Ipsilateral Lung Dose Research Articles

Deep inspiration breath-hold intensity modulated radiation therapy in a large clinical series of 239 left-sided breast cancer patients: a dosimetric analysis of organs at risk doses and clinical feasibility from a single center experience.

To evaluate dose to organs at risk, target coverage and treatment compliance in left-sided breast cancer patients (LSBCP) treated with deep inspiration breath-hold (DIBH) and intensity modulated radiation therapy (IMRT) technique in a contest of daily clinical practice. A total of 280 consecutive LSBCP referred for adjuvant radiotherapy were systematically screened for suitability of DIBH technique. 239 were able to comply with the requirement for DIBH. Whole breast or chest wall were irradiated in DIBH, monitored by Varian RPM™ Respiratory Gating System, and two tangential inverse-planned beams with dynamic dose delivery. Dose prescription was 42.4 Gy/16 fractions in 205 patients and 50 Gy/25 fractions in 34. 23 patients received local and nodal treatment. Boost to tumor bed, of 10 Gy/5 fractions was used in 135 patients. Relevant dose metrics for heart, left anterior descending (LAD) coronary artery, lungs, contralateral breast and planning target volume were retrospectively analyzed. The average mean heart dose (MHD) for all patients was 0.94 Gy and mean maximum LAD dose was 13.82 Gy. MHD and LAD maximum dose were significantly higher in patients treated with conventional fractionation whether expressed in absolute dose (1.44 vs 0.85 Gy, p < 0.0005 and 20.78 vs 12.45 Gy, p < 0.0005 respectively) or in equivalent doses of 2 Gy fractionation (0.88 vs 0.52 Gy, p =< 0.0005 and 17.68 vs 10.63 Gy, p = 0.0002 respectively). In 57 patients (23.8%) the maximum LAD dose was >20 Gy. Mean V20 ipsilateral lung dose was 8.5%. Mean doses of contralateral breast and lung were 0.13 Gy and 0.09 Gy respectively. Mean planning target volume V95% coverage was 96.1%. Compliance rate of DIBH technique was 84.5% (239/280). DIBH and IMRT in daily clinical practice are feasible in high percentage of unselected patients and allows low levels of irradiation of organs at risk without compromising target coverage. However, despite low MHD a significant proportion of patients receives a maximum LAD dose superior to 20 Gy. The value of MHD used exclusively is not able to describe entirely the risk of late heart toxicity, which can be better evaluated with the joint analysis of the maximum dose to LAD region. The vast majority of LSBCP referred to adjuvant radiotherapy in the setting of routine practice are able to comply with the requirement of DIBH.

Use of Moderate Deep Inspiration Breath Hold for Loco-Regional Radiotherapy of Right Breast Cancer including Internal Mammary Lymph Nodes

Loco-regional radiotherapy (RT) of the breast or chestwall may include the internal mammary lymph nodes (IMN). Inclusion of these lymph nodes with a conventional four field technique may give rise to an increased volume of lung in the treated volume. At our centre patients receiving RT to the left breast are usually simulated and treated using a moderate Deep Inspiration Breath Hold (mDIBH) technique in an attempt to reduce dose to the heart. Patients receiving RT to the right breast or chestwall including the IMN may benefit from treatment with the mDIBH technique by reducing doses to organs at risk (OAR). The aim of this work is to compare the dose to OARs for patients receiving loco-regional radiotherapy treatment of the right breast/chestwall including IMN using free breathing and mDIBH CT simulation datasets. Patients who are to receive loco-regional RT to the right breast or chestwall by default are CT simulated while free breathing. The IMN target is contoured by the radiation oncologist. A treatment plan is generated using the free breathing dataset. Review of this treatment plan specifically the volume of right lung receiving 20 Gy (V20) is undertaken. Right lung V20 greater than 35% triggers re-simulation with mDIBH in an attempt to reduce the V20. If a patient is unable to tolerate the mDIBH apparatus, the clinical management may be changed such that IMN may be excluded in the tangent fields thereby ensuring an acceptable dose to the right lung. Simulation and delivery of RT to patients in mDIBH can reduce the ipsilateral lung V20. Resources are impacted by utilizing this treatment technique to the right breast/chestwall loco-regional patient population. Additional resources include the following: additional CT simulation, additional contouring time and treatment plan generation, additional time on the treatment unit to treat in mDIBH, additional cost per fraction for mDIBH consumables. Right breast/chestwall loco-regional RT treatment using a mDIBH technique allows inclusion of the IMN where indicated whilst maintaining acceptable ipsilateral lung doses. In our experience the right lung V20 is reduced by 8% on average for mDIBH technique as compared with the free breathing technique with the reduction in right lung V20 ranging from 3% to 22%. A reduction of 5% in the V20 of both lungs is observed for the mDIBH technique as compared with the free breathing technique. Slight reductions in the mean heart dose are observed for mDIBH as compared with free breathing. When tolerated by patients, the mDIBH treatment enables inclusion of the IMN in the tangential beams where previously the IMN may have been omitted due to ipsilateral lung dose metrics being exceeded. Future direction includes investigating the role of mDIBH for this population as a standard of care considering resources and implementation of a voluntary breath hold delivery technique.

