The relationship between radiation doses to coronary arteries and location of coronary stenosis requiring intervention in breast cancer survivors.

BACKGROUND: To assess the relationship between radiation doses to the coronary arteries (CAs) and location of a coronary stenosis that required intervention after three-dimensional conformal radiotherapy (3DCRT) for breast cancer (BC). METHODS: The study population consisted of 182 women treated for BC in Sweden between 1992 and 2012. All women received 3DCRT and subsequently underwent coronary angiography due to a suspected coronary event. CA segments were delineated in the patient's original planning-CT and radiation doses were recalculated based on the dose distribution of the original radiotherapy (RT) plan. The location of the CA stenosis that required intervention was identified from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR). Logistic regression analysis was used to assess the relationship between CA radiation doses and risk of a later coronary intervention at this specific location. RESULTS: The odds ratio (OR) varied by radiation dose to the mid left anterior descending artery (LAD) (p = 0.005). Women receiving mean doses of 1-5 Gray (Gy) to the mid LAD had an adjusted OR of 0.90 (95% CI 0.47-1.74) for a later coronary intervention compared to women receiving mean doses of 0-1 Gy to the mid LAD. In women receiving mean doses of 5-20 Gy to the mid LAD, an adjusted OR of 1.24 (95% CI 0.52-2.95) was observed, which increased to an OR of 5.23 (95% CI 2.01-13.6) for mean doses over 20 Gy, when compared to women receiving mean doses of 0-1 Gy to the mid LAD. CONCLUSIONS: In women receiving conventional 3DCRT for BC between 1992 and 2012, radiation doses to the LAD remained high and were associated with an increased requirement of coronary intervention in mid LAD. The results support that the LAD radiation dose should be considered in RT treatment planning and that the dose should be kept as low as possible. Minimising the dose to LAD is expected to diminish the risk of later radiation-induced stenosis.

Post-mastectomy radiation therapy with or without implant-based reconstruction is safe in terms of clinical target volume coverage and survival - A matched cohort study.

BACKGROUND AND PURPOSE: Patients with breast cancer receiving mastectomy in our institution are offered immediate breast reconstruction (IBR). IBR may have an impact on the optimisation of radiation therapy (RT). Therefore, we aimed to evaluate the clinical target volume (CTV) dose coverage when disregarding the dose received by the breast implant in women treated for breast cancer. Furthermore, to investigate the safety of immediate breast reconstruction (IBR) with an implant (IBR+) in terms of recurrence and survival compared to patients without an implant (IBR-). PATIENTS AND METHODS: This matched-cohort included 128 patients with IBR+ and 252 IBR- patients (controls). The potential confounding effects of tumour stage and treatment were controlled for. For IBR+ patients, the implant volume was excluded from the CTV in the RT planning images, and the RT target coverage (V95%: CTV covered by ≥the 95% isodose) was compared between the IBR+ and IBR- groups. RESULTS: A limited under dosage was observed in patients without lymph-node irradiation; the V95% mean values for the CTV subtracting the implant were 84% and 92%, for IBR+ and IBR- groups, respectively. Median follow-up duration was 5.8 years (0.1-7.5 years). In comparing IBR+ and IBR- groups, no statistically significant differences were found in the incidence of recurrence rate ratios or recurrence free survival (log-rank p = 0.142), overall survival (log-rank p = 0.096), or breast cancer specific survival (log-rank p = 0.147). CONCLUSIONS: Post-mastectomy radiation therapy and implant-based reconstruction lead to minor under dosage of the target, due to the projection of the subcutaneous tissue in the presence of the implant. However, recurrence and survival rates were equally distributed among IBR+ and IBR- patients indicating that the overall treatment protocol used in our institution is safe.

MR-OPERA: A Multicenter/Multivendor Validation of Magnetic Resonance Imaging-Only Prostate Treatment Planning Using Synthetic Computed Tomography Images.

PURPOSE: To validate the dosimetric accuracy and clinical robustness of a commercially available software for magnetic resonance (MR) to synthetic computed tomography (sCT) conversion, in an MR imaging-only workflow for 170 prostate cancer patients. METHODS AND MATERIALS: The 4 participating centers had MriPlanner (Spectronic Medical), an atlas-based sCT generation software, installed as a cloud-based service. A T2-weighted MR sequence, covering the body contour, was added to the clinical protocol. The MR images were sent from the MR scanner workstation to the MriPlanner platform. The sCT was automatically returned to the treatment planning system. Four MR scanners and 2 magnetic field strengths were included in the study. For each patient, a CT-treatment plan was created and approved according to clinical practice. The sCT was rigidly registered to the CT, and the clinical treatment plan was recalculated on the sCT. The dose distributions from the CT plan and the sCT plan were compared according to a set of dose-volume histogram parameters and gamma evaluation. Treatment techniques included volumetric modulated arc therapy, intensity modulated radiation therapy, and conventional treatment using 2 treatment planning systems and different dose calculation algorithms. RESULTS: The overall (multicenter/multivendor) mean dose differences between sCT and CT dose distributions were below 0.3% for all evaluated organs and targets. Gamma evaluation showed a mean pass rate of 99.12% (0.63%, 1 SD) in the complete body volume and 99.97% (0.13%, 1 SD) in the planning target volume using a 2%/2-mm global gamma criteria. CONCLUSIONS: Results of the study show that the sCT conversion method can be used clinically, with minimal differences between sCT and CT dose distributions for target and relevant organs at risk. The small differences seen are consistent between centers, indicating that an MR imaging-only workflow using MriPlanner is robust for a variety of field strengths, vendors, and treatment techniques.