journalClub

November 29, 2004

EUS vs CT for pancreatic cancer

The November 16 Annals has an article from Indiana University comparing endoscopic ultrasound with multidetector CT scanning for the evaluation of suspected pancreatic cancer.

104 patients with suspected non-metastatic pancreatic malignancy underwent both EUS and high-resolution multidetector CT scanning. Of these patients, 41 were managed medically, and 63 underwent surgery. The two modalities were then compared for their accuracy in determining resectability, staging and detection of tumors.

The original hypothesis was that EUS would be better at determining resectability (in particular recognizing unresectable tumors) than CT scanning, and resectability was the study’s primary endpoint. There was no significant difference between the two modalities for this endpoint: resectable tumors were correctly identified by EUS vs CT in 88% vs. 92%. Non-resectable tumors were accurately identified by EUS vs CT in 68% vs 64%. The authors conclude that “if multidetector CT detects a pancreatic mass that seems to be resectable in an appropriate surgical candidate with suspected cancer, preoperative endoscopic ultrasonography does not seem to be necessary unless tissue confirmation of suspected malignancy is desired”.

Secondary endpoints were staging and the actual detection of tumors. In terms of overall staging, endoscopic US was superior to CT scanning, due to better recognition of T3 disease. For nodal staging, there was no significant difference.

Interestingly, EUS was superior to CT scanning in the detection of small tumors. Among the 63 patients who underwent surgery, 53 were found to have cancer. Of these 53, endoscopic ultrasound failed to diagnose 2 tumors less than 25 mm in size; CT scanning missed 10 tumors, 9 of which were less than 25 mm and one greater than 25 mm. Most of these were in the head of the pancreas. The authors do not specifically explain how 10 patients who had no pancreatic masses on CT scanning came to be evaluated for suspected pancreatic cancer, but 4 of them had had biliary stents placed, so presumably biliary obstruction was the presenting symptom for many of these CT-negative cases.

Thus, endoscopic ultrasound was not superior to CT scanning in determining resectability of pancreatic tumors but was superior in picking up small (less than 25 mm) masses that turned out to be cancers at surgery. This study, supported by grants from the American Society of Gastrointestinal Endoscopy, does not make endoscopic ultrasound an obligatory part of the resectability work-up, which was presumably the original intent. It certainly does raise the question of the role of EUS in the work-up of patients with possible pancreatic neoplasms, however, since it was able to pick up small tumors that escaped CT detection.

Filed under: gastrointestinal — mjmd @ 12:18 am

November 28, 2004

Stretching the flu vaccine?

In this flu-vaccine shortage year, any means of extending the vaccine supply is worth examining. There is evidence that giving vaccines intradermally rather than intramuscularly is more effective. In last week’s NEJM are two articles examining the effect of administering a lower dose of the flu vaccine intradermally. There is also a letter to the editor looking at the effect of simply giving a lower dose of the vaccine by the traditional i.m. route.

In the first study, sponsored by Glaxo SmithKline, 238 subjects were randomized to either a standard 0.5 ml i.m. dose of flu vaccine or a 0.1 ml intradermal dose of a candidate vaccine that was double concentrated (yielding an intradermal vaccine with 40% the concentration of antigen of the standard vaccine). 130 subjects were aged 18-60 years, 108 were over 60 years of age (average age: 69). In the younger group, the antibody responses were almost the same and were adequately protective in the intradermal group. In the group of subjects over 60 years old, the intradermal route yielded antibody titers that were generally lower, significantly lower for one strain and probably only incompletely protective.

In the second study, suppored by NIH grants, 100 subjects 18-40 years of age were randomized to receive either a standard 0.5 ml i.m. dose of a standard flu vaccine, or 0.1 ml of the same vaccine given intradermally. The intradermal route yielded, overall, a similar (for some strains better) antibody response as the i.m. route.

In the letter to the editor, a group from Canada gave healthy volunteers aged 18-40 years old either a full dose or a 1/10 dose of an influenza vaccine by the intramuscular route. Those given the 1/10 dose achieved protective antibody levels (although lower titers for most strains).

These studies indicate that the intradermal route produces better immunogenicity than the i.m. route. This could be used to enhance the immune response in populations that mount a less effective response (such as the elderly). It could also be used to stretch the vaccine supply in case of future shortages, particularly in the younger population. The practical effectiveness of these approaches will depend, at least in part, on FDA approval of different dosages and routes. It seems unlikely that a manufacturer of a conventional influenza vaccine will apply for approval of one-fifth of the dose of that same vaccine, administered intradermally. The Glaxo SmithKline approach of manufacturing a different product is more likely to be financially attractive.
 