Retrospective analysis of breast radiotherapy treatment plans: Curating the 'non-curated'.

This paper provides a demonstration of how non-curated data can be retrospectively cleaned, so that existing repositories of radiotherapy treatment planning data can be used to complete bulk retrospective analyses of dosimetric trends and other plan characteristics. A non curated archive of 1137 radiotherapy treatment plans accumulated over a 12-month period, from five radiotherapy centres operated by one institution, was used to investigate and demonstrate a process of clinical data cleansing, by: identifying and translating inconsistent structure names; correcting inconsistent lung contouring; excluding plans for treatments other than breast tangents and plans without identifiable PTV, lung and heart structures; and identifying but not excluding plans that deviated from the local planning protocol. PTV, heart and lung dose-volume metrics were evaluated, in addition to a sample of personnel and linac load indicators. Data cleansing reduced the number of treatment plans in the sample by 35.7%. Inconsistent structure names were successfully identified and translated (e.g. 35 different names for lung). Automatically separating whole lung structures into left and right lung structures allowed the effect of contralateral and ipsilateral lung dose to be evaluated, while introducing some small uncertainties, compared to manual contouring. PTV doses were indicative of prescription doses. Breast treatment work was unevenly distributed between oncologists and between metropolitan and regional centres. This paper exemplifies the data cleansing and data analysis steps that may be completed using existing treatment planning data, to provide individual radiation oncology departments with access to information on their own patient populations. Clearly, the well-planned and systematic recording of new, high quality data is the preferred solution, but the retrospective curation of non-curated data may be a useful interim solution, for radiation oncology departments where the systems for recording of new data have yet to be designed and agreed.

Comparison of deep inspiration breath hold and free breathing technique in left breast cancer irradiation: a dosimetric evaluation in 40 patients

To analyze the reduction of dose to organs at risk between deep inspiration breath hold (DIBH) and free breathing (FB) techniques in left breast irradiation. Forty left-sided breast cancer patients received adjuvant radiotherapy and were retrospectively analyzed. Treatment plans were generated on both DIBH and FB computed tomography (CT) scans. The patients were monitored by the Varian RPM™ respiratory gating system. The treatment planning was performed with conformal tangential fields by means of 6 and 10 MV photon fields. Treatment schedule were 50 Gy in 25 fractions (conventional schedule) or 40.05 Gy in 15 fractions (hypofractionated schedule), with or without sequential boost to tumor bed. Dose-volume histograms were compared for all plans. For the comparison, we considered cardiac and ipsilateral lung doses and volumes. Quantitative statistical analyses of plans dose differences were generated. In order to correlate the mean cardiac dose difference between the FB and DIBH techniques with maximum heart distance (MHD), a linear regression model was used. A statistically significant reduction of cardiac and pulmonary doses using the DIBH technique was achieved compared with FB plans, maintaining an equal coverage of planning target volume (PTV). A positive correlation was found between MHD and mean heart dose difference. Our study confirms the DIBH technique advantage in reducing cardiac and pulmonary doses for tangentially treated left-sided breast cancer patients. Further research is warranted to evaluate potential long-term clinical implications of these relevant dosimetry results.

Dosimetric Comparison of Sequential Versus Simultaneous-integrated Boost in Early-stage Breast Cancer Patients Treated With Breast-conserving Surgery.

To compare simultaneous-integrated boost (SIB) versus sequential-boost (SB) delivered in the context of whole-breast irradiation (WBI) via volumetric-modulated arc therapy (VMAT) and helical-tomotherapy (HT). Planning target-volume (PTV) dosimetric parameters and organs at risk (OAR) were analyzed for SB plan (50 Gy plus 16 Gy boost) and SIB plan (50.4 Gy WBI and 64.4 Gy tumor bed boost) in VMAT and HT techniques. Conformity and homogeneity for target-volume doses were better in HT plans compared to VMAT plans. There were no significant differences in ipsilateral lung doses between VMAT and HT plans for SB/SIB techniques, except for a significantly higher lung V5 value with VMAT-SB, and lung V13 value with HT-SIB technique. HT provided a statistically significant decrease in contralateral lung mean V5. The SIB technique showed better target-volume dose distribution in both HT and VMAT plans, and better sparing heart in HT compared to the SB technique.

Is pectus excavatum a risk factor for radiation-induced lung disease in patients undergoing radiation therapy following breast-conserving surgery?

