August 20, 2010
Headlines in the News:
Radiology: Ultrasound then CT Angiography Cost-effective for Stroke Patients with Stenosis
Sonography Better to Monitor Small Testicular Lesions
New Procedure Shows Promise for Treating Brain Tumors
Limitations to Ultrasound in the Detection and Measurement of Urinary Tract Calculi
Wide Geographic Variation Seen in Stroke-Prevention Procedure
Radiology: Ultrasound then CT Angiography Cost-Effective for Stroke Patients with Stenosis
Patients with a transient ischemic attack (TIA) orminor stroke with suspected carotid artery stenosis (CAS) should undergo duplex ultrasound and then CT angiography (CTA) after positive results as the most effective and cost-effective imaging protocol, according to a study published in this month's Radiology. Immediate CTA and surgery for 50 to 99 percent stenosis is indicated for patients with a high-risk profile, a high CAS probability or those who can proceed to surgery without delay, added the authors.
CAS in 70 percent or more causes 10 to 30 percent of TIAs, and detection is critical to reducing the probability of a recurrent stroke, wrote Aletta T.R. Tholen of Erasmus
University Medical Center in Rotterdam, the Netherlands, and colleagues. Although carotid endarterectomy reduces the risk of ipsilateral ischemic stroke, benefits from surgery decrease with delay between symptom onset and surgery, explained Tholen.
The researchers sought to assess the effectiveness and cost-effectiveness of state-of-the-art noninvasive imaging modalities including CTA alone and compared to duplex ultrasound and MR angiography using a decision model to evaluate and compare various diagnostic strategies. They also developed a Markov model with a one-year cycle length to extrapolate and evaluate long-term outcomes and subsequent treatment. Researchers paid particular attention to the time window between first symptoms and carotid endarterectomy and the
cut-off value chosen as surgical indication (70 to 99 percent versus 50 to 99 percent stenosis).
Researchers included 194 male and 139 female patients who presented with TIA or minor stroke at Erasmus between November 2002 and January 2005 in the study. The average age was 62 for males and 61 for females, and age range was 19 to 90 years. All patients underwent duplex US and CTA of the carotid arteries. If either exam showed a stenosis of
50 to 99 percent the patient was referred for digital subtraction angiography.
Researchers reported the sensitivity and specificity of CTA at a cutoff point of 70-99 percent stenosis were 0.91 and 0.99, respectively, and 1.00 and 0.98, respectively, at a cut-off point of 50 to 99 percent stenosis.
Researchers assessed the diagnostic performances of US and contrast-enhanced MR angiography using eight meta-analysis that included 41 studies published between January 1987 and April 2004. The sensitivity and specificity of duplex US were 0.89 and 0.84, respectively, at a cutoff point of 70 to 99 percent stenosis and 0.84 and 0.83, respectively, at a cutoff point of 50 to 99 percent stenosis. MR angiography provided sensitivity and specificity of 0.94 and 0.93, respectively, at a cutoff point of 70-99 percent stenosis and 0.96 and 0.96 at a cutoff point of 50-99 percent stenosis.
Researchers also compared diagnostic strategies in terms of costs, effects (in quality-adjusted life-years [QALYs]), incremental cost-effectiveness ratios and net health benefits by using a willingness-to-pay of €50,000 ($66,018) per QALY.
“All strategies that used CT angiography or contrast-enhanced MR angiography, either as a solo strategy or in combination with an initial duplex US exam, demonstrated similar costs and effectiveness, presuming a two to four week delay in surgery,” wrote the authors. Assuming a €50,000 QALY, the duplex US/CTA combination strategy yielded the highest net health benefits in both men and women, continued the authors. Surgical timing affected net health benefits of treatment strategies.
They also found that the duplex US as a solo test was the least cost-effective strategy, which conflicts with earlier studies.
“The results demonstrated that the duplex US/CT angiography strategy with a cutoff of 70-99 percent stenosis is the most cost-effective strategy,” concluded the authors. An increase in the patient risk profile, higher disease probability or possibility of surgery without delay results in more lenient surgical criterion at 50-99 stenosis with solo CT as the preferred strategy.
