Factors Involved in the Choice Between Thoracic and Abdominal Deep Inspiration Breath Holds During Left Breast Cancer Radiotherapy.

PURPOSE: Deep inspiration breath hold (DIBH) is used with adjuvant radiation therapy after left breast cancer surgery to reduce radiation dose to the heart. In this study we determined whether thoracic DIBH (T-DIBH) or abdominal DIBH (A-DIBH) should be selected based on patient background. METHODS: Three-dimensional conformal radiation therapy plans were created under the same conditions using free breathing (FB), T-DIBH, and A-DIBH CT scans of patients who had previously undergone treatment at our hospital. RESULTS: A-DIBH decreased the left lung dose compared to FB. In comparing T-DIBH and A-DIBH, the heart maximum and left lung doses were significantly lower in A-DIBH. The differences in the heart mean dose (Dmean) between FB, and T-DIBH and A-DIBH were correlated with the cardiothoracic ratio, heart volume, and left lung volume. The difference in the heart Dmean and the left lung dose of T-DIBH and A-DIBH correlated with the forced vital capacity (FVC). CONCLUSIONS: A-DIBH is preferable over T-DIBH with respect to the heart and left lung doses; however, with respect to the heart Dmean, T-DIBH was more effective in reducing the dose in some cases, and the FVC was a relevant factor in this study.

Effect on Heart and Lung Doses Reduction of Abdominal and Thoracic Deep Inspiratory Breath-hold Assuming Involved-field Radiation Therapy in Patients with Simulated Esophageal Cancer.

PURPOSE: The purpose of this study was to evaluate the lung and heart doses in volumetric-modulated arc therapy (VMAT) using involved-field irradiation in patients with middle-to-lower thoracic esophageal cancer during free breathing (FB), abdominal deep inspiratory breath-hold (A-DIBH), and thoracic DIBH (T-DIBH) images. METHODS: Computed tomography images of A-DIBH, T-DIBH, and FB from 25 patients with breast cancer were used to simulate patients with esophageal cancer. The irradiation field was set at an involved-field, and target and risk organs were outlined according to uniform criteria. VMAT optimization was performed, and lung and heart doses were evaluated. RESULTS: A-DIBH had a lower lung V20 Gy than FB and a lower lung V40 Gy, V30 Gy, V20 Gy than T-DIBH. The heart all dose indices were lower in T-DIBH than FB, and the heart V10 Gy was lower in A-DIBH than FB. However, the heart Dmean was comparable with A-DIBH and T-DIBH. CONCLUSIONS: A-DIBH had significant dose advantages for lungs compared to FB and T-DIBH, and the heart Dmean was comparable to T-DIBH. Therefore, when performing DIBH, A-DIBH is suggested for radiotherapy in patients with middle-to-lower thoracic esophageal cancer, excluding irradiation of the prophylactic area.

Dose and organ displacement comparisons with breast conservative radiotherapy using abdominal and thoracic deep-inspiration breath-holds: A comparative dosimetric study.

Deep-inspiration breath-hold (DIBH) reduces the radiation dose to the heart and lungs during breast radiotherapy in cancer. However, there is not enough discussion about suitable breathing methods for DIBH. Therefore, we investigated the radiation doses and organ and body surface displacement in abdominal DIBH (A-DIBH) and thoracic DIBH (T-DIBH). Free-breathing, A-DIBH, and T-DIBH computed tomography images of 100 patients were used. After contouring the targets, heart, and lungs, radiotherapy plans were created. We investigated the heart and lung doses, the associations between the heart and left lung displacements, and the thorax and abdominal surface displacements. No significant differences were observed in the target dose indices. However, the heart and lung doses were significantly lower in A-DIBH than in T-DIBH for all the indices; the mean heart and lung doses were 1.69 and 3.48 Gy, and 1.91 and 3.55 Gy in A-DIBH and T-DIBH, respectively. The inferior displacement of the heart and the left lung was more significant in A-DIBH. Therefore, inferior expansion of the heart and lungs may be responsible for the respective dose reductions. The abdominal surface displaced more than the thoracic surface in both A-DIBH and T-DIBH, and thoracic surface displacement was greater in T-DIBH than in A-DIBH. Moreover, A-DIBH can be identified because abdominal surface displacement was greater in A-DIBH than in T-DIBH. In conclusion, A-DIBH and T-DIBH could be distinguished by comparing the abdominal and thoracic surfaces of A-DIBH and T-DIBH, thereby ensuring the implementation of A-DIBH and reducing the heart and lung doses.

Examination of the dose distribution of volumetric modulated arc radiotherapy using a high-definition multi-leaf collimator for breast cancer patients with irradiated regional lymph nodes.

Background: A high-definition multi-leaf collimator (HD-MLC) with 5- and 10-mm fine MLCs is useful for radiotherapy. However, it is difficult to irradiate the mammary gland and supraclavicular region using a HD-MLC because of the narrow field of volumetric modulated arc radiotherapy (VMAT). Therefore, we aimed to evaluate the dose distribution of the VMAT dose using a HD-MLC in 15 patients with left breast cancer undergoing postoperative irradiation of breast and regional lymph nodes, including the internal mammary node. Materials and methods: The following four plans were generated: three-arc VMAT using HD-MLC (HD-VMAT), two tangential arcs and one-arc VMAT using HD-MLC (tHD-VMAT), three-dimensional conformal radiotherapy (3DCRT) using HD-MLC, and two-arc VMAT using the Millennium 120-leaf MLC (M-VMAT). We assessed the doses to the target volume and organs at risk. Results: The target dose distributions were higher for HD-VMAT than 3DCRT. There were no significant differences in the heart mean dose (Dmean) or lung volume receiving 20 Gy (V20 Gy) between HD-VMAT and 3DCRT. The heart Dmean and lung V20 Gy of tHD-VMAT were higher than those of HD-VMAT, and the heart Dmean of M-VMAT was higher than that of HD-VMAT. However, the target doses of tHD-VMAT, M-VMAT, and HD-VMAT were equivalent. Conclusions: In cases of the mammary gland and regional lymph node irradiation, including the internal mammary node in patients with left breast cancer, HD-VMAT was not inferior to M-VMAT and provided a better dose distribution to the target volume and organs at risk compared with 3DCRT and tHD-VMAT.

