Daily Image-guided Radiotherapy Research Articles

Modeling and prediction of set‑up errors in breast cancer image‑guided radiotherapy using the Gaussian mixture model.

The aim of the present study was to develop a prediction model for set-up error distribution in breast cancer image-guided radiotherapy (IGRT) using a Gaussian mixture model (GMM). To achieve this, the image-guided set-up errors data of 80 patients with breast cancer were selected, and the GMM was used to develop the set-up errors distribution prediction model. The predicted error center points, covariance and probability were calculated and compared with the planning target volume (PTV) margin formula. A total of 1,200 sets of set-up errors in IGRT for breast cancer were collected. The results of the Gaussian model parameters showed that the set-up errors were mainly in the direction of µ1-µ4 center points. All the raw errors in the lateral, longitudinal and vertical directions were -6.30-4.60, -5.40-1.47 and -2.70-1.70 mm, respectively. According to the probability of each center, the set-up error was most likely to shift in the µ1 direction, reaching 0.53. The set-up errors of the other three centers, µ2, µ3 and µ4, were 0.11, 0.34 and 0.12, respectively. According to the covariance parameters of the GMM, the maximum statistical standard deviation of the set-up errors reached 29.06. In conclusion, the results of the present study demonstrated that the GMM can be used to quantitatively describe and predict the distribution of set-up errors in IGRT for breast cancer, and these findings could be useful as a reference for set-up error control and tumor PTV expansion in breast cancer radiotherapy without routine, daily IGRT.

Surface-guided radiotherapy systems in locoregional deep inspiration breath hold radiotherapy for breast cancer - a multicenter study on the setup accuracy.

Daily image-guided radiotherapy (IGRT) and deep inspiration breath hold (DIBH) technique are recommended for locoregional RT of breast cancer. The optimal workflow for a combination of surface-guided RT (SGRT) with DIBH technique is of current clinical interest. The setup accuracy at three hospitals was evaluated using different SGRT workflows. A total of 150 patients (2269 image pairs) were analyzed in three groups: patient setup with the AlignRT® SGRT system in Tampere (Site 1, n = 50), the Catalyst™ SGRT system in Turku (Site 2, n = 50) and the Catalyst™ SGRT system in Jönköping (Site 3, n = 50). Each site used their routine workflow with SGRT-based setup and IGRT positioning. Residual errors of the bony chest wall, thoracic vertebra (Th 1) and humeral head were evaluated using IGRT images. Systematic residual errors in the cranio-caudal (CC) direction and in pitch were generally larger at Site 2 than those at Sites 1 and 3 (p = 0.01-0.7). With daily IGRT, only a small difference (p = 0.01-0.9) was observed in residual random errors of bony structures in other directions between sites. The introduction of SGRT and the use of daily IGRT lead to small residual errors when combining the best workflow practices from different hospitals. Our multicenter evaluation led to improved workflow by tightening the SGRT tolerances on Site 2 and fixation modification. Because of mainly small random errors, systematic posture errors in the images need to be corrected after posture correction with new setup surfaces. We recommend tight SGRT tolerances, good fixation and correction of systematic errors.

Treatment Outcomes of Stereotactic Ablative Body Radiotherapy on Extra-cranial Oligometastatic and Oligoprogressive Breast Cancer: Mature Results from a Single Institution Experience

