Whole brain radiotherapy (WBRT) is the standard of care to improve intracranial control following resection of brain metastasis. However, stereotactic radiosurgery (SRS) to the surgical cavity is ...widely used in an attempt to reduce cognitive toxicity, despite the absence of high-level comparative data substantiating efficacy in the postoperative setting. We aimed to establish the effect of SRS on survival and cognitive outcomes compared with WBRT in patients with resected brain metastasis.
In this randomised, controlled, phase 3 trial, adult patients (aged 18 years or older) from 48 institutions in the USA and Canada with one resected brain metastasis and a resection cavity less than 5·0 cm in maximal extent were randomly assigned (1:1) to either postoperative SRS (12–20 Gy single fraction with dose determined by surgical cavity volume) or WBRT (30 Gy in ten daily fractions or 37·5 Gy in 15 daily fractions of 2·5 Gy; fractionation schedule predetermined for all patients at treating centre). We randomised patients using a dynamic allocation strategy with stratification factors of age, duration of extracranial disease control, number of brain metastases, histology, maximal resection cavity diameter, and treatment centre. Patients and investigators were not masked to treatment allocation. The co-primary endpoints were cognitive-deterioration-free survival and overall survival, and analyses were done by intention to treat. We report the final analysis. This trial is registered with ClinicalTrials.gov, number NCT01372774.
Between Nov 10, 2011, and Nov 16, 2015, 194 patients were enrolled and randomly assigned to SRS (98 patients) or WBRT (96 patients). Median follow-up was 11·1 months (IQR 5·1–18·0). Cognitive-deterioration-free survival was longer in patients assigned to SRS (median 3·7 months 95% CI 3·45–5·06, 93 events) than in patients assigned to WBRT (median 3·0 months 2·86–3·25, 93 events; hazard ratio HR 0·47 95% CI 0·35–0·63; p<0·0001), and cognitive deterioration at 6 months was less frequent in patients who received SRS than those who received WBRT (28 52% of 54 evaluable patients assigned to SRS vs 41 85% of 48 evaluable patients assigned to WBRT; difference −33·6% 95% CI −45·3 to −21·8, p<0·00031). Median overall survival was 12·2 months (95% CI 9·7–16·0, 69 deaths) for SRS and 11·6 months (9·9–18·0, 67 deaths) for WBRT (HR 1·07 95% CI 0·76–1·50; p=0·70). The most common grade 3 or 4 adverse events reported with a relative frequency greater than 4% were hearing impairment (three 3% of 93 patients in the SRS group vs eight 9% of 92 patients in the WBRT group) and cognitive disturbance (three 3% vs five 5%). There were no treatment-related deaths.
Decline in cognitive function was more frequent with WBRT than with SRS and there was no difference in overall survival between the treatment groups. After resection of a brain metastasis, SRS radiosurgery should be considered one of the standards of care as a less toxic alternative to WBRT for this patient population.
National Cancer Institute.
We present the first study to investigate Large Language Models (LLMs) in answering radiation oncology physics questions. Because popular exams like AP Physics, LSAT, and GRE have large test-taker ...populations and ample test preparation resources in circulation, they may not allow for accurately assessing the true potential of LLMs. This paper proposes evaluating LLMs on a highly-specialized topic, radiation oncology physics, which may be more pertinent to scientific and medical communities in addition to being a valuable benchmark of LLMs.
We developed an exam consisting of 100 radiation oncology physics questions based on our expertise. Four LLMs, ChatGPT (GPT-3.5), ChatGPT (GPT-4), Bard (LaMDA), and BLOOMZ, were evaluated against medical physicists and non-experts. The performance of ChatGPT (GPT-4) was further explored by being asked to explain first, then answer. The deductive reasoning capability of ChatGPT (GPT-4) was evaluated using a novel approach (substituting the correct answer with "None of the above choices is the correct answer."). A majority vote analysis was used to approximate how well each group could score when working together.
