Dosimetric comparison of TomoDirect, helical tomotherapy, and volumetric modulated arc therapy for postmastectomy treatment

Training and temporally validating an NTCP model of acute toxicity after whole breast radiotherapy, including the impact of advanced delivery techniques

PURPOSE

The aim is to train and validate a multivariable Normal Tissue Complication Probability (NTCP) model predicting acute skin reactions in patients with breast cancer receiving adjuvant Radiotherapy (RT).

METHODS AND MATERIALS

We retrospectively reviewed 1570 single-institute patients with breast cancer treated with whole breast irradiation (40 Gy/15fr). The patients were divided into training (n = 878, treated with 3d-CRT, from 2009 to 2017) and validation cohorts (n = 692, treated from 2017 to 2021, including advanced RT techniques). In the validation cohort, patients were classified according to the delivery techniques into static (n = 404) and arc techniques (n = 288). Several clinical/technical information and DVHs of the "skin" (5 mm inner expansion from the body contour) were available. Skin toxicity was assessed during follow-up using the RTOG scale criteria. A multivariable logistic regression model was generated combining skin DVH and clinical parameters, using cross-validation methods that ensured high internal consistency and robustness. The performance of the model was tested in the validation cohort.

RESULTS

14.0 %/17.4 % of patients developed ≥ G2 toxicity, in the training/validation cohorts, respectively. The resulting multivariable logistic model included axillary lymph node dissection (OR = 1.58, 95 %CI = 1.01-2.48, p = 0.045), hypertension (OR = 1.54, 95 %CI = 1.04-2.27, p = 0.030) and skin V20Gy (OR = 1.008, 95 %CI = 1.004-1.013, p < 0.0001). The AUC of the model was 0.64/0.59 in training/validation, with better performance in the validation cohort if considering only V20Gy (0.62). The model showed satisfactory agreement between predicted and observed toxicity rates: in the validation group, the slope of the calibration plot was 0.96 (R2 = 0.6) with excellent goodness-of-fit (Hosmer-Lemeshow p-value = 0.99). Looking at each of the three predictors individually, only the role of V20Gy was confirmed in the validation group. Results were similar when considering patients treated with static or arc techniques.

CONCLUSION

An NTCP model for acute toxicity after moderately hypofractionated breast RT was trained. The model underwent temporal validation even for patients treated with advanced delivery techniques. Despite clinical differences and techniques, the confirmation of the dosimetry parameter in the validation cohort highlights its robustness and corroborates the hypothesis that skin DVH may assess the risk with the potential for improving plan optimisation.

Dosiomics-based detection of dose distribution variations in helical tomotherapy for prostate cancer patients: influence of treatment plan parameters

The stability of dosiomics features (DFs) and dose-volume histogram (DVH) parameters for detecting disparities in helical tomotherapy planned dose distributions was assessed. Treatment plans of 18 prostate patients were recalculated using the followings: field width (WF) (2.5 vs. 5), pitch factor (PF) (0.433 vs. 0.444), and modulation factor (MF) (2.5 vs. 3). From each of the eight plans per patient, ninety-three original and 744 wavelet-based DFs were extracted, using 3D-Slicer software, across six regions including: target volume (PTV), pelvic lymph nodes (PTV-LN), PTV + PTV-LN (PTV-All), one cm rind around PTV-All (PTV-Ring), rectum, and bladder. For the resulting DFs and DVH parameters, the coefficient of variation (CV) was calculated, and using hierarchical clustering, the features were classified into low/high variability. The significance of parameters on instability was analyzed by a three-way analysis of variance. All DF's were stable in PTV, PTV-LN, and PTV-Ring (average CV (CV ¯ )  ≤ 0.36). Only one feature in the bladder (CV ¯  = 0.9), rectum (CV ¯  = 0.4), and PTV-All (CV ¯  = 0.37) were considered unstable due to change in MF in the bladder and WF in the PTV-All. The value ofCV ¯ for the wavelet features was much higher than that for the original features. Out of 225 unstable wavelet features, 84 features hadCV ¯  ≥ 1. The CVs for all the DVHs remained very small (CV ¯ < 0.06). This study highlights that the sensitivity of DFs to changes in tomotherapy planning parameters is influenced by the region and the DFs, particularly wavelet features, surpassing the effectiveness of DVHs.

Patient and treatment-related factors that influence dose to heart and heart substructures in left-sided breast cancer radiotherapy

BACKGROUND

Cardiac substructures are critical organs at risk in left-sided breast cancer radiotherapy being often overlooked during treatment planning. The treatment technique plays an important role in diminishing dose to critical structures. This review aims to analyze the impact of treatment- and patient-related factors on heart substructure dosimetry and to identify the gaps in literature regarding dosimetric reporting of cardiac substructures.

METHODS

A systematic search of the literature was conducted in Medline/Pubmed database incorporating data published over the past 10 years, leading to 81 eligible studies. Treatment-related factors analyzed for their impact on patient outcome included the number of treatment fields, field geometry, treatment time and monitor units. Additionally, patient-related parameters such as breast size and tumor shape were considered for cardiac dosimetry evaluation.

RESULTS

Limited number of fields appeared to be an advantage for mean heart dose reduction when tangential IMRT versus multiple fields IMRT was evaluated. Larger breast size (910.20 ± 439.80 cm3) is linked to larger treatment fields and higher heart doses. Internal mammary node irradiation further escalates cardiac substructures dosimetry treated with 3DCRT and IMRT/VMAT. Proton therapy delivers lower mean heart dose regardless of breathing condition (free or respiratory-gated).

