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Anal cancer:an introduction

Last updated:

June

2020

IntroductionThis chapter provides

An overview of anal cancers and their characteristicsA review of the features and characteristics of cancers of the anal canal and cancers of the anal marginAn introduction to the burden of anal cancer, including the risk of morbidity from metastases, and mortality

Overview of anal cancer1. International Agency for Research on Cancer (IARC). http://gco.iarc.fr/today/data/factsheets/populations/900-world-fact-sheets.pdf (Accessed:

May 2020); 2. Van der Zee RP, et al. Neth J Med 2013;71(8):40111; 3. Symer MM, Yeo HL. F1000Res 2018;7:F1000 Faculty Rev-1572.*The term GI malignancies is assumed to include malignancies of the oesophagus, stomach, colon rectum, and anus.GI, gastrointestinal.

Anal cancer

is a rare cancer, accounting for ~

1.5% of GI malignancies

1

Anal

cancer

incidence has

increased in recent decades by

up to 2.2%

each year

in Western countries

2

The median

age

at

diagnosis

is

61

years

3

Anal cancers are classified as anal canal cancers or anal margin cancers1. Salati SA, et al. Int J Health Sci (Qassim)

2012;6(2):20630; 2. Glynne-Jones R, et al. Radiother Oncol 2014;111(3):3309; 3. NCCN Clinical Practice Guideline in Oncology. Anal carcinoma, Version 1.2020. November 2019. (Accessed: April 2020); 4. Wietfeldt ED, et al. Clin Colon Rectal Surg 2009;22(2):12735.Anal canal

cancers

Arise in the anal canal up to the anal

verge

1

More

common than anal margin cancers (85% of

cases)

1

Normally poorly differentiated and more common in women than anal margin cancers

2Are commonly treated with

CRT

3Anal margin

cancersAffect the perianal and surrounding skin1Generally well differentiated and often occur in men2Treatment depends on clinical stage3

Excision can be performed for smaller lesions*, otherwise CRT is recommendedPrognosis may be more favorable than anal canal tumors if lesions are localized4

Anal

canal

Rectum

Mucosa

Anal margin

(perianal skin)

Transitional

zone

Dentate

line

Anal

verge

Blood

vessels

Sphincter muscles

Anatomy of the anal canal

*T1, N0 Well or moderately differentiated or select T2, N0 (that does not involve sphincter).

CRT

, chemoradiotherapy.

Squamous cell carcinoma is the most common type of anal cancer

Anal canal cancers1Anal margin cancers1–3 SCC is the most common type of anal margin cancer, with features similar to skin lesions occurring in other cutaneous sitesTumor types include basal cell carcinoma, Paget’s disease, Bowen’s disease, malignant melanoma and Buschke–Lowenstein tumor

1. Nelson VM, et al. Surg Oncol Clin N Am 2017;26(1):9



15; 2.

Wietfeldt ED, et al. Clin Coloin Rectal Surg 2009;22(2):127



35; 3. Salati

SA, et al. Int J Health Sci (Qassim) 2012;6(2):206



30.SCC, squamous cell carcinoma.

The disease- and treatment-related burden of anal cancer is high

1. Salati SA, et al. Int J Health Sci (Qassim) 2012;6(2):20630; 2. National Cancer Institute. Surveillance, Epidemiology, and End Results Program. https://seer.cancer.gov/statfacts/html/anus.html (Accessed: May 2020); 3. Sodergren SC, et al. Clin Oncol (R Coll Radiol) 2019;31(2):6971.HRQoL, health-related quality of life.

Incidence of nodal metastases

is ~10% at diagnosis, but can increase to

20–60%

for T4

lesions

1

Potential for metastases

Treatments can result in toxicities

Five-year survival can be low

Toxicities from concurrent chemoradiotherapy

can cause bowel, urinary and sexual dysfunction, prompting

suboptimal dosing and reduced HRQoL

3The five-year survival rate depends on stage at diagnosis, and is 65.8% for regional disease, and can be as low as

33.9% for extrapelvic metastatic disease1,2

SummaryAnal cancer comprises cancer of the

anal canal, and cancer of the anal margin1,2Anal canal cancers are more common than anal margin cancers and often have a worse prognosisSCC is the most common type of anal cancer (in either canal cancer or anal margin cancer)1Anal cancer represents a significant medical burdenThe five-year survival rate for anal cancer depends on the stage at diagnosis, and is 81.9% for localized lesions, 65.8% for regional disease, and can be as low as 33.9% for patients with extrapelvic metastases1,31. Salati SA, et al. Int J Health Sci (Qassim) 2012;6(2):206



30; 2. Wietfeldt ED, et al. Clin Colon Rectal Surg 2009;22(2):127



135;

3.

National Cancer Institute. Surveillance, Epidemiology, and End Results Program. https://seer.cancer.gov/statfacts/html/anus.html

(Accessed: May 2020

).

SCC, squamous cell carcinoma.