“Implementing the results of this study should always be done with consideration of the individual patient and the local situation,” concluded the authors. Prior probability of CAS and the risk profile may affect the diagnostic strategy.
View the article online
Article written by staff at cardiovascularbusiness.com and adapted for the purposes of this newsletter.
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Sonography Better to Monitor Small Testicular Lesions
There is a lack of scientific evidence about the risk of testicular cancer associated with testicular lesions, but the conventional treatment approach has been immediate surgical removal because of the possibility of malignancy. A more conservative approach has served one Canadian institution well when it comes to active surveillance of small, incidentally discovered testicular masses.
For nearly a decade, ultrasound (US) surveillance has been offered to men as an alternative to surgical treatment at the University of Toronto, and, thus far, the approach has spared many patients from unnecessary surgery.
The majority of the men present at the Mount Sinai Hospital Fertility Clinic for a fertility evaluation. During these tests, nonpalpable testicular masses less than 1 cm have been detected incidentally.
Paul J. Toren, MD, and colleagues reviewed their experience using an ultrasound surveillance strategy between 2001 and 2008. Their series of patients is the largest to date to demonstrate the benign nature of most small, nonpalpable, incidental testicular masses, Dr. Toren said.
The series included 45 men who had one or more hypoechoic, nonpalpable intratesticular masses less than 1 cm in diameter. Infertility was the reason for referral in 39 men. On serum analysis, 16 subjects showed evidence of azoospermia, 16 men had oligospermia, and seven had normospermia. Semen analysis was not available in six men.
The mean follow-up in the study from the first to the last ultrasound was 253 days. Patients were also examined by a urologist before or after the ultrasound examination to confirm there were no palpable lesions.
Thirty-eight patients had serial ultrasound surveillance only, with a mean yearly lesional growth of 0.5 mm. Overall, eight patients underwent surgery. Three had immediate surgery and five underwent surgery after a period of initial ultrasound surveillance. Surgery was indicated in two patients because of interval growth; in the other six, the decision for surgery was made by the patient.
Only one patient had radical orchiectomy for pure seminoma following an interval growth from 3 mm to 6 mm at ultrasound at three months. He has had no recurrent disease to date, Dr. Toren reported. The other seven masses excised by partial orchiectomy were benign (2010 American Urological Association abstract 1928).
The authors concluded that most small, incidental, nonpalpable testicular masses could be safely followed with serial ultrasound and did not show significant growth requiring surgery.
"Our findings support a conservative approach involving active surveillance with ultrasound monitoring in men who have an incidental finding of a small testicular mass on ultrasound," said Dr. Toren, a urology resident.
While his group does not have formal data on the appropriate time for follow-up, the men initially seen at the fertility clinic are routinely followed with repeat serial ultrasound for at least six months.
He recommended that most men with a small nonpalpable lesion on their initial testicular ultrasound have a second ultrasound one month later and then again every three months for at least six months. Surgery should be limited to men whose lesional growth points to a malignancy and men with positive tumor markers, Dr. Toren said.
View the article online
Article written by staff at cancernetwork.com and adapted for the purposes of this newsletter.
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New Procedure Shows Promise for Treating Brain Tumors
In a study on rats, researchers use magnets, ultrasound and tiny particles to deliver chemotherapy drugs to precise locations. Clinical trials on humans are at least four to five years away.
Patients with brain tumors don't have many good options — surgery and radiation can damage crucial parts of the brain, and chemotherapy drugs don't easily cross the blood-brain barrier. A new procedure using magnets, ultrasound and minuscule drug-coated particles may be an effective solution, according to a study on rats published in Tuesday's edition of the journal Proceedings of the National Academy of Sciences.
The researchers, led by Dr. Kuo-Chen Wei of Chang Gung University in Taiwan, injected tiny magnetic beads called nanoparticles, coated with a chemotherapy drug, into the rats' tails. They used ultrasound to open up a small region of the blood-brain barrier and a magnetic field to attract the particles to a precise location in the brain.