CONCLUSION

The management of treatment- and patient-related factors must be taken into account regardless of the treatment technique when evaluating cardiac dose. Furthermore, the gap found in the literature regarding heart toxicity assessment in left-sided breast cancer patients emphasizes the need for cardiac substructure contouring to better manage and control radiation-induced cardiac toxicities in this patient group.

Dosimetric analysis of half-field-based VMAT with the deep inspiration breath-hold technique for left breast cancer patients following breast-conserving surgery

Objective

Compared the dosimetric characteristics of half-field-based VMAT and half-field-based IMRT for left breast cancer patients combined with deep inspiration breath-hold (DIBH) and free breathing (FB) techniques.

Methods

Twenty-one left breast cancer patients were included. Each patient underwent DIBH and FB CT scans, IMRT and VMAT plans in half-field beam mode for both breathing techniques, resulting in four plans: FB-IMRT (F-IMRT), FB-VMAT (F-VMAT), DIBH-IMRT (D-IMRT) and DIBH-VMAT (D-VMAT). The conformity index (CI), homogeneity index (HI), and the doses received at the heart, left anterior descending (LAD), left lung, right breast, and right lung, were compared among plans.The correlation between the difference in the volume of lung_L (ΔLVL) and the difference in the mean dose (ΔDmean) of lung_L under the DIBH and FB plans, the correlation between the difference in the heart-chest distance (ΔHCD) and the ΔDmean of the heart,LAD under the DIBH and FB plans.

Results

The D-VMAT plan lower lung_L V5 than both the F-IMRT and F-VMAT plans (p<0.05), The D-VMAT plan lower values for V10, V20, V30, and Dmean than did the other plans (p < 0.05). For the heart, the D-VMAT plan lower V5, V10, V20, and Dmean values than did the other plans (p < 0.05). The D1% and Dmax of the heart and the Dmax and Dmean of the LAD obtained with the D-VMAT plan were lower than those obtained with the F-IMRT and F-VMAT plans (p < 0.05). ΔHCD exhibited correlation with the ΔDmean of the LAD between the D-VMAT and F-IMRT plans and between the D-VMAT and F-VMAT plans (R = -0.765 and -0.774, respectively, p = 0.000).

Conclusion

the D-VMAT plan offered enhanced protection for OARs. The integration of the DIBH technique with half-field and VMAT technology in the D-VMAT plan offers a superior dose distribution.

Correlations between patient-specific parameters and dosimetric indices for personalized breast cancer radiotherapy

Treatment planning parameters in radiotherapy are key elements that dictate the success of treatment outcome. While some parameters are commonly evaluated irrespective of cancer type, others are site-dependent and strongly patient specific. Given the critical influence of planning parameters on personalized therapy, the aim of this study was to evaluate the correlations between the dosimetric indices (conformity, homogeneity and mismatch indices) related to tumor coverage and the patient-specific parameters which encompass parameters pertaining to organs at risk (widths and lengths of heart and ipsilateral lung included in treatment fields, mean/maximum doses to heart, ipsilateral lung, left anterior descending aorta and contralateral breast) and tumor volume. Forty breast cancer patients were divided into two groups according to tumor location: twenty with left-sided (group A) and twenty with right-sided breast cancer (group B). Conformal (3DCRT), intensity modulated (IMRT) and volumetric arc modulated (VMAT) radiotherapy techniques were used for plan creation. Moderate to strong correlations were found for ipsilateral lung parameters for both groups of patients regardless of the treatment technique. Moderate to strong correlations were found for heart parameters in group A patients, while no correlations were observed in group B. The mismatch index presented moderate to strong correlations with tumor volume for all treatment techniques (r = -0.861 3DCRT, r = -0.556 IMRT, r = -0.533 VMAT) particularly in group A. The evaluated correlations indicate the role of dosimetric indices in personalized treatment planning.

Cardio-oncology concerns in radiotherapy: Heart and cardiac substructure toxicities from modern delivery techniques

Cardio-oncology is lately gaining more attention due to radiation-induced cardiac events reported by a very large number of studies. In view of this, the current overview of the literature aimed to encompass all studies from the past 15 years to assess changes in cardiac dose due to treatment evolution, as well as the changes in treatment planning customs to incorporate not only the heart as a whole but also cardiac substructures. Modern treatment techniques, particularly proton therapy, offers superior cardiac sparing compared to more established radiotherapy, for all evaluated tumor sites. Intensity modulation, particularly coupled with respiratory gating shows significant improvement in dose-volume parameters pertaining to the heart. While past studies considered mean heart dose as the only reference for cardiac toxicities, recommendations for the other cardiac substructures to be dosimetrically assessed during planning are becoming more common.

Surface guided ring gantry radiotherapy in deep inspiration breath hold for breast cancer patients

PURPOSE

This study investigated the use of surface guided radiotherapy (SGRT) in combination with a tomotherapy treatment mode using discrete delivery angles for deep inspiration breath hold (DIBH) treatments of breast cancer (bc). We aimed to assess the feasibility and dosimetric advantages of this approach.

