Anal Cancer Flashcards
Epidemiology - What is the incidence, sex predominance, and median age?
2% of all GI cancers; more females, median age of diagnosis is 62
List 5 General Risk Factors
HIV (can impact mgmt, but not at BCCA), HPV, Immunosuppression, Smoking (4x risk), Chronic perianal irritation
What is the strongest risk factor?
HPV - most caused by HPV16/18 (so no history of genital warts necessary); usually in younger patients, and may be a risk factor even if no HPV DNA is detected
What are the proximal and distal borders? Where does rectal Ca begin?
Proximal: Where rectum enters puborectalis sling
Distal: Where squamous mucosa blends with perianal skin
Rectal Ca: If epicentre >2cm from dentate line (transition from glandular to squamous mucosa)
List the lymphatic drainage of the: Distal rectum, proximal anal canal, dentate region, and distal anal canal (beyond dentate)
Distal rectum: perirectal –> presacral
Prox anal: hemmoroidal –> perirectal –> obturator –> internal iliac –> common iliac
Dentate: Hypogastric, obturator & presacral
Distal anal canal: Inguinal LNs –> femoral LNs –> external iliacs
What is the blood supply of the anal canal?
Upper 2/3s of the anal canal –> portal system (aorta to IMA to SRA, as well as aorta to CI to II to middle rectal
Lower 1/3 enters the systemic system (aorta to CI to II to internal pudendal to inferior rectal
List local, regional and distant patterns of spread
Local: Commonly see invasion into sphincter muscles and perianal connective tissue (50% sphincter invasion at presentation). Also, see vaginal invasion in women and rarely prostatic in men (fistula <5% of the time)
Regional: Lymphatic spread ++ common and happens early, depending on location will vary which chains are involved (25% LN+ at presentation, 10% with inguinal)
Distant: Rarer at presentation (~10%); common sites liver, lung, extra-pelvic LN
List some benign and pre-malignant lesions to have on the ddx
Benign: hemorrhoid, anal fissure (less common AVM, peri-rectal abscess, condyloma, fistula, rectal prolapse, skin tag, lipoma, trauma)
Pre-malignant: anal intraepithelial neoplasia (AIN) - similar to cervix, at transition zone with low and high grade due to HPV
How do we approach AIN
If low grade - observation as many will spontaneously regress, but some will progress to high-grade AIN
If high grade - True precursor of anal SCC, refer for ablative procedures
What is the most common malignant pathology? List 10 other, rare, pathologies
Most common: Squamous cell (~80%); Keratinizing usually from lower anal canal (aka below dentate) and non-keratinizing above dentate
Others: Adenocarcinoma (from anal glands, usually actually distal rectal with extension, treat like low rectal ca); SCC/BCC (from perianal skin); Bowen’s disease; Paget’s disease; Melanoma; Neuroendocrine; Lymphoma; Sarcoma; Kaposi’s sarcoma; Mets
What is the roll of CT, MR, and PET in workup?
CT - Usually inferior to PE for evaluating primary, useful to look for distant dz and regional LNs
MR - no evidence this is superior to CT, so not SOC
PET - useful to evaluate dz extent (primary, regional, and distant), so standardly done for staging and 3 mos post tx to evaluate response
List 5 common clinical presentations
Rectal bleeding (most common), anorectal pain, sensation of anal/rectal mass, change in bowel habits, inguinal LAD if advanced
Is there a role for screening?
No RCT evidence & no tumour marker
In general population - too rare, so no
Screening controversial in HIV+ or those with HPV genital dz (done in Vancouver but not universal)
List 6 demonstrated prognostic factors
- Primary tumour size
- LN status (survival with LN+ about half that if LN- for same T stage)
- HgB<100
- Poor ECOG
- HIV+ with CD4<200 (higher recurrence rate)
- Poorly differentiated tumour
Does addition of chemo reduce rate of distant mets?
It seems no - addition of chemo had not decreased number of patients who develop mets post tx
Overall rare, only 10-20% will have distant relapse after curative local treatment
only ~10% with mets at presentation
