This page is for education and is not medical advice. Talk with your care team about your specific situation.

Most anal cancer is treated without surgery. Radiation and chemotherapy, given together, do the work surgery used to do. For most people that means keeping the anus and keeping bowel function. It doesn't go that way for everyone, and we won't pretend otherwise. But it's the reason this cancer is treated the way it is. Surgery is the backup plan, not the first plan.

Why this isn't "colorectal cancer"

These two get mixed up a lot, but the differences are important. Most anal cancers are squamous cell carcinomas. Same cell type as skin, same as cervical cancer. Squamous cells tend to respond well to radiation. Colon and rectal cancers are adenocarcinomas, which don't respond the same way, and that's why those usually start with a surgeon.

So colon cancer often starts with surgery. Anal cancer usually starts with a radiation oncologist and a medical oncologist, and plenty of people never see a surgeon at all.

What shapes your plan

Mostly three things.

1. How big the tumor is and whether it's grown into anything nearby.

2. Whether it's reached lymph nodes.

3. Whether it's spread further than that.

Those add up to a stage, and the stage shapes the plan. Your overall health and anything else you're managing matter too.

So does what you want out of treatment. That part is yours, and nobody will guess it for you.

Who's in the room

Anal cancer isn't common. Some cancer centers see only a few cases a year, and experience makes a difference. You'll want a radiation oncologist and a medical oncologist involved. A colorectal surgeon in the conversation early is a good sign, even if you never end up needing one.

If your center sees only a handful of these, asking about a second opinion somewhere busier is a reasonable thing to do.

Then there's who else gets to be in the room. If your partner isn't legally your spouse, or if your chosen family is who actually shows up for you, sort the paperwork out early. Medical power of attorney, HIPAA authorization, who the hospital is allowed to talk to. It's a dull afternoon that can spare you a fight at the worst possible moment. Ask your care team who handles this — most centers have someone.

Chemoradiation, the standard treatment

If your cancer hasn't spread to distant organs (stages I through III), treatment is usually radiation and chemotherapy at the same time. Clinicians call it chemoradiation. The chemo makes cancer cells more vulnerable to the radiation, so the two together tend to do more than either alone.

Radiation. Usually five to six weeks, Monday through Friday, with each session taking minutes. Many centers use IMRT, which shapes the beam around the tumor and spares more of the tissue around it. That's part of why treatment is more manageable now than it was fifteen years ago. If your center isn't using IMRT, it's fair to ask why.

Chemo. Usually mitomycin with 5-fluorouracil (5-FU), given during the first and last weeks of radiation. Two things worth raising:

Capecitabine is a pill form of 5-FU that some centers use instead. It appears to work similarly, and it means no infusion pump and no port. If needles and pumps are a real problem for you, bring it up.

Cisplatin sometimes replaces mitomycin. The evidence is split. One large trial found mitomycin did better on keeping cancer away and on avoiding a colostomy; another found the two about equal. Mitomycin is still the usual choice.

If you're living with HIV: Standard treatment generally applies, and on current antiretroviral therapy outcomes look broadly similar to everyone else's. What may change is the dose: if your CD4 count is under 200, your team might reduce or skip the mitomycin because of how hard it hits blood counts. That's a considered adjustment rather than a lesser version of treatment. Being HIV-positive isn't a reason for anyone to offer you less, and it's worth saying so out loud if it starts to feel that way.

Stage by stage

Stage I

Tumor 2 cm or smaller, no lymph nodes.

Chemoradiation is standard. But if the tumor is small and hasn't reached the sphincter muscle, a surgeon may be able to remove it with a margin around it, which can mean skipping radiation. Ask about this one specifically. It isn't always offered.

Stage IIA

Tumor between 2 cm and 5 cm, no lymph nodes. Chemoradiation.

Stage IIB

Tumor up to 5 cm that's reached nearby lymph nodes. Chemoradiation, with the radiation field widened to cover those nodes.

Stage IIIA

Tumor larger than 5 cm, nodes or no nodes. Chemoradiation, often a longer or higher-dose course.

Stage IIIB

Tumor growing into a nearby organ (vagina, urethra, bladder), no nodes. Still chemoradiation. This is the situation where keeping your organs intact matters most.

Stage IIIC

Tumor growing into a nearby organ, nodes involved. Chemoradiation.

There's a pattern there. Through stage III, chemoradiation is usually the answer. A bigger tumor tends to mean a more intensive course rather than a different approach.

Stage IV

Stage IV means the cancer has reached distant organs, most often the liver, lungs, or lymph nodes outside the pelvis. The goal shifts toward control rather than cure: slowing things down, managing symptoms, protecting how you feel and what you can still do.

First line is now immunotherapy plus chemo. In May 2025 the FDA approved retifanlimab (brand name Zynyz) alongside carboplatin and paclitaxel for anal cancer that's inoperable, has come back locally, or has spread. It's the first treatment approved specifically for this stage. Before it, every regimen used here was borrowed from another cancer.

In the trial behind the approval, adding retifanlimab reduced the risk of the cancer progressing by about a third, and more people responded to treatment (56% compared with 44%). People on it also lived longer on average, roughly 29 months against 23, though that difference wasn't large enough for researchers to be confident it wasn't chance. The progression result was.

The chemo underneath it is carboplatin with weekly paclitaxel. That pairing replaced the older cisplatin-and-5-FU combination after a trial found it worked better with fewer serious side effects. If you're being offered cisplatin and 5-FU for metastatic disease, that's worth a conversation.

Immunotherapy on its own (Retifanlimab) is also approved by itself if your cancer progresses on platinum-based chemo, or if you can't tolerate it.

Radiation still has a place here. Not to cure, but to shrink something causing pain or bleeding, particularly in bone.

Clinical trials are worth raising at every decision point, not only once other options run out. And if you're living with HIV, ask anyway. People with HIV were kept out of cancer trials for a long time, and a lot of us still assume we're ineligible. That has been changing. Retifanlimab's monotherapy trial included people living with HIV, and those participants kept their HIV under control during treatment. Eligibility still varies trial by trial, so the answer is to ask rather than to assume either way.