MATERIALS AND METHODS

We evaluated camera occlusion in the Radixact treatment system bore and the stability of DIBH signals during couch movement. The SGRT system's ability to maintain signal and surface image accuracy was analyzed at different depths within the bore. Dosimetric parameters were compared and measured for 20 left-sided bc patients receiving TomoDirect (TD) tangential radiotherapy in both DIBH and free breathing (FB).

RESULTS

The SGRT system maintained surface coverage and precise DIBH-signal at depths up to 40 cm beyond the treatment center. Camera occlusion occurred in the clavicular and neck regions due to the patient's morphology and gantry geometry. Nonetheless, the system accurately detected respiratory motion for all measurements. The DIBH plans significantly (p < 0.001) reduced mean heart and left anterior descending artery (LAD) radiation doses by up to 40%, with a 50% reduction in near-maximum heart and LAD doses, respectively. No significant dosimetric differences between DIBH and FB were observed in other investigated parameters and volumes.

CONCLUSIONS

Camera occlusion and couch movement minimally impacted the real-time surface image accuracy needed for DIBH treatments of bc. DIBH reduced heart and LAD radiation doses significantly compared to FB, indicating the feasibility and dosimetric benefits of combining these modalities.

A Comparative Analysis of Implant-sparing Plan Versus Conventional Plans Utilizing Helical Tomotherapy in Breast Cancer Patients Undergoing Breast Reconstruction

BACKGROUND/AIM

To compare implant sparing irradiation with conventional radiotherapy (RT) using helical (H) and TomoDirect (TD) techniques in breast cancer patients undergoing immediate breast reconstruction (IBR).

PATIENTS AND METHODS

The dosimetric parameters of 40 patients with retropectoral implants receiving 50.4 Gy delivered in 28 fractions were analyzed. Three plans were created: H plan using conventional planning target volume (PTV) that included the chest wall, skin, and implant; TD plan using conventional PTV; and Hs plan using implant-sparing PTV. The H, TD, and Hs plans were compared for PTV doses, organ-at-risk (OAR) doses, and treatment times.

RESULTS

Dose distribution in the Hs plan was less homogeneous and uniform than that in the H and TD plans. The TD plan had lower lung, heart, contralateral breast, spinal cord, liver, and esophagus doses than the Hs plan. Compared to the Hs plan, the H plan had lower lung volume receiving 5Gy (V5) (39.1±3.9 vs. 41.2±3.9 Gy; p<0.001), higher V20 (12.3±1.3 vs. 11.5±2.6 Gy; p=0.02), and higher V30 (7.5±1.6 vs. 4.4±1.7 Gy; p<0.001). H plan outperformed Hs plan in heart dosimetric parameters except V20. The Hs plan had significantly lower mean implant doses (43.4±2.1 Gy) than the H plan (51.4±0.5 Gy; p<0.001) and the TD plan (51.9±0.6 Gy; p<0.001). Implementing an implant sparing technique for silicone dose reduction decreases lung doses.

CONCLUSION

Conventional H and TD plans outperform the implant sparing helical plan dosimetrically. Because capsular contracture during RT is unpredictable, long-term clinical outcomes are required to determine whether silicon should be spared.

Evaluation of conventional IMRT and VMAT strategies for postmastectomy radiation therapy after immediate implant-based reconstruction using the new ESTRO-ACROP contouring guidelines

This study evaluated the usability of conventional templates based on the new contour guidelines of the European Society of Radiation and Oncology and Advisory Committee in Radiation Oncology Practice (ESTRO-ACROP) for treatment plans of postmastectomy radiotherapy after immediate implant-based reconstruction. Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans generated with two different treatment planning systems (TPSs, Eclipse and Monaco) were examined. Six computed tomography scans of patients aged 35-54 years were retrospectively analysed who had undergone mastectomy and breast reconstruction using silicone implants after being diagnosed with left breast cancer. Six radiation oncologists participated in this study, and each of them contoured the target volume of one left breast using conventional contour (CTV-CONV) and new contour (CTV-ESTRO) methods. This study showed that compared with CTV-CONV, using CTV-ESTRO with objectives and cost functions similar to those of TPSs worsened the target volume coverage and increased the total number of monitor units. Considering the organs at risk, CTV-ESTRO tended to increase the mean dose delivered to the contralateral lung. It is concluded that the approach used for the new ESTRO-ACROP contour method cannot be applied in a manner similar to that for the conventional breast contour method, implying that the new ESTRO-ACROP contour method may require more time for improving plans for a given treatment.

New Approaches in Breast Cancer Radiotherapy

Breast cancer stands as the most prevalent malignancy, necessitating a well-established approach to its management due to its sustained prevalence over decades. The implementation of intensive treatments, combining various modalities, has yielded excellent survival outcomes. Consequently, the optimization of quality of life and the mitigation of long-term side effects emerge as critical considerations for clinicians. As a result, discussions regarding treatment de-intensification strategies have been initiated for all treatment modalities, including surgery, radiotherapy (RT), and chemotherapy. RT plays a crucial role in adjuvant therapy. The efficacy of RT in disease control and overall survival across all stages of breast cancer has been demonstrated in numerous clinical trials and meta-analyses utilizing extensive datasets. However, advancements in genetic tumor profiling and improved identification of disease subgroups have prompted a reevaluation of RT omission in low-risk groups as a strategy for treatment de-intensification. Conversely, technological improvements and shortened total treatment times with hypofractionation make RT a secure and feasible option for enhancing local control and survival with minimal impact on the quality of life.

