MRI-guided stereotactic radiotherapy superior to CT in prostate cancer

20th January 2023

MRI guided stereotactic radiotherapy is superior than that provided via CT guidance with respect to adverse effects for men with prostate cancer.

A randomised trial by Californian researchers has shown that magnetic resonance imaging (MRI)-guided stereotactic body radiation, significantly reduced grade 2 or higher acute physician-scored genitourinary and gastrointestinal toxic effects as well as patient self-reported prostate cancer symptom scores, compared to computed tomography (CT)-guided radiotherapy.

Stereotactic radiotherapy delivers treatment with high precision from a number of different angles around the body and is designed to reduce adverse effects on the tissue surrounding a tumour. Furthermore, results from several trials, indicate that this approach does not increase gastrointestinal or genitourinary acute toxicity.

While stereotactic radiotherapy has traditionally been delivered using linear accelerators and guided by computed tomography (CT) imaging, MRI-guided adaptive radiotherapy is seen as an emerging and alternative approach.

Moreover, it may also be possible using MRI to reduce the radiotherapy planning target volume (PTV) which encompasses the clinical target volume to account for possible uncertainties in beam alignment, patient positioning, organ motion, and organ deformation.

In the present study, the US researchers undertook a phase 3 study, with a view to demonstrating a reduced PTV with MRI compared to CT guidance, following stereotactic body radiotherapy for men with localised prostate cancer. Eligible men were randomised 1:1 to either MRI- or CT-guided stereotactic radiotherapy although neither the treating physician or patient were blinded to the treatment allocation.

The primary outcome was set as the incidence of acute (defined by occurring less than 90 days after stereotactic therapy) grade 2 or higher genitourinary (GU) toxic effects, whereas secondary outcomes included gastrointestinal toxic effects.

Other measures assessed included changes in the international prostate symptom score (IPSS) and for which increases of 15 points or more are considered to be clinically relevant.

MRI-guided stereotactic therapy and GU toxicity

A total of 156 men with a mean age of 71 years were randomised to the MRI arm (77) or the CT arm.

The proportion of GU toxic effects of grade 2 or higher was significantly lower among those receiving MRI-guided stereotactic therapy (24.4% vs 43.4%, p = 0.01). There were no reported gastrointestinal toxic effects at grade 2 or higher compared to 10.5% in the CT-guided group (p = 0.003).

The researchers also observed a significantly lower proportion of men with an IPSS score increase of 15 points or more after 4 weeks (6.8% vs 19.4%, p = 0.01).

The authors concluded that MRI-guided stereotactic radiotherapy reduced physician-reported toxic GU and gastrointestinal adverse effects than CT-guided stereotactic radiotherapy and called for future studies to examine the sustainability of these benefits.

Citation
Kishan AU et al. Magnetic Resonance Imaging-Guided vs Computed Tomography-Guided Stereotactic Body Radiotherapy for Prostate Cancer: The MIRAGE Randomized Clinical Trial. JAMA Oncol 2023

CT chest scans reveal fewer cases of pneumonia in breakthrough COVID-19 infections

30th May 2022

CT chest scans in patients with breakthrough COVID-19 infections show lower levels of pneumonia compared to scans of unvaccinated patients

A significantly higher proportion of CT chest scans in fully vaccinated patients who experience a breakthrough infection showed no signs of pneumonia during their stay in hospital, according to a study by Korean researchers.

COVID-19 vaccination across the globe has led to a protection against both symptomatic and asymptomatic COVID-19 as well as severe disease, hospitalisation and death. Although a CT chest scan has been described as an indispensable diagnostic tool in COVID-19, no studies have reported on using this imaging modality to examine the features associated with breakthrough infections that are generally less severe.

In the present study, the Korean team compared the imaging features of fully, partially and unvaccinated patients, who were hospitalised because of a COVID-19 infection. The team focused only on patients with a PCR-confirmed positive COVID-19 test result and who underwent at least one CT chest scan during their period of hospitalisation.

Partially vaccinated individuals were defined as those for which the infection occurred less than 14 days after their first COVID-19 vaccine. In contrast, fully vaccinated individuals were those who became infected 14 days after their second vaccine dose.

Using a retrospective design, the team collected demographic and co-morbidity data for all patients, as well as whether an individual required supplemental oxygen, was admitted to an intensive care unit (ICU) admission or died in hospital. The CT chest scans were obtained either upon admission or within a week of symptom onset and follow-up chest radiographs were obtained every two to three days until discharge.

