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Local Failures After Lung SBRT and Dosimetric Analysis of Potential Surgical Resection Lung Volumes
S666
International Journal of Radiation Oncology Biology Physics
with 60 Gy in 3 fractions when V20w10%. Results are consistent with clinical RP data. Conclusions: The presented NTCP model provides an understanding of the dose-volume effect in radiation treatment of the lung, and specifically, an explanation of the advantage of SBRT treatment of smaller tumors with a higher tumor dose. The model is simple and mechanistic with its capacity to reproduce the clinical RP data. It can serve as a basic guidance for RP prediction and treatment planning optimization of both dose distribution and fractionation scheme. Author Disclosure: Y. Fan: None.
failed in locations of BED >100 Gy10. The dose to the projected SEG volume, lymphatics and ITV+2 cm did not seem to affect LF in these cases since the lesions failed either in the PTV or at the periphery, so it is unlikely that the SBRT target volumes need to be expanded over the entire projected SEG volume to decrease LF. Future comparisons to pts that did not have LF, or that failed in regional lymph nodes, may help determine if there is a need for higher doses, larger target volumes, and help estimate an adequate dose to kill microscopic disease when delivering SBRT. Author Disclosure: E. Kemmerer: None. S. Jahania: None. N. Amin: None.
3154
3155
Local Failures After Lung SBRT and Dosimetric Analysis of Potential Surgical Resection Lung Volumes E. Kemmerer, S. Jahania, and N. Amin; Wayne State University/Detroit Medical Center, Detroit, MI
Cardiac Toxicity in Intensity Modulated Radiation Therapy, Dynamic Conformal Arc Therapy, and Volumetric Modulated Arc Therapy of Lung Cancers X. Ming,1 Y. Feng,1 Y. Zhang,1 L. Zhou,2 and J. Deng3; 1Tianjin University, Tianjin, China, 2West China Hospital, Chengdu, China, 3Yale New Haven Hospital, New Haven, CT
Purpose/Objective(s): Medically inoperable early stage NSCLC and metastatic disease to the lungs can be treated with SBRT in lieu of surgical resection. A BED > 100 Gy10 offers excellent local control for gross disease; it is unknown what is adequate dose for microscopic disease. We analyzed dosimetry in the pts with local failure (LF) after SBRT and correlated them to the dosimetry of the lung volumes that would have been surgically removed in patients (pts) if they were surgical candidates in order to explain why there may be differences in LF between the treatments. Materials/Methods: A retrospective review was performed on all pts with early stage NSCLC and lung metastases who were treated with SBRT at our institution from 2008-2013 to identify pts who had radiographic LF. The initial SBRT plan had a PTV Z ITV+ 5 mm. A thoracic surgeon helped to contour a sublobar resection/segmentectomy (SEG) volume based off segmental vasculature and expanded to anatomic boundary. ITV+ 2 cm and proximal segmental lymphovascular volumes were also created. CT at time of LF was fused to the treatment CT to determine the dose at the site of recurrence and location in relation to PTV. Regional lymph node and distant failures were not analyzed. Results: Out of 76 pts with 85 lesions that were treated with lung SBRT, 6 pts (9%) with 7 tumors (8%) demonstrated LF after SBRT. The median follow-up time and time to LF was 13.4 months (0-50) and 17.5 months (749), respectively. All PTVs had adequate coverage with > 100% of the prescription dose covering the PTV. Out of five (71%) lesions that failed within the PTV, 3 had a BED < 100 at the site of failure. Two (29%) lesions failed at the PTV periphery, but only 1 of those lesions had a BED < 100 Gy10. The mean dose to the segmentectomy, lymphatics, and ITV+2 cm all had a BED < 100 Gy10, as expected. Conclusions: Lung SBRT resulted in a low rate of LF. The area of tumor recurrence could not be predicted from initial plans since some tumors