Fully automated volumetric modulated arc therapy technique for radiation therapy of locally advanced breast cancer

BACKGROUND

This study aimed to evaluate an a-priori multicriteria plan optimization algorithm (mCycle) for locally advanced breast cancer radiation therapy (RT) by comparing automatically generated VMAT (Volumetric Modulated Arc Therapy) plans (AP-VMAT) with manual clinical Helical Tomotherapy (HT) plans.

METHODS

The study included 25 patients who received postoperative RT using HT. The patient cohort had diverse target selections, including both left and right breast/chest wall (CW) and III-IV node, with or without internal mammary node (IMN) and Simultaneous Integrated Boost (SIB). The Planning Target Volume (PTV) was obtained by applying a 5 mm isotropic expansion to the CTV (Clinical Target Volume), with a 5 mm clip from the skin. Comparisons of dosimetric parameters and delivery/planning times were conducted. Dosimetric verification of the AP-VMAT plans was performed.

RESULTS

The study showed statistically significant improvements in AP-VMAT plans compared to HT for OARs (Organs At Risk) mean dose, except for the heart and ipsilateral lung. No significant differences in V95% were observed for PTV breast/CW and PTV III-IV, while increased coverage (higher V95%) was seen for PTV IMN in AP-VMAT plans. HT plans exhibited smaller values of PTV V105% for breast/CW and III-IV, with no differences in PTV IMN and boost. HT had an average (± standard deviation) delivery time of (17 ± 8) minutes, while AP-VMAT took (3 ± 1) minutes. The average γ passing rate for AP-VMAT plans was 97%±1%. Planning times reduced from an average of 6 h for HT to about 2 min for AP-VMAT.

CONCLUSIONS

Comparing AP-VMAT plans with clinical HT plans showed similar or improved quality. The implementation of mCycle demonstrated successful automation of the planning process for VMAT treatment of locally advanced breast cancer, significantly reducing workload.

From organ at risk to target organ: Dosimetric comparison of myocardial stereotactic ablative body radiotherapy between helical tomotherapy and volumetric arc therapy for refractory ventricular tachycardia

Ventricular tachycardia (VT) is an important type of arrhythmia with a risk of sudden death. Although implanted cardiac defibrillation and radiofrequency ablation are used together with medical treatments for VT, the treatment options are limited in cases that do not respond to them. Stereotactic ablative body radiotherapy (SABR) applied to VT substrates in resistant cases is an emerging treatment with positive results. Such clinical results have increased the interest in this subject. However, the ideal treatment device and method have not yet been described for this therapy, which is generally applied at a single fraction using various devices and methods. Herein, treatment planning was conducted for a total of 8 patients (11 VT substrates) using the Varian TrueBeam EDGE and TomoTherapy Radixact devices at a single center, and the results were compared dosimetrically. The Wilcoxon-signed rank test was used for the statistical analysis, and mean values were expressed as medians and interquartile ranges (IQRs). In the volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) plans, the plan coverages and conformity indexes were similar; meanwhile, the homogeneity indexes were 0.10 (IQR = 0.05) and 0.07 (IQR = 0.05), respectively, and were significantly better in the HT plan (p = 0.02). The gradient indexes were 3.18 (IQR = 0.8) and 5.33 (IQR = 3.68) in the VMAT and HT plans, respectively, and were significantly better in the VMAT plan. For the organs at risk, similar doses were observed. The maximum doses for the stomach and esophagus and the mean doses for the left lung and both lungs were significantly lower in the VMAT plan. Similarly, the maximum and mean doses for the cardiac substructures and great vessels were significantly lower in the VMAT plan. More homogeneous plans were obtained in HT, while a faster dose reduction and lower critical organ dose were observed in VMAT. Reasonable myocardial SABR plans could be obtained with both techniques. The effects of the dosimetric differences on the clinical outcomes should be evaluated in prospective clinical studies.

Comparison of helical and TomoDirect techniques with simultaneous integrated boost in early breast cancer patients

Background

The aim of the study was to perform dosimetric comparisons of helical (H) and TomoDirect (TD) plans for whole-breast irradiation (WBI) with simultaneous integrated boost (SIB) in early-stage breast cancer patients undergoing breast conserving surgery.

Materials and methods

Fifty patients, 25 with left-side and 25 with right-side tumors, were determined for a treatment planning system for a total dose of 50.4Gy in 1.8Gy per fraction to WBI, with a SIB of 2.3Gy per fraction delivered to the tumor bed. The planning target volume (PTV) doses and the conformity (CI) and homogeneity indices (HI) for PTVbreast and PTVboost, as well as organ-at-risk (OAR) doses and treatment times, were compared between the H and TD plans.

Results

All plans met the PTV coverage criteria for the H plan, except for mean V107 of PTVbreast for TD plan. The H plan yielded better homogeneity and conformity of dose distribution compared to the TD plan. The ipsilateral mean lung doses were not significantly different between the two plans. The TD plans is advantageous for mean doses to the heart, contralateral breast and lung, spinal cord, and esophagus than the H plans. In both the H and TD plans, the right-sided breast patients had lower heart dose parameters than the left-sided breast patients. The TD plan is superior to the H plan in sparing the contralateral breast and lung by decreasing low-dose volumes.

