A Research Guide for
Anal Cancer

HPV is an extremely common virus — most sexually active adults will be exposed at some point. In the vast majority of people, the immune system clears the infection without consequences. In a small percentage, persistent infection with high-risk HPV types (especially HPV-16) leads to progressive cellular changes: from normal tissue to low-grade precancerous changes (LSIL/AIN 1), to high-grade precancerous changes (HSIL/AIN 2-3), and eventually to invasive cancer. This process typically takes years to decades.

It is important to state clearly: an HPV-related cancer diagnosis is not a moral judgment. HPV is nearly ubiquitous — the CDC estimates that nearly all sexually active people will acquire HPV at some point. The virus can persist silently for decades before causing disease. Having anal cancer does not imply any particular behavior, and patients should not carry shame about their diagnosis. The medical team treats the cancer, not the circumstances of its origin.

The HPV vaccine (Gardasil 9) prevents infection with the HPV types that cause the vast majority of anal cancers. Vaccination is most effective when given before HPV exposure, but it can provide benefit even in adults who have already been exposed. The CDC recommends HPV vaccination for all individuals through age 26, and shared clinical decision-making for adults aged 27–45. Studies are examining HPV vaccination strategies for adults already at risk (verify current trials on ClinicalTrials.gov).

HPV vaccination is one of the most effective cancer prevention tools available. Parents should discuss vaccination with their children’s pediatrician.

Screening for anal precancer and early cancer is recommended for high-risk groups. The landmark ANCHOR trial (NCT02135419) demonstrated that treating high-grade anal squamous intraepithelial lesions (HSIL) in people living with HIV reduced progression to anal cancer by 57%, establishing screening and treatment of precancerous lesions as effective cancer prevention.

Groups recommended for screening include:

• People living with HIV
• Men who have sex with men (regardless of HIV status)
• Women with history of cervical, vulvar, or vaginal cancer or high-grade dysplasia
• Solid organ transplant recipients
• Other immunosuppressed individuals

Screening typically begins with an anal Pap smear (anal cytology). Abnormal results are followed by high-resolution anoscopy (HRA) — a procedure similar to colposcopy that allows the examiner to identify and biopsy suspicious areas in the anal canal.

When evaluating any treatment claim for anal cancer, ask these questions:

• Is it supported by published clinical trial data in peer-reviewed journals?
• Is it consistent with NCCN or ESMO guidelines?
• Could it delay or interfere with chemoradiation, which is the proven curative treatment?
• Does anyone with no financial stake in it recommend it?
• Are the doctors at major cancer centers using it?

Be especially cautious of anyone who suggests replacing standard chemoradiation with alternative approaches. Chemoradiation has decades of evidence showing it cures most anal cancers. Delays or replacements can allow the disease to progress to a point where a permanent colostomy becomes necessary.

• Bring a second person to every appointment. One listens; the other writes things down.
• Ask permission to record. Most clinics allow phone recording if asked first.
• Keep a single folder with all reports: biopsy pathology, imaging, blood work, and treatment records.
• Be honest about your complete medical history, including HIV status, sexual health history, and any prior HPV-related conditions. This is essential information for treatment planning and is treated confidentially.

• ☐ Diagnosis confirmed on biopsy — squamous cell carcinoma vs. other type
• ☐ HIV testing completed (required for all patients)
• ☐ HPV and p16 immunohistochemistry status noted on pathology
• ☐ Staging workup ordered: CT chest/abdomen/pelvis, pelvic MRI, PET-CT
• ☐ Examination under anesthesia (EUA) performed or scheduled for precise tumor assessment
• ☐ Digital rectal examination documented tumor size, location, and sphincter involvement
• ☐ For women: gynecologic evaluation for concurrent HPV-related cervical/vulvar disease
• ☐ Treating center identified — confirm anal cancer-specific radiation and surgical experience
• ☐ Radiation oncologist and medical oncologist appointments scheduled
• ☐ Records folder started: pathology, imaging, labs in one place
• ☐ If HIV-positive: HIV care team informed and antiretroviral therapy optimized

• Digital rectal examination (DRE): The most important initial assessment. Documents tumor size, location, distance from the anal verge, relationship to the sphincter muscles, and clinical lymph node involvement.
• Examination under anesthesia (EUA): Allows thorough assessment of the tumor and biopsies under optimal conditions.
• Pelvic MRI: Provides detailed imaging of the primary tumor and pelvic lymph nodes. Critical for radiation planning.
• CT of the chest, abdomen, and pelvis: Screens for distant metastases, particularly to the liver and lungs.
• PET-CT: Increasingly used and recommended by NCCN. Can detect lymph node involvement and distant disease not seen on CT alone. Particularly valuable for accurate radiation field design.
• Inguinal lymph node assessment: Physical examination of the groin lymph nodes. Fine-needle aspiration biopsy of any suspicious inguinal nodes.