Filed under: infectious diseases — mjmd @ 11:08 am

November 27, 2004

Six articles on postmarketing drug surveillance from JAMA

The pharmaceutical industry and the FDA are being battered by testimony and discussion in the wake of Vioxx. Presumably this will soon die down: news stories appear, flare up and soon fizzle out when their energy (and the public’s interest) is spent. For now, however, the drug surveillance story is still burning bright. David Graham, the gaunt FDA whistle-blower, is enjoying his Warholian fifteen minutes of fame. And this week’s online edition of JAMA pre-publishes six pieces that will appear in next week’s print edition. These articles are about Baycol (cerivastatin), a drug no longer in the news but relevant to the topic. Very briefly summarized:

  • The FDA’s Graham et al examine the incidence of hospitalized rhabdomyolysis in patients treated with lipid-lowering drugs, an inception cohort study of 252,460 patients treated with various statins and fibrates between 1998 and 2001. The number of patients needed to treat for one year to produce one case of severe rhabdomyolysis was roughly 23,000 for monotherapy with atorvastatin, pravastatin or simvastatin; 3500 for monotherapy with a fibrate, 2000 for monotherapy with cerivastatin, 1500 for fibrate plus a statin other than cerivastatin and only about 10 for fibrate plus cerivastatin.
     
  • Psaty et al discuss the potential for conflict of interest in the evaluation of suspected adverse drug reactions. They discuss the FDA’s regulatory process, noting that: “…the proportion of new molecular entities that are first introduced in the United States has increased from 2-3 % in the early 1980s to 60% in 1998″ and “in contrast to the highly structured premarketing evaluation, postmarketing surveillance has little structure” (and is underfunded).
     
    They describe the information that was publicly available on Baycol, mainly from SADR’s, and contrast this with the information that was available to Bayer but not to the public (which they derive from litigation documents, in which they were expert witnesses for the plaintiffs). They suggest that there was information posessed by the company which should have been made public, but which represented a conflict of interest for Bayer.
     
    The authors argue that, given the speed with which new agents enter the market, the public is at increased risk due to the lack of resources available for post-marketing surveillance and the conflict of interest inherent in the pharmaceutical companies’ positition. This should be dealt with by strengthening the post-marketing surveillance structures and possibly creating an independent agency to deal with this.
     
  • Pierkowski responds to this article on behalf of Bayer, emphasizing that Psaty et al were expert witnesses against Bayer. He argues that both the FDA and Bayer took appropriate actions at the appropriate times.
     
  • Psaty et al then respond to Pierkowski’s points, arguing that whether or not Bayer took appropriate action is less important than whether or not the post-marketing system needs to be dramatically improved.
    “While Piorkowski, as an attorney representing Bayer, properly defends some of the company’s specific actions, the purpose of our article was to raise an important public health issue. For us, the cerivastatin-rhabdomyolysis case report served as an illustration. We were primarily concerned to demonstrate how the current postmarketing surveillance system and the current FDA regulations may not, under certain circumstances, be adequate to protect the health of the public.”
  • Strom reviews the whole post-marketing surveillance system. His manuscript was submitted to JAMA by Bayer. He notes that much data is supplied by the SADR system, but the data itself is, necessarily, of limited quality and must be considered hypothesis generating. It needs to be followed up by appropriate hypothesis testing, which is where the system can and should be improved. He believes that, from a regulatory standpoint, the FDA is up to the task if given the appropriate resources. From a scientific standpoint, other organizations (such as the publicly funded Centers for Education and Research in Therapeutics) need to be developed and strengthened in order to analyze and respond to hypotheses generated from the SADR’s. This cannot be left up to the pharmaceutical industry, given its inherent conflict of interest.
     
  • Finally, in an excellent editorial, JAMA editors Fontanarosa, Rennie and DeAngelis sum it all up nicely. If you only read one of the six articles, I would suggest reading this one. The authors provide the background to the articles published in this issue, and make several suggestions, including decoupling the drug-approval and post-marketing surveillance processes, since “it is unreasonable to expect that the same agency that was responsible for approval of drug licensing and labeling would also be committed to actively seek evidence to prove itself wrong”. They conclude:
    “The postmarketing surveillance system requires a long overdue major restructuring. Until that occurs—as indicated by the articles in this issue of JAMA, as epitomized by recent evidence of serious harms from widely used and heavily promoted medications, as demonstrated by the influence of industry over postmarketing data, and as illustrated by the lengths to which some manufacturers will go to protect their interests—the United States will still be far short of having an effective, vigilant, and trustworthy system of postmarketing surveillance to protect the public.”

