Management of Carcinoma Anal CanalDR . J UNISH B AG G A

MO DE R ATO R - DR .M.S.UPPAL

Development

• During the 6th week of gestation

• Terminal part of hindgut is called cloaca

• It is divided by the urorectalseptum into rectum and urogenital sinus

• Distal anal canal is derived from infolding of the ectoderm which fuses with the rectum.

• The dentate line divides the hindgut from the ectodermal distal anal canal.

Anatomy

• Funnel shaped extension of pelvic floormusculature

• 3-4 cms

• Anorectal ring -> anal verge

• Anorectum – anal canal and the surrounding structures-

• distal rectum

• anal sphincters

• anal canal

• perianal skin

Divided into three parts-

1. Upper mucous part(15mm)- 8- 14 folds called anal columns of morgagni.Between each 2 columns – anal crypts

2. Middle part(15mm)- lined by mucous membrane.Mucosa has a bluish appearance. Sensations of heat, cold, touch, pain

3. Lower cutaneous part(8mm)- true skin containing sweat and sebaceous glands.

Arterial supply -

• Superior rectal artery

Inf. Mesenteric artery

• Middle rectal artery

• Internal iliac artery

• Inferior recalartery- inf. Pudendal atrery

Venous drainage • Superior rectal vein

• Middle rectal vein

• Inferior rectal vein

Lymphatic Drainage

• Main anatomical reference points

1. Anal verge- junction b/w anal and perianal skin

2. Dentate line- true mucocutaneousjunction. 1-1.5 cms above anal verge.

Transition zone of 6-12mm

columnar>squamous

3. Anorectal ring- upper border of sphincteric complex.

Sling- puborectalis muscle

Histology • Columnar epithelium

• ATZ – anal transition zone (1-2cm)

Columnar cells with variable amounts of squamous metaplasia

• Non-hair bearing squamous epithelium

• Perianal skin

Overview

• 2.4 % of all GI malignancies

• Anal canal cancer most commonly develops in patients 50 to 60 years of age.

• Peak incidence is in the 7oth decade of life but highly variable

• More common in women

• Squamous cell ca. is the most common – 80%

• Multimodality treatment with radiation and chemotherapy has replaced APR and wide local excision

Incidence

• Incidence of anal cancer has nearly doubled in the last two decades

• Mirrors the rise in HIV infection

• It is thought to have a viral etiology similar to that of cervical cancer.

• There is a slight female predominance with 1. 7 cases per 1 00,000 women compared with 1 .4 per 1 00,000 men per year

Risk factors

• HPV (human Papilloma Virus)

• Female gender (many series of data)

• HIV infection

• Sexual promiscuity- particularly receptive anal intercourse

• Smoking

• Chronic inflammation

Classification

• Anal cancers occur between the anal verge and 2 cm beyond the dentate line; tumors occurring further from the dentate line are called rectal cancers.

• Because of complex histology, classification has always been confusing

• 3 main anatomic regions

• Intra-anal –cant be visualized or with slight retraction of buttocks

• Perianal- fully visible and lie within 5cms of anal opening

• Skin – outside this 5cm radius

Anal Intraepithelial Neoplasms- AIN

• Pre-cancerous lesions of the anal canal

• Includes

• Carcinoma in situ

• Bowen’s disease

• Anal dyaplasia

• Squamous intraepithelial lesion

• Same spectrum of pathology

AIN

• AIN can be divided into

• LSILs- low grade squamous intraepithelial lesions

• HSILs- high grade intraepithelial lesions

• Invasive cancer

• In European literature, HSIL is known as AIN-3

And LSIL is known as AIN-1 and 2

• The true incidence of HSIL and its resultant progression to invasive SCC are not clearly known

Pathology

WHO classification of malignant epithelial tumors of the anal canal

• Squamous cell carcinoma and its variants

1. Transitional cell ca.

2. Basaloid ca

3. Mucoepidermoid ca.

• Adenocarcinoma

• Small cell ca.

• Undifferentiated ca.

More distal the tumor, more likely it is to contain keratinizing cells.

These tumors arise from ATZ and are grouped together as Cloacogenic.

Pathology

• Anal cancers occur between the anal verge and 2 cm beyond the dentate line; tumors occurring further proximal are called rectal cancers.

• Adenocarcinomas can arise from anal crypts and should be treated as a rectal cancer though with a higher risk of inguinal node spread, given their location and lymphatic flow compared with rectal adenocarcinomas.

Pathology

• Primary anal melanoma is a rare tumor that accounts for only 1% of all anal cancers. Anal melanoma is similar to melanoma of the skin and is characterized by the distant spread of disease. Outcome is poor after wide local excision or abdominoperineal resection, with just a 10% survival in most series at 5-year follow-up.

• Perianal skin and anal margin tumors include squamous cell carcinoma, giant condyloma (verrucous carcinoma), basal cell carcinoma, Bowen disease, and Paget disease.

Pathways of tumor spread

• Direct extension to surrounding tissue

• Lymphatic dissemination to pelvic and inguinal lymph nodes

• Hematogenous spread to distant viscera

At diagnosis, about half of all anal cancers have been found to invade anal sphincter or surrounding soft tissue. Although Denonvillier’s fascia is an effective barrier to prostatic invasion in men, direct extension to the rectovaginal septum is a common occurrence in women.

