Metastatic Anal Cancer: What to Ask

This page is for people with stage IV (metastatic) anal cancer and those close to them. It explains the treatments the National Cancer Institute (NCI) lists and suggests questions to bring to your care team.

Stage IV means the cancer has reached organs beyond the anal area. NCI's patient summary lists palliative surgery, radiation and chemotherapy for this stage. Its health professional summary adds named drugs. Together they include:

• Surgery and radiation used to ease symptoms
• Chemotherapy, with or without radiation
• These drug pairings:
  • Cisplatin with fluorouracil
  • Carboplatin with weekly paclitaxel
  • Docetaxel with cisplatin and fluorouracil
• Two immunotherapy drugs: nivolumab and pembrolizumab

There is a trial you can ask about by name. It is called InterAACT.

It was a phase II trial. It compared carboplatin plus weekly paclitaxel against fluorouracil plus cisplatin. Median survival (the time by which half the people in a group had died) was 20 months in the first group and 12.3 months in the second.

Serious side effects were more common with cisplatin, 62 percent against 36 percent. NCI says these results led researchers to treat carboplatin and paclitaxel as the new backbone for trials.

Immunotherapy helps your immune system fight the cancer. Nivolumab and pembrolizumab are both on the NCI list, where NCI says checkpoint inhibitors have shown activity. Neither has an FDA approval just for anal cancer. Ask where they fit in your treatment plan, and what would lead your team to switch to them.

NCI's drug pages describe retifanlimab. It is approved for anal squamous cell cancer that has spread or come back.

The FDA approved it in May 2025. It is used with carboplatin and paclitaxel as a first treatment when surgery is not possible. In the trial, adding it held the cancer back for longer. The median was 9.3 months against 7.4 months. It is not yet clear that people lived longer. It is also used alone if the cancer grew on platinum chemotherapy, or platinum could not be given. That use rests on one trial. The cancer shrank in 14% of people.

The NCI treatment summary cited below does not mention it. We point out that gap but cannot settle it. Ask your oncologist whether it applies to you.

NCI says people with HIV are generally treated the same way and do about as well. Modern HIV treatment is the reason.

One caution matters. A CD4 count (a measure of immune cells) under 200 before treatment may mean more side effects, both early and late.

NCI says a history of AIDS-related illness can make a standard plan hard to tolerate. The dose may be lowered, or mitomycin may be left out.

The tumor can hurt and bleed even when the main problem is elsewhere. Radiation and surgery are both on the NCI list to ease these symptoms.

• Which chemotherapy would you start with, and why?
• Does the InterAACT result apply to me?
• When would immunotherapy come in?
• Does retifanlimab apply to my situation?
• What is my CD4 count, and does it change my doses?
• Can radiation help the pain or bleeding I have now?
• Which trial is open for me?

• Call 911 or go to an emergency department if bleeding from the back passage is heavy or will not stop, or if bleeding comes with dizziness or fainting. Go too if you have belly pain with vomiting and are passing no gas or stool, which can mean the bowel is blocked, or if you cannot pass urine at all. Do not drive yourself.
• Call your care team at once, day or night, if you have a temperature of 100.4°F (38°C) or higher while on chemotherapy, and go to an emergency department if you cannot reach them quickly. A same-day call is too slow here. Chemotherapy drops the white cells that hold infection back, and CDC treats a fever during chemotherapy as a medical emergency. Tell whoever sees you which regimen you are on and when your last dose was.
• Call your care team right away if you are on retifanlimab or another immunotherapy and have several watery stools a day, blood or mucus in your stool, a new cough or breathlessness, yellow eyes or dark urine, or a rash that is blistering or peeling. These drugs can inflame healthy organs. Ring the 24-hour oncology line rather than waiting; the team will grade the problem and check for infection before deciding how to treat it.
• Call your care team right away, or go to an emergency room, if you have new numbness around the buttocks, inner thighs, legs or belly, new leg weakness, or new trouble controlling urine or stool. These can be signs of pressure on the spinal cord or its nerves. That is an emergency.
• Call your care team within a day or two if pain in the back passage or pelvis is getting worse and your current painkillers are not holding it. Do the same for a discharge that smells bad, or steady bleeding that is not heavy.

Cancer Staging and Biomarker Testing explain the terms behind a metastatic anal cancer diagnosis. Clinical Trial vs Standard Treatment, Palliative Care, and Questions to Ask Your Doctor cover the choices that come next with metastatic anal cancer.

These questions were drawn from current patient guidance for anal cancer:

• NCI PDQ — Anal Cancer Treatment (Patient Version)
• NCI PDQ — Anal Cancer Treatment (Health Professional Version)
• NCI — Retifanlimab-dlwr
• DailyMed — ZYNYZ (retifanlimab-dlwr) label: severe and fatal immune-mediated adverse reactions
• NCI — Infections and Neutropenia during Cancer Treatment
• FDA — Retifanlimab-dlwr approval for squamous cell carcinoma of the anal canal
• CDC — Fever during chemotherapy
• MedlinePlus — Gastrointestinal bleeding
• MedlinePlus — Abdominal pain
• NIDDK — Urinary retention
• American Cancer Society — Bone metastases and spinal cord compression