Clinically relevant quality assurance for intensity modulated radiotherapy plans: gamma maps and DVH-based evaluation.

PURPOSE: To explore a novel patient-dose DVH-based method for pretreatment dose quality assurance tests. METHODS: 20 IMRT plans for head-and-neck cancer patients were used. A comparison was performed between the planned dose distributions, the computed, and the reconstructed ones using the gamma-index (GI) method. The GI analysis was performed using both the 3%/3 mm and the 2%/2 mm criteria. RESULTS: No significant DVH-deviation was observed. Considering the 3%/3 mm criteria the mean GI% < 1 for the body and structures was significantly higher compared to 2%/2 mm criteria. CONCLUSIONS: Our results underline the importance of QA-methods based on DVH-metrics to predict the impact of delivered dose.

Clinically relevant quality assurance (QA) for prostate RapidArc plans: gamma maps and DVH-based evaluation.

The aim of this paper is to evaluate clinically relevant quality assurance (QA) tests for RapidArc prostate patients. 26 plans were verified by the COMPASS system that provides an independent angle response and a reconstruction of dose distribution in patient CT model. Plan data were imported from treatment planning system via DICOM. The fluencies, measured by a 2D detector, were used by COMPASS to forward calculate dose in CT patients and reconstruct dose-volume-histogram (DVH). The gamma analysis was performed, using both the criteria 3%-3-mm and 2%-2 mm, for the whole grid patient and the per-structure volume. A DVH-based analysis was accomplished for target and organs-at-risk (OAR). The correlation between gamma passing rates and DVH discrepancies was performed using Pearson's test. Sensitivity, specificity and accuracy of whole and per-structure gamma method were calculated. No significant DVH deviation was observed for target and OAR. Weak correlation between gamma passing rates and dosimetric deviations was observed, all significant r-values were negative. The whole gamma method shows lack of sensitivity to detect dosimetric deviations >5%. Instead, a better balance between sensitivity and specificity was obtained employing per structure gamma both with 3%-3 mm and 2%-2 mm criteria. Because of the poor correlation between DVH goals and gamma passing rates, we encourage the DVH-based gamma passing rates, when it is possible. At least, a gamma method specific for structure was strongly suggested.

Impact pf machines on plan quality: volumetric modulated arc therapy and intensity modulated radiation therapy

PURPOSE: To evaluate the impact of different machines on plan quality using both intensity modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques. MATERIALS AND METHODS: Eight patients with squamous cell carcinoma of the oropharynx were selected at random. Plans were computed for IMRT and VMAT Smart Arc, using Pinnacle TPS for an Elekta (IMRT-E, VMAT-E) and Varian linac (IMRT-V, VMAT-V). A three-dose level prescription was used to deliver 70, 63 and 58.1 Gy to regions of macroscopic, microscopic high- and low-risk disease, respectively. All doses were given in 35 fractions. Comparisons were performed on dose-volume histogram data, monitor units (MU), and delivery time. RESULTS: VMAT-E plans resulted slightly MU efficient (-24 % p < 0.05) compared to VMAT-V while IMRT-V shortened delivery time (-19 % p < 0.05) compared to IMRT-E. All the delivery techniques resulted in equivalent target coverage in terms of D(98) % and D(2) %. For VMAT technique, a significant improvement of 7 % in homogeneity index (HI) for PTV58.1 was observed for Varian machine. A slight improvement in OARs sparing was observed with Elekta machine both for IMRT and VMAT techniques. CONCLUSION: Similar plan quality was observed for Elekta and Varian linacs, significant differences were observed in delivery efficiency, as MU number and delivery times, in favor of Elekta and Varian, respectively (AU)

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To evaluate the accuracy of dynamic versus static IMRT delivery using portal dosimetry