AimsEvidence shows stereotactic ablative body radiotherapy (SABR) is used as a non-invasive ablative therapy in the treatment of multisite oligometastatic (OM) and oligoprogressive (OP) diseases originating from metastatic breast cancer. This study aims to report the treatment outcomes and to investigate what factors that are prognostic in terms of local control, progression-free survival (PFS) and overall survival (OS) in patients receiving SABR for extracranial OM and OP diseases originating from metastatic breast cancer. Materials and methodsA retrospective review on treatment records of patients with OM and OP from metastatic breast cancer who underwent SABR at a single was carried out. SABR was performed with daily image-guided radiotherapy (IGRT) using a dedicated robotic SABR machine. Local control, PFS and OS were calculated using Kaplan-Meier statistics and the post-treatment toxicity data was scored following the CTCAE v4.0 protocol. Univariate and multivariate Cox regression tests were used in the subgroup analysis of prognostic factors on PFS and OS including patients’ age, types of follow-up imaging (staging CT only vs whole-body MR/PET), metastases status (OM vs OP), primary breast cancer tumour grade, hormone receptors (ER/PR/HER2) status, change of systemic treatments at SABR, number of metastases, SABR treatment sites and doses. Results56 metastatic breast cancer patients (38 patients with OM and 18 patients with OP) were involved in this retrospective review. The median follow-up was 35.6 months (range 4.0–132.9 months). The estimated local control at 1 , 2 and 5 years were 90.9%, 88.7% and 88.7%, respectively. The estimated median PFS was 19.2 months (95%CI 10.3–28.1 months); the PFS at 1, 2 and 5 years were 63.3%, 44.4% and 33.2%. The estimated OS at 1, 2 and 5 years were 98.0%, 91.9% and 74.3%, respectively with the estimated median OS of 105.1 months (95%CI 51.5–158.7 months). The vast majority of patients tolerated the treatment well with the commonest acute side effects as grade 1 fatigue. There were no statistically significant factors found in OS regression analysis. The types of follow-up imaging, metastases status, oestrogen receptor status, and number of metastases for SABR were statistically significant factors (p < 0.05) in the multivariate Cox regression analysis on PFS. ConclusionThere are limited studies published on the efficacy and post-treatment toxicities of metastatic breast cancer OM and OP SABR with adequate length of follow-up. This study confirmed that SABR was a safe, non-invasive treatment option for patients with extracranial OM and OP diseases originated from primary breast cancer in terms of the acceptable post-treatment toxicities.

Difference between planned and delivered radiotherapy dose to the internal mammary nodes in high-risk breast cancer patients.

Chest wall movement during radiotherapy can impact the delivered dose to the internal mammary nodes (IMN) in high-risk breast cancer patients. Using portal imaging and dose reconstruction we aimed to examine the delivered IMN dose coverage. Cine MV images were recorded for 39 breast cancer patients treated with daily image-guided radiotherapy (IGRT) in deep-inspiration breath-hold (DIBH). On the final frame of each cine MV recording the chest wall was matched with the Digitally Reconstructed Radiograph (DRR) from the treatment plan. The geometrical chest wall error was determined in the imager-plane perpendicular to the cranio-caudal direction, rounded to integer millimeters, and binned. For each 1mm bin, an isocenter-shifted treatment plan was recalculated assuming that the projected error observed in the cine MV image was caused by anterior-posterior chest wall movement in the IMN region. A weighted plan sum yielded the IMN clinical target volume receiving at least 90% dose (V90_CTVn_IMN). The mean number of cine MV observations per patient was 36 (range 26-55). Most patients (67%) had on average a posterior chest wall position at treatment compared to planned. This translated into a change in the delivered median V90_CTVn_IMN of -0.7% (range, -11.9-2.9%; p<0.001). The V90_CTVn_IMN reduction wasgreater than9% in three patients. No clinically relevant differences were found for the mean lung dose or mean heart dose. Using cine MV images, we found that the delivered V90_CTVn_IMN was significantly lower than planned. In 8% of the patients, the V90_CTVn_IMN reduction exceeded 9%.

Adipose Tissue Distribution and Body Mass Index (BMI) Correlation With Daily Image-Guided Radiotherapy (IGRT) Shifts of Abdominal Radiation Therapy Patients.