BackgroundThe relationship between radiation dose to the ipsilateral lung and subsequent radiation‐induced lung disease (RILD) in breast cancer patients with pectus excavatum (PE) undergoing radiation therapy (RT) to residual breast tissue after breast‐conserving surgery has not yet been established. The incidence of RILD in such patients with PE, meaning that a large volume of the lung is within the radiation field, has not been determined. Therefore, the aim of this study was to determine the relationship between these factors.MethodsThe study cohort comprised 133 women who underwent three‐dimensional conformal RT to residual breast tissue after breast‐conserving surgery for breast cancer. Diagnoses of PE were based on Haller's, frontosagittal, and Monden's depression indices. Radiation doses to the ipsilateral lung were established from dose‐volume histograms.ResultsFifty of the 133 participants (37.6%) were diagnosed with RILD; all were asymptomatic. Multivariate analysis revealed a significant correlation between the incidence of RILD and the administration of > 30 Gy (V30). Surprisingly, although patients with PE received higher ipsilateral lung doses, they were less likely to develop RILD than those without PE.ConclusionsOur data indicate that the incidence of RILD is correlated with the administration of > 30 Gy (V30) and that PE is not a risk factor for RILD after RT to residual breast tissue after breast‐conserving surgery for breast cancer. Surprisingly, individuals with PE may have a lower incidence of RILD than those without this condition.

Evaluating risk factors of radiation pneumonitis after stereotactic body radiation therapy in lung tumor: Meta-analysis of 9 observational studies.

BackgroundIn this study, we assessed the association of SBRT (stereotactic body radiotherapy) dose and volume with radiation pneumonitis (RP) risk in lung tumor.MethodsRelevant articles were identified up to April 2018, using following databases; Medline, EMBASE, Cochrane Library, and China National Knowledge Infrastructure (CNKI). The pooled OR (odds ratio) with 95% CI (confidence interval) data [mean ± SD (standard deviation)] obtained from different studies was analyzed by statistical analysis using a fixed-effects model or a random-effects model when appropriate.ResultsThe analysis was based on nine observational studies, which were identified based on the study selection criteria. Between RP and non-RP patients, no difference was observed based on age, but significant differences were observed based on planning target volume (PTV), mean ipsilateral lung dose (MLD), total MLD, and V5, V10, V20 and V40 (the percentage of lung volume exceeding 5, 10, 20 and 40 Gy). In addition, PTV >145 cm3, total MLD ≥4.7 Gy, V5 ≥26.8%, V10 >12% and V20 ≥5.8 were associated with RP risk. Overall, the grade assessments of V5 and V20 revealed moderate quality evidence.ConclusionThe present study indicated V5 and V20 as major risk factors for RP after SBRT treatment in lung tumor. In addition, it was observed that lung DVH (Dose Volume Histogram) patterns should be assessed more carefully, while predicting RP incidence after SBRT.

Optimization of tangential fields arrangement in the breast cancer 3D conformal radiation therapy

Introduction: The incidence of breast cancer increases with the rate of 1-2% at the world. Radiation therapy is one of the available choices for breast cancer treatment. The single isocentre half-beam block technique is considered as a standard technique to avoid hot and cold spots within the PTV. The major advantage of half beam technique is that the both contralateral breast and lung are completely spared. Also, using this technique, we don’t have any field matching problem. But, Lateral and medial movement of isocenter in conjunction of supraclavicular and tangential beams affect the divergence of tangential fields. Therefore, opposite tangential field can be parallel either in posterior border or beam central axis. The aim of this study is to compare the dosimetric parameters of three plans for tangential beams arrangement and select the optimal one. Materials and Methods: In this study, we selected 6 patients with breast cancer that underwent breast conserving surgery and considered for radiotherapy. CT simulation of patients were done based on standard protocols and imported to Isogray treatment planning system. Contouring of target volume and organs at risk (OARs) was done by radiotherapist. The tangential fields were considered in three different geometries of parallel in the posterior border with divergence in back jaws, parallel in central axis with divergence in back jaws and Parallel in posterior border without divergence of back jaws (half beam). Dosimetric parameters of each plan for OARs and target volumes extracted from DVHs data and compared statistically using ANOVA one-way repeated measurement test. Results: There was no statistical difference between dosimetric parameters (D95, V95, Dmax, and Dmean) of the target volume in three mentioned plans (P-value = 0.93). Although, there was no statistical difference between mean dose of the ipsilateral lung, the difference of V10 and V20 parameters for this organ is significant (P=0.01). Furthermore, there was no statistical difference in dosimetric parameters of OARs such as contralateral breast, lung, heart, and spinal cord. Conclusion: This study showed that back jaw divergence and arrangement of parallel opposite field can affect the ipsilateral lung dose. The V20 and V10 of ipsilateral lung are two dose constraints parameters in quantitative treatment planning evaluation of breast treatment. Quantitative variations of these parameters with changing the tangential field’s arrangement was significant which depends on the isocenter position and back jaw divergence. The values of these parameters were the highest when tangential fields were arranged as parallel in posterior border with divergence in the back jaw.