Anal cancer uses the TNM staging system:

• T (Tumor size): T1 (≤2 cm), T2 (2–5 cm), T3 (>5 cm), T4 (invading adjacent organs such as the vagina, urethra, or bladder).
• N (Nodes): N0 (no lymph node involvement), N1 (spread to inguinal, mesorectal, or internal iliac lymph nodes).
• M (Metastasis): M0 (no distant spread) or M1 (distant metastases).

Overall stages: Stage I (T1 N0), Stage IIA (T2 N0), Stage IIB (T3 N0), Stage IIIA (T1-2 N1), Stage IIIB (T3-4 N1), Stage IIIC (T4 N0), Stage IV (any M1).

• Radiation oncologists experienced in intensity-modulated radiation therapy (IMRT) for anal cancer
• A multidisciplinary tumor board that includes radiation oncology, medical oncology, and colorectal surgery
• Colorectal surgeons experienced in salvage abdominoperineal resection
• Access to immunotherapy and clinical trials for advanced disease
• Supportive care services: dermatology for radiation skin toxicity, sexual health counseling, ostomy support if needed

A second opinion is valuable for any anal cancer diagnosis, particularly for locally advanced disease (T3-4 or node-positive) or recurrent disease where salvage surgery may be considered. Major centers offer remote second-opinion programs. The radiation treatment plan should ideally be reviewed by a radiation oncologist with specific anal cancer expertise.

The standard regimen combines:

• Radiation therapy: Typically 50.4–59 Gy delivered over 5–6 weeks using intensity-modulated radiation therapy (IMRT). IMRT is the current standard technique because it delivers high doses to the tumor while sparing surrounding normal tissues, reducing side effects compared to older radiation approaches.
• 5-Fluorouracil (5-FU): Given as a continuous intravenous infusion during weeks 1 and 5 of radiation (or as oral capecitabine as an alternative).
• Mitomycin C: Given as a single intravenous dose on day 1 of radiation (and sometimes day 29). This drug adds toxicity but improves cure rates compared to 5-FU alone.

Treatment typically takes about 5–6 weeks. The radiation targets the primary tumor, the draining lymph nodes in the pelvis, and the inguinal (groin) lymph nodes.

Chemoradiation for anal cancer is an effective treatment, but it causes significant side effects, particularly during and in the weeks after treatment:

• Radiation dermatitis: Skin irritation, redness, and breakdown in the treatment area (perineum, groin). This is the most common and distressing acute side effect. It peaks in the weeks after treatment and gradually heals.
• Diarrhea: Common during and after treatment. Managed with medications and dietary adjustments.
• Fatigue: Typically worsens through treatment and can persist for weeks to months afterward.
• Nausea: Usually manageable with anti-nausea medications.
• Myelosuppression: Low blood counts from chemotherapy, particularly from mitomycin C. Blood counts are monitored regularly.
• Late effects: Some patients experience long-term changes in bowel function, sexual function, or skin integrity. These are discussed in the supportive care section.

Most acute side effects resolve within 4–8 weeks after treatment ends. The radiation oncology team should provide detailed skin care instructions and supportive medications throughout treatment.

Capecitabine, an oral fluoropyrimidine, can be used instead of intravenous 5-FU during chemoradiation. This avoids the need for a central venous catheter and continuous infusion, which many patients prefer. Clinical data, including the ACT II trial, support capecitabine as a reasonable alternative, and it is included in NCCN guidelines.

For very small tumors (T1 N0, ≤2 cm) of the anal margin (the skin surrounding the anus, not the anal canal), local excision alone may be sufficient if the tumor can be removed with clear margins and the sphincter is not involved. This is an exception to the general rule that chemoradiation is the primary treatment.

For T1 tumors of the anal canal itself, chemoradiation remains the standard approach, though the radiation dose may be somewhat lower than for larger tumors.

