Anal cancer (also called Squamous Cell Carcinoma of the Anus or SCCA) is a skin cancer that arises from inside the anal canal or from the skin around the anus (anal verge).
Figure 1. Anal cancer located within the internal anal canal
Risk factors for anal cancer include immunodeficiency (eg HIV, transplant patients), those who have had previous Anal Warts due to the Human Papilloma Virus (HPV) serotypes 16 & 18, and those with Anal Intraepithelial Neoplasia (AIN). The estimated life time risk of anal cancer in HIV-negative men who have sex with men (MSM) is 30 times that of the average population. The lifetime risk of anal cancer in HIV-positive men who have sex with men (HIV-MSM) is 100 times that of the average population.
Anal cancer may be felt as a lump on digital rectal examination (DRE), or may not be noticeable at all. It may bleed from time to time.
Since February 2013, the HPV vaccine (Gardasil®) has been provided free of cost through the school-based program for males and females aged 12-13 years occurring in the first year of secondary school.
This vaccine has been shown to reduce the risk of anal and cervical cancer by targeting the Human Papilloma Virus (HPV) serotypes 16, 18, 6 and 11. There is possibly a very small advantage to those already with HPV infection also having the vaccine to help them eliminate the wart virus however this is contentious and remains debated.
Screening of high risk populations such as HIV men who have sex with men (HIV-MSM) and those with anal warts due to HPV infection is recommended, however there is much debate about the best method for screening. Screening methods most commonly used include the Pap Smear and anoscopy after painting the area with vinegar (acetic acid). These tests will allow for identification of those with anal dysplasia (AIN) which is a known risk factor for anal cancer. High risk populations (e.g HIV-msm) and those with high grade AIN should have annual digital rectal examination (DRE).
The PAP smear used for women to detect early cervical cancer, can also be used in high risk groups (e.g. those with HIV or HPV infection) to detect early anal cancer however its accuracy(sensitivity) is only 70%, therefore this practice is not endorsed by current guidelines .
Anoscopy involves viewing the anal region under magnification after the application of acetic acid (vinegar) to reveal areas of abnormality. It is currently not widely used as a screening tool, due to issues related to accuracy of this test and issues related to patient discomfort . Its main role is in screening the high risk population (e.g. HIV and HPV infected), where high resolution anoscopy is likely to be superior to conventional anoscopy . High resolution anoscopy is not widely available with only 5 centres throughout Australia having this technology. Therefor high resolution anoscopy is mainly used for research purposes.
DIGITAL RECTAL EXAMINATION
Annual digital rectal examination (DRE) in the high risk HIV-MSM group is likely to be the most effective screening method for picking up early anal cancer, and is currently the only screening method recommended.
Any suspicious lesion or lump in the anal region should be examined and biopsied. Four quadrant biopsies inside and outside of the perianal region are required in the high risk HIV-MSM patients where AIN status needs to be determined. Low grade anal neoplasia (AIN1) is not precancerous and does not progress to high grade neoplasia (AIN3), but low grade neoplasia (AIN1) is still considered a risk factor of anal cancer. High grade neoplasia (AIN3) is a pre-cancerous condition with risk of progression over time to invasive carcinoma. Once AIN has been confirmed on biopsy, there is currently no benefit in doing regular further biopsies. Rather, digital rectal examination should be performed annually to pick up early cancer.
COURSE AND PROGNOSIS
Anal cancer is locally aggressive, but distant spread (metastases) less common than many other cancers. It responds well to chemoradiotherapy. Overall survival is 69% at 5 years, but is dependent on the stage at which it is picked up.
Very small anal cancers can be managed with surgical excision alone provided this surgery does not involve damage to the anal sphincter. Superficially Invasive Squamous Cell Carcinoma of the Anus (SISCCA), refers to anal cancers less then 3mm deep and less than 7mm wide with good evidence that wide local excision with preservation of the anal sphincter gives excellent curative rates without the need for further radiotherapy. However, for lesions larger than this, the management is primary chemoradiotherapy and not surgery.
However, your colorectal surgeon is important in making the diagnosis and the ongoing surveillance of anal cancer following chemoradiotherapy treatment. Occasionally biopsies are required after radiotherapy treatment to confirm that treatment has been successful. This should not occur before 12 weeks have passed since finishing therapy. Occasionally salvage surgery is required after failed response to radiotherapy. This can range from local excision with skin grafting to more radical surgery including removal of the anus and rectum (abdominoperineal resection) with the creation of a permanent stoma.
Anal cancer responds well to radiotherapy combined with a small dose of chemotherapy (mitomycin C or cisplatin), with surgery as primary treatment only used for Superficially Invasive Squamous Cell Carcinoma of the Anus (SISCCA), or for larger cancers where primary chemoradiotherapy has failed.
WHAT TO EXPECT PRE AND POST OPERATIVELY FOR PERIANAL BIOPSY OF POSSIBLE ANAL CANCER
Fasting & Bowel Preparation
Unless you are also having a colonoscopy, a normal diet without a bowel prep, is required the day before surgery. You need to fast from midnight the night before if your surgery is scheduled for the morning, or from 7am if scheduled for the afternoon. You will be admitted as a day-stay procedure.
Recovery & transport
Following your procedure, you will recover for a hour until the effects of sedatives have worn off. You should not drive yourself home after your procedure and should have someone organised (a friend or relative) to accompany you.
Spotting of blood will occur from the biopsy sites. A sanitary napkin will be needed to prevent staining of your underwear.
For pain, a nonsteroidal is recommended such as 400mg of ibuprofen (Brufen®) along with 2 tablets of paracetamol. This should only be taken if needed and can be taken up to three times a day for five days. Opioid medications (Endone®) can usually be avoided. If required, they should be used sparingly as they cause constipation.
Excessive cleaning or scratching with abrasive toilet paper should be avoided. Washing with water or using baby wipes is preferable.
You should follow up with your colorectal surgeon in 6-8 weeks following your surgery to review your condition and discuss further management if indicated.