- Email: [email protected]
1335 poster VOLUMETRIC MODULATED INTENSITY MODULATED ARC THERAPY FOR STEREOTACTIC LUNG RADIOTHERAPY: CONSTANT DOSE RATE VERSUS VARIABLE DOSE RATE DELIVERY
IMRT: T REATMENT PLANNING AND OPTIMIZATION
TPS provides very accurate dose calculation at low dose regions, which particularly facilitates accurate evaluation of secondary cancer risk in VMAT delivery. We will retrospectively evaluate dose distributions created by SmartArc VMAT plans. 1334 poster VOLUMETRIC MODULATED ARC RADIOTHERAPY (VMAT) OF TUMOURS IN THE THORAX - ACUTE TOXICITY RESULTS FROM A SINGLE CENTRE M. Ahmed1 , J. Bedford1 , J. Warrington1 , M. Hawkins2 1 T HE R OYAL M ARSDEN NHS F OUNDATION T RUST, Sutton, United Kingdom 2 T HE R OYAL M ARSDEN NHS F OUNDATION T RUST, London, United Kingdom
Purpose: VMAT treatment delivery benefits from simultaneous variations in gantry speed, dose-rate and multi-leaf collimator leaf positions. In lung and oesophageal cancer VMAT reduces treatment delivery time and can potentially reduce normal tissue toxicity. Clinical data on this relatively novel radiotherapy technique is lacking. We present acute toxicity data on a cohort of patients treated with VMAT. Materials: Data were collected retrospectively. Patients with carcinoma of the lung (stage I-IIIB) or oesophagus (stage III) were treated radically with VMAT using a single arc technique. Patients were planned using in-house software Autobeam version 4.6. No oesophageal or cardiac dose constraints were applied in the lung patients. Stage III lung cancer patients received induction chemotherapy(IC); oesophageal patients received IC and chemoradiotherapy with capecitabine. Patients were assessed weekly during radiotherapy and at 1 and 3 months for toxicity. Toxicity was graded according to the Common Toxicity Criteria v3.0. Doses received by the heart, lungs, spinal cord and oesophagus were evaluated. Correlations between dose-volume data and toxicity scores for pneumonitis and dysphagia were assessed using Spearman’s Rank correlation. Results: Twenty-eight patients (19 NSCLC, 3 SCLC, 6 Oesophagus) treated between 03.07.08 and 28.06.10 received doses ranging from 50 - 64 Gy. Active Breathing Control (ABC) was used in 11 lung patients. Table 1 reveals dose volume parameters for lung and oesophagus. Mean lung volumes were 4138cc (range 2077 - 8210). Mean spinal cord maximum dose (>1cc) was 29.2 (range 7.8- 46.3). Mean cardiac doses to whole organ and one-third were 2.3 Gy and 14.5 Gy respectively.Pneumonitis rates were G0 61%, G1 29% G2 7% G3 3%. In lung patients, dysphagia rates were G0 57%, G1 10%, G2 33%. Fatigue was noted in 40% patients (8% G1, 32% G2). Other toxicities included skin (7%), nausea (7%), thrombocytopenia (3.5%) and depression (3.5%). Three patients did not complete radiotherapy due to development of brain metastases, chemotherapy-related thrombocytopenia and pneumonitis. There was no correlation between lung volume doses and pneumonitis scores at all dose levels. In lung patients dysphagia scores correlated strongly with oesophagus V35Gy (correlation coefficient = 0.74 p<0.001) but not with V50Gy or V60Gy. At 3 months there was 1 pneumonitis but all other toxicities had resolved.
Conclusions: VMAT was extremely well tolerated in this cohort of patients. Pneumonitis rates were low (≥ G2 = 10%). This may be due to the lung doses achieved with a combination of VMAT and ABC. Dysphagia rates were acceptable but an oesophageal dose constraint should be considered.
