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Application of stereotactic radiotherapy in the management of nasopharyngeal carcinoma: Dosimetric comparison
S520
I. J. Radiation Oncology
2306
● Biology ● Physics
Volume 60, Number 1, Supplement, 2004
Optimizing the Supraclavicular Monoisocentric Field Design in Treatment of Head and Neck Cancer Patients
G. B. Hare,1 M. Kuettel,1 E. Leon,1 R. Hackett,1 W. Jaggernauth1 Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY
1
Purpose/Objective: When using the 3-field monoisocentric slant technique to treat head and neck patients may lead to improve tumor coverage in the lateral fields but may also lead to a number of potential trade-offs. These may include: inadequate coverage of the inferior aspect of the supraclavicular nodal regions, increased peak isodoses, and increased cord doses. Examining beam angling and isodose distributions with respect to these parameters is the purpose of this study. Materials/Methods: Ten head and neck patient consecutive plans were used in this study that were treated with the a monoisocentric technique. Commonly used supraclavicular gantry angles used in our department included 15 and 20 degrees of rotation and therefore were chosen for this study. A third gantry position of 25 degrees was represented in this study as a way to illustrate a extreme example of this technique. Nodal group contouring was performed per RTOG guidelines as available on their website. All nodal group contouring was done by a single radiologist and together with a single radiation oncologist. DRRs were used to establish the traditional lower field border. Next, 15, 20 and 25-degree beams were applied to each patient after careful consideration was paid to shoulder location. Normalization occurred where the posterior aspect of the targeted nodal region was maintained within 95 to 100% isodose distributions. Results: At the 15-degree gantry angle, 3 patients required expansion of the lower border. This was required to achieve adequate coverage (95% or greater) of the inferior aspect of the targeted nodal region within the supraclavicular fossa. At the 15-degree gantry angle, the range of minimal isodose coverage averaged 93.76% (range 86.91% to 97.74%). Adequate coverage on these three cases was achieved with a 5 mm maximum addition to the lower border. At the 20-degree gantry angle, 5 of 10 patients required additions to the lower border to achieve adequate coverage. The average minimal isodose coverage was 85.76% (range from 83.06 to 97.71%). All five patients obtained adequate coverage with a maximum of a 7 mm lower border expansion. At the 25-degree gantry angle, 7 of 10 patients required lower border expansion with the largest being 1.2 cm. At the 25-degree gantry angle, the minimal isodose coverage of the inferior aspect averaged 78.81% (range from 47.03% to 96.63%). With successive increases in the gantry angle, increased peak doses occurred. Average peak point doses for the 15, 20 and 25-degree angles were 119.7, 124.31 and 131.36 % respectively. Average spinal cord doses increased with increased beam angles. Average peak spinal cord dose at 15-degree angle was 88% (range 84 to 93%). Average peak spinal cord dose for 20-degree angle was 88% (range 86 to 94%). Average peak spinal cord doses for the 25-degree gantry technique was 90% (range 86 to 97%). A correlation was not found with the amount of contoured lung volume irradiated and gantry angle. Conclusions: In this study, the unmodified monoisocentric slant technique can result in significant under dosage of the inferior aspect of the RTOG defined targeted nodal groups. This region of under dosage was amenable to lower border field adjustments. Nodal basin CT contouring may provide a more accurate way to determine the individual adjustment needed. Increased beam angling resulted in higher peak doses with anatomical normalization. In this study, spinal cord doses were also higher with increased angling especially near the match line as this is where the patient separation was the most narrow. Following spinal cord doses with this technique appears to be critical as nearing spinal tolerance with standard doses was higher than expected.