Comparing the toxicity and disease control rate of radiotherapy for prostate cancer between salvage settings after high-intensity focused ultrasound therapy and initial settings.

The purpose of this retrospective study was to compare the toxicity and disease control rate of radiotherapy for prostate cancer in salvage settings after high-intensity focused ultrasound (HIFU) therapy (HIFU cohort) with those in radical settings (non-HIFU cohort). From 2012 to 2020, 215 patients were identified for this study and 17 were treated in the salvage settings after HIFU. The median follow-up time was 34.5 months (range: 7-102 months, inter-quartile range [IQR]: 16-64 months). Genitourinary (GU) and gastrointestinal (GI) adverse events were evaluated in acute and late periods with Common Terminology Criteria for Adverse Events version 5, and the rates of biochemical-clinical failure free survival (BCFS) and overall survival (OS) were estimated. The cumulative incidence of late GU Grade 2 or greater toxicity after five years was significantly different between the non-HIFU and HIFU cohorts with rates of 7.3% and 26.2%, respectively (P = 0.03). Regarding GI Grade 2 or greater toxicity, there was no significant difference between the two cohorts. The 5y-BCFS was 84.2% in the non-HIFU cohort and 69.5% in the HIFU cohort with no significant difference (P = 0.10) and the 5y-OS was 95.9% and 92.3%, respectively (P = 0.47). We concluded that the possibility of increased late GU Grade 2 or greater should be considered when applying salvage radiotherapy for local recurrence after HIFU.

Dosimetric study of whole-brain irradiation with high-energy photon beams for dose reduction to the scalp.

OBJECTIVE: To evaluate the efficiency of high-energy photons for mitigating alopecia due to whole-brain irradiation (WBRT). METHODS: Planning CT data from 10 patients who received WBRT were collected. We prepared 4 WBRT plans that used 6 or 15 MV photon beams, with or without use of a field-in-field (FiF) technique, and compared outcomes using a treatment planning system. The primary outcome was dose parameters to the scalp, including the mean dose, maximum dose, and dose received to 50% scalp(D50%). Secondary outcomes were minimum dose to the brain surface. RESULTS: Using FiF, the mean doses were 24.4-26.0 and 22.4-24.1 Gy, and the maximum doses were 30.5-32.1 and 28.5-30.8 Gy for 6 and 15 MV photon beams, respectively. Without FiF, the mean doses were 24.6-26.9 and 22.6-24.5 Gy, and the maximum doses were 30.8-34.6 and 28.6-32.4 Gy for 6 and 15 MV photon beams. The 15 MV plan resulted in a lower scalp dose for each dose parameter (p < 0.001). Using FiF, the minimum doses to the brain surface for the 6 and 15 MV plans were 28.9 ± 0.440 and 29.0 ± 0.557 Gy, respectively (p = 0.70). Without FiF, the minimum doses to the brain surface for the 6 and 15 MV plans were 28.9 ± 0.456 and 29.0 ± 0.529, respectively (p = 0.66). CONCLUSION: Compared with the 6 MV plan, the 15 MV plan achieved a lower scalp dose without impairing the brain surface dose. ADVANCES IN KNOWLEDGE: High-energy photon WBRT may mitigate alopecia of patients who receiving WBRT.

Dosimetric evaluation of the feasibility of stereotactic body radiotherapy for primary lung cancer with lobe-specific selective elective nodal irradiation.

More than 10% of all patients treated with stereotactic body radiotherapy (SBRT) for primary lung cancer develop regional lymph node recurrence. We evaluated the dosimetric feasibility of SBRT with lobe-specific selective elective nodal irradiation (ENI) on dose-volume histograms. A total of 21 patients were treated with SBRT for Stage I primary lung cancer between January 2010 and June 2012 at our institution. The extents of lobe-specific selective ENI fields were determined with reference to prior surgical reports. The ENI fields included lymph node stations (LNS) 3 + 4 + 11 for the right upper lobe tumors, LNS 7 + 11 for the right middle or lower lobe tumors, LNS 5 + 11 for the left upper lobe tumors, and LNS 7 + 11 for the left lower lobe tumors. A composite plan was generated by combining the ENI plan and the SBRT plan and recalculating for biologically equivalent doses of 2 Gy per fraction, using a linear quadratic model. The V20 of the lung, D(1cm3) of the spinal cord, D(1cm3) and D(10cm3) of the esophagus and D(10cm3) of the tracheobronchial wall were evaluated. Of the 21 patients, nine patients (43%) could not fulfill the dose constraints. In all these patients, the distance between the planning target volume (PTV) of ENI (PTVeni) and the PTV of SBRT (PTVsrt) was ≤2.0 cm. Of the three patients who developed regional metastasis, two patients had isolated lymph node failure, and the lymph node metastasis was included within the ENI field. When the distance between the PTVeni and PTVsrt is >2.0 cm, SBRT with selective ENI may therefore dosimetrically feasible.