Purpose/Objective(s): The aim of this study is to investigate the cardiac toxicity in the three cohorts of lung cancer patients, each being treated with intensity-modulated radiation therapy (IMRT), dynamic conformal arc therapy (DAT), or volumetric modulated arc therapy (VMAT). Materials/Methods: 89 patients were selected in this comparative study: 20 treated with IMRT, 25 with DAT and 44 with VMAT. The mean tumor volumes for IMRT, DAT and VMAT plans were 243.76, 51.74 and 207.44 cm3, respectively. For comparison, all 89 plans were generated in a same treatment planning system and normalized such that the 100% isodose lines encompassed 95% of planning target volume (PTV). The plan quality was evaluated in terms of target coverage and cardiac toxicity. Particularly, the homogeneity index (HI) and 95% conformity index (%95 CI) were used for target coverage assessment. Cardiac toxicity was evaluated with mean heart dose, mean percentage dose to the heart, maximum heart dose and dose volume indexes. The effects of tumor laterality, target volume and the tumor-to-heart distances (THD) on heart sparing were also investigated. Results: When all the plans were analyzed, the VMAT plans offered the best PTV coverage with 95% CI Z 0.992 and HI Z 1.23, followed by DAT plans with 95% CI Z 0.982 and HI Z 1.37 and IMRT plans with 95% CI Z 0.957 and HI Z 1.42. On the other hand, the DAT plans provided the best heart sparing, with mean heart dose of 2.3 Gy (4.4% of Dp, prescription dose) and maximum dose of 11.6 Gy compared to 6.2 Gy (10.5% of Dp) and 35.7 Gy by IMRT as well as 4.4 Gy (7.8% of Dp) and 30.1 Gy by VMAT. The mean V30 Gy and V5 Gy of the heart were also lower in the DAT plans by up to 11.7% in comparison to IMRT and VMAT plans. When the tumor volume was less than 100 cm3 and THD < 10 cm, the DAT plans spared up to 6% more doses to heart as
Scientific Abstract 3154; Table
Pt#, Tumor Size (cm), Histology #1, 1.8, adenocarcinoma #2 (lesion #1), 1.8, metastatic rectal adenocarcinoma #3, 1.8, Non-small cell lung cancer #4, 2.0, adenocarcinoma #5, 2.2, squamous cell carcinoma #6, 1.5, papillary carcinoma #2 (lesion #2), 1.7, metastatic rectal adenocarcinoma
Mean Dose to Dose to Mean Dose to Volume of Locally Mean Dose to 90% of Mean Dose 90% of Segmental Prescribed Mean PTV Mean Dose Recurrent Segmentectomy Segmentectomy to ITV+ 2 cm ITV + 2 cm Lymphatics Dose/# Dose (Gy)/ to Site Tumor (Gy) / Dose (Gy) / Volume / (Gy) /[BED (Gy) /[BED (Gy)/[BED fractions (fx) [BED Gy10] of Recurrence [BED Gy10 ] [BED Gy10] [BED Gy10] Gy10] Gy10] Gy10] 48 Gy / 4 fx 50.0 [112.5] 48 Gy / 4 fx 48.7 [108]
Within PTV Within PTV
47.8 [104.9] 45.1 [96.0]
44.6 [94.3] 36.5 [69.8]
32.5 [58.9] 11.1 [14.2]
45.7 [97.9] 41.4 [84.2]
35.9 [68.1] 23.2 [36.7]
48.3 [106.6] 36.0 [68.4]
48 Gy / 4 fx 50.9 [115.7 ] Within PTV
49.7 [111.5]
34.2 [63.4]
14.5 [19.8]
40.7 [82.1]
27.4 [46.2]
31.9 [57.3]
48 Gy / 4 fx 50.1 [112.9] 50 Gy / 5 fx 52.2 [106.7]
Within PTV Within PTV
35.9 [68.1] 49.2 [97.6]
40.7 [82.1] 42.1 [77.5]
24.1 [38.6] 23.8 [35.1]
42.3 [87.0] 43.9 [82.4]
27.7 [46.9] 30.4 [48.9]
40.0 [80] 35.5 [60.7]
48 Gy / 4 fx 48.9 [108.7]
Anterior periphery Inferior periphery
52.1 [120.0]
32.6 [59.2]
8.2 [9.9]
42.5 [87.7]
35.9 [68.1]
47.7 [104.6]
26.6[44.3]
44.5 [94.0]
33.3 [61.0]
45.2 [96.3]
35.7 [67.6]
43.5 [90.8]
48 Gy / 4 fx 49.4 [110.4]
International Journal of Radiation Oncology Biology Physics
with 60 Gy in 3 fractions when V20w10%. Results are consistent with clinical RP data. Conclusions: The presented NTCP model provides an understanding of the dose-volume effect in radiation treatment of the lung, and specifically, an explanation of the advantage of SBRT treatment of smaller tumors with a higher tumor dose. The model is simple and mechanistic with its capacity to reproduce the clinical RP data. It can serve as a basic guidance for RP prediction and treatment planning optimization of both dose distribution and fractionation scheme. Author Disclosure: Y. Fan: None.