Conclusions

While the OAR dose advantages of TD are appealing, shorter treatment times or improved dose homogeneity and conformity for target volume may be advantageous for H plan.

Hippocampal-sparing whole-brain radiotherapy under coplanar or noncoplanar VMAT

Whole-brain radiotherapy (WBRT) can alleviate symptoms in patients with brain metastases. However, WBRT may damage the hippocampus. Volumetric modulated arc therapy (VMAT) can achieve a suitable coverage of the target region and a more conforming dose distribution whereas decreasing the dose to organs-at-risk (OARs). Herein, we aimed to compare the differences between treatment plans utilizing coplanar VMAT and noncoplanar VMAT in hippocampal-sparing WBRT (HS-WBRT). Ten patients were included in this study. For each patient, the Eclipse A10 treatment planning system was used to generate 1 coplanar VMAT (C-VMAT) and 2 noncoplanar VMAT treatment plans with various beam angles (noncoplanar VMAT A [NC-A] and noncoplanar VMAT B [NC-B]) for HS-WBRT. The prescribed dose was 30 Gy in 12 fractions. Treatment plans were established based on the OAR dose constraints of the Radiation Therapy Oncology Group 0933 (RTOG 0933). Parameters such as the global maximum dose, dose conformity, dose homogeneity of plans, and OAR doses were evaluated. The maximum biologically equivalent doses in 2-Gy fractions (EQD2) of OARs in C-VMAT were 9.17 ± 0.61, 42.79 ± 2.00, and 42.84 ± 3.52 Gy in the hippocampus, brain stem, and optic chiasm, respectively, which were the lowest among the 3 treatment plans. There was no significant difference in dose conformity among the 3 treatment plans. However, NC-A had a slightly better conformity than C-VMAT and NC-B. NC-A had the best homogeneity, and NC-B had the worst homogeneity (p = 0.042). NC-A and NC-B had the lowest and highest global dose maximum, respectively. Therefore, NC-A, which had an intermediate performance in terms of OAR doses, had the best quality parameters. We used the quality score table based on the p-value to evaluate the significant difference between each treatment technique from the multiparameter results. In terms of treatment plan parameters, only NC-A received a score of 2; for OAR doses, C-VMAT, NC-A, and NC-B received a score of 6, 3, and 5, respectively. For the overall evaluation, C-VMAT, NC-A, and NC-B received a total score of 6, 5, and 5, respectively. Rather than noncoplanar VMAT, 3 full-arc C-VMATs should be utilized in HS-WBRT. C-VMAT can simultaneously maintain treatment plan quality and decrease patient alignment time and total treatment time.

Impact of Respiratory Motion on the Skin Dose for Breast Cancer in Tomotherapy: A Study in the In-house Moving Phantom

Purpose: The dose expansion methods as the skin flash and virtual bolus were used to solve intrafraction movement for breast planning due to breathing motion. We investigated the skin dose in each planning method by using optically stimulated luminescence on an in-house moving phantom for breast cancer treatment in tomotherapy. The impact of respiratory motion on skin dose between static and dynamic phantom's conditions was evaluated. Methods: A phantom was developed with movement controlled by the respirator for generating the respiratory waveforms to simulate respiratory motion. Five optically stimulated luminescence dosimeters were placed on the phantom surface to investigate the skin dose for the TomoDirect and TomoHelical under static and dynamic conditions. Eight treatment plans were generated with and without skin flash or virtual bolus by varying the thickness. The difference in skin dose between the two phantom conditions for each plan was explored. Results: All plans demonstrated a skin dose of more than 87% of the prescription dose under static conditions. However, the skin dose was reduced to 84.1% (TomoDirect) and 78.9% (TomoHelical) for dynamic conditions. The treatment plans without skin flash or virtual bolus showed significant skin dose differences under static and dynamic conditions by 4.83% (TomoDirect) and 9.43% (TomoHelical), whereas the skin flash with two leaves (TomoDirect 2L) or virtual bolus of at least 1.0 cm thickness (VB1.0) application compensated the skin dose in case of intrafraction movements by presenting a skin dose difference of less than 2% between the static and dynamic conditions. Conclusion: The skin dose was reduced under dynamic conditions due to breathing motion. The skin flash method with TomoDirect 2L or virtual bolus application with 1.0 cm thickness was useful for maintaining skin dose following the prescription by compensating for intrafraction movement due to respiratory motion for breast cancer in tomotherapy.

Improvement of helical tomotherapy treatment plan efficiency with block techniques for left-sided post-mastectomy radiation therapy

Purpose:

To limit the entrance dose to normal tissue and achieve the appropriate treatment time (TT) by using three different virtual structures with directional blocks for left-sided post-mastectomy radiation therapy (PMRT) with regional nodal irradiation (RNI).

Methods and materials:

Ten breast cancer patients who received PMRT by helical tomotherapy were enrolled. Three virtual structures were created for each patient: Organ-based, L-shaped (LB) and C-shaped (CB). The dose to the target and organ at risk (OARs), TT, the volume which received dose 5 Gy (V5Gy), integral dose (ID) and block structure contouring workload (BSCW) of the three virtual block techniques were evaluated. The performance scores were used to explore the suitable technique.

Results:

The CB plans showed a significantly better V5Gy, ID and contralateral breast-sparing. However, the CB plans revealed the longest TT and BSCW (p < 0·001). Contrary to the LB, the LB plans showed a significantly reduced TT and BSCW and provided the balance of plan efficiency with the highest score.

