Clinical Briefs
By Louis Kuritzky, MD, Clinical Assistant Professor, University of Florida, Gainesville. Dr. Kuritzky is a consultant for GlaxoSmithKline and is on the speaker’s bureau of GlaxoSmithKline, 3M, Wyeth-Ayerst, Pfizer, Novartis, Bristol-Myers Squibb, AstraZeneca, Jones Pharma, and Boehringer Ingelheim.
Dietary Phytoestrogens and Lung Cancer Risk
Lung cancer (LCA) remains the leading cause of cancer death in the United States, and has recently surpassed even heart disease as a cause of mortality amongst men who smoke. Past epidemiologic data suggested that dietary constituents such as vitamin A and beta-carotene might be important modulators of lung cancer risk, but unfortunately, interventional trials did not support the optimism generated by observational data.
Phytoestrogens (PHY) are compounds in the diet that have weak estrogen-like activity. The 3 main PHY classes are isoflavones (ISO), lignans (LIG), and cumestrans. Epidemiologic data have shown that in populations with a low incidence of LCA, plasma levels of ISO, and LIG are high.
Schabath et al studied the relationship between intake of PHY and LCA risk in a prospective case-control study (n = 3,409). Data were obtained by personal interviews querying food intake over a 9-year period of observation.
Amongst the study population, there was an equal frequency of never-smoking history: approximately 16%. This also helps to remind us that as many as 1 out of 6 lung cancer cases occur in non-smokers.
There was a linear inverse relationship between dietary PHY and LCA which proved to be statistically significant, but was primarily driven by data accrued in men. Those individuals in the highest intake of dietary PHY enjoyed a 46% relative risk reduction for LCA compared to controls. These data are consonant with previous information suggesting that estrogenic hormone therapy is protective for lung cancer in women. In nonsmokers, trends towards benefit were more prominent than in smokers or former smokers, but the small numbers of study subjects precludes definitive conclusions.
Schabath MB, et al. JAMA. 2005;294: 1493-1504.
Effectiveness of Influenza Vaccine in the Elderly
Efficacy and effectiveness are commonly used to differentiate results from clinical trials (efficacy) from results obtained in clinical practice (effectiveness). Such terms anticipate the fact that clinical trial populations may be a very select group: they may have medications provided free-of-charge, they often enjoy the assistance of abundant support personnel, and they may be especially motivated to complete therapy, as compared to clinical practice. In this report, Jefferson et al examined the effectiveness of influenza vaccine (FLUVAX) to prevent influenza clinical symptoms (FLU-Sx), hospitalizations, and death.
Data from 64 studies were evaluated, and included populations ranging from as few as 124 subjects to as many as 750,000.
The first comparison (> 1 million observations) indicated that for community-dwelling elders overall, inactivated FLUVAX was not effective against FLU-Sx. However, a similarly large population (> 750,000) analysis indicated statistically significant effectiveness in reducing hospitalizations for pneumonia or influenza; optimum effectiveness was seen when there was a good match between circulating virus and vaccine. The second comparison looked at effectiveness among high-risk community-dwelling elders, in which group all-cause mortality was favorably impacted by FLUVAX. The 3rd comparison looked at FLUVAX among healthy community dwelling elders, in which population FLUVAX reduced hospital admission for influenza or pneumonia by approximately half.
Based upon this large data set, the authors conclude that FLUVAX effectiveness is only modest.
Jefferson T, et al. Lancet. 2005;366:1165-1174.
Why Does Tadalafil Cause Back Pain?
All 3 currently available PDE5 inhibitors (sildenafil, tadalafil, vardenafil) have been reported to be associated with the adverse effect of back pain (LBP), albeit the reported frequency and severity of back pain with tadalafil (TAD) appears to be substantially greater than with the other 2 agents. Why LBP has been more commonplace with TAD remains unclear.
LBP associated with TAD usually occurs 12-24 hours post-dose, and resolves within 48 hours. The pain is typically described as diffuse, of mild-moderate intensity involving the lower back, gluteal region, and thigh, and worsened by assuming the recumbent position. Most cases respond to simple analgesics, although 0.4% of patients discontinue because of this adverse effect.
Seftel et al used a diversity of tools to study potential etiologies of TAD-induced LBP. There were no signs of tissue inflammation or altered low back blood flow as discerned through PET or MRI. No clinically relevant differences in any measured laboratory parameter were seen.
The etiologic origin of TAD-associated LBP remains unknown. Extensive laboratory and radiographic evaluation does not demonstrate any discernible inflammatory, vascular, or myopathic process.
Seftel A, et al. Int J Impot Res. 2005; 17:455-461.
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