Pathways of tumor spread

• The inguinal nodes are the primary drainage basin for that part of the anal canal distal to the dentate line.

• Lymphatic drainage around the dentate line occurs to lymphatic plexuses of the rectal mucosa and along the pathway of the inferior and middle hemorrhoidal vessels to obturator and hypogastriclymph nodes.

Clinical presentation

• The most common presenting symptoms are bleeding (45%) and anal pain(30%). Other less common symptoms include pruritus , palpable mass ,anal swelling and changes in bowel habits are the main symptoms.

• It is common for patients and their physicians to attribute such symptoms to hemorrhoids for many months preceding the diagnosis, underscoring the importance of performing a simple anorectalexamination for patients with such symptoms.

Diagnostic Workup

• PET imaging is useful in further evaluating the extent of the primary tumor and the presence of regional lymph node metastases, and distant metastases, as well as in evaluating the response to therapy.

• For patients with HIV risk factors, a determination of HIV status should be made before the initiation of therapy.

• Female patients should be subjected to a gynecologicexamination to exclude other HPV-associated cancers.

HRA – high resolution anoscopy

• Direct corollary of cervical pap smear

• Diagnostic and screening in high risk populations

• Gauze soaked in 3%acetic acid

• 3-25 times magnification

• Suspicious lesions can be destroyed by electrocautery

Staging, AJCC TNM STAGING

Staging

• In contrast to staging parameters for other GI lesions it is based on size rather than depth of invasion

• Direct invasion of the rectal wall, perirectal skin, subcutaneous tissue, or the sphincter muscle(s) is not classified as T4.

• Anal margin tumors are staged and treated same as skin cancers.

Management

• Operative therapy for anal canal SCC has largely been supplanted by chemoradiation and is now exception rather than the rule.

• Multi modality treatment- chemotherapy and radiation

• Surgery is reserved for patients

• those do not respond to chemo radiation

• those with recurrence

• Those who require diversion colostomy

• Inguinal lymph node dissection

Chemo radiation

• Norman Nigro revolutionized the treatment

• 5-FU, Mitomycin-C, along with radiotherapy

• 30gy given in 15 sessions over 3 weeks, 5FU was given for first 4 days as a continuous infusion, repeated on 29th through 32nd days

• Intensity modulated radiotherapy

Inguinal lymph nodes metastasis

• Should be confirmed by FNAC

• Surgical clearance is palliative

• Currently, it is treated with chemotherapy and radiation concurrently with primary tumor

• Some studies have shown better survival following therapeutic inguinal lymphnode dissection

APR

• Involves en bloc excision of the tumor as well as surrounding lymph nodes and the anal sphincters, resulting in a permanent colostomy

• Traditionally it has been used to treat distal rectal cancers.

• Morbidity of 61% and mortality of 0-6.9%

Pre- Op preparation

• Bowel prepration

• clear liquid diet 2 days prior to surgery

• Use of laxatives, enemas

• Antibiotics- neomycin 1gm, erythromycin base 1g; 1,2,10pm

• Mechanical cleansing decreases the total volume of stool in the colon but the concentration of bacteria remains the same.

• Systemic antibiotics

• DVT prophylaxis

Peri-operative

• Epidural catheter

• Compression devices

• DVT prophylaxis- 5000 units heparin

• Cefazolin + metronidazole

• Modified lithotomy position

• History of previous surgery or hydronephrosis- B/L DJ stent insertion

Technique

• Total mesorectal excision

• Laterally, sigmoid mobilization by scoring white line of toldt

• Ureters must be identified and preserved

• Colon is divided at the level of sigmoid-descending junction

• Superior rectal artery + descending branch of left colic artery ligated

TME – total mesorectal excision

• Proper plane of dissection at the sacral promontory

• Location of sympathetic nerves along pelvic brim

• Rectum is retraced anteriorly and sharp dissection is done inferiorly to the coccyx

• Anterior and lateral dissections are then carried out after posterior dissection has been completed

• Care should be taken to preserve hypogastric plexus on the pelvic side walls(helps in avoiding post op potency/ urinary problems)

Mobilization ofrectum

• Peritoneal incision of the pelvis

• Rectum reflected anteriorly and posterior avascular plane entered between the presacral fascia of waldayerand fascia propria of the rectum

• Division of lateral stalks

Perineal dissection

• Anal canal closed with a purse string suture

• Anococcygeal ligament is divided anterior to the coccyx through which scissors are used to gain entrance into the pelvis

Perineal dissection

• Lateral transection of levator ani muscles

• Anterior transection of rectourethralis, puborectalis, pubococcygeus

• Removal of rectum through perineal wound

• Closure in multiple layers with drains in place.

Complications

• Perineal wound complications

• Stoma complications-

• ischemia,

• retraction,

• hernia,

• stenosis,

• prolapse

Prognosis

• Strong correlation between tumor size, lymphatic spread and prognosis

• Overall survival is diminished when tumor size is greater than 5 cms

• 1-2cms- survival 78%

• 3-5cms- survival 55%

• Greater than 6cms, only 40%

• Regional metastasis is a poor prognostic indicator.

Thank You