Purpose There are several studies suggesting a correlation between image-guided radiotherapy (IGRT) setup errors and body mass index (BMI). However, abdominal fat content has visceral and subcutaneous components, which may affect setup errors differently. This study aims to analyze a potential workflow for characterizing adipose content and distribution in the region of the target that would allow a quickly calculated metric of abdominal fat content to stratify these patients. Methods IGRT shift data was retrospectively tabulated from daily fan-beam CT-on-rails pre-treatment alignment for 50 abdominal radiation therapy (RT) patients, and systematic and random errors in the daily setup were characterized by tabulating average and standard deviations of shift data for each patient and looking at differences for different distributions of adipose content. Visceral and subcutaneous fat content were defined by visceral fat area (VFA) and subcutaneous fat area (SFA) using a region-growing algorithm to contour adipose tissue on CT simulation scans. All contours were created for a single slice at the treatment isocenter, on which the VFA and SFA were calculated. A log-rank test was used to test trends in shifts over quartiles of adiposity. Results VFA ranged from 1.9-342.8c m2, and SFA from 11.8-756.0 cm2. The standard definition (SD) of random error (σ) in the lateral axis for Q1 vs. Q4 VFA was 0.10cm vs. 0.29cm, 0.12cm vs. 0.28cm for SFA, and 0.12cm vs. 0.31cm for BMI. The percentage of longitudinal shifts greater than 10mm for Q1 vs. Q4 VFA was 0% vs. 9%, 2% vs. 19% for SFA, and 0% vs. 20% for BMI. Statistically significant trends in shifts vs. the BMI quartile were seen for both pitch and the longitudinal direction, as well as for pitch corrections vs. the VFA quartile. Conclusion Within this dataset, abdominal cancer patients showed statistically significant trends in shift probability vs. BMI and VFA. Also, patients in the upper quartiles of all adiposity metrics showed an increased SD of σ in the lateral direction and increased shifts over 10 mm in the longitudinal direction. However, despite these relationships, neither VFA nor SFA offered discernible advantages in their relationship to shift uncertainty relative to BMI.

Image-guided radiotherapy (IGRT) in Lombardy, Italy: a survey by the Lombardy section of the Italian Association of Radiotherapy and Clinical Oncology (AIRO-Lombardy)

ABSTRACT Background Image-guided radiation therapy (IGRT) has changed clinical practice. We proposed a survey to radiotherapy centers in Lombardy to picture the current clinical practice of its use. Research design and methods The survey consisted of 32 multiple-choice questions, divided into five topics: type of hospital, patients treated in 2019, number of LINACs; presence of protocols and staff involved in IGRT; IGRT in stereotaxis; IGRT in non-stereotactic treatments; availability of medical and technical staff. Results Twenty-seven directors answered (77%). Most centers (74%) have produced protocols to ensure uniformity in the IGRT process. The most widely used IGRT modality (92%) is cone-beam CT. Daily IGRT control is favored for prostate (100%), head and neck (87%), and lung (78%) neoplasms. The resident doctors can always perform supervised IGRT matching in only six centers. Radiation therapists perform IGRT controls only for some sites in 12 cases (44%) and always in 9 cases (33%). Radiation oncologists are present in real time, in most cases. Conclusions Today, IGRT can be considered standard practice but at the price of more time-consuming procedures. A balance between a fully physician-controlled process and an increased role for specifically trained RTTs is actively being sought.

Factors Affecting Isocenter Displacement and Planning Target Volume Margin for Patients With Rectal Cancer Receiving Radiation Therapy

PurposeSetup errors are inherent in the process of daily radiation therapy (RT) delivery. Pelvic RT for rectal cancer is one of the body sites associated with the largest shift among other body sites. This study aimed to evaluate interfraction random and systematic errors and hence propose the optimum planning target volume (PTV) in patients with rectal cancer. Methods and MaterialsTranslational and angular isocenter displacements were retrospectively collected for 189 patients. Random and systematic errors were determined, and then the PTV margin was computed. Effect of positioning, body mass index (BMI), and type of immobilization were studied. Portal images before and after online correction were used to define PTV for no-daily image-guided radiotherapy (IGRT) and daily IGRT respectively. ResultsBefore the online correction, the systematic errors were 2.5, 2.8, and 3.0 mm for superior-inferior (SI), right-left (RL), and anterior-posterior (AP) directions, respectively, compared with 2.1, 1.7, and 1.8 mm after online correction. The random errors were 6.2, 7.4, and 8.2 mm in SI, RL, and AP, respectively, before online correction, compared with 4, 4.2, and 4.5 mm after online correction. The recommended PTV margin was 0.7 and 1.0 cm for daily IGRT and no-daily IGRT, respectively. The prone position and BMI >30 kg/m2 warrant higher margins in no-daily IGRT cases, 1.2 and 1.4 cm, respectively. ConclusionsThe prone position, BMI >30 kg/m2, and belly board device are associated with larger daily setup errors warranting higher PTV margins for no-daily IGRT; however, that can be avoided by using daily IGRT.

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.

