A retrospective analysis to demonstrate achievable dosimetry for the left anterior descending artery in left-sided breast cancer patients treated with radiotherapy

The impact of advancing the standard of care in radiotherapy on operational treatment resources

PURPOSE

To demonstrate the impact of implementing hypofractionated prescription regimens and advanced treatment techniques on institutional operational hours and radiotherapy personnel resources in a multi-institutional setting. The study may be used to describe the impact of advancing the standard of care with modern radiotherapy techniques on patient and staff resources.

METHODS

This study uses radiation therapy data extracted from the radiotherapy information system from two tertiary care, university-affiliated cancer centers from 2012 to 2021. Across all patients in the analysis, the average fraction number for curative and palliative patients was reported each year in the decade. Also, the institutional operational treatment hours are reported for both centers. A sub-analysis for curative intent breast and lung radiotherapy patients was performed to contextualize the impact of changes to imaging, motion management, and treatment technique.

RESULTS

From 2012 to 2021, Center 1 had 42 214 patient plans and Center 2 had 43 252 patient plans included in the analysis. Averaged over both centers across the decade, the average fraction number per patient decreased from 6.9 to 5.2 (25%) and 21.8 to 17.2 (21%) for palliative and curative patients, respectively. The operational treatment hours for both institutions increased from 8 h 15 min to 9 h 45 min (18%), despite a patient population increase of 45%.

CONCLUSION

The clinical implementation of hypofractionated treatment regimens has successfully reduced the radiotherapy workload and operational treatment hours required to treat patients. This analysis describes the impact of changes to the standard of care on institutional resources.

Active Breathing Coordinator reduces radiation dose to the stomach in patients with left breast cancer

BACKGROUND/PURPOSE

Gastric dose parameters comparison for deep inspiration breath-hold (DIBH) or free breathing (FB) mode during radiotherapy (RT) for left-sided breast cancer patients (LSBCPs) has not been investigated before. This study aimed to analyze the impact of Active Breath Coordinator (ABC)-DIBH technique on the dose received by the stomach during RT for LSBCPs and to provide organ-specific dosimetric parameters.

MATERIALS AND METHODS

The study included 73 LSBCPs. The dosimetric parameters of the stomach were compared between FB and DIBH mode. The correlation between the stomach volume and dosimetric parameters was analyzed.

RESULTS

Compared to FB mode, statistically significant reductions were observed in gastric dose parameters in ABC-DIBH mode, including Dmax (46.60 vs 17.25, p < 0.001), D1cc (38.42 vs 9.60, p < 0.001), Dmean (4.10 vs 0.80, p < 0.001), V40Gy (0.50 vs 0.00, p < 0.001), V30Gy (6.30 vs 0.00, p < 0.001), V20Gy (20.80 vs 0.00, p < 0.001), V10Gy (51.10 vs 0.77, p < 0.001), and V5Gy (93.20 vs 9.60, p < 0.001). ABC-DIBH increased the distance between the stomach and the breast PTV when compared to FB, from 1.3 cm to 2.8 cm (p < 0.001). Physiologic decrease in stomach volume was not found from FB to ABC-DIBH (415.54 cm3 vs 411.61 cm3, p = 0.260). The stomach volume showed a positive correlation with V40Gy (r2 = 0.289; p < 0.05), V30Gy (r2 = 0.287; p < 0.05), V20Gy (r2 = 0.343; p < 0.05), V10Gy (r2 = 0.039; p < 0.001), V5Gy (r2 = 0.439; p < 0.001), Dmax (r2 = 0.269; p < 0.05) and D1cc (r2 = 0.278; p < 0.05) in FB mode. While in ABC-DIBH mode, most stomach dosimetric parameters were not correlated with gastric volume.

CONCLUSIONS

The implementation of ABC-DIBH in LSBCPs radiotherapy resulted in lower irradiation of the stomach. Larger stomach volume was associated with statistically significantly higher dose irradiation in FB mode. To reduce radiotherapy related side effects in FB mode, patients should be fast for at least 2 hours before the CT simulation and treatment.

