Gender and Cancer Vaccines

A number of cancer vaccines are on the market or under investigation right now, many targeted to gender-specific cancers. Along with the FDA-approved Gardasil(TM) HPV vaccine, which can prevent certain types of cervical cancer, trials are underway on the prostate cancer vaccine GVAX(R), a breast cancer vaccine, and another cervical cancer vaccine.

One important difference between all these vaccines is that Gardasil is given before any cancer diagnosis, and the other vaccines under trial that I mentioned are given after a cancer diagnosis in addition to standard cancer treatment. These post-diagnosis vaccines seem to be the trend with cancer vaccines, despite the heavy marketing of Gardasil. These vaccines are designed to "retrain" the patient's immune system to respond more effectively to proteins associated with cancer cells. Some of these vaccines are developed using the patient's own cells, and other are not.

Two promising post-diagnosis vaccines under investigation that are not gender-specific target lung cancer (the most deadly cancer among both men and women) and cutaneous melanoma (which is more deadly among men than among women).

I'm curious about the gender differences between cancer vaccines. Do women respond more favorably than men to cancer vaccines, or vice versa? Are vaccines that use the patient's own cells more or less effective than those that don't? Are vaccines for gender-specific cancers, such as prostate and cervical cancer, more or less effective than vaccines for cancers that can strike both genders? There might be no patterns here, but if there are, it would be interesting to see how physiology, sociology, and other factors impact the effectiveness of these vaccines.

BPA and Baby Bottles

A chemical often used to manufacture infant bottles, water bottles, and food packaging might be harmful to humans, according to a draft brief released this week by the NIH-funded National Toxicology Program's (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR). The NTP reviewed a number of mostly animal studies that indicated that Bisphenol A (BPA), used in resins and polycarbonate plastics, might cause neural changes, precancerous prostate and breast lesions, and early puberty, among other problems, at fairly low doses. At significantly higher doses than humans are likely to encounter, BPA has been proven to slow puberty and growth, and decrease survival rates in animal studies.

Although BPA is also sometimes found in tableware, medical devices, dental sealants, and automobiles, among other places, the draft brief stated that humans primarily absorb BPA though food and drink. The U.S. produces 2.3 billion pounds of BPA yearly, and infants and children have the greatest exposure to the chemical "because they eat, drink and breathe more than adults on a pound for pound basis," the report stated.

The draft brief points out that most ingested BPA is metabolized and eliminated in the urine. The remaining ("free") BPA in the body is probably harmful. Based on evidence from animal studies, infants and young children are thought to be less efficient at metabolizing and excreting BPA than adults, the draft brief states, so they retain higher levels of free BPA in their bodies. The draft brief also says that BPA seems to leach more easily from plastic into foods when the food is heated. As such, baby bottles (often heated up, of course, before given to the baby) seem like an especially potent source of exposure in infants.

Formula-fed infants aged 0 to 6 months, who are exposed to BPA primarily though baby bottles but also through the packaging of formula containers, might absorb about ten times the amount of BPA as a breast-fed infant, according to the draft brief.

I find this information, and the pervasiveness of BPA in the environment, disturbing news. I first read about the NTP draft brief in a story on the Washington Post online, and the writer considered the report's findings worrisome. A number of other online news outlets, such as Fox Business, on the other hand, chose to run the press release on BPA from the American Chemistry Council as an article. The American Chemistry Council press release, not surprisingly, states that the NTP draft brief proves that there are no serious human reproduction concerns about BPA.

Yes, the data is based primarily on animal rather than human studies, and the authors of the NTP draft brief pointed out a number of limitations to the studies they looked at, such the reproducibility and structure of some studies. I still think that the information in the NTP draft brief is too important to be dismissed – especially for parents, who have been concerned about the plastics in baby bottles for years.