People living with HIV develop anal cancer at higher rates, and there has historically been concern about treatment tolerance. Current evidence shows that HIV-positive patients on effective antiretroviral therapy can and should receive full-dose chemoradiation with curative intent. CD4 counts should be monitored, and antiretroviral therapy should be optimized before and during treatment. Close coordination between the oncology and HIV care teams is essential. HIV infection is not a reason to reduce treatment intensity.

After chemoradiation, the tumor does not disappear immediately. Regression is gradual and can continue for months. The standard approach:

• First assessment: Digital rectal examination and clinical assessment at approximately 8–12 weeks after completing chemoradiation.
• Ongoing observation: If the tumor is shrinking but still present, continued observation with repeat examinations every 4–8 weeks is appropriate. Complete response may take up to 26 weeks (6 months).
• Imaging: PET-CT or MRI may be used to assess response, typically not before 12 weeks after treatment (earlier imaging can show false-positive results due to post-treatment inflammation).

This observation period can be anxiety-provoking for patients and families. Premature intervention — rushing to surgery before the tumor has had time to fully respond — can result in unnecessary permanent colostomies. Patience, with careful monitoring, is the evidence-based approach.

A complete clinical response — no palpable tumor on DRE and no evidence of disease on imaging — is the goal. After achieving complete response, patients enter a structured surveillance program with regular examinations to detect any recurrence early.

When anal cancer persists after chemoradiation (confirmed on biopsy, typically after at least 26 weeks of observation) or recurs after initial complete response, the standard salvage treatment is abdominoperineal resection (APR). This operation removes the anus, rectum, and surrounding tissue, and creates a permanent colostomy.

While APR is a major operation with significant life changes, it can be curative for localized persistent or recurrent disease. Five-year survival after salvage APR ranges from roughly 40–65%, depending on the extent of disease at the time of surgery.

An experienced colorectal surgeon should perform the operation, ideally at a center that performs salvage APR regularly. Flap reconstruction of the perineum (the wound where the anus was removed) is often performed to improve healing, particularly in irradiated tissue.

A permanent colostomy is a significant life change, but patients who have one consistently report that quality of life is better than they expected. A certified wound, ostomy, and continence nurse (WOC nurse) is the single most valuable resource. They provide training, support, and ongoing troubleshooting. The United Ostomy Associations of America (ostomy.org) connects patients with peer support. A pre-operative consultation with a WOC nurse and a stoma site marking are essential before surgery.

• Will you use IMRT for my treatment? How many anal cancer cases do you treat per year?
• What radiation dose are you planning, and over how many weeks?
• What side effects should I expect, and how will skin reactions be managed?
• Will my inguinal lymph nodes be included in the radiation field?
• How will you assess my response, and when?

• Which chemotherapy regimen are you recommending — 5-FU plus mitomycin C, or capecitabine plus mitomycin C?
• What are the specific risks of mitomycin C, and how will my blood counts be monitored?
• If the cancer does not respond completely, what are the next options?
• What clinical trials might I be eligible for?

For metastatic anal squamous cell carcinoma, treatment options include:

• Carboplatin plus paclitaxel: A commonly used first-line chemotherapy combination, based on the InterAACT trial. This has been a standard backbone regimen.
• Cisplatin plus 5-FU: An alternative first-line chemotherapy option.
• Immunotherapy combinations: Adding checkpoint inhibitors to first-line chemotherapy has redefined treatment. The POD1UM-303 trial (NCT04472429) tested retifanlimab plus carboplatin-paclitaxel (leading to the May 2025 FDA approval), and the EA2176 trial (NCT04444921) is evaluating nivolumab with chemotherapy in the first-line metastatic setting.

• Nivolumab (Opdivo): Used for metastatic anal squamous cell carcinoma that has progressed after platinum-based chemotherapy, based on the CheckMate 358 trial. Note: nivolumab is not FDA-approved specifically for anal cancer — this is a guideline-based (NCCN) use rather than an anal-cancer label indication. Nivolumab is a PD-1 checkpoint inhibitor that activates the immune system to attack cancer cells.
• Pembrolizumab (Keytruda): Used for previously treated metastatic anal cancer (KEYNOTE-158). Its FDA approval is tumor-agnostic — for tumors that are MSI-H/dMMR or have high tumor mutational burden (TMB-high) — rather than an anal-cancer-specific approval; NCCN supports its use. Also a PD-1 inhibitor, with meaningful and sometimes durable responses.
• Retifanlimab (Zynyz): FDA-approved in May 2025 as the first first-line treatment for inoperable locally recurrent or metastatic squamous cell carcinoma of the anal canal, given in combination with carboplatin and paclitaxel, based on the Phase 3 POD1UM-303/InterAACT2 trial (NCT04472429). The European Commission granted the same first-line approval in March 2026.