INTRODUCTION: To evaluate the delivery accuracy of dynamic (DMLC) and static (SMLC) intensity modulated radiation therapy (IMRT) techniques using portal dosimetry (PD) in Varian Eclipse Treatment Planning System. MATERIALS AND METHODS: Seven DMLC IMRT Head and Neck plans were retrospectively generated for the study using SMLC mode at 20, 10 and 5 levels of intensity (SMLC20, SMLC10, SMLC5). Dosimetric verifications performed by PD on a total of 107 fields were evaluated using the gamma index (maximum (γmax), average (γavg), percentage of points with (γ%) ≤ 1). The images were acquired at a source-detector distance of 100 cm at gantry zero degree and also at clinically planned gantry angles. RESULTS: For both modes, measurements are within acceptable criteria. (γ%) ≤ 1 improves by increasing SMLC levels (+3.4 % from SMLC5 to SMLC20, p < 0.001) and using DMLC (+3.9 % and +0.6 % compared to SMLC5 and SMLC20, respectively, p < 0.001). Also (γmax) parameter improves significantly by increasing SMLC levels (+22 % from SMLC5 to SMLC20) and using DMLC (+34 % and +16 % compared to SMLC5 and SMLC20, respectively). The effect of the gantry rotation influences the delivery accuracy by up to -7 % (p < 0.05). The effect of leaves travelling direction was almost negligible (1 %). CONCLUSIONS: A good agreement between calculated and measured fluences was obtained for DMLC and SMLC techniques at higher intensity levels; however, DMLC delivery ensures the best reproduction of computed fluence maps. The gantry rotation influences the delivery accuracy in particular for SMLC modes at lower intensity levels (AU)

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Impact of machines on plan quality: volumetric modulated arc therapy and intensity modulated radiation therapy.

PURPOSE: To evaluate the impact of different machines on plan quality using both intensity modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques. MATERIALS AND METHODS: Eight patients with squamous cell carcinoma of the oropharynx were selected at random. Plans were computed for IMRT and VMAT Smart Arc, using Pinnacle TPS for an Elekta (IMRT-E, VMAT-E) and Varian linac (IMRT-V, VMAT-V). A three-dose level prescription was used to deliver 70, 63 and 58.1 Gy to regions of macroscopic, microscopic high- and low-risk disease, respectively. All doses were given in 35 fractions. Comparisons were performed on dose-volume histogram data, monitor units (MU), and delivery time. RESULTS: VMAT-E plans resulted slightly MU efficient (-24 % p < 0.05) compared to VMAT-V while IMRT-V shortened delivery time (-19 % p < 0.05) compared to IMRT-E. All the delivery techniques resulted in equivalent target coverage in terms of D(98) % and D(2) %. For VMAT technique, a significant improvement of 7 % in homogeneity index (HI) for PTV58.1 was observed for Varian machine. A slight improvement in OARs sparing was observed with Elekta machine both for IMRT and VMAT techniques. CONCLUSION: Similar plan quality was observed for Elekta and Varian linacs, significant differences were observed in delivery efficiency, as MU number and delivery times, in favor of Elekta and Varian, respectively.

To evaluate the accuracy of dynamic versus static IMRT delivery using portal dosimetry.

INTRODUCTION: To evaluate the delivery accuracy of dynamic (DMLC) and static (SMLC) intensity modulated radiation therapy (IMRT) techniques using portal dosimetry (PD) in Varian Eclipse Treatment Planning System. MATERIALS AND METHODS: Seven DMLC IMRT Head and Neck plans were retrospectively generated for the study using SMLC mode at 20, 10 and 5 levels of intensity (SMLC20, SMLC10, SMLC5). Dosimetric verifications performed by PD on a total of 107 fields were evaluated using the gamma index (maximum (γmax), average (γavg), percentage of points with (γ%) ≤ 1). The images were acquired at a source-detector distance of 100 cm at gantry zero degree and also at clinically planned gantry angles. RESULTS: For both modes, measurements are within acceptable criteria. (γ%) ≤ 1 improves by increasing SMLC levels (+3.4 % from SMLC5 to SMLC20, p < 0.001) and using DMLC (+3.9 % and +0.6 % compared to SMLC5 and SMLC20, respectively, p < 0.001). Also (γmax) parameter improves significantly by increasing SMLC levels (+22 % from SMLC5 to SMLC20) and using DMLC (+34 % and +16 % compared to SMLC5 and SMLC20, respectively). The effect of the gantry rotation influences the delivery accuracy by up to -7 % (p < 0.05). The effect of leaves travelling direction was almost negligible (1 %). CONCLUSIONS: A good agreement between calculated and measured fluences was obtained for DMLC and SMLC techniques at higher intensity levels; however, DMLC delivery ensures the best reproduction of computed fluence maps. The gantry rotation influences the delivery accuracy in particular for SMLC modes at lower intensity levels.