Conclusion:

The LB technique is considered to be the suitable technique for left-sided PMRT with RNI and provided the advantage of TT, V5Gy, ID and BSCW while maintaining acceptable criteria for the target and OARs.

Stereotactic radiosurgery for limited brain metastasis using three different techniques: helical tomotherapy, volumetric modulated arc therapy, and cone-based LINAC radiosurgery

PURPOSE

Specific radiation delivered to tumors by stereotactic radiosurgery (SRS) has become widely used in the treatment of brain metastasis. This study aimed to compare radiation therapy planning and its parameters from SRS using three different modalities: helical tomotherapy (HT), volumetric modulated arc therapy (VMAT), and cone-based linac radiosurgery (Cone-based).

MATERIALS AND METHODS

Each contouring dataset of patents who experienced one to four brain metastasis received SRS in our center was re-planned to create radiation therapy planning in all three treatment systems (HT, VMAT, and Cone-based). The parameters of conformity index (CI), homogeneity index (HI), CI50, and gradient index (CGI) were analyzed to compare the effects of the three techniques. Decision score analysis was used to evaluate the performance on dosimetric and organs-at-risk parameters among the different techniques by applying the Cone-based technique as a benchmark.

RESULTS

A total of 21 patients with 39 lesions were included in this study. The results from the decision score analysis demonstrated statistically identical CI, CI50, and CGI values between Cone-based and VMAT for single lesions. For multiple lesions, VMAT also provided better CI when compared to Cone-based technique while HT exhibited the poorest dosimetric parameters. Moreover, VMAT exhibited the lowest BrainV5Gy value and displayed the shortest beam-on time calculation.

CONCLUSION

We have conducted a comprehensive comparison of SRS planning approaches. The Cone-based technique revealed the highest HI value, while VMAT provided the best estimated beam-on time value. HT displayed a feasible SRS modality for single lesions, but not for multiple lesions.

Cardiac Function after Modern Radiation Therapy with Volumetric Modulated Arc Therapy or Helical Tomotherapy for Advanced Left-Breast Cancer Receiving Regional Nodal Irradiation

Background: Protecting cardiac function in patients with advanced left-breast cancer receiving radiation therapy (RT) with regional nodal irradiation (RNI) is an important issue. Modern RT techniques can limit cardiac exposure. The aim of this study was to explore the association be-tween cardiac dose and cardiac function. Methods: Between 2017 and 2020, we retrospectively reviewed left-breast cancer patients who received adjuvant RT, including RNI with either volumetric-modulated arc therapy (VMAT) or helical tomotherapy (HT). Left ventricular ejection fraction (LVEF) was assessed by echocardiography before RT and 1 year after RT to detect any early deterioration in cardiac systolic function. Results: A total of 30 eligible patients were enrolled. The median follow-up time from the initiation of RT was 3.9 years (range 0.6–5 years). Seventeen patients received VMAT, and the other 13 patients received HT. The median RT dose was 55 Gray (Gy), and the mean heart dose was 3.73 Gy (range 1.95–9.36 Gy). The median LVEF before and after RT was 68% and 68.5%, respectively. No obvious deterioration was found. There was no association between cardiac dose (mean heart dose, V5–V30) and LVEF (change in values or post-RT). Conclusions: For left-breast cancer patients undergoing RT with RNI, VMAT, or HT can be used to limit cardiac exposure. Cardiac function as evaluated by LVEF revealed no obvious deterioration after RT in our patients, and no association was found between cardiac dose and LVEF in those treated with either VMAT or HT in early cardiac surveillance.

Artificial Intelligence-Based Automated Treatment Planning of Postmastectomy Volumetric Modulated Arc Radiotherapy

As a useful tool, artificial intelligence has surpassed human beings in many fields. Artificial intelligence-based automated radiotherapy planning strategies have been proposed in lots of cancer sites and are the future of treatment planning. Postmastectomy radiotherapy (PMRT) decreases local recurrence probability and improves overall survival, and volumetric modulated arc therapy (VMAT) has gradually become the mainstream technique of radiotherapy. However, there are few customized effective automated treatment planning schemes for postmastectomy VMAT so far. This study investigated an artificial intelligence based automated planning using the MD Anderson Cancer Center AutoPlan (MDAP) system and Pinnacle treatment planning system (TPS), to effectively generate high-quality postmastectomy VMAT plans. In this study, 20 patients treated with PMRT were retrospectively investigated, including 10 left- and 10 right-sided postmastectomy patients. Chest wall and the supraclavicular, subclavicular, and internal mammary regions were delineated as target volume by radiation oncologists, and 50 Gy in 25 fractions was prescribed. Organs at risk including heart, spinal cord, left lung, right lung, and lungs were also contoured. All patients were planned with VMAT using 2 arcs. An optimization objective template was summarized based on the dose of clinical plans and requirements from oncologists. Several treatment planning parameters were investigated using an artificial intelligence algorithm, including collimation angle, jaw collimator mode, gantry spacing resolution (GSR), and number of start optimization times. The treatment planning parameters with the best performance or that were most preferred were applied to the automated treatment planning method. Dosimetric indexes of automated treatment plans (autoplans) and manual clinical plans were compared by the paired t-test. The jaw tracking mode, 2-degree GSR, and 3 rounds of optimization were selected in all the PMRT autoplans. Additionally, the 350- and 10-degree collimation angles were selected in the left- and right-sided PMRT autoplans, respectively. The uniformity index and conformity index of the planning target volume, mean heart dose, spinal cord D_0.03cc, mean lung dose, and V_5Gy and V_20Gy of the lung of autoplans were significantly better compared with the manual clinical plans. An artificial intelligence-based automated treatment planning method for postmastectomy VMAT has been developed to ensure plan quality and improve clinical efficiency.

