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R. Rengan



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

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P1.08-024 - Functional imaging for normal lung avoidance with proton radiotherapy (ID 2918)

      09:30 - 09:30  |  Author(s): R. Rengan

      • Abstract

      Background
      Preservation of lung function is critical for patients undergoing radiotherapy for thoracic malignancies, especially in patients with compromised lung function at diagnosis. Physical properties of proton radiotherapy may permit selection of beam pathways that avoid functional lung while providing adequate tumor coverage. We demonstrate the potential for proton radiotherapy avoidance of functional lung volumes defined on SPECT/CT perfusion and ventilation imaging.

      Methods
      SPECT/CT imaging was performed with [99m]Tc-MAA for lung perfusion and [99m]Tc-DTPA for lung ventilation assessment. SPECT/CT images were co-registered to treatment planning CT images and avoidance structures representing perfused or ventilated lung regions were defined using a gradient search algorithm in MIM 6.0. Photon and proton radiotherapy plans were calculated to spare lung avoidance structures in Pinnacle 9.0 and XiO 4.8, respectively, and dose-volume parameters in total lung and functional lung avoidance structures were compared.

      Results
      A representative thoracic cancer patient with compromised and spatially heterogeneous lung function is reported on (Fig. 1). Relative to the photon plan, the proton plan provided superior total lung dose sparing (V~5~=9% vs. 25%, mean dose = 1.6 Gy vs 4.5 Gy; Fig. 2) while achieving similar tumor coverage. Additionally, superior sparing of functional lung was achieved by protons in perfused regions (V~5~<1% vs. 22%, mean dose = 0.1 Gy vs 3.1 Gy) and ventilated regions (V~5~=1% vs. 33%, mean dose = 0.1 Gy vs 4.5 Gy). Figure 1 Figure 2

      Conclusion
      Functional avoidance treatment planning for thoracic patients receiving radiotherapy has been demonstrated with SPECT/CT imaging. In particular, proton radiotherapy may provide strong advantages in this paradigm. Future investigation will focus on regional dose-response modeling and radiotherapy targeting strategies for functional avoidance.

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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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      P3.08-027 - Radiation Pneumonitis in IMRT vs. 3D Conformal Radiation Therapy (ID 3161)

      09:30 - 09:30  |  Author(s): R. Rengan

      • Abstract

      Background
      Radiation pneumonitis is a common cause of morbidity and is a radiation dose-limiting toxicity in patients with locally advanced NSCLC treated with definitive radiotherapy. NSCLC patients are increasingly receiving intensity modulated radiation therapy (IMRT), in part in an attempt to reduce irradiation doses to organs at risk, like the lungs. It is unclear whether the incidence of pneumonitis in IMRT patients differs from that in patients receiving the more commonly available 3D conformal radiation therapy (3DCRT). This retrospective study reports on outcomes at the University of Pennsylvania.

      Methods
      All consecutive patients with non-metastatic locally advanced NSCLC treated with curative intent at the University of Pennsylvania between January 2003 and October 2011 with 3DCRT (n=208) and IMRT (n=58) were graded for post-treatment radiation pneumonitis using Common Toxicity Criteria (CTC) and SWOG criteria in this IRB-approved study. Any short- or long-course initiation of prednisone for dyspnea 1-10 months following treatment was scored as grade 3 pneumonitis. Associations between type of treatment and clinical and demographic factors and outcomes were assessed using Χ[2] and non-parametric equality-of-medians tests. Logistic regression was used to determine predictors of pneumonitis.

      Results
      Patient characteristics, including age, gender, race, marital status, smoking history and pulmonary function were well balanced across treatment groups (p = 0.18 – 0.97). Patients also had similar tumor TNM-stage, histology, differentiation, and involved lobe (p = 0.26 – 0.62). No differences in the proportion receiving concurrent chemotherapy, radiation prescription, lung V5, lung V20 and mean lung doses, or planning target volume (PTV) were identified (p >0.05 for all). Pneumonitis rates did not differ between the IMRT and 3DCRT patients. In 3DCRT patients, 54% had grade 2+ and 27% had grade 3+ CTC pneumonitis compared to 59% and 34% in IMRT patients, respectively (p >0.05). Additionally, 45% and 17% of 3DCRT patients had grade 2+ and 3+ SWOG pneumonitis compared to 45% and 16% in IMRT patients, respectively (p> 0.05). Lower lung lobe, single marital status, pack-years smoked, low pre-treatment pulmonary function DLCO status, increased lung V5, increased lung V20 and mean lung dose all associated with pneumonitis on univariate logistic regression for both 3DCRT and IMRT patients (p <0.05 for all). A multivariate analysis was performed but yielded no significant results.

      Conclusion
      Our findings suggest that treatment with IMRT is associated with similar rates of pneumonitis as treatment with 3DCRT for locally advanced NSCLC patients treated with definitive radiation therapy. As opposed to treatment modality, several factors were identified that were associated with pneumonitis risk, included lung lobe, marital and smoking status, pre-treatment lung function, and irradiation dose received by the lung. Thus, care should be taken to limit the lung V5, lung V20, and mean lung doses when administering curative-intent radiotherapy, regardless of treatment with IMRT or 3DCRT.