When they applied the treatment to rats with brain tumors, the tumor growth was slowed and the rats lived two-thirds longer than untreated rats. "The technology's not very difficult," Wei said, "but the idea is novel." Clinical trials in human beings are at least four to five years away, he added.
Brain tumors are difficult to treat with traditional drug delivery methods because the brain is insulated from circulating blood. Focused ultrasound — similar to, but much stronger than, the ultrasound technique used on pregnant women — temporarily disrupts the barrier, allowing drugs to enter.
Once the drugs get into the brain, they should ideally be delivered to a precise location to cut down on the damage to healthy tissue. This report is the first in which magnetic targeting was combined with ultrasound to attract the nanoparticles — and their drug passengers — to a specific part of the brain.
"The method has significant clinical potential," said Dr. Kullervo Hynynen of the University of Toronto Medical School, who conducts similar research but was not involved in the new study.
Wei and his team are working to improve the treatment so they can apply it to human patients. He said they needed to try additional chemotherapy drugs and nanoparticle types, as well as improve the ultrasound and magnetic-targeting technology.
Still, some scientists worry that opening the blood-brain barrier to allow powerful chemicals into the brain is too dangerous.
"The potential for toxicity in normal brain regions could cause all kinds of problems," said Allan David, a drug delivery researcher at the University of Michigan. "I think it's an interesting study, but it's still far from clinical studies."
Some of the danger of opening the blood-brain barrier may be avoided by combining Wei's approach with a type of drug that is activated only upon reaching the tumor, David said, so that healthy brain tissue is left unharmed.
View the article online
Article written by staff at latimes.com and adapted for the purposes of this newsletter.
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Limitations to Ultrasound in the Detection and Measurement of Urinary Tract Calculi
Urinary tract stones are commonly diagnosed and followed by ultrasound (US). Our study highlights several important limitations to the test that should be recognized by the clinician. First, compared with axial unenhanced CT, stone size tends to be overestimated, particularly when up to 10mm. This finding illustrates the danger of using US as the sole diagnostic test when planning treatment. In this setting, surgical intervention could be planned when a more conservative management strategy may be warranted. In part, this effect may be due to the operator-dependent nature of the test and the difficulty in defining the interface between the stone and kidney. Ultrasound measurements should be conducted in a minimum of two orthogonal planes and the maximal length reported. Interestingly, we also found that there was a direct correlation between over-estimation of stone size and distance of the stone from the US transducer. To date, this "lensing" effect has not adequately been explained.
Second, compared to unenhanced CT, we found that US has both poor sensitivity and specificity for detecting stones in the ureter and kidney. In a meta-analysis of all published studies, we found that the sensitivity of US when detecting stones among patients presenting to the emergency department with renal colic was approximately 45% and the specificity approximately 90%. Given these findings, the utility of a negative study should be questioned and US should be considered to be of limited value in the work-up of urolithiasis. Even when stones are detected, with these findings, it is reasonable to question whether the clinician has a complete knowledge of the patient's true stone burden.
It is not our intention to eliminate the use of US entirely. Instead, US should be limited to the routine follow-up of radiolucent calculi as well as a first-line investigative tool for pediatric and pregnant patients with suspected urolithiasis in whom radiation exposure is undesirable. US may also be of benefit in the evaluation of hydronephrosis and should be considered in patients at risk of repetitive CT scans.
Solitary stone present in the mid pole of the left kidney. The maximal CT measurement was 4.0mm, and the maximal US measurement was 7.3mm.
View the article online
Article written by staff at medicalnewstoday.com and adapted for the purposes of this newsletter.
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Wide Geographic Variation Seen in Stroke-Prevention Procedure
Wide geographic variation was found in two procedures to prevent stroke from diseased carotid arteries, according to a government report.
In a study published last week and commissioned by the Agency for Healthcare Research and Quality (AHRQ), researchers examined all claims filed for Medicare beneficiaries who underwent the procedures, carotid endarterectomy and carotid stenting, between 2003 and 2006. 