ChatGPT GPT-4 outperformed all other LLMs and medical physicists, on average, with improved accuracy when prompted to explain before answering. ChatGPT (GPT-3.5 and GPT-4) showed a high level of consistency in its answer choices across a number of trials, whether correct or incorrect, a characteristic that was not observed in the human test groups or Bard (LaMDA). In evaluating deductive reasoning ability, ChatGPT (GPT-4) demonstrated surprising accuracy, suggesting the potential presence of an emergent ability. Finally, although ChatGPT (GPT-4) performed well overall, its intrinsic properties did not allow for further improvement when scoring based on a majority vote across trials. In contrast, a team of medical physicists were able to greatly outperform ChatGPT (GPT-4) using a majority vote.
This study suggests a great potential for LLMs to work alongside radiation oncology experts as highly knowledgeable assistants.
Background
Mechanical accuracy should be verified before implementing a proton stereotactic radiosurgery (SRS) program. Linear accelerator (Linac)‐based SRS systems often use electronic portal ...imaging devices (EPIDs) to verify beam isocentricity. Because proton therapy systems do not have EPID, beam isocentricity tests of proton SRS may still rely on films, which are not efficient.
Purpose
To validate that our proton SRS system meets mechanical precision requirements and to present an efficient method to evaluate the couch and gantry's rotational isocentricity for our proton SRS system.
Methods
A dedicated applicator to hold brass aperture for proton SRS system was designed. The mechanical precision of the system was tested using a metal ball and film for 11 combinations of gantry and couch angles. A more efficient quality assurance (QA) procedure was developed, which used a scintillator device to replace the film. The couch rotational isocentricity tests were performed using orthogonal kV x‐rays with the couch rotated isocentrically to five positions (0°, 315°, 270°, 225°, and 180°). At each couch position, the distance between the metal ball in kV images and the imaging isocenter was measured. The gantry isocentricity tests were performed using a cone‐shaped scintillator and proton beams at five gantry angles (0°, 45°, 90°, 135°, and 180°), and the isocenter position and the distance of each beam path to the isocenter were obtained. Daily QA procedure was performed for 1 month to test the robustness and reproducibility of the procedure.
Results
The gantry and couch rotational isocentricity exhibited sub‐mm precision, with most measurements within ±0.5 mm. The 1‐month QA results showed that the procedure was robust and highly reproducible to within ±0.2 mm. The gantry isocentricity test using the cone‐shaped scintillator was accurate and sensitive to variations of ±0.2 mm. The QA procedure was efficient enough to be completed within 30 min. The 1‐month isocentricity position variations were within 0.5 mm, which demonstrating that the overall proton SRS system was stable and precise.
Conclusion
The proton SRS Winston–Lutz QA procedure using a cone‐shaped scintillator was efficient and robust. We were able to verify radiation delivery could be performed with sub‐mm mechanical precision.
We have previously shown that intensity-modulated radiotherapy (IMRT) can reduce dose to small bowel, bladder, and bone marrow compared with three-field conventional radiotherapy (CRT) technique in ...the treatment of rectal cancer. The purpose of this study was to review our experience using IMRT to treat rectal cancer and report patient clinical outcomes.
A retrospective review was conducted of patients with rectal cancer who were treated at Mayo Clinic Arizona with pelvic radiotherapy (RT). Data regarding patient and tumor characteristics, treatment, acute toxicity according to the Common Terminology Criteria for Adverse Events v 3.0, tumor response, and perioperative morbidity were collected.
From 2004 to August 2009, 92 consecutive patients were treated. Sixty-one (66%) patients were treated with CRT, and 31 (34%) patients were treated with IMRT. All but 2 patients received concurrent chemotherapy. There was no significant difference in median dose (50.4 Gy, CRT; 50 Gy, IMRT), preoperative vs. postoperative treatment, type of concurrent chemotherapy, or history of previous pelvic RT between the CRT and IMRT patient groups. Patients who received IMRT had significantly less gastrointestinal (GI) toxicity. Sixty-two percent of patients undergoing CRT experienced ≥Grade 2 acute GI side effects, compared with 32% among IMRT patients (p = 0.006). The reduction in overall GI toxicity was attributable to fewer symptoms from the lower GI tract. Among CRT patients, ≥Grade 2 diarrhea and enteritis was experienced among 48% and 30% of patients, respectively, compared with 23% (p = 0.02) and 10% (p = 0.015) among IMRT patients. There was no significant difference in hematologic or genitourinary acute toxicity between groups. In addition, pathologic complete response rates and postoperative morbidity between treatment groups did not differ significantly.