2307
Application of Stereotactic Radiotherapy in the Management of Nasopharyngeal Carcinoma: Dosimetric Comparison
M. Heydarian,1,3 B. Fung,4 L. Gitterman,2 J. Waldron2,3 Radiation Physics, Princess Margaret Hospital, Toronto, ON, Canada, 2Radiation Oncology, Princess Margaret Hospital, Toronto, ON, Canada, 3Radiation Oncology, University of Toronto, Toronto, ON, Canada, 4Radiation Therapy, Michener Institute, Toronto, ON, Canada
1
Purpose/Objective: Radiation treatment of nasopharyngeal carcinoma (NPC) requires delivery of 70 Gy to the primary tumor GTV. Because of the limitations of conventional conformal radiation in achieving this objective while sparing critical organs
Proceedings of the 46th Annual ASTRO Meeting
at risk (OARs) we have introduced stereotactic radiation therapy (SRT) into the final phase of NPC treatment as a boost of 10 to 24 Gy to the GTV, depending on the nodal involvement. The purpose of this study was to compare different SRT planning techniques, including intensity modulated stereotactic radiation therapy (IMSRT), with non-stereotactic techniques for the boost phase. The comparison was made to explore advantages and disadvantages of each technique in terms of target volume dose coverage and sparing of organs at risk. Materials/Methods: Radionics treatment planning and delivery system, including circular collimators, a Mini Multileaf Collimator (MMLC) and 6 MV photon beams on a dedicated Clinac 2100C are used at our institution for stereotactic radiotherapy of intracranial lesions. Stereotactic treatment planning techniques include non-coplanar arcs using circular collimators, 3D conformal and step and shoot intensity modulated stereotactic radiotherapy. Non-stereotactic techniques include Cadplan 3D conformal, Cadplan/Helios IMRT and Pinnacle IMRT. The treatment plans comparison was made for small (31cc), medium (95cc) and large (215cc) size target volumes. Identical CT data and contours were used on all planning systems and a 20 Gy boost dose was selected for all cases in this study. Treatment plans were evaluated based on 2D and 3D dose distributions, dose volume histograms (DVH), maximum (Dmax), minimum (Dmin) and median (Dmedian) doses as well as dose of 95% volume (D95), conformity index (CI), and dose heterogeneity (DH). Parameters used for OARs dose comparison were DVHs, Dmax and Dmedian as well as dose of 10% to 50% volumes (D10, D20 and D50), when the dose values were normalized so that 95% of the target volume received at least 95% of the prescribed dose. Results: It was found that the IMRT techniques produced superior results compared with non-IMRT techniques for medium and large size tumors. For small size tumors, however, stereotactic non-coplanar arcs technique using circular collimators showed comparable results with less dose heterogeneity. There were some limitations for IMRT of small tumors, especially by Helios and Pinnacle. IMSRT resulted in a better tumor dose coverage than other IMRT techniques for small and medium size tumors by producing sharper dose fall off and up to 70% less dose heterogeneity. This is mainly due to smaller MMLC leaf thickness of 4mm compared to 5mm to 10mm for Helios and Pinnacle. For the large size tumor, however, the above results were comparable for all IMRT techniques. Pinnacle and Helios IMRT produced comparable results for the tumor dose coverage to that of stereotactic 3D conformal with greater dose heterogeneity but less dose to OARs. Also, Cadplan conformal produced inferior results, compared to all other techniques, for the target volume dose coverage and sparing OARs. OARs doses were compared for the brain stem and optic chiasm for the same tumor dose coverage that is for a normalized dose. The normalization was performed so that 95% of the target volume would receive 19 Gy, that is 95% of the prescribed dose. It was shown that IMSRT would result in up to 40% less dose to OARs for the small and medium size tumors, compared to other IMRT techniques for the same tumor dose coverage. Pinnacle IMRT results were slightly better results than those of Helios. Conclusions: Bases on the results of this study, it is concluded that IMSRT boost to the primary lesion following or overlapping with standard radiation therapy would result in a better dose coverage of the target volume and a reduced dose to OARs. This, together with stereotactic superior localization and immobilization, will allow greater confidence in target coverage, OARs avoidance and therefore opportunities for dose escalation.
2308
IMRT for Head and Neck Cancer: The University of Arkansas Experience
J. A. Penagaricano1 Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR
1
Purpose/Objective: To evaluate patient outcome following IMRT for squamous cell carcinoma of the head and neck utilizing the simultaneous integrated boost (SIB) technique. Materials/Methods: Between August 2001 and December 2003, 32 patients with squamous cell carcinoma of the head and neck with no evidence of distant metastasis were treated with curative intent at our institution. All patients received either neo-adjuvant or concomitant 5-FU/cisplatin chemotherapy. The mean age was 54 years (range 38 –71), with male to female ratio of 3.57 (25 males, 7 female). The T&N-stages according to the 1997 AJCC Classification were: 4 T1, 11 T2, 15 T3, 2 T4 and 9 N0, 6 N1, 10 N2 (1 N2a, 8 N2b, and 1 N2c), 7 N3. Stage grouping was: 0 stage I, 3 stage II, 13 stage III, and 16 stage IV. Median follow-up is 9 months (range 1–18 months). For all patients, a planning CT was obtained using a Philips CT- simulator. The patients were immobilized using a custom made aquaplast mask from head to shoulders and were subsequently scanned using 3mm contiguous slices. The gross tumor volume (GTV) and organs at risk (OAR) were outlined and the planning target volume (PTV) was defined by uniformly expanding the GTV. In a similar fashion the uninvolved lymph-nodes were outlined and expanded uniformly in order to obtain a PTV for uninvolved lymph-nodes (PTV-LN). GTV outline was performed with the aide of MRI or CT fusion. The spinal cord was expanded uniformly by 0.5 cm to account for daily set-up variation. For all patients, nine co-axial fields were defined. The IMRT software used was Pinnacle P3 