Significantly Reduced Normal Tissue Dose with Proton Radiotherapy Compared with 3D-CRT or IMRT in...
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2292 Significantly Reduced Normal Tissue Dose with Proton Radiotherapy Compared with 3D-CRT or IMRT in Stage I or Stage III Non-Small Cell Lung Cancer J.Y. Chang, 1 X. Zhang, 2 X. Wang, 2 Y. Kang, 2 S. Bilton, 2 B. Riley, 2 Z. Liao, 1 M.D. Jeter, 1 R. Mohan, 2 R. Komaki, 1 J.D. Cox 1 1 Radiation Oncology, MD Anderson Cancer Center, Houston, TX, 2 Radiation Physics, MD Anderson Cancer Center, Houston, TX Purpose/Objective: Photon-based radiotherapy is the standard treatment for medically inoperable stage I-III non-small cell lung cancer (NSCLC) with a conventional dose of 60 – 66 Gy. Dose escalation can improve local-regional control and possibly survival, but toxicities limit its potential. Because of its physical characteristics, proton radiotherapy may allow further radiation dose escalation/acceleration without increasing toxicities. We compared dose volume histograms (DVH) in patients with stage I and III NSCLC treated with either a standard dose of photon 3D-CRT or IMRT or with proton radiotherapy with standard or escalated doses. Materials/Methods: Twenty patients with medically inoperable stage I (n10) and stage III (n10) NSCLC were included. All patients were clinically staged using PET/CT. Plans were evaluated using 4D methods to take respiratory motion into consideration. Internal gross target volume was delineated using the maximum intensity projection technique. For stage I, patients were treated with standard 3-D photon radiotherapy to 66 Gy with 2 Gy/fraction. The isodose displays and DVHs were compared with those of the proton treatment plan in the same patient treated with either 66 Gy or 87.5 cobalt gray equivalents (CGE) at 2.5 CGE/fraction as clinically planned dose escalation/acceleration. For stage III, patients were treated with 63 Gy with 1.8 Gy/fraction by either standard 3-D photon radiotherapy or IMRT in selected patients with either bilateral hilums involvement, supraclavicular lymph nodes involvement, or contralateral mediastinal lymph node involvement and minimal tumor motion as assessed by 4-D CT. The isodose displays and DVHs were compared with those of the proton treatment plan in the same patient at the same dose and escalated dose of 74 CGE. Results: For stage I, the average total lung V5, V10, and V20 were 31.8%, 24.6%, and 15.8%, respectively, for the photon plan with a prescribed dose of 66 Gy compared with 13.0%, 11.7%, and 9.8%, respectively, for the proton plan with prescribed dose of 66 CGE (p0.002) and 13.4%, 12.3%, and 10.9% for proton plan with dose escalation to 87.5 CGE (p0.002). In particular, the average contralateral lung low-dose exposure such as V5 reduced from 14.1% to 0.1%. The spinal cord maximal dose reduced from 14.1 Gy to 4.7 CGE, and the heart V40 reduced from 3% to 0%. For stage III, the average total lung V5, V10, and V20 were 53.8%, 44.8%, and 32.9%, respectively, for the photon plan with a prescribed dose of 63 Gy compared with 40.3%, 35.3%, and 29.5%, respectively, for the proton plan with a prescribed dose of 63 CGE (p0.002) and 41.1%, 37%, and 30.8%, respectively, for the proton plan with dose escalation to 74 CGE (p0.002). Again, the average contralateral lung-low dose exposure such as V5 reduced from 41.9% to 22.1%. The spinal cord maximal dose reduced from 41.1 Gy to 27.3 CGE, the heart V40 reduced from 20.6% to 9%, and the esophageal V55 reduced from 38.5% to 29.5%. When compared with the IMRT plan, the regular proton plan still reduced all the normal tissue doses. Conclusions: Proton radiotherapy seems to significantly improve the dose to the normal tissues even with dose-escalated proton therapy, compared with the standard dose of photon therapy using either 3-D or IMRT. Proton therapy with dose escalation/ acceleration may lead to better local control and survival without increasing toxicities in NSCLC, which needs to be confirmed clinically. Further improvement of proton planning particularly for complicated stage III cases can be achieved through gating, optimizing beam arrangements and intensity modulated proton radiotherapy. 