The news reports are cryptic. One news report about Farah Fawcett's cancer went on for five paragraphs before they told us what type of cancer. Cancer is a tough enough diagnosis---there is still a fear and stigma associated with the "C" word which may lead to people putting off diagnosis and treatment. This effect may be magnified when the cancer occurs on the "naughty bits", such as the breasts, vulva, penis, or in Farah Fawcett's case, the anus (at least according to news reports). In general, the later a cancer is diagnosed, the worse the prognosis, so it's important to reduce this stigma. With that in mind, let's shed some light on anal cancer. (And yes, there are pictures of anuses below the fold---they won't kill you.)
Anal cancer, like cervical cancer (and some penile and oral cancers) is in most cases caused by a virus. This virus is human papilloma virus (HPV). This virus commonly causes anogenital warts.
A large number of patients with squamous cell carcinomas of the anus
have a history of this lesion
Anogenital warts are often asymptomatic, and HPV infection can lead to cancer even without causing warts. In looking at risk factors for anal cancer, in men anal-receptive intercourse is strongly associated with anal cancer. In women it is strongly associated with greater than ten sexual partners and with a history of other sexually transmitted diseases. In other words, like cervical cancer, many anal cancers (mostly the squamous cell type) are a sexually transmitted disease, and therefore preventable. (For a little detail on how this virus causes cancer, see this.)
Anal cancers used to be treated by big-ass surgeries (pun intended) which left patients with a colostomy, that is, a hole in their abdomen to which they hook up a bag to catch their poop. Now it is usually treated with a combination of chemotherapy and radiation.
Whenever I have a patient who complains of genital warts, I check them for anal warts (and often find them, in both men and women). There has been research into using anal Pap smears in high-risk individuals, just as we do cervical Pap smears for most women. There has also been promising work on DNA tests for HPV. But none of this will do us any good if we don't focus on prevention and do our best to destigmatize discussions of "naughty bits".
We must remember that the fact that a disease is preventable does not mean that culpability must be assigned. Once someone is sick, judging them based on their illness is a nasty, nasty thing to do. But we can make strides in prevention by encouraging condom use and looking more closely at HPV vaccination for boys and girls. It's time to remind ourselves that avoiding talking about diseases of the penis, vulva, anus or any other part only leads to more disease.