Hypo-Fractionated Intensity Modulated Radiotherapy (IMRT) After Prostatectomy: Results of a Prospective Study

<h3>Purpose/Objective(s)</h3> To assess the toxicity profile and biochemical control of a moderately hypo-fractionated radiotherapy (RT) to the prostatic bed after prostatectomy. <h3>Materials/Methods</h3> From Sep. 2017 to Nov. 2020, 215 Patients with prostate adenocarcinoma who were recommended to receive adjuvant or salvage RT were prescribed to moderately hypo-fractionated RT (62.75 Gy delivered in 2.51 Gy per fractions) to prostatic bed. Whole-pelvis irradiation was performed in 93.0% of patients. Concurrent hormone therapy was administrated in 97.2% of patients. All patients received IMRT with daily image-guided radiotherapy (IGRT). Acute and late toxicity was recorded and graded according to CTCAE 4.0. <h3>Results</h3> The median follow-up was 22 months (range, 1-46 months). Acute grade 2 GI and GU toxicities were 9.3% (20/215) and 11.6% (25/215) respectively. Late grade 2 GI and GU toxicity were 3.7% (8/215) and 16.3% (35/215). No patients complained of acute and late grade ≥3 GI, GU toxicities. The actuarial three-year estimated biochemical progression-free survival (b-PFS) was 89.6% for the entire population. <h3>Conclusion</h3> After prostatectomy, moderately hypo-fractionated RT (2.51 Gy/f25 f) demonstrated promising early biochemical control and acceptable toxicity profile. Prospective randomized trials are warranted with longer follow-up in larger cohorts to confirm these findings.

Evaluation of an ultrasound bladder scanner in supine and standing position.

PurposeThis study examined the performance of a bladder volume measuring device, the BladderScan (BS) BVI9400. The use of the BS offers the possibility of assessing the bladder volume before positioning the patient and performing the daily image‐guided radiotherapy procedure. Patients often cannot lie down before entering the treatment vault. Therefore, the BS was also assessed in a standing position.MethodsThe repeatability precision was first evaluated, which is the variability of immediate repeated measures of the BS with same operator and subject. This was followed by the reproducibility precision of the BS in which the operator and subjects differ. Finally, the trueness was evaluated in terms of fixed and proportional bias of the results by applying weighted least‐squares fitting. Note that 53 and 85 patient measurements were carried out in supine and standing position, respectively, each consisting of three repeated BS measurements. These were compared with the computed tomography (CT)‐delineated bladder volume.ResultsRepeatability was dependent on measurement value (heteroscedasticity) with σ repeatability (BS) = ±15 cm3 ± 10%. However, the total agreement between BS and CT was low with the 95% limits of agreement (LOAs) exceeding ±200 cm3 due to poor patient reproducibility and presence of fixed and proportional bias. Only in the best case of male patients in the supine position, three BS measurements, and correction for the fixed and proportional bias, 95% LOAs of [–147, +114] cm3 were obtained between CT and BS.ConclusionThe agreement of the BVI9400 BS with CT was found to be too low for radiotherapy applications.

Simulated daily plan adaptation for magnetic resonance-guided liver stereotactic body radiotherapy

Introduction Liver cancers are challenging to treat using image-guided radiotherapy (IGRT) due to motion and deformation of target volumes and organs at risk (OARs), as well as difficulties in visualising liver tumours using cone-beam computed tomography (CBCT) based IGRT. Liver cancer patients may thus benefit from magnetic resonance (MR)-guided daily adaptive re-planning. We evaluated the dosimetric impact of a daily plan adaptation strategy based on daily MR imaging versus CBCT-based IGRT. Methods Ten patients were studied who were treated with CBCT-guided five-fraction stereotactic body radiotherapy (SBRT) and underwent MR imaging before each fraction. Simulated reference plans were created on computer tomography (CT) images and adapted plans were created on the daily MR images. Two plan adaptation strategies were retrospectively simulated: (1) translational couch shifts to match liver, mimicking standard CBCT guidance and (2) daily plan adaptation based on reference plan clinical goals and daily target and OAR contours. Dose statistics were calculated for both strategies and compared. Results Couch shifts resulted in an average reduction in GTV D99% relative to reference plan values of 5.2 Gy (−12.5% of reference values). Daily plan adaptation reduced this to 0.8 Gy (−2.0%). For six patients who were OAR dose-limited on reference plans, couch shifts resulted in OAR dose violations in 28 out of 28 simulated fractions, respectively; no violations occurred using daily plan adaptation. No OAR dose violations occurred using either strategy for the four cases not OAR dose-limited at reference planning. Conclusions MR-guided daily plan adaptation ensured OAR dose constraints were met at all simulated treatment fractions while CBCT-based IGRT resulted in a systematic over-dosing of OARs in patients whose doses were limited by OAR dose at the time of reference planning.