Predictors of Local Control and Symptomatic Pneumonitis after Lung SBRT

Stereotactic body radiation therapy (SBRT) is commonly used to treat primary or oligometastatic malignancies in the lung, though most of the available data describing the safety and efficacy of SBRT is for smaller tumors. The purpose of this study was to evaluate the impact of tumor size, among other factors, on local control (LC) and radiation pneumonitis (RP) in patients who received lung SBRT. This retrospective study included patients with primary and metastatic lung tumors treated with SBRT at a single institution from 2012 - 2017. Patients were excluded for prior radiation to the targeted site. All patients underwent 4D-CT simulation with respiratory motion management as needed, and received 3-5 fractions of varying doses prescribed to the PTV on a linear accelerator using a highly conformal IMRT or VMAT technique. Factors evaluated for association with LC included GTV diameter and volume, PTV diameter and volume, volumetric ratio of PTV:GTV, histology, prescription biologically effective dose (BED10), and PTV maximum dose (Dmax). Additional factors evaluated for association with grade 2 or higher (symptomatic) RP included BED3, conformity index (CI), max and mean dose to the heart and central airway, mean lung dose (MLD), and the volume of lung that received at least 2.5 Gy (V2.5), 5 Gy (V5), 13 Gy (V13), 20 Gy (V20), 30 Gy (V30), 40 Gy (V40), and 50 Gy (V50). Analysis included the Mann-Whitney U-test and binary logistic regression. Recursive partitioning analysis was used to determine the optimal dose constraint (OC) predictive of RP. A total of 125 patients with 150 irradiated sites, consisting of 104 (69.3%) primary lung tumors and 46 (30.7%) metastatic lung tumors were included in the study. The median follow-up for survival/toxicity analysis and LC analysis were 13.0 months (IQR 7.0 - 26.0) and 11.5 months (IQR 6.0 – 20.0), respectively. A large range of tumor sizes were represented with a median GTV volume of 6.02 cm3 (IQR 2.19 – 13.79). LC rates at 12 and 24 months post-treatment were 92.6% and 85.9%, respectively. LC was associated with higher BED10 (median 112.5 Gy vs. 92.8 Gy, p=0.02), PTV Dmax (62.5 Gy vs. 53.1 Gy, p<0.01), and PTV:GTV (5.8 vs. 3.5, p=0.01), and there was a trend towards improved LC with smaller tumor diameter (2.8 cm vs. 4.0 cm, p=0.08). RP was associated with higher ipsilateral lung MLD (7.3 Gy vs. 5.3 Gy, p=0.02, OC=8.6 Gy), V2.5 (38.8% vs. 32.0%, p=0.03, OC=30.8%), V5 (32.9% vs. 24.9%, p=0.02, OC=26.8%), V13 (18.8% vs. 13.4%, p=0.03, OC=21.8%), V20 (11.7% vs. 8.0%, p=0.05, OC=14.9%), and heart Dmax (14.4 Gy vs. 6.1 Gy, p=0.02, OC=31.7 Gy). A higher PTV prescription dose, greater dose heterogeneity within the target, and larger PTV margins were significantly associated with improved LC, whereas a weaker association was observed between tumor size and LC. Ipsilateral lung doses were most correlated with RP.

Left Anterior Descending Coronary Artery Dose-Sparing Effects of Volumetric Modulated Arc Therapy in Patients Ineligible for Deep-Inspiration Breath-Hold in Left Breast Radiation Therapy

Deep-inspiration breath-hold (DIBH) is a widely used and highly efficient technique of adjuvant left breast radiotherapy (RT), associated with lower radiation exposure to the left anterior descending artery (LAD). This technique involves patient training and coaching and high level of compliance is required. Hence, DIBH cannot be performed in some patients with left-sided breast cancer and free-breathing (FB) tangential RT is usually used. Volumetric modulated arc therapy (VMAT) can achieve highly conformal dose distributions and reduces treatment time. The aim of our study was to evaluate whether the patients who are ineligible for DIBH will benefit from free-breathing volumetric modulated arc therapy (FB-VMAT). Twenty patients with left-sided breast cancer underwent computed tomography simulation and images were obtained in both FB and DIBH. Ten patients were ineligible for DIBH and in this group FB-VMAT plans were generated. In FB and DIBH plans 42.72 Gy in 16 fractions was prescribed to breast tissue with 10.0 Gy boost in 4 fractions to the tumor bed. In FB-VMAT group simultaneous integrated boost planning was performed and 54.0 Gy in 20 fractions was prescribed. Treatment plans (DIBH, FB and FB-VMAT) were compared using various parameters, including mean heart dose, mean and maximal LAD dose, mean ipsilateral lung dose, percentage of ipsilateral lung receiving 20 Gy (Lung V20), mean contralateral lung dose and mean contralateral breast dose. Statistical analysis was performed using one-way ANOVA and with post-hoc Tukey test. Mean heart dose was significantly lower in DIBH plans (1.96 Gy, p<0.001) compared to FB (7.05 Gy) and FB-VMAT plans (6.99 Gy). Mean LAD doses for DIBH, FB and FB-VMAT plans were 10.61 Gy, 35.71 Gy and 20.15 Gy (p < 0.001) and maximal LAD doses were 33.64 Gy, 45.59 Gy and 35.20 Gy (p<0.001), respectively. Mean ipsilateral lung dose was significantly higher in FB-VMAT plans (11.32 Gy, p=0.006) compared to FB (7.72 Gy) and DIBH (8.49 Gy) plans while no significant difference was noted for Lung V20 (15.74 Gy, 15.42 Gy and 14.91 Gy, respectively; p=0.956). Mean contralateral lung dose was significantly higher in FB-VMAT plans (3.31 Gy, p<0.001) compared to FB (0.31 Gy) and DIBH (0.28 Gy) plans. Mean contralateral breast dose was also significantly higher in FB-VMAT plans (2.65 Gy, p<0.001) compared to FB (0.47 Gy) and DIBH (0.43 Gy) plans. Compared to the FB plans, the FB-VMAT plans allowed significant dose sparing in LAD in terms of both mean and maximal dose. However, mean heart dose reduction was achieved only in DIBH plans. In addition, VMAT-FB plans resulted in significantly higher mean doses for both ipsi- and contralateral lung and contralateral breast which may be attributed to a higher whole-body exposure to leakage radiation described in this technique. This trade-off should be considered before implementation of VMAT-FB treatment planning in patients ineligible for DIBH.

