Newly Diagnosed With Anal Cancer: First Steps

Most people newly diagnosed with anal cancer assume the plan is a big operation and a permanent bag. For most, it is not.

The National Cancer Institute (NCI) lists external beam radiation therapy with chemotherapy among the treatments for stages I, II, and III. The large operation, called abdominoperineal resection, is reserved. NCI states plainly that this procedure "is used only for cancer that remains or comes back after treatment with radiation therapy and chemotherapy."

That is the whole shape of modern anal cancer care. Radiation and chemotherapy go first, together, with the goal of keeping your anus and your normal bowel control. Surgery is the backup plan.

SEER, NCI's cancer statistics program, puts new cases of anal cancer in the United States at 11,270 for 2026, with 1,700 deaths. Both are American Cancer Society projections rather than counts SEER has observed. That is about 0.5% of all new cancer diagnoses, so this is an uncommon cancer, and it is worth being treated somewhere that sees it regularly.

By stage at diagnosis, using cases from 2016 to 2022: 39% are found while still confined to the anus, with five-year relative survival of 85.0%. Another 38% have reached nearby lymph nodes, at 70.1%. About 14% are found after spread to distant sites, at 36.5%.

Notice that more than a third are caught with node involvement. That is not a treatment failure. Node spread is common in this cancer and is usually included in the radiation field rather than treated by cutting.

NCI is direct: infection with human papillomavirus (HPV) "is the main risk factor for anal cancer," and "about nine out of every ten cases of anal cancer are found in patients with anal HPV infection."

The Centers for Disease Control and Prevention (CDC) counts an average of 8,348 anal cancers diagnosed a year in its surveillance data and estimates about 7,600 of them, or 91%, are caused by HPV.

NCI also lists conditions that raise risk by weakening immune control of HPV. HIV infection is called "a strong risk factor." Long-term immunosuppression after an organ transplant increases risk. So does having had cervical, vaginal, or vulvar cancer, which are also HPV-related. NCI notes that autoimmune conditions such as Crohn disease or psoriasis may raise risk, while adding that it is not clear whether the condition or its treatment is responsible. In people with HIV, NCI notes studies suggesting that injection drug use or cigarette smoking may raise risk further.

None of this is your fault, and HPV is extremely common. It is worth knowing because it explains why your team may ask about HIV status and vaccination history.

NCI lists: "bleeding from the anus or rectum. A lump near the anus. Pain or pressure in the area around the anus. Itching or discharge from the anus. A change in bowel habits."

Every one of those reads as hemorrhoids. That is why anal cancer is often treated as hemorrhoids for months first. If you were in that group, you are in the majority, and it does not mean you did something wrong.

The rule going forward: anal bleeding that keeps returning after treatment for hemorrhoids deserves a look and a biopsy, not a third cream.

NCI's stages are refreshingly concrete.

• Stage 0. Abnormal cells in the innermost lining, also called high-grade squamous intraepithelial lesion (HSIL).
• Stage I. The tumor is 2 centimeters or smaller.
• Stage IIA. Larger than 2 cm but not larger than 5 cm.
• Stage IIB. Larger than 5 cm.
• Stage IIIA. 5 cm or smaller, with spread to lymph nodes near the anus or groin.
• Stage IIIB. Any size, spread to nearby organs such as the vagina, urethra, or bladder, with no lymph node spread.
• Stage IIIC. Any size, possibly into nearby organs, with lymph node spread near the anus or groin.
• Stage IV. Spread to distant parts of the body, such as the liver or lungs.

Two centimeters is about the size of a peanut. Five centimeters is about the size of a lime. NCI actually uses those comparisons.

Stage 0. NCI says treatment is usually local resection, meaning the abnormal area is cut out.

Stages I through III. NCI lists local resection for tumors on the skin around the outside of the anus, and for tumors inside the opening that do not involve the anal sphincter. Otherwise: external beam radiation with chemotherapy, or radiation alone. If cancer remains or returns, abdominoperineal resection becomes an option, or further chemoradiation, chemotherapy alone, or immunotherapy.