Volumetric and dosimetric assessment by cone-beam computed tomography scans in head and neck radiation therapy: a monitoring in four phases of treatment.

Due to the anatomical changes frequently occurring during the course of head and neck (H&N) cancer radiotherapy, the dose distribution, which was actually delivered to the patient, might significantly differ from that planned. The aim of this paper is to investigate these volumetric changes and the resulting dosimetric implications on organs at risk (OARs) and clinical target volumes (CTVs) by cone beam computed tomography (CBCT) scans throughout the treatment. Ten H&N patients, treated by Intensity Modulated Radiotherapy, were analyzed. CTVs and OARs were delineated on four CBCT, acquired at the 10(th), 15(th), 20(th) and 25(th) treatment session, and then compared with the ones at planning CT. The planned beams were applied to each CBCT to recalculate the dose distribution and the corresponding dose volume histograms were compared with those generated on planning CT. To evaluate the HU discrepancies between the conventional CT and CBCT images we used a Catphan(r) 504, observing a maximum discrepancy of about 30 HU. We evaluated the impact of this HU difference in dose calculation and a not clinically relevant error, within 2.8%, was estimated. No inhomogeneity correction was used. The results showed an increased CTV mean dose (Dmean) of about 3% was found, without significant reduction in volume. Due to the parotids' shrinkage (up to 42%), significant dosimetric increases were observed: ipsilateral gland at 15th CBCT (Dmean by 18%; V30 by 31%); controlateral gland at the 10(th) CBCT (Dmean by 12.2%; V30 by 18.7%). For the larynx, a significant increase of volume was found at the 20th (15.7%) and 25th CBCT (13.3%) but it complied with dose constraint. The differences observed for the spinal cord and mandible maximum doses were not clinically relevant. In conclusion, the dosimetric analysis on CBCT can help clinicians to monitor treatment progress and to evaluate whether and when a new plan is necessary. The main benefit of replanning could be to preserve the parotids and our data support the hypothesis that the 3rd week of radiotherapy should be a check point for parotids.

Planning target volume assessment in lung tumors dring 3D conformal radiotherapy by means of an aSi electronic portal imaging device in cine mode

PURPOSE: The major uncertainties in treating lung cancer are the repositioning errors and respiratory lung tumor motion. Typically, margins are added to the clinical target volume (CTV) to obtain a planning target volume (PTV) allowing the accommodation of such uncertainties. We want to test a new technique to assess the adequacy of the chosen PTV using an aSi electronic portal imaging device (EPID). METHODS: Four patients affected by lung cancer and treated by radical 3D conformal radiotherapy (3DRT) were studied. During treatment the EPID was used in cine mode acquisition: acquired images were used to the aim. RESULTS AND CONCLUSIONS: Treatment monitoring with an EPID in cine mode is shown to be a clinically feasible and useful tool (AU)

Do comorbidity influences acute toxicity and outcome in elderly patients with endometrial cancer treated by adjuvant radiotherapy plus brachytherapy?

PURPOSE: To correlate comorbidity and acute radiation toxicity in elderly patients treated with adjuvant external beam radiotherapy (EBRT) plus brachytherapy-high dose rate (HDR-BRT) for endometrial cancer (EC). METHODS: Endometrial cancer patients over 65 were treated and evaluated for comorbidity assessment with ACE-27 and Charlson comorbidity index (CCI). EBRT total dose was 45-50.4 Gy (1.8 Gy/day). The vault vagina boost of dose was performed by HDR-BRT with 2/3 fractions with a total dose of 10-15 Gy. RESULTS: From 2008 to 2011, 35 patients were analyzed. Eighteen patients (51.43 %) had not ACE-27 comorbidity; while 27 patients (77.14 %) had CCI lower than three. During treatment, acute toxicity was mild and not influenced by the comorbidity score. Two-year Progression Free and Overall Survival were 69 and 80 %. ACE-27 and CCI did not affect progression-free survival (p = 0.51, p = 0.3) and OS (p = 0.26, p = 0.5). CONCLUSION: External beam radiotherapy plus BRT-HDR are well tolerated in EC elderly with good performance status and low comorbidity profile (AU)

Cone-beam computed tomography dose monitoring during intensity-modulated radiotherapy in head and neck cancer: parotid glands