Treatment-Related Adverse Effects in Lung Cancer Patients after Stereotactic Ablative Radiation Therapy.

Introduction Lung cancer is a disease which, despite the advancements in treatment, still has a very poor 5-year survival rate. Stereotactic ablative radiation therapy (SABR) is a highly advanced, sophisticated, and safe treatment which allows patients with early stage lung cancer to be treated effectively without invasive procedures and with excellent clinical outcomes. Avoiding surgery minimises morbidity and recovery time, bettering patients' quality of life. Furthermore, SABR allows patients unsuitable for surgery to still undergo curative treatment. Methods We aimed to review SABR-related normal tissue toxicities reported in the literature. While many studies assess safety, clinical efficacy, and disease control of SABR for lung cancer, the number of comprehensive reviews that analyse SABR-related side-effects is scarce. This integrative review summarises the toxicities reported in literature based on published clinical trials and tumour location (central or peripheral tumours) for available SABR techniques. Given that the majority of the clinical studies did not report on the statistical significance (e.g., p-values and confidence intervals) of the toxicities experienced by patients, statistical analyses cannot be performed. As a result, adverse events are compiled from clinical reports; however, due to various techniques and nonstandard toxicity reports, no meta-analysis is possible at the current stage of reported data. Results When comparing lobectomy and SABR in phase III trials, surgery resulted in increased procedure-related morbidity. In phase II trials, very few studies showed high grade toxicities/fatalities as a result of SABR for lung cancer. Gross target volume size was a significant predictor of toxicity. An ipsilateral mean lung dose larger than 9 Gy was significantly associated with radiation pneumonitis. Conclusions Based on the studies reviewed SABR is a safe treatment technique for lung cancer; however, further well-designed phase III randomised clinical trials are required to produce timely conclusive results and to enable their comparison and statistical analysis.

Impact of Tumor Size on Local Control and Pneumonitis After Stereotactic Body Radiation Therapy for Lung Tumors

PurposeStereotactic body radiation therapy (SBRT) is commonly used to treat primary or oligometastatic malignancies in the lung, but most of the available data that describe the safety and efficacy of SBRT are for smaller tumors. The purpose of this study was to evaluate the impact of tumor size, among other factors, on local control (LC) and radiation pneumonitis (RP) in patients who received lung SBRT. Methods and materialsThis retrospective study included 144 patients with 100 primary (57.1%) and 75 metastatic (42.9%) lung tumors treated with SBRT between 2012 and 2018. Measurements of tumor size, treatment volume, histology, and radiation dose were evaluated for association with LC. Additional factors evaluated for association with the development of symptomatic RP included volume of the lung, heart, and central airway exposed to relevant doses of radiation. ResultsThe median follow-up time was 15.0 months (interquartile range, 8.0-26.0 months). LC rates at 12 and 24 months posttreatment were 95.1% and 92.7%, respectively. LC at 1 year was higher for tumors <5 cm in diameter than for tumors >5 cm in diameter (98.2% vs 79.8%, respectively; P < .01). On univariate analysis, LC was associated with a smaller gross tumor volume (GTV) diameter (P < .01), GTV volume (P < .01), planning target volume (PTV) diameter (P < .01), PTV volume (P < .01), and larger PTV-to-GTV ratio (P = .04). Tumor histology and treatment intent were not correlated with LC. RP was associated with a higher ipsilateral lung mean lung dose (P = .02), V2.5 (P = .03), V5 (P = .02), V13 (P = .03), V20 (P = .05), V30 (P = .02), V40 (P = .02), and V50 (P = .03), and several similar total lung dose parameters and heart maximum point dose (P = .02). The optimal mean ipsilateral lung dose cutoff predictive of RP was 8.6 Gy. ConclusionsA larger tumor size and smaller PTV-to-GTV ratio was associated with local recurrence of lung tumors treated with SBRT, but ipsilateral lung doses were most associated with symptomatic RP.

