Antibiotic and Cancer Link?

OVERUSE OF ANTIBIOTIS LEADS TO RESISTANCE - AND CANCER TOO?

In an editorial published in last week's British Medical Journal (BMJ), a group of prominent medical researchers and infectious disease experts led by Sweden's Professor Otto Cars called for a concerted worldwide effort to combat the growing problem of antibiotic resistance. (Cars, 2008)
Antibiotic resistance - the emergence of new strains of bacteria, which are impervious to a broad range of antibiotics - has become a very serious public health threat. New and deadly bacterial infections are emerging for which few, if any, of our current antibiotics are effective, and we can no longer take for granted that potentially life-threatening infections such as pneumonia or bacterial meningitis will be amenable to treatment with antibiotics, as they once were. An article in the medical journal The Lancet has documented that 70 percent of all hospital-acquired infections among newborns in developing countries are now untreatable with standard antibiotic regimens (Zaidi, 2005). The European Center for Disease Prevention and Control (Europe's equivalent of our Centers for Disease Control) has stated that the most important disease threat in Europe is from micro -organisms that have become resistant to antibiotics (European Center, 2007).
TWO MAIN CAUSES
The growing problem of antibiotic resistance has come about largely as a result of two separate kinds of antibiotic misuse: the over-prescription of antibiotics in clinical medicine, and the widespread agricultural practice of feeding antibiotics to livestock. Of the two, agricultural antibiotic use is undoubtedly the more insidious and the greater culprit. To be sure, there are certain legitimate uses for antibiotics in agriculture: the prevention and treatment of infectious disease among livestock being the prime one. However, the vast majority of antibiotics used in agriculture serve no therapeutic purpose at all, but are given to healthy livestock purely in order to promote rapid weight gain so that animals more quickly reach their slaughter weight while consuming less food.
While the practice of feeding antibiotics to livestock has now been banned outright by the European Union, it is still legal and continues apace in the US. Seventy percent of all antibiotics consumed in the USA - 24 million pounds of antibiotics per year - goes into such non-therapeutic uses, and more than half of the antibiotics used are identical to those used in humans. This has unquestionably resulted in the emergence of many new strains of antibiotic resistant bacteria, which in turn are responsible for various life-threatening infections in humans. The National Academy of Sciences has estimated that the annual cost of treating such infections is approximately $30 billion per year, and rising. At least 76 million cases of food-borne illness occur each year in the US, including 40,000 cases of Salmonella and 73,000 cases of antibiotic-resistant E. coli 0157-H7, the latter being clearly correlated to the use of antibiotics in cattle.
A LINK TO CANCER?
However, it is with the overuse of antibiotics in medical practice that I am primarily concerned here. In clinical situations, antibiotics are routinely prescribed inappropriately, for example for conditions caused by viruses, which are not responsive to antibiotics. Part of the problem is that patients commonly pressure their physicians to prescribe antibiotics for colds and upper respiratory infections - self-limiting illnesses for which antibiotics are not only not needed but not effective. Physicians themselves are far from blameless, though: most ear infections in children do not require antibiotics, but 97 percent of US physicians nevertheless treat ear infections with immediate antibiotics: 15 million prescriptions for antibiotics are handed out annually for this reason (Spiro, 2006).
Not only is such overuse of antibiotics contributing directly to antibiotic resistance and the emergence of dangerous new pathogens, research shows that it may also have a significant effect on the risk of developing cancer.
A 2004 study published in the Journal of the American Medical Association (JAMA) provided substantial evidence that frequency of antibiotic usage is associated with an increased risk of breast cancer. Several studies have confirmed a link between frequent antibiotic usage and an increased incidence of non-Hodgkin's lymphoma. Now Finnish scientists have published a study in the International Journal of Cancer showing a link between frequency of antibiotic use and the long term risk of several other kinds of cancer, including cancers of the lung, ovary, prostate and colon (Kilkkinen, 2008). The researchers found that antibiotic use was particularly strongly associated with an increased risk of lung cancer: individuals who received 2-5 prescriptions for antibiotics over the period 1995-1997 exhibited a 79 percent increase in relative risk for lung cancer.
Let me emphasize that these studies do not show that antibiotics cause cancer; they simply indicate that the more courses of antibiotics a person takes over time, the greater the risk of developing certain cancers. The reasons for this association are still obscure, and it will take a great deal more research to establish the precise nature of the link. It is quite possible, for example, that people who succumb to repeated infections for which antibiotics are prescribed may have an underlying immune inadequacy, and therefore may be more likely to develop cancer. Or those very infections and inflammatory conditions themselves may have a predisposing effect. Whatever the nature of the link, one thing is clear: the gratuitous and unnecessary use of antibiotics, whether in agriculture or in medicine, represents a potentially serious threat to public health, and needs to be urgently addressed. ~~~ Ralph W. Moss, Ph.D. www.cancerdecisions.com