S 499
Purpose: Volumetric Modulated Arc Therapy (VMAT) that combines dynamic gantry motion with beam intensity modulation has become clinically available for planning and delivery of VMAT treatments. In this work, we carry out assessment of constant dose rate (CDR) - and variable dose rate (VDR)based VMAT planning and delivery methods for lung stereo treatments. Materials: Ten patients with lung cancer who were previously treated with stereotactic conformal arc technique were selected for this study. Prescription doses to PTVs ranged from 30Gy in 5 fractions to 48Gy in 4 fractions. Conformal arc (C_ARC) plans consisted of a combination of 6-8 co-planar static and step-and-shoot IMRT beams. C_ARC plans were generated using Philips Pinnacle 9.0. Pinnacle’s SmartArc module which supports generation of both CDR -(200 MU/min) and VDR-based (0 through 600 MU/min) plans was used to generate VMAT plans. For each patient, both VMAT plans consisted of two 180o arcs with 4o arc sampling. The collimator angles of the two arcs were orthogonal to each other. The same planning objectives for PTVs and OARs (cord, esophagus, lungs, heart and non-PTV-tissue) were used for optimization of C_ARC, plans. All plans were compared using MUs, delivery times and dose-volume parameters for targets and OARs, including conformity index (CI) and homogeneity index (HI) for PTVs, the maximum dose (D2 used as a surrogate), D30 and D50 for OARs. For all comparisons, clinically delivered C_ARC plans were used as a benchmark. The isodose distributions for each plan were normalized at PTV D98 of the C_ARC plans. The comparisons between all plans were made relative to the C_ARC technique using a paired two-tailed student’s t-test. Results: On average, the differences in PTV D2, D50, HI and CI were statistically insignificant, indicating very similar coverage for PTV for C_ARC and VMAT plans. As far the sparing of OARs, all dose-volume parameters met the clinical requirements for all sets of plans. Although use of VDR VMAT reduced cord D2 by 8.3%, it was 2.8% higher with CDR VMAT as compared to conformal arc stereo plans. The average esophagus D30 was 17% and 19% higher with VDR- and CDR- VMAT respectively although the absolute value of the doses was very low. Lung D30 was also 11% and 25% higher with VDR- and CDR- VMAT compared to the C_ARC plans. The mean MUs were 1683, 1669, 1880 for C_ARC, VDR- and CDR- VMAT plans respectively with a 12.7% reduction from CDR- to VDR VMAT. The mean treatment times were 10.1 min, 9.3 min and 2.8 min for C_ARC, CDR- and VDR- VMAT plans respectively. Conclusions: This study showed that both CDR- and VDR-based VMAT techniques produced similar target coverage that is comparable to that of C_ARC. Although the critical structure sparing with both VMAT techniques was generally worse than the ones obtained with the C_ARC, the absolute value of the doses to the OARs were very low. In general, the VDR-based VMAT provided much better treatment efficiency.
IMRT: Treatment planning and optimization
1335 poster
1336 poster
VOLUMETRIC MODULATED INTENSITY MODULATED ARC THERAPY FOR STEREOTACTIC LUNG RADIOTHERAPY: CONSTANT DOSE RATE VERSUS VARIABLE DOSE RATE DELIVERY N. Dogan1 , Y. Wu1
A COMPARISON OF DOSES TO OARS IN INVERSE PLANNED IMRT AND 3D CONFORMAL PROSTATE TREATMENT PLANNING B. Mzenda1 , P. Peters1 , J. Pettingell2 , H. Kerr3 , K. Walsh3 , N. Mc Andrew4 , M. Robb4 1 C ANCER PARTNERS UK LTD., Southampton, United Kingdom 2 C ANCER PARTNERS UK, London, United Kingdom 3 C ANCER PARTNERS UK, Elstree, United Kingdom 4 C ANCER PARTNERS UK LTD., Portsmouth, United Kingdom
1
V IRGINIA C OMMONWEALTH U NIVERSITY, Radiation Oncology, Richmond, VA, USA
TPS provides very accurate dose calculation at low dose regions, which particularly facilitates accurate evaluation of secondary cancer risk in VMAT delivery. We will retrospectively evaluate dose distributions created by SmartArc VMAT plans. 1334 poster VOLUMETRIC MODULATED ARC RADIOTHERAPY (VMAT) OF TUMOURS IN THE THORAX - ACUTE TOXICITY RESULTS FROM A SINGLE CENTRE M. Ahmed1 , J. Bedford1 , J. Warrington1 , M. Hawkins2 1 T HE R OYAL M ARSDEN NHS F OUNDATION T RUST, Sutton, United Kingdom 2 T HE R OYAL M ARSDEN NHS F OUNDATION T RUST, London, United Kingdom
Purpose: VMAT treatment delivery benefits from simultaneous variations in gantry speed, dose-rate and multi-leaf collimator leaf positions. In lung and oesophageal cancer VMAT reduces treatment delivery time and can potentially reduce normal tissue toxicity. Clinical data on this relatively novel radiotherapy technique is lacking. We present acute toxicity data on a cohort of patients treated with VMAT. Materials: Data were collected retrospectively. Patients with carcinoma of the lung (stage I-IIIB) or oesophagus (stage III) were treated radically with VMAT using a single arc technique. Patients were planned using in-house software Autobeam version 4.6. No oesophageal or cardiac dose constraints were applied in the lung patients. Stage III lung cancer patients received induction chemotherapy(IC); oesophageal patients received IC and chemoradiotherapy with capecitabine. Patients were assessed weekly during radiotherapy and at 1 and 3 months for toxicity. Toxicity was graded according to the Common Toxicity Criteria v3.0. Doses received by the heart, lungs, spinal cord and oesophagus were evaluated. Correlations between dose-volume data and toxicity scores for pneumonitis and dysphagia were assessed using Spearman’s Rank correlation. Results: Twenty-eight patients (19 NSCLC, 3 SCLC, 6 Oesophagus) treated between 03.07.08 and 28.06.10 received doses ranging from 50 - 64 Gy. Active Breathing Control (ABC) was used in 11 lung patients. Table 1 reveals dose volume parameters for lung and oesophagus. Mean lung volumes were 4138cc (range 2077 - 8210). Mean spinal cord maximum dose (>1cc) was 29.2 (range 7.8- 46.3). Mean cardiac doses to whole organ and one-third were 2.3 Gy and 14.5 Gy respectively.Pneumonitis rates were G0 61%, G1 29% G2 7% G3 3%. In lung patients, dysphagia rates were G0 57%, G1 10%, G2 33%. Fatigue was noted in 40% patients (8% G1, 32% G2). Other toxicities included skin (7%), nausea (7%), thrombocytopenia (3.5%) and depression (3.5%). Three patients did not complete radiotherapy due to development of brain metastases, chemotherapy-related thrombocytopenia and pneumonitis. There was no correlation between lung volume doses and pneumonitis scores at all dose levels. In lung patients dysphagia scores correlated strongly with oesophagus V35Gy (correlation coefficient = 0.74 p<0.001) but not with V50Gy or V60Gy. At 3 months there was 1 pneumonitis but all other toxicities had resolved.