Image-Guided Radiotherapy for Pelvic Cancers: A Review of Current Evidence and Clinical Utilisation

The meticulous selection and utilisation of image-guided radiotherapy (IGRT) are essential for optimal radiotherapy treatment delivery when using highly conformal treatment techniques in pelvic radiotherapy. Pelvic IGRT has several general IGRT issues to consider (such as choice of match strategy, prioritisation between multiple treatment targets and margin estimates) as well as issues specific to pelvic radiotherapy, in particular large inter-fraction organ variation. A range of interventions, including adaptive treatment strategies, have been developed to address these challenges. This review covers general considerations for the clinical implementation of pelvic IGRT in routine practice and provides an overview of current knowledge regarding pelvic inter-fraction organ motion. Published IGRT evidence for each of the major tumour sites (gynaecological, prostate, bladder, rectal and anal cancer) is summarised, as are state-of-the-art adaptive approaches. General recommendations for the implementation of an institutional pelvic IGRT strategy include.•Ensuring consistency between treatment intent and the IGRT approach utilised.•Ensuring minimum national and international IGRT guidance is followed while considering the benefit of daily volumetric IGRT.•Ensuring the appropriate allied health professionals (namely therapy radiographers/radiation therapists) lead on undertaking IGRT.•Ensuring the IGRT workflow procedure is clear and includes an escalation process for difficult set-ups.•Ensuring a robust IGRT service is in place before implementing advanced adaptive approaches.

Factors influencing the use of adaptive radiation therapy in vulvar carcinoma.

We aim to evaluate the variables affecting the frequency of adaptive radiotherapy (ART) in vulvar cancer. ART may be needed throughout a definitive RT course for vulvar carcinoma due to changes in patient's anatomy and tumor response. Charts of patients charts who had been treated with definitive concurrent chemo-radiotherapy for vulvar carcinoma, between January 2015 and December 2019 were inquired. Radiation therapy was delivered using intensity modulated radiotherapy (IMRT) with daily image-guided radiotherapy (IGRT). ART was defined as re-simulation and re-planning based on deformation in the irradiated volume by more than 1 cm. Univariate analysis was conducted to study the impact of patient's demographics as well as tumor characteristics on the frequency of ART. 22 patients were eligible for analysis. Median age at diagnosis was 55 years (range 43-82). Radiotherapy dose was 60-66 Gy over 30-35 fractions (fx). Median primary tumor volume was 30cc (9-140). Median Body Mass Index (BMI) was 32 (range 21-40). Thirteen out of 22 patients (59%) required ART, with median timing at 25 fx (19-31). On univariate analysis, larger primary tumor volume (> = 30cc) was associated significantly with increased frequency of ART (p value = 0.0005). There was no significant impact of ART on the frequency with respect to patient's age, BMI, tumor stage, grade and location. Changes in radiation target volume are common among vulvar carcinoma patients who are treated with definitive radiotherapy, especially large primary tumors. This review highlights the importance of ART for patients with vulvar carcinoma treated with definitive radiotherapy.

Daily adaptive radiotherapy for patients with prostate cancer using a high field MR-linac: Initial clinical experiences and assessment of delivered doses compared to a C-arm linac

IntroductionMR-guided adapted radiotherapy (MRgART) using a high field MR-linac has recently become available. We report the estimated delivered fractional dose of the first five prostate cancer patients treated at our centre using MRgART and compare this to C-Arm linac daily Image Guided Radiotherapy (IGRT). MethodsPatients were treated using adapted treatment plans shaped to their daily anatomy. The treatments were recalculated on an MR image acquired immediately prior to treatment delivery in order to estimate the delivered fractional dose. C-arm linac non-adapted VMAT treatment plans were recalculated on the same MR images to estimate the fractional dose that would have been delivered using conventional radiotherapy techniques using a daily IGRT protocol. Results95% and 93% of mandatory target coverage objectives and organ at risk dose constraints were achieved by MRgART and C-arm linac delivered dose estimates, respectively. Both delivery techniques were estimated to have achieved 98% of mandatory Organ At Risk (OAR) dose constraints whereas for the target clinical goals, 86% and 80% were achieved by MRgART and C-arm linac delivered dose estimates. ConclusionsProstate MRgART can be delivered using the a high field MR-linac. Radiotherapy performed on a C-arm linac offers a good solution for prostate cancer patients who present with favourable anatomy at the time of reference imaging and demonstrate stable anatomy throughout the course of their treatment. For patients with critical OARs abutting target volumes on their reference image we have demonstrated the potential for a target dose coverage improvement for MRgART compared to C-arm linac treatment.