HPV-driven anal cancers express viral proteins that are foreign to the immune system, making them natural targets for immune recognition. PD-1 checkpoint inhibitors release the brakes on the immune system, allowing T cells to recognize and kill cancer cells displaying these viral antigens. This is why response rates to immunotherapy are generally higher in HPV-positive anal cancer than in many other tumor types.

Immunotherapy side effects differ fundamentally from chemotherapy. Rather than hair loss or nausea, immune-related side effects can affect virtually any organ and are caused by the activated immune system attacking normal tissues. Common immune-related adverse events include skin rashes, diarrhea/colitis, thyroid dysfunction, liver inflammation, and fatigue. Less common but serious events include pneumonitis, myocarditis, and adrenal insufficiency. Most are manageable if recognized early. Report any new symptoms promptly to the medical team.

Combining PD-1 inhibitors with other immunotherapy agents (such as anti-CTLA-4 antibodies like ipilimumab) is being investigated to improve response rates. The EA2176 trial (NCT04444921) is evaluating nivolumab with or without ipilimumab combined with carboplatin-paclitaxel as first-line treatment for metastatic anal cancer.

Adding immunotherapy before or during chemoradiation for localized anal cancer is a major area of investigation. The rationale: the immune system may be more effectively activated when the primary tumor is still present as a source of tumor antigens. Several trials are exploring this approach, including studies combining pembrolizumab or nivolumab with standard chemoradiation.

For patients with early-stage, HPV-positive anal cancer that responds well to treatment, radiation dose de-escalation trials are investigating whether lower doses of radiation (combined with immunotherapy or standard chemotherapy) can maintain high cure rates while reducing long-term side effects. This is analogous to successful de-escalation strategies in HPV-positive oropharyngeal cancer.

Unlike preventive vaccines (which prevent new HPV infections), therapeutic HPV vaccines are designed to stimulate the immune system to attack existing HPV-infected cancer cells. Several candidates are in clinical trials for HPV-related cancers, including anal cancer. These represent a potential future approach but are not yet available outside of clinical trials.

Radiation to the pelvis and perineum causes predictable side effects. Proactive management makes a significant difference:

• Skin care: Keep the treatment area clean and dry. Use recommended barrier creams (such as aquaphor, calendula, or prescribed products). Wear loose, soft clothing. Report any skin breakdown to the radiation team immediately.
• Diarrhea: Follow dietary recommendations (low-residue diet during treatment). Use prescribed anti-diarrheal medications. Stay hydrated.
• Pain management: Perineal pain during treatment is common. Sitz baths, prescribed pain medications, and topical treatments help.
• Nutrition: Consult an oncology dietitian. Maintaining nutrition during treatment improves tolerance and recovery.

Some patients experience long-term effects after chemoradiation that should be discussed openly with the medical team:

• Bowel function changes: Increased frequency, urgency, or occasional incontinence. These often improve over time but may persist. Pelvic floor physical therapy can help significantly.
• Sexual function: Vaginal dryness, stenosis, and dyspareunia in women; erectile dysfunction in men. These are treatable with appropriate support. Vaginal dilator use should be discussed early with women who have received pelvic radiation.
• Pelvic fractures: A risk after pelvic radiation, particularly in postmenopausal women. Bone density monitoring may be appropriate.
• Lymphedema: Swelling in the legs or genital area from radiation to inguinal lymph nodes. Compression garments and lymphedema therapy help.

Anal cancer carries a unique emotional burden because of its location, its association with HPV, and societal discomfort with these topics. Patients frequently report feeling isolated, embarrassed, or unable to discuss their diagnosis openly. These feelings are normal and understandable, but they should not prevent patients from seeking support.

Resources include oncology social workers and psychologists, the HPV and Anal Cancer Foundation (analcancerfoundation.org), online support communities, and peer support programs. Many patients find that connecting with others who have been through anal cancer treatment is profoundly helpful.