from Philips Medical Systems (version 6.2b). A downhill gradient technique was used to find the optimal solution based on the objectives specified. The optimal solution was converted using the K-mean Clustering algorithm at a 2% error tolerance. The Intensity matrix was filtered prior to conversion to remove any sharp peaks from the distribution. In order to approximate the optimal and converted solutions segment weight optimization was run. For all patients, the prescription was set to uniform dose of 66 Gy to the PTV based on 2.2 Gy per fraction and uniform dose of 54 Gy to the PTV-LN based on 1.8 Gy per fraction. Treatment delivery was via the step and shoot technique. Results: All patients received radiation as planned. The local control rate is 84.4% (100% for T1, 91 % for T2, 73 % for T3 and 100 % for T4). There were five treatment failures (one local and distant, one regional only and three local only). None of these were at the margin of the PTV but true in-field failures. At the time of analysis 96.8 % (31/32) of patients are alive and with no evidence of disease. This includes the 4 patients after salvage surgery. One patient died of progressive metastatic disease. Overall, 34 % and 3 % of patients had Common Toxicity Criteria (CTC), version 2.0 –1999, grade 3 and grade 4 acute reactions, respectively. The most common acute treatment toxicities were mucositis and moist desquamation of the skin. The most common late treatment toxicities were dysphagia and xerostomia. Of the 32 patients, 14 had follow-up of more than 6 months and sufficient data to evaluate the degree of dysphagia. At the time of study, 43 %, 29 %, 21 %, 0 % and 7 % of patients had CTC grade 0, 1, 2, 3 and 4 dysphagia, respectively. Of the 32 patients, 13 had follow-up of more than 6 months and sufficient data to evaluate the degree of xerostomia. At the time of study, 69 % and 31% of patients had CTC grade 1 and 2 xerostomia, respectively. There were no deaths attributed to treatment. Conclusions: Excellent loco-regional control was found with SIB-IMRT. Treatment time was shortened as compared to conventional radiation therapy. A higher dose per fraction was delivered to the PTV with no unexpected adverse reactions.
S521
I. J. Radiation Oncology
2306
● Biology ● Physics
Volume 60, Number 1, Supplement, 2004
Optimizing the Supraclavicular Monoisocentric Field Design in Treatment of Head and Neck Cancer Patients
G. B. Hare,1 M. Kuettel,1 E. Leon,1 R. Hackett,1 W. Jaggernauth1 Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY
1
Purpose/Objective: When using the 3-field monoisocentric slant technique to treat head and neck patients may lead to improve tumor coverage in the lateral fields but may also lead to a number of potential trade-offs. These may include: inadequate coverage of the inferior aspect of the supraclavicular nodal regions, increased peak isodoses, and increased cord doses. Examining beam angling and isodose distributions with respect to these parameters is the purpose of this study. Materials/Methods: Ten head and neck patient consecutive plans were used in this study that were treated with the a monoisocentric technique. Commonly used supraclavicular gantry angles used in our department included 15 and 20 degrees of rotation and therefore were chosen for this study. A third gantry position of 25 degrees was represented in this study as a way to illustrate a extreme example of this technique. Nodal group contouring was performed per RTOG guidelines as available on their website. All nodal group contouring was done by a single radiologist and together with a single radiation oncologist. DRRs were used to establish the traditional lower field border. Next, 15, 20 and 25-degree beams were applied to each patient after careful consideration was paid to shoulder location. Normalization occurred where the posterior aspect of the targeted nodal region was maintained within 95 to 100% isodose distributions. Results: At the 15-degree gantry angle, 3 patients required expansion of the lower border. This was required to achieve adequate coverage (95% or greater) of the inferior aspect of the targeted nodal region within the supraclavicular fossa. At the 15-degree gantry angle, the range of minimal isodose coverage averaged 93.76% (range 86.91% to 97.74%). Adequate coverage on these three cases was achieved with a 5 mm maximum addition to the lower border. At the 20-degree gantry angle, 5 of 10 patients required additions to the lower border to achieve adequate coverage. The average minimal isodose coverage was 85.76% (range from 83.06 to 97.71%). All five patients obtained adequate coverage with a maximum of a 7 mm lower border expansion. At the 25-degree gantry angle, 7 of 10 patients required lower border expansion with the largest being 1.2 cm. At the 25-degree gantry angle, the minimal isodose coverage of the inferior aspect averaged 78.81% (range from 47.03% to 96.63%). With successive increases in the gantry angle, increased peak doses occurred. Average peak point doses for the 15, 20 and 25-degree angles were 119.7, 124.31 and 131.36 % respectively. Average spinal cord doses increased with increased beam angles. Average peak spinal cord dose at 15-degree angle was 88% (range 84 to 93%). Average peak spinal cord dose for 20-degree angle was 88% (range 86 to 94%). Average peak spinal cord doses for the 25-degree gantry technique was 90% (range 86 to 97%). A correlation was not found with the amount of contoured lung volume irradiated and gantry angle. Conclusions: In this study, the unmodified monoisocentric slant technique can result in significant under dosage of the inferior aspect of the RTOG defined targeted nodal groups. This region of under dosage was amenable to lower border field adjustments. Nodal basin CT contouring may provide a more accurate way to determine the individual adjustment needed. Increased beam angling resulted in higher peak doses with anatomical normalization. In this study, spinal cord doses were also higher with increased angling especially near the match line as this is where the patient separation was the most narrow. Following spinal cord doses with this technique appears to be critical as nearing spinal tolerance with standard doses was higher than expected.