In the management of rectal cancer, IMRT is associated with a clinically significant reduction in lower GI toxicity compared with CRT. Further study is needed to evaluate differences in late toxicity and long-term efficacy.
Carbon-fiber-reinforced polyetheretherketone (CFR-PEEK) orthopedic implants are gaining popularity in oncologic applications as they offer many potential advantages over traditional metallic ...implants. From an imaging perspective, this instrumentation allows for improved evaluation of adjacent anatomic structures during radiography, computed tomography (CT), and magnetic resonance imaging (MRI). This results in improved postoperative surveillance imaging quality as well as easier visualization of anatomy for potential image-guided percutaneous interventions (e.g., pain palliation injections, or ablative procedures for local disease control). CFR-PEEK devices are also advantageous in radiation oncology treatment due to their decreased imaging artifact during treatment planning imaging and decreased dose perturbation during radiotherapy delivery. As manufacturing processes for CFR-PEEK materials continue to evolve and improve, potential orthopedic applications in the spine and appendicular skeleton increase. An understanding of the unique properties of CFR-PEEK devices and their impact on imaging is valuable to radiologists delivering care to orthopedic oncology patients in both the diagnostic and interventional settings. This multidisciplinary review aims to provide a comprehensive insight into the radiologic, surgical, and radiation oncology impact of these innovative devices.
Purpose
To compare the dosimetric performances of small‐spot three‐dimensional (3D) and four‐dimensional (4D) robustly optimized intensity‐modulated proton (IMPT) plans in the presence of ...uncertainties and interplay effect simultaneously for distal esophageal carcinoma.
Method and Materials
Thirteen (13) patients were selected and re‐planned with small‐spot (σ ~ 2–6 mm) 3D and 4D robust optimization in IMPT, respectively. The internal clinical target volumes (CTVhigh3d, CTVlow3d) were used in 3D robust optimization. Different CTVs (CTVhigh4d, CTVlow4d) were generated by subtracting an inner margin of the motion amplitudes in three cardinal directions from the internal CTVs and used in 4D robust optimization. All patients were prescribed the same dose to CTVs (50 GyRBE for CTVhigh3d/CTVhigh4d and 45 GyRBE for CTVlow3d/CTVlow4d). Dose–volume histogram (DVH) indices were calculated to assess plan quality. Comprehensive plan robustness evaluations that consisted of 300 perturbed scenarios (10 different motion patterns to consider irregular motion (sampled from a Gaussian distribution) and 30 different uncertainties scenarios (sampled from a 4D uniform distribution) combined), were performed to quantify robustness to uncertainties and interplay effect simultaneously. Wilcoxon signed‐rank test was used for statistical analysis.
Results
Compared to 3D robustly optimized plans, 4D robustly optimized plans had statistically improved target coverage and better sparing of lungs and heart (heart Dmean, P = 0.001; heart V30GyRBE, P = 0.001) in the nominal scenario. 4D robustly optimized plans had better robustness in target dose coverage (CTVhigh4d V100%, P = 0.002) and the protection of lungs and heart (heart Dmean, P = 0.001; heart V30GyRBE, P = 0.001) when uncertainties and interplay effect were considered simultaneously.
Conclusions
Even with small spots in IMPT, 4D robust optimization outperformed 3D robust optimization in terms of normal tissue protection and robustness to uncertainties and interplay effect simultaneously. Our findings support the use of 4D robust optimization to treat distal esophageal carcinoma with small spots in IMPT.
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