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Anal Cancer
Overview
Anal cancer is a rare cancer caused by the presence of the human papillomavirus (HPV) in the body.
The anal canal is a short tube, averaging about 2 cm long in women and 3 cm in men, into which the rectum passes. The anal canal is formed by a muscular complex, which includes two sphincters (internal and external) and the most distant bundles of levators (muscles that lift the anus). Sphincters, like two rings, are located one above the other and are separated by a special anatomical structure - a jagged line, which allows you to feel the urge to defecate.
This disease is often associated with a decrease in immunity, for example, after an organ transplant or while taking medication. Other risk factors are:
• Cervical dysplasia as an HPV-associated condition;
• Autoimmune diseases (eg, systemic lupus erythematosus);
• Rheumatoid arthritis;
• Ulcerative colitis ;
• Anal canal polyps;
• Smoking cigarettes ;
• Severe course of the fistulous form of Crohn's disease
• Anal cancer is not a hereditary disease, its development is associated primarily with HPV.
Anal cancer is 100% fatal if untreated. But malignant tumors of this localization can be completely cured if therapy is started on time. According to statistics, this disease most often develops after 45 years, but people between 35 and 44 years old make up 10% of patients.
The spread of the malignant process to the lymph nodes is diagnosed in 15-30% of patients at the time of diagnosis. Distant metastases to other organs, such as the lungs, liver, and bones, occur in 10-17% of cases. With prolonged growth, the tumor can damage the elements of the sphincter apparatus, which regulates the process of defecation.
Symptoms
The most common complaint that patients in the presence of anal canal cancer turn to a coloproctologist with is pain in the anus.
Often, when bloody marks appear on paper or drops of blood in the anus, people confuse these warning symptoms with manifestations of hemorrhoids or anal fissure. This is often the reason why patients delay diagnosis.
The presence of a “bump” or sore can also be an alarming signal - even the most, at first glance, harmless defects can turn out to be a malignant tumor.
Itching in the anus is not always a sign of an anal fissure or an allergic reaction, sometimes malignant tumors of the anal canal can also be accompanied by this symptom.
Sometimes anorectal fistulas can be a manifestation of an oncological process in the anal canal, but this is a rather rare symptom. Anorectal fistulas are manifested by purulent or bloody discharge from the anus or a pathological opening in the perianal region, as well as periodic fevers.
Fecal incontinence as a result of the spread of the tumor to the sphincter muscles is an alarming symptom that requires urgent treatment.
An increase in inguinal lymph nodes may also indicate the spread of the disease.
Another symptom may be the sensation of a foreign body in the anus. A digital examination of the rectum can palpate a mass formation.
Prevention
After completion of the course of chemotherapy, regular examinations of the patient are required for the next two years. This is necessary in order to track the occurrence of a relapse in time. The final effect of chemotherapy is assessed 6 months after completion of treatment.
The histological form of the anal canal tumor does not affect the prognosis of the disease. One of the most important factors unfavorable for the prognosis is the defeat of the lymph nodes, which provokes the development of relapse. Male sex is also an unfavorable factor.
In HIV-infected patients, the disease is more severe, but antiretroviral therapy allows the use of standard treatments for neoplasms.
Several studies have examined the effect of smoking on prognosis in anal cancer. Their results reliably indicate that in smokers the course of the disease is worse, and the prognosis during treatment is more unfavorable.
Certain lifestyle choices can help prevent anal cancer. One of the most important tasks is to prevent HPV infection. Some ways to reduce your chances of contracting HPV include:
• use condoms during intercourse;
• avoid smoking;
• HPV vaccinations help protect against certain types of the virus. The use of the HPV vaccine has been shown to be associated with a significant reduction in the risk of developing anal cancer. But if the human papillomavirus is already present in the body, the vaccine will not be effective.
As part of screening for anal cancer, a colonoscopy should be performed every three years starting at the age of 40, and a coloproctologist should be consulted if any neoplasms appear in the perianal area.
Treatment
In the treatment of anal canal formations, various methods are used, but in most cases a complete cure can be achieved without the use of radical surgical intervention.
