AlignRT®, Catalyst™ and RPM™ in locoregional radiotherapy of breast cancer with DIBH. Is IGRT still needed?

Background: In locoregional radiotherapy of breast cancer with deep inspiration breath hold (DIBH), setup accuracy may depend on hospital protocol. At present, comparison between different positioning devices is challenging due to differing hospital protocols. The aim of this study was to evaluate the setup accuracy obtained with surface-guided radiation therapy (SGRT; AlignRT®, Catalyst™) or with lasers and real-time position management (RPM™) in DIBH. Materials and methods: A total of 1692 image pairs were analyzed in three groups: positioning using AlignRT® surface guidance system (Group A, n = 45), Catalyst™ (Group C, n = 50) and conventional lasers and tattoos (Group L, n = 46). We evaluated residual errors for the bony chest wall, th1 and humeral head in kV images with laser- or SGRT-based setup with and without daily image-guided radiation therapy (IGRT). Results: Less isocenter variance was found in Group A than in Group L or C (p ≤ 0.05) and in Group C than in L (p = 0.02-0.6). With SGRT only, the smallest random rotation error was found in Group A (p = 0.01). With daily IGRT, only a small difference was found for residual errors between the groups. Conclusion: Setup with SGRT improves the isocenter reproducibility compared to lasers and RPM™. Only small differences were found in setup accuracy between the SGRT devices. Due to improved isocenter accuracy, daily orthogonal IGRT is suggested in all the groups.

Patient setup accuracy in DIBH radiotherapy of breast cancer with lymph node inclusion using surface tracking and image guidance.

Studying setup accuracy in breast cancer patients with axillary lymph node inclusion in deep inspiration breath-hold (DIBH) after patient setup with surface-guided radiotherapy (SGRT) and image-guided radiotherapy (IGRT). Breast cancer patients (N = 51) were treated (50 Gy in 25 fractions) with axillary lymph nodes within the planning target volume (PTV). Patient setup was initiated with tattoos and lasers, and further adjusted with SGRT. The DIBH guidance was based on SGRT. Orthogonal and/or tangential imaging was analyzed for residual position errors of bony landmarks, the breath-hold level (BHL), the skin outline, and the heart; and setup margins were calculated for the PTV. The calculated PTV margins were 4.3 to 6.3 and 2.8 to 4.6 mm before and after orthogonal imaging, respectively. The residual errors of the heart were 3.6 ± 2.2 mm and 2.5 ± 2.4 mm before and 3.0 ± 2.5 and 2.9 ± 2.3 mm after orthogonal imaging in the combined anterior-posterior/lateral and the cranio-caudal directions, respectively, in tangential images. The humeral head did not benefit from daily IGRT, but SGRT guided it to the correct location. We presented a slightly complicated but highly accurate workflow for DIBH treatments. The residual position errors after both SGRT and IGRT were excellent compared to previous literature. With well-planned SGRT, IGRT brings only slight improvements to systematic accuracy. However, with the calculated PTV margins and the number of outliers, imaging cannot be omitted despite SGRT, unless the PTV margins are re-evaluated.

Comparison of three differently shaped ROIs in free breathing breast radiotherapy setup using surface guidance with AlignRT®.

BACKGROUND: Setup accuracy within adjuvant radiotherapy of breast cancer treated in free breathing is well studied, but a comparison of the typical regions of interest (ROI) used in surface guided radiation therapy (SGRT) does not exist. The aim of this study was to estimate the setup accuracy obtained with differently shaped ROIs in SGRT. MATERIALS AND METHODS: A total of 573 orthogonal image pairs were analyzed from free breathing breast patients in two groups: positioning using AlignRT® surface guidance system (Group A, n = 20), and setup using conventional laser and tattoo setup (Group L, n = 20). For SGRT, three different setup ROIs were used: a Breast-shaped, O-shaped and T-shaped (B-O and T-ROI). We evaluated the isocenter-, rotation-, pitch and arm position accuracy and residual errors for the chest wall and shoulder joint in kV orthogonal and tangential setup images with laser- or SGRT-based setup. RESULTS: Less isocenter variance was found in Group A than in Group L. Rotations and posture errors were larger in group L than in Group A (p ≤ 0.05). Rotation error was smaller with T-shaped ROI than with O- or B-shape (p = 0.01-0.04). CONCLUSION: Setup with AlignRT® improves reproducibility compared to laser setup. Between the different ROI shapes only small differences were found in the patient posture or the isocenter position in the images. The T-ROI is recommended to set up the chest wall bony structure and an additional B-ROI may be used to fine-tune the soft tissue accuracy.