failed in locations of BED >100 Gy10. The dose to the projected SEG volume, lymphatics and ITV+2 cm did not seem to affect LF in these cases since the lesions failed either in the PTV or at the periphery, so it is unlikely that the SBRT target volumes need to be expanded over the entire projected SEG volume to decrease LF. Future comparisons to pts that did not have LF, or that failed in regional lymph nodes, may help determine if there is a need for higher doses, larger target volumes, and help estimate an adequate dose to kill microscopic disease when delivering SBRT. Author Disclosure: E. Kemmerer: None. S. Jahania: None. N. Amin: None.
3154
3155
Local Failures After Lung SBRT and Dosimetric Analysis of Potential Surgical Resection Lung Volumes E. Kemmerer, S. Jahania, and N. Amin; Wayne State University/Detroit Medical Center, Detroit, MI
Cardiac Toxicity in Intensity Modulated Radiation Therapy, Dynamic Conformal Arc Therapy, and Volumetric Modulated Arc Therapy of Lung Cancers X. Ming,1 Y. Feng,1 Y. Zhang,1 L. Zhou,2 and J. Deng3; 1Tianjin University, Tianjin, China, 2West China Hospital, Chengdu, China, 3Yale New Haven Hospital, New Haven, CT
Purpose/Objective(s): Medically inoperable early stage NSCLC and metastatic disease to the lungs can be treated with SBRT in lieu of surgical resection. A BED > 100 Gy10 offers excellent local control for gross disease; it is unknown what is adequate dose for microscopic disease. We analyzed dosimetry in the pts with local failure (LF) after SBRT and correlated them to the dosimetry of the lung volumes that would have been surgically removed in patients (pts) if they were surgical candidates in order to explain why there may be differences in LF between the treatments. Materials/Methods: A retrospective review was performed on all pts with early stage NSCLC and lung metastases who were treated with SBRT at our institution from 2008-2013 to identify pts who had radiographic LF. The initial SBRT plan had a PTV Z ITV+ 5 mm. A thoracic surgeon helped to contour a sublobar resection/segmentectomy (SEG) volume based off segmental vasculature and expanded to anatomic boundary. ITV+ 2 cm and proximal segmental lymphovascular volumes were also created. CT at time of LF was fused to the treatment CT to determine the dose at the site of recurrence and location in relation to PTV. Regional lymph node and distant failures were not analyzed. Results: Out of 76 pts with 85 lesions that were treated with lung SBRT, 6 pts (9%) with 7 tumors (8%) demonstrated LF after SBRT. The median follow-up time and time to LF was 13.4 months (0-50) and 17.5 months (749), respectively. All PTVs had adequate coverage with > 100% of the prescription dose covering the PTV. Out of five (71%) lesions that failed within the PTV, 3 had a BED < 100 at the site of failure. Two (29%) lesions failed at the PTV periphery, but only 1 of those lesions had a BED < 100 Gy10. The mean dose to the segmentectomy, lymphatics, and ITV+2 cm all had a BED < 100 Gy10, as expected. Conclusions: Lung SBRT resulted in a low rate of LF. The area of tumor recurrence could not be predicted from initial plans since some tumors