Effectiveness of image-guided radiotherapy for locally advanced esophageal squamous cell carcinoma patients treated with definitive concurrent chemoradiotherapy.

BackgroundImage‐guided radiotherapy (IGRT) is an advanced radiotherapy technique to improve the accuracy of treatment delivery. However, a recent randomized controlled trial (RCT) for prostate cancer patients treated with radiotherapy either via IGRT or routine care (no daily IGRT) reported a statistically significant worse overall survival for those treated with IGRT. This raised the concern regarding the effectiveness of IGRT for definitive concurrent chemoradiotherapy (dCCRT) for locally advanced esophageal squamous cell carcinoma (LA‐ESqCC).MethodsEligible LA‐ESqCC patients diagnosed between 2011 and 2015 were identified via the Taiwan Cancer Registry. We estimated propensity scores to construct a 1:1 propensity‐score‐matched groups and balance observable potential confounders. The hazard ratio (HR) of death as well as other outcomes was compared between IGRT and non‐IGRT matched groups during the entire follow‐up period. The impact of additional covariables was considered in the sensitivity analysis.ResultsOur study population included 590 patients in the primary analysis. The HR for death when IGRT was compared with non‐IGRT was 0.92 (95% confidence interval 0.77–1.10, P = 0.35). There were also no significant differences for other outcomes or sensitivity analyses.ConclusionsIn this updated nonrandomized study using real world data, we found that the overall survival of LA‐ESqCC patients treated with dCCRT was not statistically different between those treated with IGRT versus those without IGRT, although the hazard ratio was less than unity, ie, in favor of IGRT. The results should be interpreted with caution given the nonrandomized design and RCTs are needed to clarify our findings.Key points Significant findings of the study: The OS of LA‐ESqCC patients treated with dCCRT was not statistically different between those treated with IGRT versus those without IGRT, although the hazard ratio was less than unity, ie, in favor of IGRT.What this study adds: In this updated nonrandomized study using real world data with additional potential confounders, our study provided a reasonable tentative evidence of lack of RCT as suggested in the literature.

Intensity Modulated Radiotherapy (IMRT) after Prostatectomy: Acute Toxicity Comparison of Conventional Versus Moderately Hypo-Fractionated Radiation Regimens

To compare the acute toxicity of a moderately hypo-fractionated radiotherapy (RT) with that of conventionally fractionated RT to the prostatic bed after prostatectomy. From September 2011 to Jul. 2018, Patients with prostate adenocarcinoma who were recommended to receive adjuvant or salvage RT were prescribed to moderately hypo-fractionated RT (62.75 Gy delivered in 2.51 Gy per fractions) or conventionally fractionated RT (72 Gy delivered in 2 Gy per fraction). All patients received IMRT with daily image-guided radiotherapy (IGRT). Patients who received hypo-fractionated RT were matched (for age, hormonal therapy, irradiated volume, interval between surgery and RT, and comorbidities such as diabetes mellitus and hypertension.) with propensity scores to patients who underwent conventionally fractionated RT. Acute and late toxicity was recorded and graded according to CTCAE 4.0. One hundred and fifty-one patients were enrolled with seventy-nine patients received moderately hypo-fractionated RT versus seventy-two patients received conventionally fractionated RT. The median follow-up is 13 and 50 months respectively. Grade 2 acute GI and GU toxicities were 8.8% vs 6.9% and 13.9% vs 16.6%, respectively (p>0.05). After propensity score matching, there are fifty-eight patients in hypoPORT and coPORT groups respectively. Grade 2 acute gastrointestinal (GI) and genitourinary (GU) toxicity were observed in 10.3% vs 8.6% and 13.7% vs 15.5% of patients, respectively (p>0.05). None of patients reported ≥ grade 3 acute and late GI or GU toxicity. After prostatectomy, moderately hypo-fractionated RT (2.51 Gy/f X 25 f) demonstrated an acute toxicity profile which compares favorably with that of conventionally fractionated RT.