Single dose partial breast irradiation using an MRI linear accelerator in the supine and prone treatment position

BackgroundIn selected patients with early-stage and low-risk breast cancer, an MRI-linac based treatment might enable a radiosurgical, non-invasive alternative for current standard breast conserving therapy. AimTo investigate whether single dose accelerated partial breast (APBI) to the intact tumor in both the prone and supine radiotherapy positions on the MRI-linac is dosimetrically feasible with respect to predefined coverage and organs at risk (OAR) constraints. Material & methodsFor 20 patients with cTis or low-risk cT1N0M0 non-lobular breast carcinoma, previously treated with single dose preoperative APBI in the supine (n = 10) or prone (n = 10) position, additional intensity modulated radiotherapy plans with 7 coplanar beams in the presence of a 1.5T magnetic field were generated. A 20 Gy and 15 Gy dose was prescribed to the gross tumor and clinical target volume, respectively. The percentage of plans achieving predefined organ at risk (OAR) constraints, currently used in clinical practice, was assessed. Dosimetry differences between the prone versus supine approach and the MRI-linac versus clinically delivered plans were evaluated. ResultsAll MRI-linac plans met the coverage and predefined OAR constraints. The prone approach appeared to be more favorable with respect to the chest wall, and ipsilateral lung dose compared to the supine position. No dosimetric differences were observed for the ipsilateral breast. No treatment position was clearly more beneficial for the skin or heart, since dosimetry varied among parameters. Overall, the MRI-linac and clinical plans were comparable, with minor absolute dosimetric differences. ConclusionMRI-linac based single dose APBI to the intact tumor is a promising and a dosimetrically feasible strategy in patients with low-risk breast cancer. Preliminary OAR dosimetry favored the prone radiotherapy position.

Heart and Ipsilateral Lung Doses in Left Breast Cancer Patients Treated with Hdr Apbi Compared to Nsabp B-51 Protocol Using α/β Ratio

Heart and Ipsilateral Lung Doses in Left Breast Cancer Patients Treated with Hdr Apbi Compared to Nsabp B-51 Protocol Using α/β Ratio

Abdominal DIBH reduces the cardiac dose even further: a prospective analysis

BackgroundDeep inspiration breath hold (DIBH) can be performed using different breathing maneuvers, such as DIBH with a thoracic breathing maneuver (T-DIBH) and DIBH with an abdominal breathing maneuver (A-DIBH). Dosimetric benefits of A-DIBH were investigated in the treatment of left-sided breast cancer radiotherapy (RT) with both 3-Dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) techniques.MethodsTwenty-two patients with left-sided breast cancer were enrolled in this study. 3D-CRT and IMRT plans were generated for each patient with three different CT scans of free breathing (FB), T-DIBH and A-DIBH. There were total of six treatment plans generated for each patient: FB_3D-CRT; TDIBH_3D-CRT; ADIBH_3D-CRT; FB-IMRT; TDIBH-IMRT; ADIBH-IMRT. Doses to the heart, left anterior descending coronary artery (LADCA), and ipsilateral lung were evaluated and compared using the Wilcoxon signed-rank test.ResultsThe mean doses to the heart, LADCA and ipsilateral lung in 3D-CRT plans generated from 3D-CRT with FB, T-DIBH and A-DIBH were (2.89 ± 1.30), (1.67 ± 0.90) and (1.34 ± 0.43) Gy (all P < 0.05), respectively, with FB; (29.08 ± 16.72), (13.94 ± 14.74) and (10.22 ± 10.30) Gy (all P < 0.05), respectively, with T-DIBH; and (7.77 ± 2.71), (7.32 ± 1.42) and (6.90 ± 1.60) Gy (all P < 0.05), respectively, with A-DIBH. The mean doses to the heart, LADCA and ipsilateral lung in IMRT plans were generated from IMRT with FB, T-DIBH and A-DIBH were (1.96 ± 2.25), (1.37 ± 0.44) and (1.18 ± 0.26) Gy (all P < 0.05), respectively, with FB; (16.10 ± 7.45), (8.6 ± 6.60) and (7.35 ± 5.42) Gy (all P < 0.05), respectively, with T-DIBH; and (5.90 ± 2.24), (5.65 ± 1.58) and (5.62 ± 1.05) Gy (all P > 0.05), respectively, with A-DIBH.ConclusionsThis study indicates that both 3D-CRT and IMRT plans with A-DIBH achieved lower cardiac and LADCA doses than plans with FB and T-DIBH; 3D-CRT plans with A-DIBH achieved lower ipsilateral lung doses than plans with FB and T-DIBH; and IMRT plans with A-DIBH had better outcomes than 3D-CRT plans with A-DIBH with respect to the mean dose to the heart, LADCA and ipsilateral lung. IMRT plans with A-DIBH should be incorporated into the daily routine for left-sided breast RT.