AlignRT® and Catalyst™ in whole-breast radiotherapy with DIBH: Is IGRT still needed?

PURPOSE: Surface guided radiotherapy (SGRT) is reported as a feasible setup technique for whole-breast radiotherapy in deep inspiration breath hold (DIBH), but position errors of bony structures related to deeper parts of the target are not fully known. The aim of this study was to estimate patient setup accuracy and margins obtained with two different SGRT workflows with and without daily kV- and/or MV-based image guidance (IGRT). METHODS: A total of 50 breast cancer patients were treated in DIBH, using SGRT for the patient setup, and IGRT for isocenter corrections. The patients were treated at two different departments, one using AlignRT® (25 patients) and the other using Catalyst™ (25 patients). Inter-fractional position errors were analyzed retrospectively in orthogonal and tangential setup images, and analyzed with and without IGRT. RESULTS: In the orthogonal kV-kV images, the systematic residual errors of the bony structures were ≤ 3 mm in both groups with SGRT-only. When fine-adjusted by daily IGRT, the errors decreased to ≤ 2 mm; except for the shoulder joint. The residual errors of the ribs in tangential images were between 1 and 2 mm with both workflows. The heart planning margins were between 3 and 7 mm. CONCLUSIONS: The frequency of IGRT may be considerably reduced with a well-planned SGRT-workflow for whole-breast DIBH with residual errors ≤ 3 mm. This accuracy can be further improved with an IGRT scheme.

Dosimetric effects of anatomical deformations and positioning errors in VMAT breast radiotherapy.

AIM: Traditional radiotherapy treatment techniques of the breast are insensitive for deformations and swelling of the soft tissue. The purpose of this study was to evaluate the dose changes seen with tissue deformations using different image matching methods when VMAT technique was used, and compare these with tangential technique. METHODS: The study included 24 patients with breast or chest wall irradiations, nine of whom were bilateral. In addition to planar kV setup imaging, patients underwent weekly cone-beam computed tomography (CBCT) imaging to evaluate soft tissue deformations. The effect of the deformations was evaluated on VMAT plans optimized with 5-mm virtual bolus to create skin flash, and compared to standard tangential plans with 2.5 cm skin flash. Isocenter positioning using 2D imaging and CBCT were compared. RESULTS: With postural changes and soft tissue deformations, the target coverage decreased more in the VMAT plans than in the tangential plans. The planned V90% coverage was 98.3% and 99.0% in the tangential and VMAT plans, respectively. When tattoo-based setup and online 2D match were used, the coverage decreased to 97.9% in tangential and 96.5% in VMAT plans (P < 0.001). With automatic CBCT-based image match the respective coverages were 98.3% and 98.8%. In the cases of large soft tissue deformations, the replanning was needed for the VMAT plan, whereas the tangential plan still covered the whole target volume. CONCLUSIONS: The skin flash created using an optimization bolus for VMAT plans was in most cases enough to take into account the soft tissue deformations seen in breast VMAT treatments. However, in some cases larger skin flash or replanning were needed. The use of 2D match decreased the target coverage for VMAT plans but not for FinF plans when compared to 3D match. The use of CBCT match is recommended when treating breast/chest wall patients with VMAT technique.

Effects of multiple breath hold reproducibility on treatment localization and dosimetric accuracy in radiotherapy of left-sided breast cancer with voluntary deep inspiration breath hold technique.