Chemoradiation for anal cancer is demanding, and caregivers play a critical role. Key strategies include setting up practical help (meals, rides, household tasks) before the hardest weeks of treatment, understanding the side effect timeline so you can prepare, attending key appointments to hear information together, and accessing caregiver support resources through the cancer center and organizations like the Family Caregiver Alliance (caregiver.org, 800-445-8106).

Anal cancer and its treatment can affect intimacy and sexual health. Open communication between partners is important. The treating team should include discussion of sexual health in follow-up care. Sexual health counselors with oncology experience can help couples navigate these challenges. Treatment-related sexual side effects are medical conditions, not personal failures, and they are treatable.

Anal cancer is one of the genuine success stories in oncology. The fact that a disease previously requiring mutilating surgery can now be cured with chemoradiation while preserving normal function is a remarkable achievement. The addition of immunotherapy for advanced disease has added another meaningful treatment option. The majority of anal cancer patients diagnosed today will be cured and will maintain normal bowel function. For those with metastatic disease, immunotherapy has extended lives in ways that were not possible even a few years ago. There is genuine, well-founded reason for hope.

• Localized (roughly 80–85% five-year survival): The vast majority are cured with chemoradiation. The treatment is demanding but highly effective.
• Regional (roughly 60–70%): Still very treatable. Chemoradiation cures many node-positive patients.
• Metastatic (roughly 30–35%): The most difficult situation, but immunotherapy has improved outcomes meaningfully beyond what chemotherapy alone could achieve. Some patients with metastatic disease achieve durable responses.

• What is the exact stage of my cancer?
• Is this squamous cell carcinoma? Is it HPV-related?
• Do I need HIV testing (if not already done)?
• How many anal cancer patients does this center treat per year?
• Will IMRT be used for my radiation?
• How long will treatment take, and what side effects should I expect?
• Should I get a second opinion?

• What is the realistic chance of cure with chemoradiation?
• How and when will you know if the treatment has worked?
• If the cancer does not respond completely, what are the next steps?
• What are the long-term effects I should prepare for?
• Are there clinical trials I should consider?
• What sexual health support is available?
• Should my family members get HPV vaccination?

• The treating center’s financial counseling office. Engage them early for insurance navigation, copay assistance, and payment plans.
• The oncology social worker. Connects families to assistance, transportation, and lodging resources.

• Patient Advocate Foundation — 800-532-5274. patientadvocate.org
• CancerCare — 800-813-4673. cancercare.org
• HealthWell Foundation — 800-675-8416. healthwellfoundation.org
• PAN Foundation — 866-316-7263. panfoundation.org
• Family Reach — familyreach.org
• NeedyMeds — 800-503-6897. needymeds.org

• HPV and Anal Cancer Foundation — analcancerfoundation.org. Education, support, awareness for anal cancer patients.
• United Ostomy Associations of America — ostomy.org. For patients who require colostomy.
• American Cancer Society — 800-227-2345. cancer.org. General cancer support and resources.
• National Cancer Institute — 1-800-4-CANCER. cancer.gov. Information and trial search.

Retifanlimab (Zynyz) was approved by the FDA in May 2025 as the first first-line therapy for inoperable recurrent or metastatic anal squamous cell carcinoma, used in combination with carboplatin and paclitaxel (via POD1UM-303); the European Commission granted the same first-line approval in March 2026. Pembrolizumab is available for anal cancers that are MSI-high or TMB-high through its tissue-agnostic approvals (KEYNOTE-158), and nivolumab has been studied in this setting (CheckMate 358). Standard chemoradiation agents (5-FU, mitomycin C, capecitabine) have long-standing approvals. NCCN Anal Carcinoma Guidelines are the primary clinical reference.

Nivolumab and pembrolizumab are available in Europe for various indications. Access for anal cancer specifically varies by country and funding mechanisms. The ACT II trial, which contributed key evidence for anal cancer chemoradiation, was led by UK investigators. ESMO guidelines cover anal cancer management and may differ in nuance from NCCN.

Anal cancer is relatively uncommon in Japan compared to Western countries. Standard chemoradiation protocols are used. Nivolumab and pembrolizumab are approved in Japan for multiple tumor types, with availability for anal cancer through specific indications or clinical trials.

Standard chemoradiation is widely available. Pembrolizumab and nivolumab are available through provincial formularies for various indications. Access for anal cancer specifically may require special authorization. Canadian guidelines generally align with NCCN and ESMO.