2293 Thresholding Segmentation of FDG PET Lung Lesions for RT Planning Purposes L. Soma, M. Picchio, M. Gilardi, C. Messa, V. Bettinardi, M. Danna, R. Giovanna, I. Dell’Oca, S. Schipani, N. Di Muzio, F. Fazio IBFM CNR, University of Milano Bicocca, Scientific Institute H S.Raffaele, Milan, Italy Purpose/Objective: PET with FDG is showing increasing usefulness in radiotherapy for the definition of treatment plans. In particular, by using integrated PET/CT, an accurate definition of biological target volume (BTV) is possible, accounting not only the morphological aspect of the tumour but also its metabolic behavior. However, methods to delineate BTVs on PET images are needed to provide an objective measure of viable tumor margins. Aim of this study was the implementation of a threshold segmentation method based on measured lesion-to-background ratio (L/B) (Daisne 2003) in lung tumors FDG PET, by comparison with the conventional fixed threshold method. Materials/Methods: Phantom and patients 2D PET studies were performed (4 min/bed position) by using a GE PET/CT Discovery ST system. Data were scatter, random and CT attenuation corrected. Images were reconstructed by OSEM algorithm. Phantom studies: in order to simulate thorax acquisitions, the NEMA-01 IQ phantom was studied with inserts in the range 0,5–342,3 cc. Three experiments were performed by varying the L/B radioactivity concentration ratio (4, 8 and 15, respec- tively). In both threshold segmentation methods, the threshold value for each lesion (insert) was defined as a % of the maximum lesion radioactivity concentration. First, the fixed threshold method was applied for those lesions with volume larger than 4cc and contrast higher than 5.1 assuming a constant threshold of 42% (as recommended in Erdi 1997 and 2002). The implementation of the L/B method was performed as follows: for each experiment, the volume of each lesion was calculated using an increasing threshold until the minimum calculated-true volume difference was obtained (Th). Curves of Th versus measured L/B values were created (Th-L/B curves), combining data from the three L/B experiments. Patients studies: 12 FDG PET whole body studies of patients with metabolically active lung tumors (NSCLC) were included in the analysis. For each lesion, the 42% and L/B segmentation methods were applied. As for the latter, different L/B values were measured for each lesion, accounting for the different FDG uptake in the tissues surrounding tumors (background). For each L/B, lesion contours were generated by deriving the appropriate threshold from the phantom Th-L/B curve. The resulting contours were combined to obtain a single contour following the anatomical shape of the lesion. Results: Phantom studies: The fixed threshold method could be applied on 8 out of 19 lesions in the three L/B experiments. In these lesions the method underestimated volume (mean difference 29%, p 0.00015). In the L/B method, Th-L/B curves showed an inverse behaviour, being best fitted by an inverse square (R2 0.9). Patient studies: The fixed threshold method could be applied only on 6 lesions, given the constraints in L/B contrast and lesion size. In the application of the L/B method, S403 Proceedings of the 47th Annual ASTRO Meeting
Transcript of Significantly Reduced Normal Tissue Dose with Proton Radiotherapy Compared with 3D-CRT or IMRT in...
2292 Significantly Reduced Normal Tissue Dose with Proton Radiotherapy Compared with 3D-CRT or IMRTin Stage I or Stage III Non-Small Cell Lung Cancer
J.Y. Chang,1 X. Zhang,2 X. Wang,2 Y. Kang,2 S. Bilton,2 B. Riley,2 Z. Liao,1 M.D. Jeter,1 R. Mohan,2 R. Komaki,1
J.D. Cox1
1Radiation Oncology, MD Anderson Cancer Center, Houston, TX, 2Radiation Physics, MD Anderson Cancer Center,Houston, TX
Purpose/Objective: Photon-based radiotherapy is the standard treatment for medically inoperable stage I-III non-small celllung cancer (NSCLC) with a conventional dose of 60–66 Gy. Dose escalation can improve local-regional control and possiblysurvival, but toxicities limit its potential. Because of its physical characteristics, proton radiotherapy may allow further radiationdose escalation/acceleration without increasing toxicities. We compared dose volume histograms (DVH) in patients with stageI and III NSCLC treated with either a standard dose of photon 3D-CRT or IMRT or with proton radiotherapy with standard orescalated doses.
Materials/Methods: Twenty patients with medically inoperable stage I (n�10) and stage III (n�10) NSCLC were included.All patients were clinically staged using PET/CT. Plans were evaluated using 4D methods to take respiratory motion intoconsideration. Internal gross target volume was delineated using the maximum intensity projection technique. For stage I,patients were treated with standard 3-D photon radiotherapy to 66 Gy with 2 Gy/fraction. The isodose displays and DVHs werecompared with those of the proton treatment plan in the same patient treated with either 66 Gy or 87.5 cobalt gray equivalents(CGE) at 2.5 CGE/fraction as clinically planned dose escalation/acceleration. For stage III, patients were treated with 63 Gywith 1.8 Gy/fraction by either standard 3-D photon radiotherapy or IMRT in selected patients with either bilateral hilumsinvolvement, supraclavicular lymph nodes involvement, or contralateral mediastinal lymph node involvement and minimaltumor motion as assessed by 4-D CT. The isodose displays and DVHs were compared with those of the proton treatment planin the same patient at the same dose and escalated dose of 74 CGE.