The extent of pneumonia was scored from 0 to 2 (i.e., 0 = no evidence, 1 = 1 – 25% involvement and 2 = > 25% involvement) and the patterns of pneumonia were categorised as either typical, indeterminate, atypical or negative. The researchers used logistic regression to evaluate any associations between clinical factors such as vaccination status and clinical outcomes.

CT chest scan and clinical outcomes

A total of 761 patients with a mean age of 47 years (51% women) were included, of whom, 77% were unvaccinated, 17% partially vaccinated and 6% fully vaccinated. Relevant co-morbidities for the whole cohort included hypertension (22%), diabetes (13%) and cardiovascular disease (5%).

All 761 patients underwent a CT chest scan at admission and 86% had at least one follow-up scan. During the initial scan, 63% of unvaccinated individuals had negative chest radiographs (i.e., a score of 0) whereas 75% of fully vaccinated patients were negative.

In 412 patients who underwent a CT chest scan during their stay in hospital, there was no evidence of pneumonia in 59% of those who were fully vaccinated compared to 22% of those who were unvaccinated (p < 0.01).

Fully vaccinated patients were also significantly less likely to need supplemental oxygen (Odds ratio, OR = 0.24, 95% CI 0.09 – 0.64, p = 0.05) compared to unvaccinated patients and to be admitted to an ICU (OR = 0.08, 95% CI 0.09 – 0.78, p = 0.02).

The authors concluded that fully vaccinated individuals who experienced a breakthrough COVID-19 infection had a higher proportion of CT chest scans without signs of pneumonia compared with unvaccinated individuals.

Citation
Lee JE et al. Imaging and Clinical Features of COVID-19 Breakthrough Infections: A Multicenter Study Radiology 2022

Dark field X-ray detects emphysema in patients with COPD

15th November 2021

Dark field x-ray has been found to detect structural changes in the lungs of patients with COPD that are associated with emphysema.

Using dark field x-ray, a team from the Department of Physics, Munich School of BioEngineering, Germany, were able to diagnosis emphysema in patients with COPD which to date has not been possible with conventional x-ray methods. Emphysema is caused by the irreversible destruction of alveolar walls, leading to enlargement of distal airspaces. Although this leads to changes in the lung structure, it is not possible to detect the early stages of emphysema with a conventional chest x-ray. As x-rays are subject to other effects such as refraction and ultra small-angle scattering which are not visualised with a conventional X-ray imaging system, in DFX, the contrast is produced by these multiple refractions on microstructures in the object. Hence, the dark-field signal enables visualisation of structural information that is inaccessible with conventional medical x-ray systems and dark field imaging has, for example, enabled the identification of acute lung inflammation in animal models.

With the potential to identify changes at the micro-structural level with dark field x-ray, indicative of emphysema, the German team undertook their study to examine whether this approach could improve the medical lung assessment in patients with COPD. Included patients were those with an initial indication of emphysema as revealed by a CT scan but still absent based on spirometry readings. However, a small number of patients with moderate to severe emphysema were also included. COPD classification was based on the post forced expiratory volume in one second (FEV1) and the forced vital capacity (FVC) as proposed by GOLD classification and patients with a FEV1/FVC value of 0.70 were assessed as having no COPD. Dark field x-rays were performed and visually assessed by five readers.

Findings

A total of 77 patients with a mean age of 65.9 years (male) and 63.3 years (female) were recruited with the majority (83%) at GOLD stage 0. Focusing on the first patient examined, the researchers described how the DFX showed that most parts of the lung yielded dark field values comparable with a healthy lung. A group of 42 patients from the cohort underwent diffusion capacity testing and it was found that the dark field signal gave a strong correlation than with either the CT emphysema index or the visual emphysema grading based on the CT-images.

Commenting on their findings, the authors reported that “in direct comparison, dark-field images and visual evaluation of CT images yield consistent findings regarding emphysema diagnosis.” They also added that the visual features seen with the dark field appeared to provide a greater diagnostic value than conventional emphysema charactering parameters. Moreover, while noting that there are currently no commercially available dark field systems available, their study has shown how the system does not require specialist knowledge and that it is operationally comparable to conventional radiography systems.

In their conclusion, they noted how DRX could offer a low radiation alternative to CT in patients with COPD adding that “x-ray dark-field chest imaging could contribute to improving the detection, diagnosis, and thus treatment and care of pulmonary disorders.”

Citation

Willer K et al. X-ray dark-field chest imaging for detection and quantification of emphysema in patients with chronic obstructive pulmonary disease: a diagnostic accuracy study. Lancet Digit Health 2021