Comparison of Stereotactic Body Radiotherapy Delivery Techniques for Early-Stage Lung Cancer Using Lung Toxicity Modeling

Purpose: Lung toxicity is a primary side effect in stereotactic radiotherapy (SBRT) for early-stage non-small cell lung cancer (NSCLC). We aimed to use a set of radiobiological models to evaluate and compare modern IMRT delivery techniques with three-dimensional conformal techniques for SBRT treatment of NSCLC in terms of lung toxicity, and aimed to compare the results from different radiobiologcal models. Methods: Ten early-stage NSCLC patients treated with SBRT were retrospectively selected. Five treatment plans were generated to deliver 50 Gy in five fractions to the planning target volume for each case: a helical tomotherapy (HT) plan, two three-dimensional cofnromal radiotherapy (3D-CRT) plans using 6-MV and 10-MV photon beams respectively, and two volumetric modulated arc therapy (VMAT) plans using one and two arc fields respectively. The lung RDV was calculated with three parallel functional sub-unit (FSU) models and two normal tissue complication probability (NTCP) models. Results: Both the HT and VMAT plans showed significantly higher contralateral mean lung dose and lower ipsilateral mean lung dose compared to the 3D-CRT plans. There was no statistically significant difference in terms of lung toxicities between the IMRT and 3D-CRT techniques using either the FSU models or the NTCP models. Based on both the FSU and the NTCP models, there was strong correlation between lung toxicity and the mean lung dose in SBRT treatment plans. Conclusions: Based on both the NTCP and parallel FSU models, both IMRT and traditional 3D-CRT delivery techniques could achieve comparable lung sparing inn SBRT treatment of early-stage lung cancer. However, the validity of the radiobiological model results should be checked by clinical data.

Dosimetric Comparison of Irregular Surface Compensator and Field-in-Field for Whole Breast Radiotherapy.

Purpose:The purpose of the present study was to evaluate the dosimetric benefits of the irregular surface compensator (ISC) technique for whole breast radiotherapy compared with the field-in-field (FIF) technique.Materials and Methods:Radiotherapy was planned using both techniques in 50 breast cancer patients (25 left sided and 25 right sided). The Eclipse treatment planning system (Varian Medical Systems) was used for dose calculations. For the FIF technique, subfields were added to the main fields to reduce hot and cold regions; for the ISC technique, the fluence editor application was used to extend the optimal fluence. Planning target volume dose, dose homogeneity index (DHI), maximum dose, ipsilateral lung, and heart doses for the left breast irradiation and monitor unit (MU) counts required for treatment were compared between the two techniques.Results:Compared with the FIF technique, the ISC technique significantly decreased DHI values and volumes receiving >105% of the prescription dose, and increased volumes receiving >95% of the dose and MU count (P < 0.01 for all comparisons). For the heart and ipsilateral lung, the FIF technique significantly reduced volumes receiving >5 Gy compared with the ISC technique (P < 0.01); however, volumes receiving >10, 20, and 30 Gy and the values of a mean dose did not differ significantly between the techniques (P > 0.05).Conclusions:The ISC technique is preferred over the FIF technique.

Exposure of the lungs in breast cancer radiotherapy: A systematic review of lung doses published 2010–2015

Background and purposeWe report a systematic review of lung radiation doses from breast cancer radiotherapy. Methods and materialsStudies describing breast cancer radiotherapy regimens published during 2010–2015 and reporting lung dose were included. Doses were compared between different countries, anatomical regions irradiated, techniques and use of breathing adaptation. Results471 regimens from 32 countries were identified. The average mean ipsilateral lung dose (MLDipsi) was 9.0 Gy. MLDipsi for supine radiotherapy with no breathing adaption was 8.4 Gy for whole breast/chest wall (WB/CW) radiotherapy, 11.2 Gy when the axilla/supraclavicular fossa was irradiated, and 14.0 Gy with the addition of internal mammary chain irradiation; breathing adaptation reduced MLDipsi by 1 Gy, 2 Gy and 3 Gy respectively (p < 0.005). For WB/CW radiotherapy, MLDipsi was lowest for tangents in prone (1.2 Gy) or lateral decubitus (0.8 Gy) positions. The highest MLDipsi was for IMRT in supine position (9.4 Gy).The average mean contralateral lung dose (MLDcont) for WB/CW radiotherapy was higher for IMRT (3.0 Gy) than for tangents (0.8 Gy). ConclusionsLung doses from breast cancer radiotherapy varied substantially worldwide, even between studies describing similar regimens. Lymph node inclusion and IMRT use increased exposure, while breathing adaptation and prone/lateral decubitus positioning reduced it.