Inoperable Pulmonary Carcinoid Tumors: Local Control Rates With Stereotactic Body Radiotherapy/Hypofractionated RT With Image-Guided Radiotherapy

IntroductionSurgery is the standard of care for pulmonary carcinoid tumors; however, options for inoperable patients are few. We report the outcomes of inoperable pulmonary carcinoid patients treated with stereotactic body radiotherapy (SBRT). Patients and MethodsFrom an institutional database, we retrospectively identified patients treated with SBRT for pulmonary carcinoid tumors from 2007 to 2017. Additional inclusion criteria were previous histopathologic diagnosis, age older than 18 years and Karnofsky performance status ≥ 70. ResultsTen patients were treated for 12 pulmonary carcinoid lesions with 5 to 10 fractions of SBRT. Their median age was 66.5 years (range, 40-83 years) and most presented with nonspecific symptoms of cough, shortness of breath, or hemoptysis. Pathology revealed typical carcinoid for 9 patients, with the 10th with atypical histology. The median prescription dose for all patients was 50 Gy in 5 to 10 fractions (range, 40-60 Gy) with SBRT/hypofractionated radiation with daily image-guided radiotherapy (IGRT) delivered using a linear accelerator with respiratory monitoring. Four patients received 10-fraction hypofractionated radiation with daily IGRT and 6 others received 5-fraction SBRT. The follow-up after SBRT/hypofractionated IGRT ranged from 6 to 56 months (median, 25 months). Four patients were alive with stable disease at their last follow-up. Two patients died from disease progression in the mediastinal lymph nodes as well as in the lung. Both opted for palliative treatment. The other 4 patients died from their comorbid medical conditions, but had stable disease at their last follow-up. Median overall survival was 27.1 months (range, 5.5-56 months). ConclusionPulmonary carcinoid tumors treated with SBRT have a promising tumor control rate and survival.

207. Impact of IGRT on correct set-up of patients with prostate cancer: Experience of our center

Purpose The purpose of this study is to quantify displacements in image-guided radiotherapy (IGRT) for prostate cancer patients and to evaluate the impact of IGRT on the quality of radiotherapy treatments in terms of rectal toxicities. Methods From January to October 2017, 46 patients with prostate cancer were treated. All patients were planned with volumetric-modulated arc therapy (VMAT) technique, receiving hypofractionated radiotherapy for a total dose of 67.5 Gy in 25 fractions or conventionally fractionated radiotherapy for a total dose of 70–80 Gy in 35–40 fractions. Daily IGRT using cone-beam computed tomography (CBCT) was performed for all patients. Setup corrections were determined and corrected by means of registrations of CBCT images with the planning CT using online 3D fusion and for each session displacements were evaluated to analyze the setup errors. Weekly clinical visits were made to all patients; rectal toxicities were evaluated according to CTCAE (Common Terminology Criteria for Adverse Events) scales and compared with a group of prostate cancer patients treated with intensity modulated radiotherapy without daily CBCT from January 2013 to July 2014. Results Significative differences in setup displacements were found for each treatment session. The range of displacements in the three space directions was calculated for each patient, as showed in Fig. 1, and the average of all ranges was 1.6 cm in vertical direction, 1.3 cm in lateral direction and 1.4 cm in longitudinal direction. Symptomatic grade 1 (G1) rectal toxicity was found in 17% of daily IGRT patients and in 49% of no-daily IGRT patients; asymptomatic G1 rectal toxicity was found in 79% and 47% of IGRT and no-daily IGRT patients, respectively (Fig. 2). Conclusions Daily CBCT allows real-time verification and correction of set-up and organ-motion errors and improves treatment quality by reducing rectal toxicity. More cases and a longer follow-up are needed to confirm the preliminary results of this study. Download : Download high-res image (413KB) Download : Download full-size image Download : Download high-res image (236KB) Download : Download full-size image