The purpose of this study was to investigate the effects of breath hold reproducibility on positional and dosimetric errors in radiotherapy of patients with left-sided breast cancer (LSBC) treated with voluntary deep inspiration breath hold (vDIBH) technique. Clinical data from 2 groups of patients with LSBC were retrospectively investigated: (1) those irradiated for the whole breast only (WB group, n = 20) using typically from 3 to 5 breath holds per treatment session and (2) those irradiated simultaneously also for supraclavicular lymph nodes (WB + SLN group, n = 27) using from 7 to 9 breath holds per fraction. Setup and field images (n = 1365) from tangential breast fields, and anterior and posterior lymph node fields were analyzed to obtain total, inter-, and intrafractional residual positional errors of the chest wall and clavicle. The dosimetric effect of intrafractional positional errors was investigated at the abutment level of breast and lymph node fields. The total systematic setup error in the longitudinal (superior-inferior [SI]) direction was 1.4 and 1.9 mm (1 standard deviation, p = 0.049) for the WB and WB + SLN groups, respectively, whereas in the anterior/lateral direction, the error was 1.2 mm for both groups. In the SI direction, the systematic intrafractional error was also larger in the WB + SLN group (1.9 vs 1.1 mm, p = 0.003). The latter positional errors correlated moderately (ρ = 0.51) with the number of breath holds. Mean intrafractional errors of at least 2 mm were observed for 38% of the patients in the WB + SLN group. These errors resulted in a dosimetric error from 8.3% to 10.1% (1 cc). The total localization errors and needed setup margins were wider for the WB + SLN group, due to increased amount of breath holds in treatment session. Mean intrafraction movements ≥ 2 mm were shown to occur with this patient group in the SI direction, requiring intrafractional positional monitoring and corrective actions in daily practice.

Treatment accuracy without rotational setup corrections in intracranial SRT.

The aim of this study was to evaluate the impact of actual rotational setup errors on dose distributions in intracranial stereotactic radiotherapy (SRT) with different alternatives for treatment position selection. A total of 38 SRT fractions from 18patients were retrospectively evaluated with rotational setup errors obtained from actual treatments. The planning computed tomography (CT) images were rotated according to online cone-beam CT (CBCT) images and the dose distribution was recalculated to the rotated CT images using three different patient positionings derived from: 1) an automatic 6D match neglecting rotation correction (Auto6D); 2) an automatic 3D match (Auto3D); and 3) a manual 3D match from actual treatment (Treat3D). The mean conformity index (CI) was 0.92 for the original plans and 0.91 for the Auto6D plans. The mean CI decreased significantly (p < 0.01) to 0.78 and 0.80 for the Auto3D and the Treat3D plans, respectively. The mean minimum dose of the planning target volume (PTVmin) was 91.9% of the prescribed dose for the original plans and 92.1% for the Auto6D plans, while for the Auto3D and the Treat3D plans PTVmin decreased significantly (p < 0.01) to 78.9% and 80.2%, respectively. No significant differences were seen between the Auto6D and the original treatment plans in terms of the dose parameters. However, the Auto3D and the Treat3D plans were statistically significantly inferior (p < 0.01) to the Auto6D and the original plans. In addition, a significant negative correlation (p < 0.01, |r| > 0.38) was found in the Auto3D and the Treat3D cases between the rotation error and CI, PTVmin or minimum dose of gross tumour volume. In SRT, a treatment plan of comparable quality to 6D rotation correction can be achieved by using 6D registration without a rotational correction in the selection of patient positioning. This was demonstrated for typical rotation errors seen in clinical practice.

Improving the reproducibility of voluntary deep inspiration breath hold technique during adjuvant left-sided breast cancer radiotherapy.