Conclusions: VMAT was extremely well tolerated in this cohort of patients. Pneumonitis rates were low (≥ G2 = 10%). This may be due to the lung doses achieved with a combination of VMAT and ABC. Dysphagia rates were acceptable but an oesophageal dose constraint should be considered.
S 499
Purpose: Volumetric Modulated Arc Therapy (VMAT) that combines dynamic gantry motion with beam intensity modulation has become clinically available for planning and delivery of VMAT treatments. In this work, we carry out assessment of constant dose rate (CDR) - and variable dose rate (VDR)based VMAT planning and delivery methods for lung stereo treatments. Materials: Ten patients with lung cancer who were previously treated with stereotactic conformal arc technique were selected for this study. Prescription doses to PTVs ranged from 30Gy in 5 fractions to 48Gy in 4 fractions. Conformal arc (C_ARC) plans consisted of a combination of 6-8 co-planar static and step-and-shoot IMRT beams. C_ARC plans were generated using Philips Pinnacle 9.0. Pinnacle’s SmartArc module which supports generation of both CDR -(200 MU/min) and VDR-based (0 through 600 MU/min) plans was used to generate VMAT plans. For each patient, both VMAT plans consisted of two 180o arcs with 4o arc sampling. The collimator angles of the two arcs were orthogonal to each other. The same planning objectives for PTVs and OARs (cord, esophagus, lungs, heart and non-PTV-tissue) were used for optimization of C_ARC, plans. All plans were compared using MUs, delivery times and dose-volume parameters for targets and OARs, including conformity index (CI) and homogeneity index (HI) for PTVs, the maximum dose (D2 used as a surrogate), D30 and D50 for OARs. For all comparisons, clinically delivered C_ARC plans were used as a benchmark. The isodose distributions for each plan were normalized at PTV D98 of the C_ARC plans. The comparisons between all plans were made relative to the C_ARC technique using a paired two-tailed student’s t-test. Results: On average, the differences in PTV D2, D50, HI and CI were statistically insignificant, indicating very similar coverage for PTV for C_ARC and VMAT plans. As far the sparing of OARs, all dose-volume parameters met the clinical requirements for all sets of plans. Although use of VDR VMAT reduced cord D2 by 8.3%, it was 2.8% higher with CDR VMAT as compared to conformal arc stereo plans. The average esophagus D30 was 17% and 19% higher with VDR- and CDR- VMAT respectively although the absolute value of the doses was very low. Lung D30 was also 11% and 25% higher with VDR- and CDR- VMAT compared to the C_ARC plans. The mean MUs were 1683, 1669, 1880 for C_ARC, VDR- and CDR- VMAT plans respectively with a 12.7% reduction from CDR- to VDR VMAT. The mean treatment times were 10.1 min, 9.3 min and 2.8 min for C_ARC, CDR- and VDR- VMAT plans respectively. Conclusions: This study showed that both CDR- and VDR-based VMAT techniques produced similar target coverage that is comparable to that of C_ARC. Although the critical structure sparing with both VMAT techniques was generally worse than the ones obtained with the C_ARC, the absolute value of the doses to the OARs were very low. In general, the VDR-based VMAT provided much better treatment efficiency.
IMRT: Treatment planning and optimization
1335 poster
1336 poster
VOLUMETRIC MODULATED INTENSITY MODULATED ARC THERAPY FOR STEREOTACTIC LUNG RADIOTHERAPY: CONSTANT DOSE RATE VERSUS VARIABLE DOSE RATE DELIVERY N. Dogan1 , Y. Wu1
A COMPARISON OF DOSES TO OARS IN INVERSE PLANNED IMRT AND 3D CONFORMAL PROSTATE TREATMENT PLANNING B. Mzenda1 , P. Peters1 , J. Pettingell2 , H. Kerr3 , K. Walsh3 , N. Mc Andrew4 , M. Robb4 1 C ANCER PARTNERS UK LTD., Southampton, United Kingdom 2 C ANCER PARTNERS UK, London, United Kingdom 3 C ANCER PARTNERS UK, Elstree, United Kingdom 4 C ANCER PARTNERS UK LTD., Portsmouth, United Kingdom
1
V IRGINIA C OMMONWEALTH U NIVERSITY, Radiation Oncology, Richmond, VA, USA