2307
Application of Stereotactic Radiotherapy in the Management of Nasopharyngeal Carcinoma: Dosimetric Comparison
M. Heydarian,1,3 B. Fung,4 L. Gitterman,2 J. Waldron2,3 Radiation Physics, Princess Margaret Hospital, Toronto, ON, Canada, 2Radiation Oncology, Princess Margaret Hospital, Toronto, ON, Canada, 3Radiation Oncology, University of Toronto, Toronto, ON, Canada, 4Radiation Therapy, Michener Institute, Toronto, ON, Canada
1
Purpose/Objective: Radiation treatment of nasopharyngeal carcinoma (NPC) requires delivery of 70 Gy to the primary tumor GTV. Because of the limitations of conventional conformal radiation in achieving this objective while sparing critical organs
Proceedings of the 46th Annual ASTRO Meeting
at risk (OARs) we have introduced stereotactic radiation therapy (SRT) into the final phase of NPC treatment as a boost of 10 to 24 Gy to the GTV, depending on the nodal involvement. The purpose of this study was to compare different SRT planning techniques, including intensity modulated stereotactic radiation therapy (IMSRT), with non-stereotactic techniques for the boost phase. The comparison was made to explore advantages and disadvantages of each technique in terms of target volume dose coverage and sparing of organs at risk. Materials/Methods: Radionics treatment planning and delivery system, including circular collimators, a Mini Multileaf Collimator (MMLC) and 6 MV photon beams on a dedicated Clinac 2100C are used at our institution for stereotactic radiotherapy of intracranial lesions. Stereotactic treatment planning techniques include non-coplanar arcs using circular collimators, 3D conformal and step and shoot intensity modulated stereotactic radiotherapy. Non-stereotactic techniques include Cadplan 3D conformal, Cadplan/Helios IMRT and Pinnacle IMRT. The treatment plans comparison was made for small (31cc), medium (95cc) and large (215cc) size target volumes. Identical CT data and contours were used on all planning systems and a 20 Gy boost dose was selected for all cases in this study. Treatment plans were evaluated based on 2D and 3D dose distributions, dose volume histograms (DVH), maximum (Dmax), minimum (Dmin) and median (Dmedian) doses as well as dose of 95% volume (D95), conformity index (CI), and dose heterogeneity (DH). Parameters used for OARs dose comparison were DVHs, Dmax and Dmedian as well as dose of 10% to 50% volumes (D10, D20 and D50), when the dose values were normalized so that 95% of the target volume received at least 95% of the prescribed dose. Results: It was found that the IMRT techniques produced superior results compared with non-IMRT techniques for medium and large size tumors. For small size tumors, however, stereotactic non-coplanar arcs technique using circular collimators showed comparable results with less dose heterogeneity. There were some limitations for IMRT of small tumors, especially by Helios and Pinnacle. IMSRT resulted in a better tumor dose coverage than other IMRT techniques for small and medium size tumors by producing sharper dose fall off and up to 70% less dose heterogeneity. This is mainly due to smaller MMLC leaf thickness of 4mm compared to 5mm to 10mm for Helios and Pinnacle. For the large size tumor, however, the above results were comparable for all IMRT techniques. Pinnacle and Helios IMRT produced comparable results for the tumor dose coverage to that of stereotactic 3D conformal with greater dose heterogeneity but less dose to OARs. Also, Cadplan conformal produced inferior results, compared to all other techniques, for the target volume dose coverage and sparing OARs. OARs doses were compared for the brain stem and optic chiasm for the same tumor dose coverage that is for a normalized dose. The normalization was performed so that 95% of the target volume would receive 19 Gy, that is 95% of the prescribed dose. It was shown that IMSRT would result in up to 40% less dose to OARs for the small and medium size tumors, compared to other IMRT techniques for the same tumor dose coverage. Pinnacle IMRT results were slightly better results than those of Helios. Conclusions: Bases on the results of this study, it is concluded that IMSRT boost to the primary lesion following or overlapping with standard radiation therapy would result in a better dose coverage of the target volume and a reduced dose to OARs. This, together with stereotactic superior localization and immobilization, will allow greater confidence in target coverage, OARs avoidance and therefore opportunities for dose escalation.