BACKGROUND: Adjuvant radiotherapy (RT) of left-sided breast cancer (LSBC) with voluntary deep inspiration breath hold (vDIBH) technique reduces the cardiac dose. In this study, the effect of marker block position and the efficacy of breath hold level (BHL) correction based on lateral kV setup images are evaluated to improve the daily reproducibility. MATERIAL AND METHODS: A total of 148 consecutive LSBC patients treated with vDIBH RT were included in this study. The real-time position management (RPM) marker block was placed on the abdominal wall in 63 patients (group A) and on the sternum in 85 patients (group S). Acquired 900 (group A) + 1040 (group S) orthogonal image pairs were retrospectively analyzed. The actual BHL was determined from the lateral kV images. The height of the BHL gating window in RPM was corrected if errors of the actual BHL exceeded 4 mm. Setup margins were calculated for the chest wall and for bony surrogates of the lymph node regions. RESULTS: The sternal marker block reduced the random residual errors in the actual BHL (p < 0.05). The BHL correction was required for 26/63 patients in group A and for 26/85 patients in group S. Correction of the BHL window significantly reduced both the systematic and the random residual error in both groups. In patients with lymph node irradiation, the effect of both marker placement and BHL window correction was significant in the superior-inferior direction. Correction of the BHL reduced the mean cardiac dose by 0.5 Gy (p < 0.01) in group A and 0.6 Gy (p < 0.05) in group S. CONCLUSIONS: Reproducibility of the BHL can be improved by placing the marker block on the sternum and correcting the height of the BHL window based on lateral kV setup images. Acquisition of lateral kV images in the first 3 fractions and once a week during RT is recommended.

Residual position errors of lymph node surrogates in breast cancer adjuvant radiotherapy: Comparison of two arm fixation devices and the effect of arm position correction.

Residual position errors of the lymph node (LN) surrogates and humeral head (HH) were determined for 2 different arm fixation devices in radiotherapy (RT) of breast cancer: a standard wrist-hold (WH) and a house-made rod-hold (RH). The effect of arm position correction (APC) based on setup images was also investigated. A total of 113 consecutive patients with early-stage breast cancer with LN irradiation were retrospectively analyzed (53 and 60 using the WH and RH, respectively). Residual position errors of the LN surrogates (Th1-2 and clavicle) and the HH were investigated to compare the 2 fixation devices. The position errors and setup margins were determined before and after the APC to investigate the efficacy of the APC in the treatment situation. A threshold of 5mm was used for the residual errors of the clavicle and Th1-2 to perform the APC, and a threshold of 7mm was used for the HH. The setup margins were calculated with the van Herk formula. Irradiated volumes of the HH were determined from RT treatment plans. With the WH and the RH, setup margins up to 8.1 and 6.7mm should be used for the LN surrogates, and margins up to 4.6 and 3.6mm should be used to spare the HH, respectively, without the APC. After the APC, the margins of the LN surrogates were equal to or less than 7.5/6.0mm with the WH/RH, but margins up to 4.2/2.9mm were required for the HH. The APC was needed at least once with both the devices for approximately 60% of the patients. With the RH, irradiated volume of the HH was approximately 2 times more than with the WH, without any dose constraints. Use of the RH together with the APC resulted in minimal residual position errors and setup margins for all the investigated bony landmarks. Based on the obtained results, we prefer the house-made RH. However, more attention should be given to minimize the irradiation of the HH with the RH than with the WH.

Effects of remedies made in patient setup process on residual setup errors and margins in head and neck cancer radiotherapy based on 2D image guidance.