Electron postmastectomy chest wall plus comprehensive nodal irradiation technique using Electron Monte Carlo dose algorithm

For left-sided postmastectomy patients requiring chest wall plus comprehensive nodal irradiation, sometimes traditional techniques such as partial wide tangents or electron/tangents combination are not feasible due to abnormal chest wall contour or heart position or unusually wide excision scar. We developed electron chest wall irradiation technique using Electron Monte Carlo (EMC) dose algorithm that will achieve heart sparing with acceptable ipsilateral lung dose, minimal contralateral lung, and breast dose. Ten left-sided postmastectomy patients with very challenging anatomy were selected for this dosimetry study. The en face electron fields were designed from a single isocenter and gantry angle with different energy beams using different cutouts that matched on the skin. Smaller energy was used in the central thin chest wall part and higher energy in the medial internal mammary nodes (IMN) area, superior part of the thick chest wall, and/or axillary nodal area. The electron fields were matched to the photon supraclavicular field in the superior region. Daily field junctions were used to feather the match lines between all the fields. Electron field dose calculations were done with Monte Carlo. Five patients' chest wall fields were planned with 6/9MeVcombination, 1 with 6/12 MeV, 2 with 9/12 MeV, 1 with 9/16 MeV, and 1 with 6/9/12 MeV. Institutional criteria of prescription dose of 50 Gy for target volumes and normal tissue dose were met with this technique in spite of the challenging anatomy. Mean heart dose averaged 3.0 Gy ± 0.8 Gy. For ipsilateral lung, V20Gy and V5Gy averaged 33.2% ± 4.5% and 64.6% ± 9.6%, respectively. For contralateral lung, V5Gy averaged 5.1% ± 5.0%. For contralateral breast, V5Gy averaged 3.3% ± 3.1%. The electron chest wall irradiation technique using EMC dose algorithm can provide adequate dose coverage to the chest wall, IMNs, and/or axillary nodes while achieving heart sparing with acceptable ipsilateral lung dose, minimal contralateral lung, and breast dose.

A Six-year Experience of Using Moderate Deep Inspiration Breath-Hold for Patients With Early-Stage Breast Cancer and Dosimetric Comparison

We present our six-year experience of using moderate deep inspiration breath-hold (mDIBH) with an active breathing control (ABC) device for patients with early-stage breast cancer and dosimetric comparison to evaluate the benefit of mDIBH on the heart, lung, and liver. We retrospectively reviewed all patients with newly diagnosed early, node-negative breast cancer treated between November 2010 and October 2016. Among the 312 patients included in this study, 94 patients were treated with mDIBH and 218 patients were treated with free breathing. Dosimetric analysis was performed to compare dose distribution in the heart, lung, and liver between the two treatment groups. All planning and dosimetric evaluations were performed on the treatment planning system. The calculated DVH was compared between the non-ABC and ABC groups. The chi-square test was used to compare the distribution of stage and tumor site between the two groups. The independent samples t-test was used to compare the remaining parameters between the two groups. Analysis was performed using SPSS v.19. There was no significant difference in the distribution of stage (p=0.130), tumor site (p=0.068), age (p=0.065), volume of CTV (p=0.119), and volume of heart (p=0.851) between the non-ABC and ABC groups. For all 312 patients, there was a significantly lower ipsilateral lung V5 (p<0.001), ipsilateral lung V10 (p<0.001), ipsilateral lung V20 (p<0.001), mean ipsilateral lung dose (p<0.001), whole lung V5 (p<0.001), whole lung V10 (p<0.001), whole lung V20 (p<0.001), mean whole lung dose (p<0.001), heart V10 (p<0.001), heart V30 (<0.001), heart V40 (<0.001), and mean heart dose (<0.001) in the ABC group. For 158 patients with a left-sided breast tumor, significantly lower ipsilateral lung V5 (p=0.004), ipsilateral lung V10 (p<0.001), ipsilateral lung V20 (p<0.001), mean ipsilateral lung dose (p<0.001), heart V10 (p<0.001), heart V30 (p<0.001), heart V40 (p<0.001), and mean heart dose (p<0.001) were observed in the ABC group. For 154 patients with a right-sided breast tumor, significantly lower ipsilateral lung V5 (p=0.006), ipsilateral lung V10 (p<0.001), ipsilateral lung V20 (p<0.001), mean ipsilateral lung dose (p<0.001), heart V10 (p<0.001), heart V30 (p=0.012), heart V40 (p=0.046), mean heart dose (p<0.001), liver V30(p<0.001), and mean liver dose (p<0.001) were observed in the ABC group. For early-stage breast cancer patients, mDIBH reduces not only the heart dose but also the lung and liver doses. Our study showed that mDIBH can significantly reduce the heart and lung dose for left-sided breast cancer patients and also reduce the liver, lung, and heart dose for right-sided breast cancer patients. The routine integration of mDIBH using an ABC device may decrease radiation-induced toxicity in the heart, lung, and liver.