Today's post focuses on three of the most frequently googled questions about cancer causes. There are hundreds of things that can cause cancer, so this article is certainly not exhaustive. It addresses questions about HPV, smoking, and where cancer comes from.
What cancer does HPV cause?
Here's the short answer: cervical, vaginal, vulvar, penile, anal, rectal, and oropharyngeal (soft palate, base of tongue, and tonsils) cancers.
And here's the long answer:
HPV is the most common STD in the U.S.—so common that 90% of sexually active men and 80% of sexually active women will have it at some point in their lives.
There are more than 200 kinds of HPV (which stands for human papillomavirus), about 40 of which are sexually transmitted. These 40 kinds are further split into two groups:
- Low risk HPV: These don’t cause cancer but do cause genital warts. In fact, the National Cancer Institute says two specific types cause 90% of all cases of genital warts.
- High risk HPV: There are about 12 types of HPV which can cause cancer, although two specific types account for most cases of HPV-related cancer. Around half of the cases in the U.S. are a high-risk type of HPV. Having said that, most of the time HPV infections are symptomless and go away in 1-2 years. Only some infections persist and progress to become cancer.
- Nearly all cases of cervical cancer (about 13,000 U.S. cases in a year)
- 65% of vaginal cancers (about 3,300 U.S. cases in a year)
- 50% of vulvar cancers (about 3,000 U.S. cases in a year)
- 35% of penile cancers (about 800 U.S. cases in a year)
- 95% of anal cancer (about 8,000 U.S. cases in a year)
- 70% of oropharyngeal cancer (about 36,000 U.S. cases in a year)
HPV infections are very common. It is possible for someone who has only had one sexual partner to get HPV. It’s also possible to become infected with HPV even with perfect condom use, because it can be spread via contact between areas other than the genitals. The best way to prevent infection with HPV is by vaccination against it.
It can be difficult to detect an HPV infection once a person has it. Women over the age of 25 are commonly screened for cervical cancer. Beyond that, there are no easy screenings for HPV infections in the anal, vulvar, vaginal, penile, or oropharyngeal areas; and there are no tests currently in use for HPV infection in men at all. Research is ongoing.
There is also currently no treatment for an HPV infection itself, but there are treatments for the genital warts, precancerous changes, and cancers the infection can cause.
What cancer does smoking cause?
Researchers discovered in 2015 that at least 12 types of cancer are caused by smoking:
- Colon and rectum
- Oral cavity and throat
- Acute myeloid leukemia
In 2011, about 346,000 people with these cancers died and about 168,000 of these deaths were estimated to be caused by smoking cigarettes. That’s nearly 50%.
In addition, male smokers with prostate cancer are more likely to die than their nonsmoker counterparts.
Where cancer came from
In 1900, a cook named Mary Mallon got a new job working for several families in New York. Less than two weeks later, many of the family members became very ill—fevers, headache, rashes, stomach pain. Typhoid fever. Mallon found work elsewhere, and the same thing continued to happen. She carried the disease and could pass it along but was unaffected by symptoms herself. About 8 years later, Mallon was arrested and quarantined for three years, until she agreed to change jobs and take measures to avoid passing typhoid fever. But other jobs paid less. Mallon eventually changed her last name to Brown and began working again as a cook. In 1915, only four years after her release, Mallon caused an outbreak of typhoid fever in which 25 people become infected with the disease and two died. Authorities again arrested and quarantined her—this time for the rest of her life. She died still in vehement denial that she carried typhoid fever or had made anyone sick. She has been frequently blamed for the infection of hundreds or even thousands of people.
In each of the outbreaks caused by Mallon, she would be considered what’s sometimes called the index case, or a patient zero. The phrases are usually used to describe the first incidence of a disease in a major trend—often regarding an infectious disease or a genetically inherited one.
I suspect this frequently googled query about the origins of cancer is searching for an index case, but there is none. Cancer is not an infectious disease and cannot be spread from person to person in the way typhoid fever or a cold can. Cancer itself also cannot be passed genetically—when we talk about inherited cancers, what we’re really talking about is cancer that came about after a patient inherited a genetic vulnerability to developing the disease.
The potential to develop cancer lies within each one of us, and within every human who has ever lived. As cancer physician Siddhartha Mukherjee writes in his book The Emperor of All Maladies,
Cancer, we now know, is a disease caused by the uncontrolled growth of a single cell. This growth is unleashed by mutations—changes in DNA that specifically affect genes that incite unlimited cell growth. In a normal cell, powerful genetic circuits regulate cell division and cell death. In a cancer cell, the circuits have been broken, unleashing a cell that cannot stop growing…malignant growth and normal growth are so genetically intertwined that unbraiding the two might be one of the most significant scientific challenges faced by our species. Cancer is built into our genomes: the genes that unmoor normal cell division are not foreign to our bodies, but rather mutated, distorted versions of the very genes that perform vital cellular functions.”
So we can’t really talk about where cancer came from in the way that we might be able to with other diseases. Each person’s cancer comes from within themselves. Something we can discuss, though, is when humans first began to notice cancer.
Cancer is more common in modern times than in antiquity because humans live longer now than ever before, which gives the disease more time and opportunity to develop. But cancer is not a modern disease. The first known writings about cancer date to about 2625 BC in Egypt. A physician named Imhotep wrote about the injuries and diseases he encountered—how to diagnose them, how to treat them, and what the prognosis was. There are 48 cases in his notes, one of which is regarded as a case of breast cancer. Under the section for treatment, Imhotep wrote only, “There is none.”
Outside of writings, there is also evidence of cancer preserved in mummies—sometimes even mummified tumors themselves. The oldest mummified tumor dates to 400 BC, but the oldest mummified remains with evidence of cancer dates to about 4000 BC. Mukherjee writes that, if that case is indeed a case of ancient cancer, that would make the disease “one of the oldest diseases ever seen in a human specimen—quite possibly the oldest.”
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