Investigation of Intra-fraction Stability and Inter-fraction Consistency of Active Breathing Coordinator (ABC)-Based Deep Inspiration Breath Holds in Left-Sided Breast Cancer.

Background Deep inspiration breath-hold (DIBH) has been established as a standard technique to reduce cardiac dose. The part of the heart exposed to radiation can be significantly decreased using the DIBH technique during tangential left-sided breast cancer (LSBC) irradiation. Aim The objective of this study was to investigate the intra-fraction breath-hold stability and inter-fraction consistency of patient breath-hold against the threshold as a function of air volumes in the setting of active breathing coordinator (ABC)-based DIBH (ABC-DIBH) treatment to LSBC. Methods A total of 34 patients treated with external beam radiation therapy (EBRT) to the left breast using the ABC-DIBH device were included. The frequency of breath-holds per fraction and the entire course of treatment along with the total treatment time was evaluated for all patients. A prescription dose of either 200 cGy (conventional) or 267 cGy (hypofractionation) was administered during 649 fractions, resulting in a total of 4,601 breath-hold measurements being evaluated. The amplitude of deviation in terms of air volumes between the baseline threshold and the patient-specific measurement (during each breath-hold) per fraction was used to define the DIBH stability. Likewise, the consistency of the breathing amplitudes was used to define the compliance of patient breath-holds throughout the entire treatment period. Positional accuracy was evaluated using orthogonal (portal) images. Results The average number of breath-holds measured over the entire course of treatment for each patient was 144 inspirations (58-351). Similarly, the average number of breath-holds for each fraction during the course of treatment was 11 inspirations (7-21), which included setup imaging and treatment. The total number of breath-holds reduced significantly (p-value < 0.05) with hypofractionation (104 inspirations; range 58-170) as compared to conventional fractionation (145 inspirations; 58-351). The average breath-hold threshold in terms of air volume was 1.41 L (0.6-2.1 L) for all patients. The total treatment time reduced significantly after the third fraction (p-value < 0.05). The average deviation between the measured and baseline threshold breath-holds during the course of treatment was 0.5 L/sec (0.12-1.32 L/sec). The consistency of the breathing amplitudes were maintained within ±0.05 L during the entire treatment for all patients. The average translational shifts measured during setup were 0.28 cm ± 0.3 cm, 0.38 cm ± 0.4 cm, and 0.21 cm ± 0.3 cm in the lateral, longitudinal, and vertical directions, respectively. Conclusion The study has demonstrated the variations in intra-fraction breath-hold stability and inter-fraction breath-hold consistency in terms of air volumes for patients who were treated for LSBC. The frequency of breath-holds was observed to be higher with increased total treatment time for the first few fractions and reduced over the course of treatment.

Re-irradiation Using Stereotactic Radiotherapy: A Bibliometric Analysis of Research Trends.

The objective of this research is to conduct a comprehensive bibliometric analysis using the Web of Science Core Collection (WoSCC) to examine the current research topics and trends pertaining to stereotactic-based re-irradiation. A bibliometric search was conducted for re-irradiation-related literature published in English from the WoSCC database from 1991 to 2022, using VOSviewer to visualize the results. The extracted information comprises the publication year, overall citation count, average citation rate, keywords, and research domains. We conducted a literature review to identify trends in research on re-irradiation. A total of 19,891 citations were found in 924 qualifying papers that came from 48 different nations. The number of publications and citations has grown steadily since 2008 with the highest number of publications in the year 2018. Similarly, a substantial increase in the number of citations has increased since 2004 and the citation growth rate has been positive between 2004 and 2019 with a peak in 2013. The top authorship patterns were six authors (111 publications and 2498 citations), whereas the highest number of citations per publication was attained with an authorship pattern of 17 authors (C/P = 41.1). The collaboration patterns analysis showed that the largest proportion of publications emanated from the United States with 363 publications (30.9%), followed by Germany with 102 publications (8.7%), and France with 92 publications (7.8%). The majority of the analyzed studies were focused on the brain (30%), head and neck (13%), lung (12%), and spine (10%) and there have been emerging studies on the use of re-irradiation for lung, prostate, pelvic and liver utilizing stereotactic radiotherapy. The main areas of interest have changed over time and are now based on a multidisciplinary approach that integrates advanced imaging techniques, stereotactic treatment delivery, the toxicity of organs at risk, quality of life, and treatment outcomes.

