Anal Cancer Treatment

Anal cancer begins in the tissues of the anus, the short tube at the end of the rectum where stool leaves the body. Most anal tumors are classified as squamous cell carcinoma, which develops in the flat cells that line the anal canal. Less common types include adenocarcinoma, melanoma and neuroendocrine tumors.

The primary cause of anal cancer is infection with certain high-risk strains of the human papillomavirus (HPV). Persistent HPV infection can lead to abnormal cell changes (dysplasia), which may progress to cancer over time. Additional risk factors include a weakened immune system, smoking, multiple sexual partners, receptive anal intercourse and a history of cervical, vulvar or vaginal cancer.

Symptoms of anal cancer can include rectal bleeding, anal pain or pressure, itching, a lump or mass near the anus, changes in bowel habits and swollen lymph nodes in the groin or anal area. Because these warning signs can resemble those of a more common benign condition, such as hemorrhoids, a prompt evaluation is important.

Anal cancer is relatively rare. According to the American Cancer Society, several thousand new cases are diagnosed in the United States each year, accounting for only a small percentage of all gastrointestinal cancers. For reasons that are not well understood, anal cancer is more frequently diagnosed in women than men and is most common in adults 50 and older, although it can occur at any age.

Treatment for anal cancer can vary depending on the size, location and stage of the tumor, the extent of lymph node involvement, if any, and the patient’s overall health. Many patients benefit from a combination of chemotherapy and radiation therapy, although surgery and immunotherapy may also play a role in certain situations.

Chemotherapy for anal cancer

Chemotherapy uses powerful medications to destroy widespread cancer cells or stop them from growing. For anal cancer, chemotherapy is most often given in combination with radiation therapy, a strategy known as chemoradiation. This approach is the standard first-line treatment for most localized anal tumors, allowing the patient to avoid major surgery. Chemotherapy may also be considered for recurrent anal cancer or metastatic anal cancer that has spread to distant organs or tissues.

Chemotherapy drugs that may be used to treat anal cancer include:

• 5-fluorouracil (5-FU)
• Capecitabine
• Carboplatin
• Cisplatin
• Mitomycin

The side effects of chemotherapy can vary depending on the specific drugs and doses used, but may include fatigue, nausea, vomiting, diarrhea, mouth sores, hair loss, low blood cell counts and an increased risk of infection. Many side effects are temporary and can be managed with supportive care.

Radiation therapy for anal cancer

Radiation therapy uses high-energy beams, such as X-rays, to destroy cancer cells. For most patients with anal cancer, the treatment is delivered externally and combined with chemotherapy for heightened effectiveness. As a frontline treatment, radiation therapy can target the primary tumor and nearby lymph nodes. In select cases, it may also be administered after surgery to destroy any remaining microscopic cancer cells and help reduce the risk of recurrence. If surgical treatment is not an option, radiation therapy may be used to help relieve the symptoms of advanced or metastatic anal cancer.

Radiation delivery techniques that may be used to treat anal cancer include:

• External beam radiation therapy (EBRT)
• Image-guided radiation therapy (IGRT)
• Intensity-modulated radiation therapy (IMRT)

Potential side effects of radiation therapy for anal cancer include skin irritation in the treated area, fatigue, rectal discomfort and sexual dysfunction. Some patients may also experience long-term changes, such as bowel or bladder urgency, fecal incontinence, diarrhea, rectal bleeding, scar tissue formation and decreased bladder elasticity. Careful planning and advanced radiation delivery techniques can help minimize any damage to healthy tissues.

HPV vaccination has been shown to decrease pre-cancerous anal lesions and will likely translate to preventing a proportion of anal cancers.

Seth Felder, MD

Surgeon, Gastrointestinal Oncology Program.

Surgery for anal cancer

In most cases, surgery is not the primary treatment for anal cancer, mainly because chemoradiation can be highly effective. However, surgical treatment may be considered for a very small, early-stage tumor that can be completely removed or if the cancer persists or recurs after chemoradiation.

Surgery for anal cancer may involve:

• Local excision, which removes a small tumor and a margin of healthy tissue
• Abdominoperineal resection, which removes the anus, rectum and part of the sigmoid colon and requires a permanent colostomy

The risks and side effects of surgery for anal cancer can vary depending on the type of procedure performed, but may include bleeding, infection, pain, changes in bowel function and the need for a permanent colostomy. Recovery time can also vary. The patient will receive detailed guidance on postoperative care to promote full healing and the best possible outcome.

Immunotherapy for anal cancer

Immunotherapy aims to help the body’s immune system recognize and attack cancer cells. For anal cancer, immunotherapy is typically used for advanced or metastatic disease that has progressed or returned after chemoradiation.

Immunotherapy drugs that may be used to treat anal cancer include:

• Nivolumab
• Pembrolizumab
• Retifanlimab

These medications are immune checkpoint inhibitors that target specific proteins found on the surface of cancer cells, such as PD-1, which can enhance the immune response against the cancer cells.

The side effects of immunotherapy can include fatigue, skin rash, diarrhea and inflammation of organs, such as the lungs, liver or thyroid. Because immunotherapy stimulates the immune system, it can cause immune-related side effects that require careful monitoring and prompt treatment.

Targeted therapy, hormone therapy and other treatment options for anal cancer

At this time, targeted therapy and hormone therapy do not play a significant role in the standard treatment of most anal cancers. However, research is ongoing, and scientists are currently studying new targeted agents and combination approaches in clinical trials. Supportive treatments, including pain management and skin care, may be considered to help improve the quality of life for a patient with advanced anal cancer.

Clinical trials for anal cancer

Clinical trials are carefully designed research studies that evaluate new treatments or new combinations of existing therapies and compare them with the current standard of care. These studies play a vital role in advancing cancer treatment, helping researchers develop more effective therapies and improve outcomes for patients.

For an interested patient, a specialist can help determine whether a clinical trial is an appropriate option based on the patient’s diagnosis, cancer stage and treatment history. Participation in a research study may provide the patient with access to innovative therapies that are not yet widely available. Throughout the trial, the patient will be monitored closely by a multispecialty team while contributing to research that may benefit future patients.

Benefit from world-class care at Moffitt Cancer Center

Moffitt offers comprehensive, multispecialty care for patients with anal cancer. Experts in medical oncology, radiation oncology, surgical oncology, pathology and supportive services work together to develop highly individualized treatment plans. Our approach is further distinguished by advanced technologies, a robust portfolio of clinical trials and a commitment to patient-centered care.

If you would like to learn more about anal cancer treatment, you can request an appointment with a specialist in the Gastrointestinal Oncology Program at Moffitt by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.