212. RapidArc versus IMRT for postoperative irradiation of a case of recurrent breast cancer with internal mammary lymph node involvement

Purpose The aim of this case-report is a dosimetric comparison between RapidArc and IMRT treatment plans for a recurrent breast cancer with internal mammary chain (IMC) involvement. Methods A 46 years old woman with peri-prosthetic recurrent breast cancer was evaluated for postoperative left chest wall and homolateral periclavicular and IMC irradiation, with the inclusion of internal mammary lymph node (IMN) that uptaked fluoro-deoxyglucose at postoperative PET. Prescription dose (PD) to PTV (left chest wall and homolateral IMC) was 50 Gy(2 Gy/die); PD to left periclavicular region was 46,8 Gy (1,87 Gy/die); the PET-positive IMN received a simultaneous integrated boost up to 59,25 Gy (2,37 Gy/die; EQD2 of 64 Gy with estimated α/ β3). A 1 cm-tissue equivalent bolus was used on the skin. We compared RapidArc with 5-beams step-and-shot IMRT plans according to target coverage, conformity and dose-homogeneity index, Organs at Risk (OARs) sparing (heart, lungs, spinal cord). Controlateral breast was not evaluated because of a previously implanted prosthesis. Number of monitor units (MU) and treatment delivery time were also considered. Daily image-guided radiotherapy was performed in order to reduce inter fraction organ motion. Results RapidArc achieves better PTV and boost dose coverage and dose-homogeneity compared to IMRT. RapidArc also allows a better normal OARs sparing, with fewer monitor units and shorter delivery time. Target coverage and dose-sparing for OARs were not acceptable with 3DCRT because of chest’s anatomical conformation. Conclusion Our dosimetric results confirmed that RapidArc allows to obtain optimal target-coverage and adequate dose-sparing for OARs as reported in literature [1] . It could be appropriate to reduce the respiration-induced intra-fraction target motion using breath-hold techniques.

P181] Establishing margins from clinical to planning target volume for low-risk prostate cancer radiotherapy: A multi institutional study

Purpose The aim of this study was to determine the appropriate margins from clinical target volume (CTV) to planning target volume (PTV) in low risk prostate cancer irradiation, in terms of image guided radiotherapy (IGRT) protocol from three radiotherapy (RT) centers. Methods Twenty patients with low risk prostate cancer were selected from each RT center for retrospective review. Prescribed dose of 78 Gy in 39 fractions was delivered with volumetric modulated arc therapy (VMAT). Pretreatment preparation was applied in accordance with institutional protocol. Cone beam computed tomography (CBCT) was daily co-registered with planning Computed Tomography (CT), using two registration protocols: bone match and prostate (soft tissue) match. Based on this data, set up errors and inter-fraction prostate motion were calculated in three RT centers. Literature data for delineation errors and intra-fraction motions were used to determine CTV-PTV margins for different imaging protocols (online 2D/2D bone match and online CBCT or 2D/2D prostate fiducial markers match). Results The standard deviation of the systematic set up errors was in the range of 1.6–3.0 mm and for random set up errors 1.8–3.0 mm. The overall mean prostate movement, relative to bone anatomy, in anterior/posterior (A/P), inferior/superior (I/S), and left/right (L/R) direction, respectively was for: 1st RT center 0.5 ± 1.9 (1 SD), 0.1 ± 0.8 and 0.1 ± 0.7 mm, 2nd RT center 0.1 ± 1.4 (1 SD), 0.1 ± 1.4 and 0.1 ± 1.5 mm, and. 3rd RT center 0.6 ± 2.2 (1 SD), 0.6 ± 2.2 and 0.3 ± 1.3 mm. According to the IGRT modalities and frequency of use, the calculated CTV-PTV margins of A/P, I/S and L/R directions, respectively were in the range of: -for online 2D/2D bone match 7.4–9.1, 7.4–10.1 and 5.5–7.0 mm, respectively, -for online CBCT or 2D/2D prostate fiducial markers matching: 5.7, 7.0 and 5.0 mm, respectively. Conclusions In low risk prostate cancer irradiation, CTV-PTV margins less than 10 mm could not be used safely without daily CBCT prostate based soft tissue matching, due to the increased risk of missing the CTV. Generally smaller, precise margins followed with daily IGRT and online corrections, may influence the local control and lower toxicity rates.