For warts or low-grade dysplasia of the anal canal ( precancerous conditions ), topical drugs (for example, 5-fluorouracil) are used or local excision of the neoplasm is performed. However, there is a high percentage of recurrences of formations (about 59%), which requires careful monitoring after treatment.
For carcinoma in situ (without metastasis), local excision is performed within healthy tissues. Laser tumor removal is possible in certain clinical situations.
Small tumors of the anal canal (T1N0) can be removed by local excision within healthy tissue (1 cm from the border of the tumor). In case of tumor recurrence after local excision, repeated minimally invasive intervention is possible only in patients who can maintain the function of holding (normal sphincter function).
T2N0 carcinomas have an increased risk of metastasizing to the inguinal lymph nodes, in which case both the primary tumor and both sides of the inguinal lymph nodes are irradiated. The use of chemoradiotherapy is advisable in certain clinical situations. This makes it possible to increase the efficiency of treatment of early-stage tumors by 55%.
Chemoradiotherapy is the standard of care for advanced tumors (T3-T4 or N1-N3). The detection of single tumor cells according to biopsy data after undergoing therapy may indicate remission of the disease, however, in such cases, a second biopsy should be performed after 6 weeks. For patients who have already undergone courses of chemoradiotherapy, in case of relapse, surgical intervention is effective - abdominal-perineal extirpation of the rectum with the removal of a permanent stoma (tube) to the anterior abdominal wall. With this intervention, the rectum is permanently removed.
In cases of locally advanced carcinoma, chemoradiotherapy is the treatment of choice.
Treatment of locally advanced anal tumors involves radiotherapy in combination with 5-fluorouracil and mitomycin C. This strategy reduces the number of recurrences by 23% compared with radiotherapy. A 13-year follow-up showed a significant 33% reduction in cancer mortality in the combination therapy group.
Current recommendations for the treatment of patients with anal cancer over 75 years of age do not imply a reduction in radiation dose in patients whose physical condition is satisfactory (without severe comorbidities and leading an active lifestyle).
In case of recurrence of a tumor in the pelvic lymph nodes, radiation therapy is indicated (if not previously performed).
Lymph node dissection - removal of lymph nodes along with the tumor and subcutaneous tissue at the site of its formation (Duken's operation) is performed in case of ineffective radiation therapy.
Tests Required for Diagnosis
Careful digital examination of the anal canal, rectum, and visual examination (sigmoidoscopy) of the perianal region can provide important information about the presence, location, and extent of an anal tumor.
In women, examination and palpation of the vagina and perineum helps to determine the degree of involvement in the disease of the septum between the rectum and the vagina. If the digital examination is accompanied by severe pain, the examination should be repeated in the operating room with general or spinal anesthesia.
If a malignant process is suspected, the doctor must take a biopsy - a piece of altered tissue, which is then sent for histological examination.
Approximately one third of patients with anal cancer have enlarged inguinal nodes, but only 50% of them are metastatic. Lymph nodes with metastases near the rectum can also be detected by digital examination, but modern methods of radiation diagnostics for imaging the tumor are more accurate.
Positron emission tomography (PET) can assess the condition of the lymph nodes with the detection of pathological absorption, even if there is no clinical evidence of involvement. In addition, if lymph node involvement is suspected, a biopsy should be performed. In the case of a negative result according to the biopsy, diagnostic surgery is recommended - complete removal of the inguinal lymph node for a more accurate and extended histological examination.
Magnetic resonance imaging (MRI) is widely used in the diagnosis of anal cancer. This method, safe from the point of view of radiation, allows to assess the degree of invasion (spread) of the tumor to the surrounding structures, as well as to suspect the presence of metastatic lymph nodes.
In order to exclude metastases to distant organs, such as the lungs and liver, computed tomography (CT) with intravenous contrast is often used. This method is also necessary for the preparation of a tumor treatment plan.
A blood test for the SCC marker (tumor marker) can be informative only during the treatment process to monitor its effectiveness; it is not necessary to take it as a primary diagnosis.