Modern Rotational Radiation Techniques with Volumetric Modulated Arc Therapy or Helical Tomotherapy for Optimal Sparing of the Lung and Heart in Left-Breast Cancer Radiotherapy Plus Regional Nodal Irradiation: A Comparative Dosimetric Analysis

Simple Summary

For advanced left-breast cancer patients, adjuvant radiotherapy (RT) with regional nodal irradiation (RNI) has been indicated to reduce cancer recurrence and mortality. Modern arc RT techniques, volumetric-modulated arc therapy (VMAT), or helical tomotherapy (HT), can minimize normal organ exposure without compromising disease control. The aim of this study is to identify which arc technique is optimal for patients receiving left-breast RT with RNI, and to explore distinct RNI volumes with or without IMN. A total of 108 eligible patients were enrolled (70 VMAT, 38 HT). VMAT reduced the mean dose and low-dose exposure to the heart, ipsilateral lung, whole lung, contralateral breast, and esophagus compared with HT. The advantage of VMAT for normal organ sparing was distinct when performing RNI with IMN irradiation. To limit normal organ exposure and reduce potential toxicities, VMAT is the optimal technique for patients with left-breast cancer who are undergoing RT with RNI.

Abstract

Background: For advanced breast cancer with lymph node involvement, adjuvant radiotherapy (RT) with regional nodal irradiation (RNI) has been indicated to reduce cancer recurrence and mortality. However, an extensive RT volume is associated with normal organ exposure, which increases the toxicity and affects patient outcomes. Modern arc RT techniques can improve normal organ sparing compared with conventional techniques. The aim of this study was to explore the optimal technique for left-breast RT with RNI. Methods: We retrospectively reviewed patients receiving RT with RNI for left-breast cancer. We used modern arc RT techniques with either volumetric-modulated arc therapy (VMAT) or helical tomotherapy (HT) with a novel block technique, and compared differences in dosimetry parameters between the two groups. Subgroup analysis of RNI with or without internal mammary node (IMN) volume was also performed. Results: A total of 108 eligible patients were enrolled between 2017 and 2020, of whom 70 received VMAT and 38 received HT. The median RT dose was 55 Gy. No significant differences were found regarding the surgery, RT dose, number of fractions, target volume, and RNI volume between the VMAT and HT groups. VMAT reduced the heart mean dose more than HT (3.82 vs. 5.13 Gy, p < 0.001), as well as the cardiac parameters of V5–V20, whole-lung mean dose, lung parameters of V5–V20, and contralateral-breast and esophagus mean dose. In the subgroup analysis of RNI with IMNs, the advantage of VMAT persisted in protecting the heart, lung, contralateral breast, and esophagus. HT was beneficial for lowering the thyroid mean dose. For RNI without IMN, VMAT improved the low-dose exposure of the heart and lung, but HT was similar to VMAT in terms of heart, whole-lung, and contralateral-breast mean dose. Conclusions: For patients with left-breast cancer receiving adjuvant RT with RNI, VMAT reduced the exposure dose to the heart, lung, contralateral breast, and esophagus compared with HT. VMAT was superior to HT in terms of normal organ sparing in the patients who underwent RNI with IMN irradiation. Considering the reduction in normal organ exposure and potential toxicity, VMAT is the optimal technique for patients receiving RNI when deep inspiration breath-hold is not available.

Comparing TomoHelical and TomoDirect in postmastectomy hypofractionated radiotherapy after immediate breast reconstruction

BACKGROUND

Postmastectomy radiotherapy (PMRT) with TomoHelical™ (TH) or TomoDirect™ (TD) allows a uniform target coverage. In this study, we compare treatment plans using TD and TH in the setting of hypofractionated PMRT and immediate breast reconstruction.

MATERIAL AND METHODS

The TD-treatment plans of breast cancer patients treated between May 2016 and August 2019 were retrospectively selected. All the TD plans were re-planned on TH with the same prescription dose (40.05 Gy/15 fractions) and according to our dose/volume constraints. Data about the 2 treatment plans were compared with a focus on PTV coverage and all the organs at risk (OARs) constraints.

RESULTS

Fifty patients for a total number of 100 treatment plans (50 with TD and 50 re-planned with TH) were analyzed. All the median value in the TD PTV CHEST WALL plans fulfilled the predefined planning objectives, even though TH emerged as best for target coverage with statistically significant difference for V90%. TD provided the lowest V95% for the PTV SVC, but the median value was near to the recommended value of 90% (89.8 % vs 98.6% for TD and TH, respectively). Overall, TD reached the best OARs sparing. The main statistically significant differences with TH were for contralateral breast, ipsilateral and contralateral lung. All the other dose values for TH were higher than TD, but they fulfilled the recommended/acceptable predefined planning objectives.

CONCLUSIONS

In the setting of PMRT, TD compared to TH reached an acceptable target volume coverage, with an optimal sparing of OARs.

