Rectal Cancer vs. Anal Cancer: What's the difference and why does it matter?
Fast Facts
- Rectal cancer and anal cancer are completely different types of cancer, although they happen close together in the body
- Rectal cancer is more closely related to colon cancer (colorectal cancer) and anal cancer is more closely related to skin cancer
- Anal cancer is rare and is linked to infection with HPV. Rectal cancer is much more common and its major risk factors are similar to those for colon cancer: family or personal history, age, obesity, exercise, smoking and other factors.
The rectum and the anus make up the lower part of the gastrointestinal tract (GI tract, gut).
Both the rectum and the anus can develop cancer. Since the areas are so close together on the body (and really hard to see!) it can be easy to confuse the two areas. As a matter of fact, people use the terms interchangeably. But the tissues in rectum and anus are very different. And the cancers they develop are also very different. Here are some key differences, and a few similarities, between rectal and anal cancer.
Anatomy of the lower GI tract
The first part of the gut after the stomach is called the small intestine. Food passes from the stomach into the small intestine, past the appendix and into the cecum. From the cecum, it goes into the colon (made up of the ascending, transverse and descending colon). The sigmoid colon comes next followed by the rectum. Finally, stool passes through the anal canal and out of the body through the anus. The large intestine begins at the cecum and ends with the rectum.
The lining of the rectum closely resembles the lining of the colon. Whereas the tissue lining the anus more like skin. This difference means that different types of cancer can develop in the rectum and anus even though they sit right next to each other.
How does rectal cancer differ from anal cancer?
Rectal cancer and anal cancer differ from each other in a number of ways. Here are some of the main differences:
- Location: Rectal cancer happens in the rectum. Anal cancer happens in the anus. This may seem obvious, but it’s important to know which one you’re dealing with because the risk factors, treatment and prognosis are different for the two types of cancer.
- Risk factors: Human papillomavirus (HPV) is the major risk factor for anal cancer. There is a vaccine for HPV. Major risk factors for rectal cancer are the same as for colon cancer– age, gender, family history, lifestyle and obesity.
- Type of cells that turn into cancer: Anal cancers are mostly caused by squamous cells (skin). Rectal cancers are mostly caused by glandular cells.
- Treatment: When caught early, rectal cancer can be treated with surgery alone. If the cancer has spread, chemotherapy and radiation are done before surgery.On the other hand, anal cancer is treated with radiation and chemotherapy when caught early. Most people with anal cancer don’t ever have to have surgery.
- Incidence: Rectal cancer (about 1 in 25 lifetime risk) is much more common than anal cancer (1 in 500 lifetime risk)
How are rectal cancer and anal cancer similar?
Although they are very different diseases, anal and rectal cancers have a few similarities. Some of the biggest similarities are:
- Survival rate: The 5 year survival rate for colorectal cancer overall is 64%. For anal cancer it’s 69%. The specific rate varies based on stage at the time of diagnosis.
- Early detection saves lives: the earlier anal and rectal cancers are caught, the better the chance of survival. Early detection can also mean less dramatic treatment. Keeping up with regular health check-ups and routine screening will help with earlier detection.
Blood on the toilet paper after wiping is a common reason people see their doctor for both rectal and anal cancer.
The bottom line
Rectal and anal cancers occur within very close proximity to each other, so the terms are frequently used interchangeably. But they’re very different from one another. They grow from different cell types, have different treatments and risk factors. Rectal cancer is much more common than anal cancer. The most important similarities is that both can show up as blood on the toilet paper and that early detection can save lives. If you experience symptoms, like blood in your stool, see your doctor right away. Remember to keep up with routine physical exams and talk to your doctor about the right time for screening tests. Get checked for you, get checked for your family. CheckIt4Andretti.