Changing nature of anal cancer.

Abstract

Anal cancer is rare, accounting for about 2% of all anorectal cancers or 300 cases a year in Britain.' Epidemiological studies from the United States have highlighted the striking association of syphilis and anal warts with anal cancer in unmarried men.23 Gonorrhoea, syphilis, and anal warts are more common in homosexual than heterosexual men,4 and carcinoma in situ may develop in the anal warts of young anoreceptive homosexual men, a change that has been seen in patients with AIDS.5 In a recent comparison of risk factors for squamous cell carcinoma of the anus and cancer of the colon receptive anal intercourse and anal warts were high risk factors for anal cancer in men but not in women.6 Squamous cell carcinomas of the cervix, vulva, and penis are associated with the sexual transmission of human papillomaviruses. Human papillomavirus 16 is the predominant type associated with invasive cervical cancer, but it is less often associated with cervical dysplasia and genital warts.7 The types of human papillomavirus most commonly identified in anal warts are 6 and 11, but human papillomavirus 16 has been found in 8%.8 Identification of DNA from human papillomavirus 16 in anal warts has been related to the degree of dysplasia of the wart.9 '° In one study patients with dysplasia of the anorectal mucosa and no warts had evidence of infection with human papillomavirus, while patients with long standing dysplasia had antibodies to human immunodeficiency virus. " Preliminary data from a controlled study reported DNA sequences from human papillomavirus in six out of 10 patients with squamous cell carcinoma of the anus but in none of the 10 patients undergoing haemorrhoidectomy or in the three patients with malignant melanoma or adenocarcinoma of the anus.'2 Risk factors for venereal transmission of human papillomavirus and for squamous cell carcinoma of the cervix and anus are similar. Deficient cellular control of papillomavirus gene expression may be responsible for the oncogenic potential of human papillomavirus, accounting for the long period between infection and the development of the tumour and the small proportion of the infected population developing tumours. 3 Recent reports of anal squamous cell carcinoma in young homosexual men with and without AIDS should alert doctors to this diagnosis. ' 15 Anatomically anal cancer is subdivided into cancer of the anal margin, which arises below the dentate line and accounts for a third of cases, and cancer of the anal canal, which arises astride or above the dentate line and accounts for the other two thirds of cases.'6 It is controversial whether this anatomical separation matters, but cancer of the anal canal is more common in women and cancer of the margin is far more common in men. 16 Just over half of anal cancers are squamous cell carcinomas, and a third are basaloid tumours arising from the transitional area of mucosa just above the dentate line.'7 Other rarer tumours include the highly malignant small cell cancer, mucoepidermoid cancer, adenocarcinoma arising in the anal glands, and malignant melanoma. Anal cancer occurs at a mean age of 57 but has been reported in much younger homosexual men. The commonest presenting symptoms are bleeding and pain with or without a change in bowel habit, pruritis ani, and a mass. Tumours are usually ulcerated but may present as a submucosal mass or a stricture. Diagnosis may be made difficult by the many conditions that coexist with anal cancer, including condyloma acuminatum, Bowen's disease, Paget's disease, leukoplakia, lichen sclerosus, and Crohn's disease.'8 Early assessment and biopsy of the tumour under anaesthetic, together with examination of inguinal nodes, and computed tomography of the pelvis and pelvic nodes are important investigations for planning treatment. Cancer of the anal canal has been treated by a radical operation-combined excision of the rectum and anus and formation of a permanent colostomy. 6 Radical operations are still popular in Britain despite the poor results. In a series of 188 cases from the Mayo Clinic 40% of patients developed recurrent disease (locally in 84% of cases) after a radical operation. 7 The five year survival for those given an operation was 71%, but if patients with inoperable tumours were included it was only 60%.'7 Tumours under 2 cm arising at the anal margin were excised locally, and in the small subset of patients with this kind of tumour local recurrence was rare. Most anal cancers are not suitable for local excision, but squamous cell carcinoma of the anus and its metastases in lymph nodes are particularly radiosensitive. In an attempt to reduce local and regional recurrences Papillon treated a series of patients with r4diotherapy with or without a subsequent operation. ' He reported a five year survival comparable with that achieved by a radical operation (65%), but three quarters of his patients retained normal anal function. Nigro combined preoperative radiotherapy and chemotherapy but abandoned radical surgery after five of the first six patients had no residual tumour.20 Subsequently 83 out of a series of 104 patients had no tumour on excision or biopsy. Four fifths survived five years-three quarters with normal anal function.20 A study comparing patients given chemotherapy and radiotherapy with historical controls given only radiotherapy reported similar survival but improved control of primary disease and a lower rate of colostomy in those given chemotherapy and radiotherapy.2' Acute haematological and enterocolic toxicity was more common in those given both treatments. Squamous cell carcinoma of the anus can now be treated without a radical operation. Small tumours, in situ tumours, and areas of persistent dysplasia of the anal margin are suitable for local excision. The United Kingdom Coordinating Committee for Cancer Research (Anal Cancer Trial, CRC Clinical Trials Centre, Rayne Institute, 123 Coldharbour Lane, London SE5 9NU) is conducting a controlled trial of radiotherapy versus combined treatments, and patients with tumours unsuitable for local excision should be considered for treatment within this or an alternative protocol. A radical operation may be reserved for those with residual or recurrent disease. ROBERTW TALBOT Senior Surgical Registrar, St Mark's Hospital, London EC1V 2PS

Cite this paper

@article{Talbot1988ChangingNO, title={Changing nature of anal cancer.}, author={Rhiannon Talbot}, journal={BMJ}, year={1988}, volume={297 6643}, pages={239-40} }