Tangential Beam Radiotherapy Research Articles

Outcomes of immediate oncoplastic surgery and adjuvant radiotherapy in breast cancer patients

BackgroundOncoplastic surgery techniques lead to a rearrangement of the breast tissue and impede target definition during adjuvant radiotherapy (RT). The aim of this study was to assess local control rates after immediate oncoplastic surgery and adjuvant RT.MethodsThis study comprises 965 patients who underwent breast-conserving therapy and adjuvant RT between 01/2000 and 12/2005. 288 patients received immediate oncoplastic surgery (ONC) and 677 patients breast-conserving surgery only (NONC). All patients were treated with adjuvant external tangential-beam RT (total dose: 50/50.4 Gy; fraction dose 1.8/2.0 Gy). An additional boost dose of 10–16 Gy to the primary tumor bed was given in 900 cases (93.3%). Local control rates (LCR), Progression free survival (PFS) and overall survival (OS) were assessed retrospectively after a median follow-up period of 67 (Q25-Q75: 51–84) months.ResultsNo significant difference was found between ONC and NONC in regard to LCR (5-yr: ONC 96.8% vs. NONC 95.3%; p = 0.25). This held also true for PFS (5-yr: ONC 92.1% vs. NONC 89.3%; p = 0.09) and OS (5-yr: ONC 96.0% vs. NONC 94.8%; p = 0.53). On univariate analyses G2–3 (p = 0.04), a younger age (p = 0.01), T-stage (p < 0.01) lymph node involvement (p < 0.01) as well as triple negative tumors (p < 0.01) were identified as risk factors for local recurrence. In a propensity score stratified Cox-regression model no significant impact of oncoplastic surgery on local control rate was found (HR: 2.05, 95% CI [0.93; 4.51], p = 0.08).ConclusionImmediate oncoplastic surgery seems not to affect the effectiveness of adjuvant whole breast RT on local control rates in breast cancer patients.

Quantification of cardiac subvolume dosimetry using a 17 segment model of the left ventricle in breast cancer patients receiving tangential beam radiotherapy

PurposeSubacute changes following breast radiotherapy have been demonstrated in discrete areas of the left ventricle (LV), with recent guidelines being developed to help determine dose to subvolumes of the LV. This study aims to determine doses to the 17 segments of the LV as per the American Heart Association (AHA) and other cardiac subvolumes, and to correlate mean heart (MHD) dose with various subvolume dosimetric indices. These results may direct focus to specific left ventricular segments in studies of radiation-related heart disease incorporating surveillance imaging, help to determine more precise dose response relationships, and potentially aid prediction of late radiation effects. Methods and materialsThe heart and cardiac subvolumes of 29 patients treated with tangential radiotherapy for left breast cancer were contoured. Delineation of cardiac subvolumes (cardiac chambers, cardiac valves and the 17 segments of the LV) was undertaken using a novel contouring method on planning CT data reformatted into the cardiac axis. Individual segments were then combined to determine doses to the basal, mid and apical left ventricular regions, and the anterior, septal, inferior and lateral ventricular walls. Radiotherapy doses (including maximum, mean, D1cc, V25) were determined. Correlation analyses were performed between MHD and various substructure dosimetric indices. ResultsTwenty five patients received tangential breast free breathing radiotherapy alone, and four patients received regional nodal irradiation including the internal mammary chain with deep inspiration breath hold (DIBH). For patients receiving breast only radiation, the median mean heart radiation dose was 2.62 Gy (range 1.52–3.90 Gy), and a heterogeneous dose distribution to the LV was noted, with the apical region receiving the highest median mean dose (14.99 Gy) compared with the mid and basal regions (3.10 Gy and 1.51 Gy respectively). The anterior LV wall received the highest median mean dose (9.21 Gy) with the remaining walls receiving similar mean doses (range 1.79–3.05 Gy). The anterior LV apical segment (segment 13) and apex (segment 17) received the highest individual median mean segment doses (26.73 Gy and 30.02 Gy respectively). Apical segments received the highest median mean doses (segments 13, 14, 15, 16), followed by the mid anterior (segment 7) and anteroseptal (segment 8) segments. Segments receiving the highest doses remained unchanged between the DIBH cohort and free breathing cohort. MHD showed a high correlation with the anterior wall r = 0.71, p < 0.05 and entire left ventricle r = 0.82, p < 0.05, but correlations varied from weak to high when MHD was correlated with segments receiving highest doses (range r = 0.43–0.76), p < 0.05. ConclusionsIn the setting of breast cancer radiotherapy, there are substantial RT dose variations within specific LV segments, with mid and apical anterior ventricular segments (segments 7, 13) and the apical region of the LV (segments 13, 14, 15, 16, 17) being consistently exposed to the highest radiation doses. Determining segmental and regional RT doses to the left ventricle may help guide focus in diagnostic cardiology in the post radiotherapy setting.

Assessment of leakage dose in vivo in patients undergoing radiotherapy for breast cancer.