Regional nodal irradiation in breast cancer patients: Effects of deep inspiration breath hold on the internal mammary chain location

The purpose of this study was to investigate the impact of deep inspiration breath hold (DIBH) on the positioning of thoracic structures and provide treatment planning recommendations for internal mammary chain (IMC) irradiation in breast cancer patients. Thirty-two breast cancer patients from our database underwent both DIBH and free breathing (FB) treatment planning. Contouring of the axillary lymph node clinical target volumes (CTVs: level I, II, III, IV, and IMC according to ESTRO), the internal mammary artery (IMA), the heart, and the left anterior descending artery (LAD) was performed. The following were then analyzed: the distance between the IMA and the heart, the craniocaudal distance in which IMC-CTV and heart coexist, the craniocaudal distance between the lower end of the of level III and IV and the upper end of the heart. Several significant geometric differences were observed between DIBH and FB that explain the efficacy of the DIBH for regional nodal irradiation. In >80% of patients the cranial origin of the LAD lies below the lower edge of the IMC-CTV in DIBH. In addition the slices in which the heart/LAD and IMC-CTV coexist decrease during DIBH. The IMA-heart distance is significantly larger in DIBH. Also the craniocaudal distance between the lower border of the CTV level III and IV and the upper border of the heart is larger in DIBH. The observed mechanisms during DIBH contribute significantly to the dose reduction in regional nodal irradiation. To further enhance the benefits of DIBH for the irradiation of the IMC-CTV, it is recommended to implement steep dose gradients in the caudal plane.

The effect of respiratory capacity for dose sparing in left-sided breast cancer irradiation with active breathing coordinator technique

Background and aim

A subsequent cardiac toxicity is deemed to be dose-dependent for left-sided breast cancer irradiation. This study aims to demonstrate the effect of respiratory capacity for dose sparing when the deep inspiration breath hold with Active Breathing Coordinator technique (ABC-DIBH) is used in left-sided breast cancer irradiation.

Methods

74 left-sided breast cancer patients, who received whole breast or post-mastectomy chest wall radiotherapy with ABC-DIBH between 2020 and 2021 in our center, were retrospectively reviewed in this study. CT scans of free breath (FB) and ABC-DIBH were done for each patient, and two treatment plans with a prescription dose of 5000 cGy/25 Fr were designed separately. The dose to heart, left anterior descending artery (LAD) and lungs was compared between FB and ABC-DIBH. The correlation between individual parameters (dose to organs at risk (OARs) and minimum heart distance (MHD)) was analyzed, and the effect of respiratory capacity for dose sparing was assessed.

Results

The plans with ABC-DIBH achieved lower Dmean for heart (34.80%, P &lt; 0.01) and LAD (29.33%, P &lt; 0.01) than those with FB. Regression analysis revealed that both Dmean and D2 of heart were negatively correlated with MHD in the plans with FB and ABC-DIBH, which decreased with the increase in MHD by 37.8 cGy and 309.9 cGy per 1mm, respectively. Besides, a lower Dmean of heart was related to a larger volume of ipsilateral lung in plans with FB. With the increase in volume of ipsilateral lung, the linear correlation was getting weaker and weaker until the volume of ipsilateral lung reached 1700 cc. Meanwhile, a negative linear correlation between Dmean of LAD and MHD in plans with FB and ABC-DIBH was observed, whose slope was 162.5 and 135.9 cGy/mm, respectively. Furthermore, when the respiratory capacity of ABC-DIBH reached 1L, and the relative ratio (ABC-DIBH/FB) reached 3.6, patients could obtain the benefit of dose sparing. The larger difference in respiratory capacity had no significant effect in the larger difference of MHD, Dmean of heart and Dmean of LAD between FB and ABC-DIBH.

Conclusion

This study demonstrates the sufficiently good effect of ABC-DIBH when utilizing for cardiac sparing. It also reveals the correlations among individual parameters and the effect of respiratory capacity for dose sparing. This helps take optimal advantage of the ABC-DIBH technique and predict clinical benefits.

Association between the cardiac contact distance and the maximum dose at the left anterior descending coronary artery in post mastectomized patients

The clinical information on the relationship between the cardiac contact distance (CCD), the maximum dose (D_max) delivered to the left anterior descending (LAD) coronary artery and the mean heart dose has mostly focused on patients with breast-conserving surgery (BCS), being scarce in postmastectomy patients. The aim of this study is to determine the association between the CCD and the D_max delivered to the LAD. The secondary objective was to evaluate the dosimetric results of comparing three-dimensional conformal radiotherapy (3D-CRT) to intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques for post mastectomized breast cancer patients with irradiation to the left chest wall. 53 cases of women who received adjuvant standard fractionated postmastectomy radiotherapy (PMRT) were used. Three types of plans were created for each patient: 3D-CRT, seven equidistant IMRT fields, and four partial VMAT arcs. Correlations were evaluated using Pearson's correlation coefficient. Plans made with IMRT and VMAT showed improved homogeneity and conformity. Associations between CCD and D_max to LAD were positive for all three plan types. Compared to 3D-CRT, the modulated intensity plans obtained better dose homogeneity and conformity to the target volume. The LAD and heart doses were significantly lower for IMRT and VMAT plans. The CCD can be used as a predictor of the maximum and mean doses of the LAD. Modulated intensity techniques allow for better dose distribution and dose reduction to the heart and LAD.