Effectiveness of Robotic Stereotactic Radiotherapy in Patients Undergoing Re-irradiation: A Review.

Stereotactic ablative radiotherapy (SABR) is a possible treatment option for patients who develop recurrence within or at the edge of a previously irradiated volume. Robotic stereotactic radiotherapy is the result of technological advances in robotic precision, real-time imaging, non-invasive, highly customizable treatment plan, and delivery with sub-millimeter accuracy. This article reviews the radiobiologic, technical, and clinical aspects of robotic-based SABR re-irradiation for various anatomical sites. An extensive literature search was performed to identify articles on the utilization of robotic stereotactic radiotherapy for patients undergoing re-irradiation. The reported prescription dose and fractionation data along with outcomes such as overall survival, local control rates, and toxicities were qualitatively reviewed. The findings consistently indicate that re-irradiation using robotic SABR provides encouraging survival rates with minimal toxicity in the clinical setting of various anatomical sites delivered using locally non-invasive means where other treatment options are scarce.

Sector analysis provides additional spatial information on the permanent prostate brachytherapy learning curve.

PURPOSE: To evaluate the permanent prostate brachytherapy (PPB) learning curve using postimplant multisector dosimetric analysis and to assess the correlation between sector -specific dosimetry and patient-reported outcome measures (PROMs). METHODS AND METHODS: First 200 patients treated with (125)I PPB monotherapy (145 Gy) at a single institution were assessed. Postimplant dosimetry (PID) using CT was evaluated for whole prostate (global) and 12 sectors, assessing minimum dose to 90% of prostate (D90) and dose to 0.1 cm(3) of rectum (D0.1cc). Global and sector PID results were evaluated to investigate changes in D90 with case number. Urinary and bowel PROMs were assessed using the International Prostate Symptom Score and the Expanded Prostate Cancer Index Composite questionnaire. The correlation between global and individual sector PID and urinary/bowel PROMs was also evaluated. RESULTS: Linear regression confirmed a significant improvement in global D90 with case number (r(2) = 0.20; p = 0.001) at a rate of 0.11 Gy/case. Postimplant D90 of base sectors increased at a rate of 0.11-0.15 Gy/case (p = 0.0001) and matched global improvement. The regression lines of midgland and apex sectors were significantly different from global D90 (p = 0.01). Posterior midgland sectors showed a significant reduction in D90 with case number at a rate of 0.13-0.19 Gy/case (p = 0.01). Dose to posterior midgland sectors correlated with rectal D0.1cc dose but not bowel PROMs. Dose to posterior midgland sectors correlated with urinary International Prostate Symptom Score change, which was not apparent when global D90 alone was considered. CONCLUSIONS: Sector analysis provided increased spatial information regarding the PPB learning curve. Furthermore, sector analysis correlated with urinary PROMs and rectal dose.

Sector analysis of 125I permanent prostate brachytherapy provides a rapid and effective method of evaluating and comparing pre- and post-implant dosimetry.

PURPOSE: To evaluate a sector analysis program in the assessment and comparison of pre- and post-implant dosimetric parameters during the development of an (125)I permanent prostate brachytherapy service. METHODS AND MATERIALS: A total of 50 consecutive men being treated with permanent prostate brachytherapy had dose-volume analysis in 12 sectors of their pre-implant ultrasound (USpre) and post-implant CT (CTpost) studies. Individual sectors were created by dividing prostate into three equal lengths, namely base, midgland, and apex. Each of these volumes was then divided into four axial sectors. Dosimetric parameters were compared in adjoining sectors within each study and between studies. RESULTS: There were statistically significant differences between individual sectors on USpre and CTpost volumes with CTpost higher than USpre (p=0.001). Statistically significant differences were found in corresponding sectors on USpre and CTpost for all dosimetric parameters. The dosimetric parameters were significantly lower on CTpost in the anterior base and midgland (p=0.001) and significantly higher at the posterior apex and midgland (p=0.05). Dose homogeneity was demonstrated in adjoining sectors in all USpre and most adjoining sectors on CTpost. CONCLUSIONS: Sector analysis allows rapid assessment of USpre and CTpost dosimetry. It offers a scientific method of identifying areas of increased and reduced dosing on CTpost when compared with USpre, providing a learning tool to refine dosimetric analysis and highlight sectors where implant quality could be improved.