 1.49±0.8 L, suggesting an increase in ventilation inhomogeneity of the lung. Arterial oxygen pressure decreased from 75.8±7.2 to 71.6±10.4 mmHg (p=0.056 NS) and the variation correlated with TLC-VA (r=-0.72, p<0.001) and DLCO variations (r=-0.67, p<0.03). We observed a low toxicity profile during the first evaluation at 45 days, with only 1 RTOG grade 2 and 1 grade 3 post actinic pneumonia, both treated with systemic corticosteroids. Only three patients reported fatigue as the only adverse event. At the first radiological re-evaluation we didn’t observe any progression disease, with a 59% rate of partial response.

    Conclusion
    Preliminary findings suggest that no major changes in lung function can be detected at 45 days after SABR. A slight reduction in D~L~CO can be observed, and this could reflect a transitory increase in pulmonary ventilation inhomogeneity caused by RT rather than a direct membrane damage. Study prosecution will hopefully clear the physiopathological evolution at several months after SABR, and further analyses will be carried out investigating for a potential correlation with radiological toxicity and dosimetric profiles.