The chemotherapy drugs NCI names for anal cancer are capecitabine, cisplatin, fluorouracil, and mitomycin. Combinations are used.

Stage IV. NCI lists palliative surgery, palliative radiation, and palliative chemotherapy with or without radiation, aimed at symptoms and quality of life.

Recurrence. NCI lists radiation with chemotherapy for cancer that returns after surgery, and surgery for cancer that returns after radiation or chemotherapy.

NCI gives an unusually specific one. People treated in a way that saves the sphincter muscles "may receive follow-up exams every 3 months for the first 2 years, including rectal exams with endoscopy and biopsy, as needed to check for recurrence."

Every three months, for two years. Put those dates in a calendar now. Tumors here can take months to fully shrink after chemoradiation, so an incomplete response at the first check is not automatically a failure. Ask your team how long they will wait before calling it residual disease.

NCI addresses this directly. "In general, treatment for people who have anal cancer and HIV is similar to treatment for other people, and these patients have similar outcomes."

It adds one caution: treatment can further stress a weakened immune system, and people with a history of AIDS-related complications "may require lower doses of anticancer drugs and radiation therapy" than others.

Tell your oncology and radiation teams your HIV status and current CD4 count and viral load at the first visit, and make sure your HIV clinician is looped in.

Get the biopsy report and confirm the exact cell type, which is usually squamous cell carcinoma. Ask for the tumor size in centimeters and whether groin or pelvic nodes are involved on imaging. Ask whether the plan is sphincter-preserving and what the odds are of avoiding a permanent colostomy. Ask which chemotherapy drugs will be used and on what days. Ask about skin care in the radiation field, because that area gets sore. Ask about fertility and sexual health before treatment starts, not after. And schedule the three-month follow-ups before you leave.

Chemoradiation to this area is demanding, and the pelvis is a bad place to wait things out.

• Call 911 or go to an emergency department if you cannot pass stool or wind at all and your abdomen is swollen and painful, or you are vomiting repeatedly. NCI treats a possible bowel obstruction as needing immediate attention. Heavy anal bleeding that soaks through pads belongs here too.
• Call the chemoradiation team immediately, whatever time it is, if your temperature climbs to 100.4°F (38°C) or higher, or you get chills. Mitomycin and fluorouracil drop the white cell count, and NCI describes infection during treatment as life threatening. This needs assessing and antibiotics within the hour, so if the team cannot be reached fast, go to an emergency department and say you are having chemoradiation.
• Call your care team the same day if the skin in the radiation field breaks down and turns painful and weeping. NCI calls this a moist reaction, and it is treated with dressings and sometimes antibiotics rather than left to dry out.
• Call your care team within a day or two if diarrhoea runs well above your usual pattern, or you cannot keep fluids down, or you are becoming lightheaded. NCI counts seven or more extra bowel movements a day as the severe band.
• Call your care team within a day or two if you cannot empty your bladder properly, or passing urine becomes painful, since the treatment field sits close by.

See also Cancer Staging, Getting a Second Opinion, and Cancer and Fertility.

• https://www.cancer.gov/types/anal/patient/anal-treatment-pdq
• https://www.cancer.gov/types/anal/stages
• https://www.cancer.gov/types/anal/symptoms
• https://www.cancer.gov/types/anal/causes-risk-factors
• https://seer.cancer.gov/statfacts/html/anus.html
• https://www.cancer.org/research/cancer-facts-statistics.html
• https://www.cdc.gov/cancer/hpv/cases.html
• https://www.cancer.gov/about-cancer/treatment/side-effects/infection
• https://www.cancer.gov/about-cancer/treatment/side-effects/skin-nail-changes
• https://www.cancer.gov/about-cancer/treatment/side-effects/bowel-obstruction
• https://www.cancer.gov/about-cancer/treatment/side-effects/diarrhea