Evaluation of Hybrid VMAT Advantages and Robustness Considering Setup Errors Using Surface Guided Dose Accumulation for Internal Lymph Mammary Nodes Irradiation of Postmastectomy Radiotherapy

Objectives

Setup error is a key factor affecting postmastectomy radiotherapy (PMRT) and irradiation of the internal mammary lymph nodes is the most investigated aspect for PMRT patients. In this study, we evaluated the robustness, radiobiological, and dosimetric benefits of the hybrid volumetric modulated arc therapy (H-VMAT) planning technique based on the setup error in dose accumulation using a surface-guided system for radiation therapy.

Methods

We retrospectively selected 32 patients treated by a radiation oncologist and evaluated the clinical target volume (CTV), including internal lymph node irradiation (IMNIs), and considered the planning target volume (PTV) margin to be 5 mm. Three different planning techniques were evaluated: tangential-VMAT (T-VMAT), intensity-modulated radiation therapy (IMRT), and H-VMAT. The interfraction and intrafraction setup errors were analyzed in each field and the accumulated dose was evaluated as the patients underwent daily surface-guided monitoring. These parameters were included while evaluating CTV coverage, the dose required for the left anterior descending artery (LAD) and the left ventricle (LV), the normal tissue complication probability (NTCP) for the heart and lungs, and the second cancer complication probability (SCCP) for contralateral breast (CB).

Results

When the setup error was accounted for dose accumulation, T-VMAT (95.51%) and H-VMAT (95.48%) had a higher CTV coverage than IMRT (91.25%). In the NTCP for the heart, H-VMAT (0.04%) was higher than T-VMAT (0.01%) and lower than IMRT (0.2%). However, the SCCP (1.05%) of CB using H-VMAT was lower than that using T-VMAT (2%) as well as delivery efficiency. And T-VMAT (3.72) and IMRT (10.5).had higher plan complexity than H-VMAT (3.71).

Conclusions

In this study, based on the dose accumulation of setup error for patients with left-sided PMRT with IMNI, we found that the H-VMAT technique was superior for achieving an optimum balance between target coverage, OAR dose, complication probability, plan robustness, and complexity.

Gastric side effects and the stomach dosimetric analysis in left-sided breast cancer radiotherapy in free-breathing and deep inspiration breath-hold technique

Background

Adjuvant radiotherapy following surgery reduces the local recurrence and improves the prognosis. However, a considerable part of patients developed digestive reaction in daily treatment. In order to explore the correlation between breast radiotherapy and gastric toxicity, we investigated the clinic symptoms and stomach dose during DIBH or FB mode while left-sided breast cancer patients (LSBCP) receiving radiotherapy.

Methods

In the study, 124 LSBCP received adjuvant radiotherapy after surgery at our department were analyzed clinical characteristics and enquired about gastrointestinal side effects after treatment. Moreover, dosimetric parameters were assessed.

Results

There was no statistically significant difference between the two groups in age, T staging, N staging, hormone receptors, human epidermal receptor-2 (HER2), surgical methods, fractionated regimen, and chemotherapy conditions. However, larger stomach volumes and higher fractionated dose (Dmax/F) were associated with a statistically significantly greater risk for acute radiotherapy toxicity. In addition, the use of the DIBH gating technique (FB/DIBH) reduced the incidence of digestive reactions.

Conclusion

In order to cut down gastric side effects after breast radiotherapy, large meals should be avoided before treatment. DIBH treatment should be implemented in centers where conditions are satisfied to reduce radiotherapy side effects. Furthermore, dose limitation in stomach should be considered when the radiotherapy plan was formulated, especially for the patients treated with hypofractionated radiotherapy.

Impact of lung block shape on cardiac dose for total body irradiation

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Partial cardiac shielding in TBI is not commonly reported and varies among clinics.