A dosimetric and radiobiological evaluation of VMAT following mastectomy for patients with left-sided breast cancer

Background

To compare the dosimetric, normal tissue complication probability (NTCP), secondary cancer complication probabilities (SCCP), and excess absolute risk (EAR) differences of volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for left-sided breast cancer after mastectomy.

Methods and materials

Thirty patients with left-sided breast cancer treated with post-mastectomy radiation therapy (PMRT) were randomly enrolled in this study. Both IMRT and VMAT treatment plans were created for each patient. Planning target volume (PTV) doses for the chest wall and internal mammary nodes, PTV1, and PTV of the supraclavicular nodes, PTV2, of 50 Gy were prescribed in 25 fractions. The plans were evaluated based on PTV1 and PTV2 coverage, homogeneity index (HI), conformity index, conformity number (CN), dose to organs at risk, NTCP, SCCP, EAR, number of monitors units, and beam delivery time.

Results

VMAT resulted in more homogeneous chest wall coverage than did IMRT. The percent volume of PTV1 that received the prescribed dose of VMRT and IMRT was 95.9 ± 1.2% and 94.5 ± 1.6%, respectively (p < 0.001). The HI was 0.11 ± 0.01 for VMAT and 0.12 ± 0.02 for IMRT, respectively (p = 0.001). The VMAT plan had better conformity (CN: 0.84 ± 0.02 vs. 0.78 ± 0.04, p < 0.001) in PTV compared with IMRT. As opposed to IMRT plans, VMAT delivered a lower mean dose to the ipsilateral lung (11.5 Gy vs 12.6 Gy) and heart (5.2 Gy vs 6.0 Gy) and significantly reduced the V₅, V₁₀, V_20, V_30, and V₄₀ of the ipsilateral lung and heart; only the differences in V₅ of the ipsilateral lung did not reach statistical significance (p = 0.409). Although the volume of the ipsilateral lung and heart encompassed by the 2.5 Gy isodose line (V_2.5) was increased by 6.7% and 7.7% (p < 0.001, p = 0.002), the NTCP was decreased by 0.8% and 0.6%, and SCCP and EAR were decreased by 1.9% and 0.1% for the ipsilateral lung. No significant differences were observed in the contralateral lung/breast V_2.5, V_5, V₁₀, V₂₀, mean dose, SCCP, and EAR. Finally, VMAT reduced the number of monitor units by 31.5% and the treatment time by 71.4%, as compared with IMRT.

Conclusions

Compared with IMRT, VMAT is the optimal technique for PMRT patients with left-sided breast cancer due to better target coverage, a lower dose delivered, NTCP, SCCP, and EAR to the ipsilateral lung and heart, similar doses delivered to the contralateral lung and breast, fewer monitor units and a shorter delivery time.

The advantages of abdominal compression with shallow breathing during left-sided postmastectomy radiotherapy by Helical TomoTherapy

BACKGROUND

Left-sided post-mastectomy radiotherapy (PMRT) certainly precedes some radiation dose to the cardiopulmonary organs causing many side effects. To reduce the cardiopulmonary dose, we created a new option of the breathing adapted technique by using abdominal compression applied with a patient in deep inspiration phase utilizing shallow breathing. This study aimed to compare the use of abdominal compression with shallow breathing (ACSB) with the free breathing (FB) technique in the left-sided PMRT.

MATERIALS AND METHODS

Twenty left-sided breast cancer patients scheduled for PMRT were enrolled. CT simulation was performed with ACSB and FB technique in each patient. All treatment plans were created on a TomoTherapy planning station. The target volume and dose, cardiopulmonary organ volume and dose were analyzed. A linear correlation between cardiopulmonary organ volumes and doses were also tested.

RESULTS

Regarding the target volumes and dose coverage, there were no significant differences between ACSB and FB technique. For organs at risk, using ACSB resulted in a significant decrease in mean (9.17 vs 9.81 Gy, p<0.0001) and maximum heart dose (43.79 vs 45.45 Gy, p = 0.0144) along with significant reductions in most of the evaluated volumetric parameters. LAD doses were also significantly reduced by ACSB with mean dose 19.24 vs 21.85 Gy (p = 0.0036) and the dose to 2% of the volume (D2%) 34.46 vs 37.33 Gy (p = 0.0174) for ACSB and FB technique, respectively. On the contrary, the lung dose metrics did not show any differences except the mean V5 of ipsilateral lung. The positive correlations were found between increasing the whole lung volume and mean heart dose (p = 0.05) as well as mean LAD dose (p = 0.041) reduction.

CONCLUSIONS

The ACSB technique significantly reduced the cardiac dose compared with the FB technique in left-sided PMRT treated by Helical TomoTherapy. Our technique is uncomplicated, well-tolerated, and can be applied in limited resource center.

Methodologies to Increase the Level of Evidence of Real-life Proton Therapy in Head and Neck Tumors

This review aims to present and assess available and new methodologies to increase the clinical evidence of proton therapy data for patients with head and neck cancer. Despite the increasing number of scientific reports showing the feasibility and effectiveness of proton therapy in head and neck cancer, clinical evidence on the potential benefits of its use remains low for several reasons. In this article, the pros and cons of consolidated and new methodologies in this setting such as randomized clinical trials, the model-based approach, and the use of prospective multicentric registries will be detailed.