PURPOSE: To evaluate the dosimetric changes of parotid glands (PG) during a course of intensity-modulated radiotherapy (IMRT) in head and neck (H&N) cancer patients. METHODS: Ten patients with H&N cancer treated by IMRT were analyzed. The original treatment plan (CT(plan)) was transferred to cone-beam computed tomography (CBCT) acquired at the 15th and 20th treatment day (CBCT(plan) I and II, respectively). The PG mean dose (D(mean)), the dose to 50 % of the volume, and the percent of volume receiving 30 and 50 Gy were measured by the dose volume histogram. RESULTS: 30 IMRT plans were evaluated (3 plans/patient). All dosimetric end points increased significantly for both PG only when CT(plan) was compared to CBCT(plan) I. The D(mean) increased significantly only for ipsilateral PG (p = 0.02) at week 3. CONCLUSION: During a course of IMRT, CBCT is a feasible method to heck the PG dosimetric variations. Perhaps, the 3rd week of radiotherapy could be considered as the time-check-point (AU)

Do comorbidity influences acute toxicity and outcome in elderly patients with endometrial cancer treated by adjuvant radiotherapy plus brachytherapy?

PURPOSE: To correlate comorbidity and acute radiation toxicity in elderly patients treated with adjuvant external beam radiotherapy (EBRT) plus brachytherapy-high dose rate (HDR-BRT) for endometrial cancer (EC). METHODS: Endometrial cancer patients over 65 were treated and evaluated for comorbidity assessment with ACE-27 and Charlson comorbidity index (CCI). EBRT total dose was 45-50.4 Gy (1.8 Gy/day). The vault vagina boost of dose was performed by HDR-BRT with 2/3 fractions with a total dose of 10-15 Gy. RESULTS: From 2008 to 2011, 35 patients were analyzed. Eighteen patients (51.43 %) had not ACE-27 comorbidity; while 27 patients (77.14 %) had CCI lower than three. During treatment, acute toxicity was mild and not influenced by the comorbidity score. Two-year Progression Free and Overall Survival were 69 and 80 %. ACE-27 and CCI did not affect progression-free survival (p = 0.51, p = 0.3) and OS (p = 0.26, p = 0.5). CONCLUSION: External beam radiotherapy plus BRT-HDR are well tolerated in EC elderly with good performance status and low comorbidity profile.

Planning target volume assessment in lung tumors during 3D conformal radiotherapy by means of an aSi electronic portal imaging device in cine mode.

PURPOSE: The major uncertainties in treating lung cancer are the repositioning errors and respiratory lung tumor motion. Typically, margins are added to the clinical target volume (CTV) to obtain a planning target volume (PTV) allowing the accommodation of such uncertainties. We want to test a new technique to assess the adequacy of the chosen PTV using an aSi electronic portal imaging device (EPID). METHODS: Four patients affected by lung cancer and treated by radical 3D conformal radiotherapy (3DRT) were studied. During treatment the EPID was used in cine mode acquisition: acquired images were used to the aim. RESULTS AND CONCLUSIONS: Treatment monitoring with an EPID in cine mode is shown to be a clinically feasible and useful tool.

Low-dose rate brachytherapy of the prostate in elderly patients.

PURPOSE: This study evaluated the biochemical diseasefree survival (bDFS) rate, overall survival rate (OS) and toxicity after low-dose rate I(125) permanent-implant prostate brachytherapy (LDR-BRT) in elderly patients affected by prostate cancer. METHODS AND MATERIALS: Patients aged ≥65 years with a diagnosis of prostate cancer and treated at our institution were retrospectively evaluated. All patients received LDR-BRT as monotherapy; the prescribed dose was 145 Gy to the prostate. Patients were stratified according to the National Comprehensive Cancer Network (NCCN) recurrence risk groups. Biochemical failure was defined according to the American Society of Therapeutic Radiology and Oncology (ASTRO) criteria. The Radiation Therapy Oncology Group (RTOG) scale was used for toxicity. The bDFS was calculated from implant date to biochemical recurrence. RESULTS: Between June 2003 and December 2008, 80 elderly patients with a median age of 75 (range, 65-86) years were treated with LDR-BRT: 51 low risk (64%), and 29 intermediate risk (36%). Over a median follow-up period of 53 (range, 28-94) months, the global actuarial 5-year bDFS rate was 91.3% and the 5-year OS was 95%. Toxicity was mild: late grade-3 genitourinary toxicity was observed in only four patients (5%). CONCLUSIONS: Our data suggest that LDR-BRT is effective and safe as monotherapy in elderly patients.