AIM: Patient setup errors were aimed to be reduced in radiotherapy (RT) of head-and-neck (H&N) cancer. Some remedies in patient setup procedure were proposed for this purpose. BACKGROUND: RT of H&N cancer has challenges due to patient rotation and flexible anatomy. Residual position errors occurring in treatment situation and required setup margins were estimated for relevant bony landmarks after the remedies made in setup process and compared with previous results. MATERIALS AND METHODS: The formation process for thermoplastic masks was improved. Also image matching was harmonized to the vertebrae in the middle of the target and a 5 mm threshold was introduced for immediate correction of systematic errors of the landmarks. After the remedies, residual position errors of bony landmarks were retrospectively determined from 748 orthogonal X-ray images of 40 H&N cancer patients. The landmarks were the vertebrae C1-2, C5-7, the occiput bone and the mandible. The errors include contributions from patient rotation, flexible anatomy and inter-observer variation in image matching. Setup margins (3D) were calculated with the Van Herk formula. RESULTS: Systematic residual errors of the landmarks were reduced maximally by 49.8% (p ≤ 0.05) and the margins by 3.1 mm after the remedies. With daily image guidance the setup margins of the landmarks were within 4.4 mm, but larger margins of 6.4 mm were required for the mandible. CONCLUSIONS: Remarkable decrease in the residual errors of the bony landmarks and setup margins were achieved through the remedies made in the setup process. The importance of quality assurance of the setup process was demonstrated.

Determination of the optimal matching position for setup images and minimal setup margins in adjuvant radiotherapy of breast and lymph nodes treated in voluntary deep inhalation breath-hold.

BACKGROUND: Adjuvant radiotherapy (RT) of left-sided breast cancer is increasingly performed in voluntary deep inspiration breath-hold (vDIBH). The aim of this study was to estimate the reproducibility of breath-hold level (BHL) and to find optimal bony landmarks for matching of orthogonal setup images to minimise setup margins. METHODS: 1067 sets of images with an orthogonal setup and tangential field from 67 patients were retrospectively analysed. Residual position errors were determined in the tangential treatment field images for different matches of the setup images. Variation of patient posture and BHL were analysed for position errors of the vertebrae, clavicula, ribs and sternum in the setup and tangential field images. The BHL was controlled with a Varian RPM® system. Setup margins were calculated using the van Herk's formula. Patients who underwent lymph node irradiation were also investigated. RESULTS: For the breast alone, the midway compromise of the ribs and sternum was the best general choice for matching of the setup images. The required margins were 6.5 mm and 5.3 mm in superior-inferior (SI) and lateral/anterior-posterior (LAT/AP) directions, respectively. With the individually optimised image matching position also including the vertebrae, slightly smaller margins of 6.0 mm and 4.8 mm were achieved, respectively. With the individually optimised match, margins of 7.5 mm and 10.8 mm should be used in LAT and SI directions, respectively, for the lymph node regions. These margins were considered too large. The reproducibility of the BHL was within 5 mm in the AP direction for 75% of patients. CONCLUSIONS: The smallest setup margins were obtained when the matching position of the setup images was individually optimised for each patient. Optimal match for the breast alone is not optimal for the lymph node region, and, therefore, a threshold of 5 mm was introduced for residual position errors of the sternum, upper vertebrae, clavicula and chest wall to retain minimal setup margins of 5 mm. Because random interfraction variation in patient posture was large, we recommend daily online image guidance. The BHL should be verified with image guidance.

Estimation of optimal matching position for orthogonal kV setup images and minimal setup margins in radiotherapy of whole breast and lymph node areas.

AIM: The aim was to find an optimal setup image matching position and minimal setup margins to maximally spare the organs at risk in breast radiotherapy. BACKGROUND: Radiotherapy of breast cancer is a routine task but has many challenges. We investigated residual position errors in whole breast radiotherapy when orthogonal setup images were matched to different bony landmarks. MATERIALS AND METHODS: A total of 1111 orthogonal setup image pairs and tangential field images were analyzed retrospectively for 50 consecutive patients. Residual errors in the treatment field images were determined by matching the orthogonal setup images to the vertebrae, sternum, ribs and their compromises. The most important region was the chest wall as it is crucial for the dose delivered to the heart and the ipsilateral lung. Inter-observer variation in online image matching was investigated. RESULTS: The best general image matching position was the compromise of the vertebrae, ribs and sternum, while the worst position was the vertebrae alone (p ≤ 0.03). The setup margins required for the chest wall varied from 4.3 mm to 5.5 mm in the lung direction while in the superior-inferior (SI) direction the margins varied from 5.1 mm to 7.6 mm. The inter-observer variation increased the minimal margins by approximately 1 mm. The margin of the lymph node areas should be at least 4.8 mm. CONCLUSIONS: Setup margins can be reduced by proper selection of a matching position for the orthogonal setup images. To retain the minimal margins sufficient, systematic error of the chest wall should not exceed 4 mm in the tangential field image.