In carotid endarterectomy, doctors surgically remove plaque from diseased carotid arteries, the blood vessels that carry blood to the brain. Stenting involves inserting a wire mesh into the arteries to keep the blood flowing, and is used in patients deemed unfit for the other procedure, the report said. Stenting was approved by Medicare, only for high-risk patients, in 2004.
In the report, widespread regional variation with the procedures was found, with parts of the South and Midwest having the highest rates.
"The New England, Mountain, and Pacific regions tended to have the lowest rates of both procedures, whereas the East South Central, West South Central, East North Central, and West North Central regions tended to have higher rates of revascularization," said the report, led by Dr. Manesh R. Patel and based on Duke University research.
According to the report, there was nearly a sevenfold difference in carotid endarterectomy rates in the most recent years studied, 2005 and 2006, between the lowest rate and highest rate regions. Beaumont, Texas, with 5.5 per 1,000 person-years, was the highest, and Honolulu, Hawaii, with 0.8 per 1,000 person-years, was the lowest.
Variation also applied to the diagnostic imaging modality chosen by doctors to help diagnose blocked carotid arteries.
Prior to carotid endarterectomies, most patients, about one-third, had the procedure preceded by ultrasound and x-ray angiography, while 27 percent had ultrasound and magnetic resonance angiography.
Controversially, another 27 percent had the procedure done based on ultrasound alone. For stenting, about 10 percent had only ultrasound, the report said.
Relying only on ultrasound scans is tricky, the report said, as previous research has suggested it can misclassify up to 28 percent of patients.
Nonetheless, a recent survey of Canadian surgeons found one out of ten neurosurgeons, and about half of vascular surgeons, said ultrasound alone was sufficient for diagnosis.
"Our findings highlight the need for consensus regarding diagnostic imaging criteria for the identification and management of carotid artery disease," the authors wrote.
Other findings
Endarterectomy rates fell from 3.2 per 1,000 person-years in 2003 to 2.6 per 1,000 person-years in 2006, while stenting rates rose about a tenth of a percent, from 0.3 in 2005 to 0.4 in 2006. Previously the estimated rate of carotid stenting, in 2003 and 2004 before Medicare coverage began, was 0.3 per 1,000, the report said.
"The similarly low rate of carotid stenting we observed is likely related to the fact that the CMS national coverage decision for carotid stenting was limited to patients at high surgical risk," the authors wrote.
Unsurprisingly, prior diagnosis of diseased arteries and having previous procedures increased the likelihood of getting treatment, the study found. More than two-thirds of those getting endarterectomy had a prior diagnosis of coronary artery disease, while 37 percent had peripheral vascular disease. About half had cerebrovascular disease. For stenting, two-thirds had a prior diagnosis of coronary artery disease; nearly half had a prior diagnosis of peripheral vascular disease, and 61 percent had cerebrovascualr disease. They were also likely to have had a previous endarterectomy.
Also unsurprising, the reports said, stenting was linked with higher morality rates.
For carotid endarterectomies, 1 percent died within a month, and 7 percent within 1 year, for the most recent year, 2005. But for stenting, 2 percent died within a month and almost one out of ten died within a year. The higher mortality for stenting is likely because patients getting stents are sicker; as noted, Medicare only covers the procedure for high-risk patients.
"The differences likely reflect the differential selection of high-risk patients into the carotid stenting cohort, consistent with the CMS national coverage decision," the report said.
Of note, the mortality rates for both procedures were higher than those reported in the clinical studies that led to regulatory approval of the procedures, the report said. While mortality rates for the endarterectomy in 2005 declined almost 50 to 100 percent from some reported death rates in the mid-1990s, they were substantially higher than those in the regulatory-granting studies of 0.5 to 0.8 percent, according to the report.
But this was also not entirely surprising, the report said.
"Because this analysis was limited to elderly Medicare beneficiaries, the differences between the mortality rates we observed and those reported in clinical trials are not unexpected," concluded the report.
View the article online
Article written by staff at dotmed.com and adapted for the purposes of this newsletter.
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