Purpose/Objective(s): The aim of this study is to investigate the cardiac toxicity in the three cohorts of lung cancer patients, each being treated with intensity-modulated radiation therapy (IMRT), dynamic conformal arc therapy (DAT), or volumetric modulated arc therapy (VMAT). Materials/Methods: 89 patients were selected in this comparative study: 20 treated with IMRT, 25 with DAT and 44 with VMAT. The mean tumor volumes for IMRT, DAT and VMAT plans were 243.76, 51.74 and 207.44 cm3, respectively. For comparison, all 89 plans were generated in a same treatment planning system and normalized such that the 100% isodose lines encompassed 95% of planning target volume (PTV). The plan quality was evaluated in terms of target coverage and cardiac toxicity. Particularly, the homogeneity index (HI) and 95% conformity index (%95 CI) were used for target coverage assessment. Cardiac toxicity was evaluated with mean heart dose, mean percentage dose to the heart, maximum heart dose and dose volume indexes. The effects of tumor laterality, target volume and the tumor-to-heart distances (THD) on heart sparing were also investigated. Results: When all the plans were analyzed, the VMAT plans offered the best PTV coverage with 95% CI Z 0.992 and HI Z 1.23, followed by DAT plans with 95% CI Z 0.982 and HI Z 1.37 and IMRT plans with 95% CI Z 0.957 and HI Z 1.42. On the other hand, the DAT plans provided the best heart sparing, with mean heart dose of 2.3 Gy (4.4% of Dp, prescription dose) and maximum dose of 11.6 Gy compared to 6.2 Gy (10.5% of Dp) and 35.7 Gy by IMRT as well as 4.4 Gy (7.8% of Dp) and 30.1 Gy by VMAT. The mean V30 Gy and V5 Gy of the heart were also lower in the DAT plans by up to 11.7% in comparison to IMRT and VMAT plans. When the tumor volume was less than 100 cm3 and THD < 10 cm, the DAT plans spared up to 6% more doses to heart as
Scientific Abstract 3154; Table
Pt#, Tumor Size (cm), Histology #1, 1.8, adenocarcinoma #2 (lesion #1), 1.8, metastatic rectal adenocarcinoma #3, 1.8, Non-small cell lung cancer #4, 2.0, adenocarcinoma #5, 2.2, squamous cell carcinoma #6, 1.5, papillary carcinoma #2 (lesion #2), 1.7, metastatic rectal adenocarcinoma
Mean Dose to Dose to Mean Dose to Volume of Locally Mean Dose to 90% of Mean Dose 90% of Segmental Prescribed Mean PTV Mean Dose Recurrent Segmentectomy Segmentectomy to ITV+ 2 cm ITV + 2 cm Lymphatics Dose/# Dose (Gy)/ to Site Tumor (Gy) / Dose (Gy) / Volume / (Gy) /[BED (Gy) /[BED (Gy)/[BED fractions (fx) [BED Gy10] of Recurrence [BED Gy10 ] [BED Gy10] [BED Gy10] Gy10] Gy10] Gy10] 48 Gy / 4 fx 50.0 [112.5] 48 Gy / 4 fx 48.7 [108]
Within PTV Within PTV
47.8 [104.9] 45.1 [96.0]
44.6 [94.3] 36.5 [69.8]
32.5 [58.9] 11.1 [14.2]
45.7 [97.9] 41.4 [84.2]
35.9 [68.1] 23.2 [36.7]
48.3 [106.6] 36.0 [68.4]
48 Gy / 4 fx 50.9 [115.7 ] Within PTV
49.7 [111.5]
34.2 [63.4]
14.5 [19.8]
40.7 [82.1]
27.4 [46.2]
31.9 [57.3]
48 Gy / 4 fx 50.1 [112.9] 50 Gy / 5 fx 52.2 [106.7]
Within PTV Within PTV
35.9 [68.1] 49.2 [97.6]
40.7 [82.1] 42.1 [77.5]
24.1 [38.6] 23.8 [35.1]
42.3 [87.0] 43.9 [82.4]
27.7 [46.9] 30.4 [48.9]
40.0 [80] 35.5 [60.7]
48 Gy / 4 fx 48.9 [108.7]
Anterior periphery Inferior periphery
52.1 [120.0]
32.6 [59.2]
8.2 [9.9]
42.5 [87.7]
35.9 [68.1]
47.7 [104.6]
26.6[44.3]
44.5 [94.0]
33.3 [61.0]
45.2 [96.3]
35.7 [67.6]
43.5 [90.8]
48 Gy / 4 fx 49.4 [110.4]