Cone-beam computed tomography dose monitoring during intensity-modulated radiotherapy in head and neck cancer: parotid glands.

PURPOSE: To evaluate the dosimetric changes of parotid glands (PG) during a course of intensity-modulated radiotherapy (IMRT) in head and neck (H&N) cancer patients. METHODS: Ten patients with H&N cancer treated by IMRT were analyzed. The original treatment plan (CT(plan)) was transferred to cone-beam computed tomography (CBCT) acquired at the 15th and 20th treatment day (CBCT(plan) I and II, respectively). The PG mean dose (D(mean)), the dose to 50 % of the volume, and the percent of volume receiving 30 and 50 Gy were measured by the dose volume histogram. RESULTS: 30 IMRT plans were evaluated (3 plans/patient). All dosimetric end points increased significantly for both PG only when CT(plan) was compared to CBCT(plan) I. The D(mean) increased significantly only for ipsilateral PG (p = 0.02) at week 3. CONCLUSION: During a course of IMRT, CBCT is a feasible method to check the PG dosimetric variations. Perhaps, the 3rd week of radiotherapy could be considered as the time-check-point.

[Adjuvant radiochemotherapy in the elderly affected by glioblastoma: single-institution experience and literature review]. / Radiochemioterapia adiuvante nei pazienti anziani affetti da glioblastoma: esperienza di un singolo istituto e revisione della letteratura.

PURPOSE: Radiochemotherapy (RCT) is the standard adjuvant treatment for patients affected by glioblastoma (GBM). As there is no evidence in elderly patients with GBM, combined, single modality or best supportive care is used. The aim of this retrospective study was to evaluate acute toxicity and outcome of elderly patients with GBM treated with RCT with temozolomide (TMZ). MATERIALS AND METHODS: Patients >65 years with newly diagnosed GBM who underwent surgery or biopsy and RCT were evaluated. Recursive Partitioning Analysis (RPA) class and National Cancer Institute--Common Toxicity Criteria (NCI-CTC) version 3 were used to classify patients and evaluate acute toxicity, respectively. RESULTS: From April 2005 to January 2011, 35 patients (18 women and 17 men) with GBM were treated at our institution. Only 31.43% of cases underwent complete resection. Median progression-free survival (PFS) was 8 months and median overall survival (OS) 13 months. At univariate and multivariate analysis, only RPA class correlated with OS (p=0.01, p=0.03, respectively). During RCT, toxicity was mild (thrombocytopaenia G3-4, 11.43%; neurological toxicity, G3-4, 8.57%). CONCLUSIONS: Our data suggest that RCT with TMZ seems to produce a better outcome with a mild toxicity profile in elderly patients affected by GBM.

Parotid gland volumetric changes during intensity-modulated radiotherapy in head and neck cancer.

OBJECTIVE: To evaluate volumetric changes of parotid glands (PGs) during intensity-modulated radiotherapy (IMRT) in head and neck cancer patients. METHODS: During IMRT all patients underwent kilovolt cone-beam CT (CBCT) scans to verify the set-up positioning in a protocol study. On each CBCT scan, the PGs were retrospectively contoured and evaluated with a dose-volume histogram. RESULTS: From February to June 2011, 10 patients were enrolled. 140 CBCT scans were registered (280 PGs): for each patient, a median of 14 CBCT scans were performed (range 14-16). At the start of radiation, the average volume for ipsilateral PGs (iPGs) was 18.77 ml (range 12.9-31.2 ml), whereas for contralateral PGs (cPGs) it was 16.63 ml (range 8.3-28.7 ml). At the last CBCT scan, the average volume loss was 43.5% and 44.0% for the iPG and cPG, respectively. When we analysed the percentage of volume loss, we observed that the volume decreased by linear regression (r(2)=0.92 for iPG; r(2)=0.91 for cPG), with an average volume loss rate of 1.5% per day for both PGs. During the third week of treatment the volume of both PGs reduced by 24-30%. CONCLUSION: Our data show that, during IMRT, the shrinkage of PGs should be taken into account. A replan could be indicated in the third week of radiotherapy.