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We evaluated the effects of cardiac shielding in TBI using 3D beam modeling in a commercial TPS.

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Partial cardiac shielding can reduce mean heart dose and reduce LAD dose up to 30%.

Evaluating cardiac dose during total body irradiation (TBI) is of increasing interest. A three-dimensional beam model for TBI was commissioned and lung shielding was simulated in a treatment planning system with the cardiac silhouette partially blocked and unblocked. When blocked, the median heart dose decreased by 6% (IQR = 6%) and the median cardiac V12Gy decreased by 27% (IQR = 17%). The median left anterior descending artery dose decreased 20% (IQR = 12%) for blocked cases. Because using partial heart shielding may result in considerable changes in dose to cardiac structures, TBI protocols should explicitly consider lung block design parameters and their potential effects.

Retrospective Study on Left-Sided Breast Radiotherapy: Dosimetric Results and Correlation with Physical Factors for Free Breathing and Breath Hold Irradiation Techniques

Objectives: In breast radiotherapy, the proximity of the target to sensitive structures together with the uncertainty introduced by respiratory movement, make this treatment one of the most studied to increase its effectiveness. Dosimetric and physical variables play an important role and the study of their correlation and impact on treatment is fundamental. This retrospective study aims to highlight the dosimetric differences of 2 different clinical data sets of patients receiving left-sided breast irradiation in free breathing (FB) or breath hold (BH). Methods: A total of 155 left breast carcinoma patients receiving whole-breast irradiation in FB (73 patients) and BH (82 patients) were enrolled in this study. The dosimetric parameters of the target, heart, left and right lung and right breast were evaluated and compared, and possible correlations were studied in both groups. Results: No significant difference (P > .05) was found in the target dosimetry; a clear advantage in BH for both high and low doses received by the heart, with reductions of the dosimetric parameters between 27.1% and 100% (P < .003); for the left lung reductions decreased with increasing dose (-22.4% and -13.4% for doses of 5 and 20 Gy, respectively, P < .003). Conclusion: Significant correlations for BH treatments were registered between the volumes of the target and left lung, and the dosimetric parameters of the heart and left lung. BH treatment brings significant dosimetric advantages to organs at risk for a wide range of patients with different anatomy, target volumes and lung capacity, with additional benefits for small-sized breasts and important lung capacity.

Patient-Specific Heart Constraint: A Tool for Optimization and Evaluation of Mean Heart Dose in Breast Cancer Patients

PURPOSE

Our institution introduced a patient-specific heart constraint (PSHC) and a mean heart dose (MHD) constraint of 4 Gy for all patients receiving breast radiation therapy (RT) with a simultaneous boost (SIB). This was introduced as a method to calculate the predicted MHD before optimizing IMRT fields. We sought to determine whether the introduction of a PSHC reduced MHD, while maintaining optimally dosed treatment plans.

MATERIAL/METHODS

Patients were retrospectively divided into 2 groups, pre- and postintroduction of the PSHC. The breast and SIB Planning Target Volumes (PTVs) were prescribed to 50 Gy and 57 Gy, respectively, in 25 fractions. Plans were generated using a hybrid IMRT technique, 30 Gy using an open tangential field arrangement, and 27 Gy using IMRT fields. The PSHC was calculated using MHD of open tangential field × 2. A paired t test compared PTV coverage and heart doses between cohorts (P < .05 significant).

RESULTS

A total of 264 patients were included (138 pre-PSHC and 126 post-PSHC) with 137 right-sided and 127 left-sided treatments. MHD was significantly reduced across both right-sided (-0.4 Gy, P < .0001) and left-sided (-1.2 Gy, P < .0001) treatments overall. Left-sided treatments were further examined between free breathing and deep inspiration breath-hold (DIBH). DIBH showed reduction in MHD, although it was not significant (-0.46 Gy, P = .34). Heart V5 Gy showed reduction in right-sided (-1%, P = .002) and left-sided (-9.2%, P < .0001) treatments overall. Left-sided free breathing showed significant reduction (-8.8%, P < .0001), and DIBH also showed significant reduction (-5.1%, P = .0034). Tumor bed doses remained above the 54.15 Gy (95% of 57 Gy) threshold for all plans.

CONCLUSION

Introduction of a PSHC can reduce MHD and V5 Gy for patients receiving whole breast RT with SIB while maintaining optimally dosed plans, with the greatest benefit shown for left-sided, free-breathing treatments.