2308
IMRT for Head and Neck Cancer: The University of Arkansas Experience
J. A. Penagaricano1 Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR
1
Purpose/Objective: To evaluate patient outcome following IMRT for squamous cell carcinoma of the head and neck utilizing the simultaneous integrated boost (SIB) technique. Materials/Methods: Between August 2001 and December 2003, 32 patients with squamous cell carcinoma of the head and neck with no evidence of distant metastasis were treated with curative intent at our institution. All patients received either neo-adjuvant or concomitant 5-FU/cisplatin chemotherapy. The mean age was 54 years (range 38 –71), with male to female ratio of 3.57 (25 males, 7 female). The T&N-stages according to the 1997 AJCC Classification were: 4 T1, 11 T2, 15 T3, 2 T4 and 9 N0, 6 N1, 10 N2 (1 N2a, 8 N2b, and 1 N2c), 7 N3. Stage grouping was: 0 stage I, 3 stage II, 13 stage III, and 16 stage IV. Median follow-up is 9 months (range 1–18 months). For all patients, a planning CT was obtained using a Philips CT- simulator. The patients were immobilized using a custom made aquaplast mask from head to shoulders and were subsequently scanned using 3mm contiguous slices. The gross tumor volume (GTV) and organs at risk (OAR) were outlined and the planning target volume (PTV) was defined by uniformly expanding the GTV. In a similar fashion the uninvolved lymph-nodes were outlined and expanded uniformly in order to obtain a PTV for uninvolved lymph-nodes (PTV-LN). GTV outline was performed with the aide of MRI or CT fusion. The spinal cord was expanded uniformly by 0.5 cm to account for daily set-up variation. For all patients, nine co-axial fields were defined. The IMRT software used was Pinnacle P3 from Philips Medical Systems (version 6.2b). A downhill gradient technique was used to find the optimal solution based on the objectives specified. The optimal solution was converted using the K-mean Clustering algorithm at a 2% error tolerance. The Intensity matrix was filtered prior to conversion to remove any sharp peaks from the distribution. In order to approximate the optimal and converted solutions segment weight optimization was run. For all patients, the prescription was set to uniform dose of 66 Gy to the PTV based on 2.2 Gy per fraction and uniform dose of 54 Gy to the PTV-LN based on 1.8 Gy per fraction. Treatment delivery was via the step and shoot technique. Results: All patients received radiation as planned. The local control rate is 84.4% (100% for T1, 91 % for T2, 73 % for T3 and 100 % for T4). There were five treatment failures (one local and distant, one regional only and three local only). None of these were at the margin of the PTV but true in-field failures. At the time of analysis 96.8 % (31/32) of patients are alive and with no evidence of disease. This includes the 4 patients after salvage surgery. One patient died of progressive metastatic disease. Overall, 34 % and 3 % of patients had Common Toxicity Criteria (CTC), version 2.0 –1999, grade 3 and grade 4 acute reactions, respectively. The most common acute treatment toxicities were mucositis and moist desquamation of the skin. The most common late treatment toxicities were dysphagia and xerostomia. Of the 32 patients, 14 had follow-up of more than 6 months and sufficient data to evaluate the degree of dysphagia. At the time of study, 43 %, 29 %, 21 %, 0 % and 7 % of patients had CTC grade 0, 1, 2, 3 and 4 dysphagia, respectively. Of the 32 patients, 13 had follow-up of more than 6 months and sufficient data to evaluate the degree of xerostomia. At the time of study, 69 % and 31% of patients had CTC grade 1 and 2 xerostomia, respectively. There were no deaths attributed to treatment. Conclusions: Excellent loco-regional control was found with SIB-IMRT. Treatment time was shortened as compared to conventional radiation therapy. A higher dose per fraction was delivered to the PTV with no unexpected adverse reactions.
S521