Background and purposeAccurate quantification of the relatively small radiation doses delivered to untargeted regions during breast irradiation in patients with breast cancer is of increasing clinical interest for the purpose of estimating long-term radiation-related risks. Out-of-field dose calculations from commercial planning systems however may be inaccurate which can impact estimates for long-term risks associated with treatment. This work compares calculated and measured dose out-of-field and explores the application of a correction for leakage radiation.Materials and methodsDose calculations of a Boltzmann transport equation solver, pencil beam-type, and superposition-type algorithms from a commercial treatment planning system (TPS) were compared with in vivo thermoluminescent dosimetry (TLD) measurements conducted out-of-field on the contralateral chest at points corresponding to the thyroid, axilla and contralateral breast of eleven patients undergoing tangential beam radiotherapy for breast cancer.ResultsOverall, the TPS was found to under-estimate doses at points distal to the radiation field edge with a modern linear Boltzmann transport equation solver providing the best estimates. Application of an additive correction for leakage (0.04% of central axis dose) improved correlation between the measured and calculated doses at points greater than 15 cm from the field edge.ConclusionsApplication of a correction for leakage doses within peripheral regions is feasible and could improve accuracy of TPS in estimating out-of-field doses in breast radiotherapy.

Note: Utilization of polymer gel as a bolus compensator and a dosimeter in the near-surface buildup region for breast-conserving therapy.

Tangential beam radiotherapy is routinely used for radiation therapy after breast conserving surgery. A tissue-equivalent bolus placed on the irradiated area shifts the depth of the dose distribution; this bolus provides uniform dose distribution to the breast. The gel bolus made by the BANG-Pro(®) polymer gel and in an oxygen non-transmission pack was applicable as a dosimeter to measure dose distribution in near-surface buildup region. We validated the use of the gel bolus to improve in the whole-breast/chest wall, including the near-surface buildup region.

Dosimetric comparison of tangential beam radiotherapy of the chest wall in patients with breast cancer: IMRT versus 3DRT.

e11087 Background: To evaluate whether tangential beam intensity modulated radiotherapy (IMRT) provides a better dose distribution to the planning target volume (PTV; chest wall) and organs at risk than standard tangential wedged three-dimensional radiotherapy (3DRT). Methods: For 20 subsequent breast cancer patients after mastectomy a 3D treatment plan and a tangential beam IMRT plan was generated for the adjuvant radiotherapy of the chest wall. The dose-volume histograms were evaluated for the PTV and organs at risk. Parameters of the dose distribution were compared using the two-sided paired student-t-test. Results: IMRT reduced significantly the percentage of tissue encompassed by the 95% isodose line (V 95%) of the ipsilateral lung from 6.3% to 2.6% (p < 0.01). Of the patients with left-sided breast cancer, the V95% of the heart was significantly reduced from 2.8% to 0.7% (p < 0.01). No significant difference of the dose distribution was found for the PTV. Conclusions: Tangential beam IMRT significantly reduced the volume of ipsilateral lung exposed to relatively high radiation dose and the volume of heart in patients with left-sided breast cancer. This might translate into reduced toxicity. No significant financial relationships to disclose.

IMRT for the breast: a comparison of tangential planning techniques

Three intensity-modulated tangential beam radiotherapy plan types for breast cancer treatment were evaluated based on PTV homogeneity index (HI) and equivalent uniform dose (EUD), heart V30 and EUD, whole lung V20 and EUD, and typical planning time compared to conventional 2D plans. 20 early-stage breast cancer patients were CT-scanned in the supine position, and tangential field extent, gantry and collimator angles were chosen. Four treatment plans were created for each patient: conventional, dynamically wedged plan based on the dose distribution on the central axial slice; forward planned IMRT; surface compensated plan created using an Eclipse tool and hybrid IMRT plan combining open and inverse-optimized fields. All three IMRT planning techniques represent significant improvement in PTV HI and EUD compared to conventional plans. Among the IMRT plans, the hybrid IMRT plan produced the best HI. IMRT lowered heart V30 and lung V20, but no significant differences in heart or lung EUD were detected between IMRT techniques. The IMRT technique with the shortest planning time was the compensated plan, followed by the hybrid IMRT. IMRT planning provides dosimetric benefits in breast cancer patients. The selection of the most appropriate IMRT technique must include careful consideration of the resources available.

Estimating Irradiated Heart Volume from 2D-Simulation Films in Tangential Beam Radiotherapy for Breast Cancer

Estimating Irradiated Heart Volume from 2D-Simulation Films in Tangential Beam Radiotherapy for Breast Cancer

Arterial rupture after microwave-induced hyperthermia and radiotherapy: With reference to two patients treated for recurrence in previously operated and irradiated areas

Two patients who developed frank arterial bleeding after combined microwave-induced hyperthermia and radiotherapy are described. One patient received re-irradiation and hyperthermia for recurrent metastatic neck nodes of a mesopharyngeal carcinoma. Full course radiotherapy had been given 6 years previously and a right-sided radical neck node dissection had been performed 4 months earlier because of recurrent neck node metastases. Six weeks after the combined therapy for a second recurrence, which achieved complete remission, a fatal rupture of the carotid artery occurred. The other patient received re-irradiation and hyperthermia for a chest wall recurrence of a breast carcinoma, treated 5.5 years previously by sector resection and tangential beam radiotherapy, and treated again 2 years earlier with extensive surgery for a local recurrence. A frank arterial bleeding from the treated region was seen after 7 months, but could be arrested with surgery. This important complication in combined hyperthermia and radiotherapy does not seem to have been recognized before. Different explanations are discussed, such as the previous local treatment as well as high temperature and atherosclerosis per se.