Evaluation of overall setup accuracy and adequate setup margins in pelvic image-guided radiotherapy: comparison of the male and female patients.

We evaluated adequate setup margins for the radiotherapy (RT) of pelvic tumors based on overall position errors of bony landmarks. We also estimated the difference in setup accuracy between the male and female patients. Finally, we compared the patient rotation for 2 immobilization devices. The study cohort included consecutive 64 male and 64 female patients. Altogether, 1794 orthogonal setup images were analyzed. Observer-related deviation in image matching and the effect of patient rotation were explicitly determined. Overall systematic and random errors were calculated in 3 orthogonal directions. Anisotropic setup margins were evaluated based on residual errors after weekly image guidance. The van Herk formula was used to calculate the margins. Overall, 100 patients were immobilized with a house-made device. The patient rotation was compared against 28 patients immobilized with CIVCO's Kneefix and Feetfix. We found that the usually applied isotropic setup margin of 8mm covered all the uncertainties related to patient setup for most RT treatments of the pelvis. However, margins of even 10.3mm were needed for the female patients with very large pelvic target volumes centered either in the symphysis or in the sacrum containing both of these structures. This was because the effect of rotation (p ≤ 0.02) and the observer variation in image matching (p ≤ 0.04) were significantly larger for the female patients than for the male patients. Even with daily image guidance, the required margins remained larger for the women. Patient rotations were largest about the lateral axes. The difference between the required margins was only 1mm for the 2 immobilization devices. The largest component of overall systematic position error came from patient rotation. This emphasizes the need for rotation correction. Overall, larger position errors and setup margins were observed for the female patients with pelvic cancer than for the male patients.

Estimation of adequate setup margins and threshold for position errors requiring immediate attention in head and neck cancer radiotherapy based on 2D image guidance.

BACKGROUND: We estimated sufficient setup margins for head-and-neck cancer (HNC) radiotherapy (RT) when 2D kV images are utilized for routine patient setup verification. As another goal we estimated a threshold for the displacements of the most important bony landmarks related to the target volumes requiring immediate attention. METHODS: We analyzed 1491 orthogonal x-ray images utilized in RT treatment guidance for 80 HNC patients. We estimated overall setup errors and errors for four subregions to account for patient rotation and deformation: the vertebrae C1-2, C5-7, the occiput bone and the mandible. Setup margins were estimated for two 2D image guidance protocols: i) imaging at first three fractions and weekly thereafter and ii) daily imaging. Two 2D image matching principles were investigated: i) to the vertebrae in the middle of planning target volume (PTV) (MID_PTV) and ii) minimizing maximal position error for the four subregions (MIN_MAX). The threshold for the position errors was calculated with two previously unpublished methods based on the van Herk's formula and clinical data by retaining a margin of 5 mm sufficient for each subregion. RESULTS: Sufficient setup margins to compensate the displacements of the subregions were approximately two times larger than were needed to compensate setup errors for rigid target. Adequate margins varied from 2.7 mm to 9.6 mm depending on the subregions related to the target, applied image guidance protocol and early correction of clinically important systematic 3D displacements of the subregions exceeding 4 mm. The MIN_MAX match resulted in smaller margins but caused an overall shift of 2.5 mm for the target center. Margins ≤ 5mm were sufficient with the MID_PTV match only through application of daily 2D imaging and the threshold of 4 mm to correct systematic displacement of a subregion. CONCLUSIONS: Adequate setup margins depend remarkably on the subregions related to the target volume. When the systematic 3D displacement of a subregion exceeds 4 mm, it is optimal to correct patient immobilization first. If this is not successful, adaptive replanning should be considered to retain sufficiently small margins.