That being the case, what is the practitioner to do? Assuming that there will continue to be delays before adverse drug effects are discovered and publicized, prudence before prescribing the latest “hot” drugs seems warranted, more than ever. About a year ago, the pharmaceutical rep promoting one of the newer statins asked me when I would be comfortable prescribing this particular medication. I said I would wait at least a year. Now that same representative is reminding me that it’s been a year. I’m still not ready.

Filed under: cardiovascular, medico-legal — mjmd @ 12:15 pm

November 22, 2004

The vitamin E study

I just got around to looking at the vitamin E study that was publicized at the AHA meetings two weeks ago and published online at the Annals website (to be published in print in January).

It is a meta-analysis of randomized trials of vitamin E, that looks at overall mortality. Trials were analyzed by vitamin E dosage. There were 8 low-dose trials where the vitamin E dose was less than 400 IU daily, with a total of 95,000 subjects; there was no effect on mortality. Pooling the results of the 11 trials (about 41,000 subjects) where the dose was 400 IU or greater, there was an increase in mortality in the vitamin E group. The actual calculated number was 63 deaths per 10,000 persons.

My take on this:

The actual derived number is not meaningful, since results are pooled across a heterogeneous group of subjects, methods and doses. The number 63 per 10,000 should not be taken as is, especially since the confidence interval is 6-119!

On the other hand, the graphic representation of the 19 trials is highly instructive (a picture really is worth a lot of words). Even if one doesn’t place any stock in the pooling of results, just looking at the graphic summary of the trials is very convincing. I believe this is the biggest value of metanalyses: providing a graphic summary of multiple studies.

Since the inflection point for increased risk seems to be around 400 IU daily, and since that is a rather common vitamin E dose, it’s not clear exactly what to think about that dose. But I do feel fairly comfortable telling people who ask about 400 IU of vitamin E or more that I wouldn’t recommend it for prevention and would consider stopping it if they are taking this dose.

Filed under: cardiovascular — mjmd @ 10:42 pm

November 19, 2004

Ultrasound enhanced tPA for stroke

An article in yesterday’s NEJM on Ultrasound-enhanced systemic thrombolysis for acute ischemic stroke was the first I had seen on thrombolysis for CVA in quite a while (the last major trial on t-PA for stroke published in the NEJM, which I reviewed here, was 9 years ago). And a quick PubMed search yielded this study from Cleveland, which indicates that only about 2% of strokes nationwide receive t-PA, mainly because of the 3 hour time requirement from onset of symptoms.

Ultrasound energy has been shown to facilitate the activity of fibrinolytic agents. Experimental work with lower frequency (Kilohertz) ultrasound in conjunction with t-PA had previously shown an increased risk of hemorrhage. This effect has not been noted with higher frequency (MHz) transcranial diagnostic ultrasound which has been used to look at the patency of cerebral arteries. The current phase II trial was designed to examine the effects of continuous, high frequency transcranial doppler monitoring, in conjunction with t-PA, on hemorrhage, patency and recovery rates.

126 stroke patients who presented early with evidence of abnormal flow through the middle cerebral artery were randomized into two groups of 63 patients. Both groups received t-PA, and both groups had transcranial doppler measurements that checked the flow at 0, 30, 60, 90 and 120 minutes. Patients in the target, ultrasound group had diagnostic ultrasound insonation that was continuous for the two hours; patients in the placebo group only received the diagnostic ultrasound at the prespecified times.

Patients in the target ultrasound group did better, in terms of both recanalization and clinical improvement (NS, however), without any difference in intracranial hemorrhage:

Continuous ultrasound Placebo ultrasound
Complete recanalization within 2 hours 46% 18% (p<0.001)
Clinical recovery within 2 hours 29% 21% (NS)
Favorable outcome at 3 months (modified Rankin score of 0 or 1) 42% 29% (NS)

These results are encouraging and presumably more studies will be undertaken to see what the optimal ultrasound approach should be (energy level, duration of therapy). If this pans out, the benefit of thrombolytic therapy would be more convincing than it is at present, and might bolster enthusiasm for its use. The addition of another technological requirement to stroke management would complicate matters somewhat, and might make a more effective case for centralizing stroke treatment.

Most fascinating is a report, cited by Medpundit, that indicates a possible beneficial effect of ultrasound alone in the management of stroke! This comes from an anecdotal report by a physician in Scotland.

Filed under: cardiovascular, neurology — mjmd @ 3:10 pm
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