• Cisplatin replacing mitomycin C in chemoradiation FAILED
  The RTOG 98-11 trial tested whether cisplatin could replace mitomycin C as the chemotherapy partner during radiation. The cisplatin arm showed inferior disease-free survival and colostomy-free survival. Mitomycin C remains the standard despite its toxicity.
• Neoadjuvant chemotherapy before chemoradiation FAILED
  The ACCORD 03 trial tested induction chemotherapy (cisplatin plus 5-FU) before chemoradiation for locally advanced anal cancer. No improvement in complete response rate or colostomy-free survival was demonstrated.
• Maintenance chemotherapy after chemoradiation FAILED
  The ACT II trial tested maintenance cisplatin plus 5-FU after completing chemoradiation. No benefit in response or survival was found. Maintenance chemotherapy is not recommended after definitive chemoradiation.
• Primary surgery (APR) as initial treatment DE-ADOPTED
  Before the Nigro protocol, APR with permanent colostomy was the standard treatment. Chemoradiation was shown to achieve equivalent cure rates while preserving the sphincter. Primary surgery is now reserved only for salvage after failed chemoradiation or for very small anal margin tumors amenable to local excision.

• Abdominoperineal resection (APR) — surgical removal of the anus, rectum, and surrounding tissue; creates a permanent colostomy. Used as salvage for persistent or recurrent anal cancer.
• Anal canal — the short passage at the end of the digestive tract where stool exits the body.
• Anal margin — the skin surrounding the anal opening.
• Chemoradiation — combination of radiation therapy and chemotherapy given simultaneously; the standard curative treatment for anal cancer.
• Checkpoint inhibitor — a type of immunotherapy drug that activates the immune system to recognize and attack cancer cells.
• Colostomy — a surgically created opening on the abdomen through which stool passes into a pouch.
• DRE — digital rectal examination; a key part of anal cancer assessment.
• HSIL — high-grade squamous intraepithelial lesion; a precancerous change in the anal canal that can progress to cancer if untreated.
• HPV — human papillomavirus; a common virus that causes the vast majority of anal squamous cell carcinomas.
• HRA — high-resolution anoscopy; a procedure to examine the anal canal and identify precancerous or cancerous changes.

• IMRT — intensity-modulated radiation therapy; the standard radiation technique for anal cancer that reduces side effects.
• Immunotherapy — treatment that activates the immune system to fight cancer; checkpoint inhibitors are the main type used in anal cancer.
• Mitomycin C — a chemotherapy drug given with radiation as part of the standard Nigro protocol for anal cancer.
• Nigro protocol — the standard chemoradiation regimen for anal cancer, combining radiation with 5-FU and mitomycin C.
• Nivolumab (Opdivo) — a PD-1 checkpoint inhibitor used for metastatic anal cancer (NCCN-recommended; not an anal-cancer-specific FDA approval).
• p16 — a protein that serves as a marker of HPV-driven cancer when detected by immunohistochemistry.
• PD-1 — a protein on immune cells that cancer uses to hide from the immune system; blocked by nivolumab and pembrolizumab.
• Pembrolizumab (Keytruda) — a PD-1 checkpoint inhibitor used for metastatic anal cancer (FDA approval is tumor-agnostic, for MSI-H/dMMR or TMB-high tumors).
• Retifanlimab (Zynyz) — a PD-1 checkpoint inhibitor approved as first-line therapy (with carboplatin-paclitaxel) for metastatic anal cancer (FDA May 2025; EU March 2026).
• Salvage surgery — surgery performed when chemoradiation does not eliminate the cancer; typically APR.
• Squamous cell carcinoma — the most common type of anal cancer, arising from the lining cells of the anal canal.

Guidelines:

• NCCN Clinical Practice Guidelines — Anal Carcinoma (current version)
• ESMO Clinical Practice Guidelines for anal cancer

Landmark trials referenced in this guide:

• HPV and Anal Cancer Foundation (analcancerfoundation.org) — Education, support, awareness for anal cancer patients.
• PubMed (pubmed.ncbi.nlm.nih.gov) — Free public database of medical research.
• ClinicalTrials.gov (clinicaltrials.gov) — Official U.S. registry of clinical trials.
• National Cancer Institute (cancer.gov) — Information and trial search (1-800-4-CANCER).
• American Cancer Society (cancer.org) — 800-227-2345. General cancer support.