Lung cancer reirradiation: Exploring modifications to utilization, treatment modalities and factors associated with outcomes.

BACKGROUND: Patients treated for lung cancer (LC) often experience locoregional failure after initial treatment. Due to technological advances, thoracic reirradiation (re-RT) has become a viable treatment option. We sought to investigate the use of thoracic re-RT in LC patients over a time period characterized by technological advances in a large, multi-center cohort. METHODS AND MATERIALS: LC patients treated with thoracic re-RT in two University Hospitals from 2010-2020 were identified. Clinical variables and RT data were extracted from the medical records and treatment planning systems. Overall survival (OS) was calculated from the last day of re-RT until death or last follow up. RESULTS: 296 patients (small cell LC n=30, non-small cell LC n=266) were included. Three-dimensional conformal radiation therapy was the RT technique used most frequently (63%), and 86% of all patients were referred for re-RT with palliative treatment intent. During the second half of the study period, the use of thoracic re-RT increased in general, more patients received curative re-RT, and there was an increased use of stereotactic body radiation therapy (SBRT). Median time between initial RT and re-RT was 18 months (range 1-213 months). Only 83/296 patients had combined treatment plans that allowed for registration of combined doses to organs at risk (OAR). Most of the combined doses to OAR were below recommendations from guidelines. Multivariate analysis showed superior OS (p<0.05) in patients treated with curative intent, SBRT or intensity modulated radiation therapy or had excellent performance status prior to re-RT. CONCLUSIONS: The use of re-RT increased in the second half of the study period, although 2020 did not follow the trend. The use of SBRT and IMRT became more frequent over the years, yet the majority received palliative re-RT. Combined dose plans were only created for one third of the patients.

Can bronchoscopically implanted anchored electromagnetic transponders be used to monitor tumor position and lung inflation during deep inspiration breath-hold lung radiotherapy?

PURPOSE: To evaluate the efficacy of using bronchoscopically implanted anchored electromagnetic transponders (EMTs) as surrogates for 1) tumor position and 2) repeatability of lung inflation during deep-inspiration breath-hold (DIBH) lung radiotherapy. METHODS: Forty-one patients treated with either hypofractionated (HF) or conventional (CF) lung radiotherapy on an IRB-approved prospective protocol using coached DIBH were evaluated for this study. Three anchored EMTs were bronchoscopically implanted into small airways near or within the tumor. DIBH treatment was gated by tracking the EMT positions. Breath-hold cone-beam-CTs (CBCTs) were acquired prior to every HF treatment or weekly for CF patients. Retrospectively, rigid registrations between each CBCT and the breath-hold planning CT were performed to match to 1) spine, 2) EMTs and 3) tumor. Absolute differences in registration between EMTs and spine were analyzed to determine surrogacy of EMTs for lung inflation. Differences in registration between EMTs and the tumor were analyzed to determine surrogacy of EMTs for tumor position. The stability of the EMTs was evaluated by analyzing the difference between inter-EMT displacements recorded at treatment from that of the plan for the CF patients, as well as the geometric residual (GR) recorded at the time of treatment. RESULTS: A total of 219 CBCTs were analyzed. The average differences between EMT centroid and spine registration among all CBCTs were 0.45±0.42 cm, 0.29±0.28 cm, and 0.18±0.15 cm in superior-inferior (SI), anterior-posterior (AP) and lateral directions, respectively. Only 59% of CBCTs had differences in registration < 0.5 cm for EMT centroid compared to spine, indicating that lung inflation is not reproducible from simulation to treatment. The average differences between EMT centroid and tumor registration among all CBCTs were 0.13±0.13 cm, 0.14±0.13 cm and 0.12±0.12 cm in SI, AP and lateral directions, respectively. Ninety-five percent of CBCTs resulted in a < 0.5 cm change between EMT centroid and tumor registration, indicating that EMT positions correspond well with tumor position during treatments. Six out of the seven recorded CF patients had average differences in inter-EMT displacements ≤0.26 cm and average GR ≤0.22 cm, indicating that the EMTs are stable throughout treatment. CONCLUSIONS: Bronchoscopically implanted anchored EMTs are good surrogates for tumor position and are reliable for maintaining tumor position when tracked during DIBH treatment, as long as the tumor size and shape are stable. Large differences in registration between EMTs and spine for many treatments suggest that lung inflation achieved at simulation is often not reproduced.

Measurement reproducibility of magnetic resonance imaging-based finite element analysis of proximal femur microarchitecture for in vivo assessment of bone strength.

INTRODUCTION: Osteoporosis is a disease of weak bone. Our goal was to determine the measurement reproducibility of magnetic resonance assessment of proximal femur strength. METHODS: This study had institutional review board approval, and written informed consent was obtained from all subjects. We obtained images of proximal femur microarchitecture by scanning 12 subjects three times within 1 week at 3T using a high-resolution 3-D FLASH sequence. We applied finite element analysis to compute proximal femur stiffness and femoral neck elastic modulus. RESULTS: Within-day and between-day root-mean-square coefficients of variation and intraclass correlation coefficients ranged from 3.5 to 6.6 % and 0.96 to 0.98, respectively. CONCLUSION: The measurement reproducibility of magnetic resonance assessment of proximal femur strength is suitable for clinical studies of disease progression or treatment response related to osteoporosis bone-strengthening interventions.