Results: For stage I, the average total lung V5, V10, and V20 were 31.8%, 24.6%, and 15.8%, respectively, for the photon planwith a prescribed dose of 66 Gy compared with 13.0%, 11.7%, and 9.8%, respectively, for the proton plan with prescribed doseof 66 CGE (p�0.002) and 13.4%, 12.3%, and 10.9% for proton plan with dose escalation to 87.5 CGE (p�0.002). In particular,the average contralateral lung low-dose exposure such as V5 reduced from 14.1% to 0.1%. The spinal cord maximal dosereduced from 14.1 Gy to 4.7 CGE, and the heart V40 reduced from 3% to 0%. For stage III, the average total lung V5, V10,and V20 were 53.8%, 44.8%, and 32.9%, respectively, for the photon plan with a prescribed dose of 63 Gy compared with40.3%, 35.3%, and 29.5%, respectively, for the proton plan with a prescribed dose of 63 CGE (p�0.002) and 41.1%, 37%, and30.8%, respectively, for the proton plan with dose escalation to 74 CGE (p�0.002). Again, the average contralateral lung-lowdose exposure such as V5 reduced from 41.9% to 22.1%. The spinal cord maximal dose reduced from 41.1 Gy to 27.3 CGE,the heart V40 reduced from 20.6% to 9%, and the esophageal V55 reduced from 38.5% to 29.5%. When compared with theIMRT plan, the regular proton plan still reduced all the normal tissue doses.
Conclusions: Proton radiotherapy seems to significantly improve the dose to the normal tissues even with dose-escalated protontherapy, compared with the standard dose of photon therapy using either 3-D or IMRT. Proton therapy with dose escalation/acceleration may lead to better local control and survival without increasing toxicities in NSCLC, which needs to be confirmedclinically. Further improvement of proton planning particularly for complicated stage III cases can be achieved through gating,optimizing beam arrangements and intensity modulated proton radiotherapy.
2293 Thresholding Segmentation of FDG PET Lung Lesions for RT Planning Purposes
L. Soma, M. Picchio, M. Gilardi, C. Messa, V. Bettinardi, M. Danna, R. Giovanna, I. Dell’Oca, S. Schipani, N. Di Muzio,F. Fazio
IBFM CNR, University of Milano Bicocca, Scientific Institute H S.Raffaele, Milan, Italy
Purpose/Objective: PET with FDG is showing increasing usefulness in radiotherapy for the definition of treatment plans. Inparticular, by using integrated PET/CT, an accurate definition of biological target volume (BTV) is possible, accounting notonly the morphological aspect of the tumour but also its metabolic behavior. However, methods to delineate BTVs on PETimages are needed to provide an objective measure of viable tumor margins. Aim of this study was the implementation of athreshold segmentation method based on measured lesion-to-background ratio (L/B) (Daisne 2003) in lung tumors FDG PET,by comparison with the conventional fixed threshold method.
Materials/Methods: Phantom and patients 2D PET studies were performed (4 min/bed position) by using a GE PET/CTDiscovery ST system. Data were scatter, random and CT attenuation corrected. Images were reconstructed by OSEM algorithm.Phantom studies: in order to simulate thorax acquisitions, the NEMA-01 IQ phantom was studied with inserts in the range0,5–342,3 cc. Three experiments were performed by varying the L/B radioactivity concentration ratio (4, 8 and 15, respec-tively). In both threshold segmentation methods, the threshold value for each lesion (insert) was defined as a % of the maximumlesion radioactivity concentration. First, the fixed threshold method was applied for those lesions with volume larger than 4ccand contrast higher than 5.1 assuming a constant threshold of 42% (as recommended in Erdi 1997 and 2002). Theimplementation of the L/B method was performed as follows: for each experiment, the volume of each lesion was calculatedusing an increasing threshold until the minimum calculated-true volume difference was obtained (Th). Curves of Th versusmeasured L/B values were created (Th-L/B curves), combining data from the three L/B experiments. Patients studies: 12 FDGPET whole body studies of patients with metabolically active lung tumors (NSCLC) were included in the analysis. For eachlesion, the 42% and L/B segmentation methods were applied. As for the latter, different L/B values were measured for eachlesion, accounting for the different FDG uptake in the tissues surrounding tumors (background). For each L/B, lesion contourswere generated by deriving the appropriate threshold from the phantom Th-L/B curve. The resulting contours were combinedto obtain a single contour following the anatomical shape of the lesion.
Results: Phantom studies: The fixed threshold method could be applied on 8 out of 19 lesions in the three L/B experiments.In these lesions the method underestimated volume (mean difference �29%, p� 0.00015). In the L/B method, Th-L/B curvesshowed an inverse behaviour, being best fitted by an inverse square (R2 � 0.9). Patient studies: The fixed threshold methodcould be applied only on 6 lesions, given the constraints in L/B contrast and lesion size. In the application of the L/B method,
S403Proceedings of the 47th Annual ASTRO Meeting
