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I.Y. Jo



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

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P3.08-004 - Significance of low dose distribution in developing radiation pneumonitis after helical tomotherapy based hypofractionated radiotherapy for pulmonary metastases (ID 936)

      09:30 - 09:30  |  Author(s): I.Y. Jo

      • Abstract

      Background
      Hypofractionated radiotherapy (HRT) for pulmonary malignancies has been now commonly used, as a tumorcidal dose can be accurately delivered to the target without any consequential dose to adjacent normal tissues. However, radiation pneumonitis (RP) is still a major problem after HRT. To determine the significant parameters in developing RP, we retrospectively investigated data from patients treated with HRT using helical tomotherapy for lung metastases.

      Methods
      A total of 45 patients were included in the study and the median age was 53 years old. The median prescriptive doses were 50 Gy to internal target volume and 40 Gy to planning target volume in 10 fractions over 2 weeks. RP was diagnosed by chest X-ray or computed tomography after HRT and its severity was determined by CTCAE version 4.0.

      Results
      The incidence of symptomatic RP was 26.6%. Univariate analysis showed that mean lung doses, V5, V10, V15, V20 and V25 were statistically significant in developing symptomatic RP (P<0.05). However, only V5 was statistically significant in developing symptomatic RP in multivariate analysis (p=0.019). In the ROC curve, V5 was the most powerful predictor of symptomatic RP, and its AUC was 0.780 (p=0.004). In addition, the threshold value of V5 to develop symptomatic RP was 65%. The large distribution of a low dose resulted in a higher risk of lung toxicity.

      Conclusion
      To prevent symptomatic RP, we should limit the V5 to less than 65%, in addition to considering conventional dosimetric factors. However, a further clinical study must be done in oreder to confirm this result.