RECTAL CANCER

Diagnosis and Treatment:

• Rectal cancer represents 30% of the cancers of the large intestine
• Surgical Outcomes is effected by:
• Presence of iliac nodes
• Difficulty in obtaining clear surgical margins
• Quality of life Issues such as : sphincter preservation

Epidiemiology and Etiology:

• Used to be the most common site for cancers of the large intestine; now the right colon  is the most common site
• Rectal cancer is attributed to high fat, low fiber diets
• (Japanese immigrants to the US have a 2.5 greater risk than if they stayed in Japan)
• Large or Dysplastic polyps, Inflammatory Bowel Disease and Genetic Conditions can be precursors

Anatomy :

• The rectum begins at the point where the large bowel loses its mesentery, which is at the level of the body of the third sacral vertebra
• Rectum extends from the dentate line to the anal verge
• Dentate line -  The line between the simple columnar epithelium of the rectum and the stratified epithelium of the anal canal
• Anal Verge - The distal end of the anal canal, forming a transitional zone between the skin of the anal canal and the perianal skin.
• Lymphatic drainage is to the hemorrhoidal vessels to the illiac chain
• The rectum is a retro and infra peritoneal structure
• The levator musculature surrounds the distal few centimeters of the rectum (this are must be sparred for sphincter preservation)
• Levator muscles – operate the involuntary sphincter (if surgery in done patient will most likely loose continance)

Screening and Early Detection:

• For the average risk populations : digital exam and occult blood test every year after age 40 ; sigmoidoscopy every 3 – 5 years
• For people with a family history : beginning screening at age 36; BaE every 3 years
• For people with Ulcerative Colitis : annual colonoscopy with biopsies

Patient Evaluation:

• Most common presenting symptom is bleeding
• Other symptoms include: change in bowel habits, narrowing of stools, pain and systemic symptoms, tenesmus (desire to empty the bowel when not needed)
• Clinical evaluation rarely valuable; pathological staging is more common (BaE and Colonoscopy)

Treatment Options:

• Surgery remains the main treatment with removal of the retum the definitive treatment
• Some proximal rectal cancers are treated with sphincter preserving techniques (must eb at least 6cm from the anal verge)
• Overall risk of local recurrance after surgery increases for stage with up to 50% for Stage III
• Therefore,  Radiation Therapy is initiated post operatively in many Stage II and III Cancers
• Preoperative Radiation Therapy may be suggested for patients for whom adequate surgical margins seem difficult to obtain
• About 20% of Rectal Cancers are considered favorable and may be treated with “conservative” approaches; such as local excision or endocavitary irradiation

Criteria for Conservative Management:

• Free mobility of the tumor
• No extension in perirectal fat
• No clinically involved nodes
• Favorable histology
• Less than 3 cm in diameter
• These are evaluated with a transrectal ultrasound

Is Radiation Therapy used in Conservative Management?

Yes, if there are close margins, or if lymph proves to be involved at the time of surgery or if the tumor is bigger than was first thought

• 45 Gy in 25 fractions in 5 weeks to the Pelvis, followed by a 5 Gy Boost

Rationale for Pre-Operative Radiation Therapy:

• Advantages:
• To make unresectable tumors respectable
• To reduce tumor spillage
• Has a better biological effect than post operative
• The tumor will usually be poorly oxygenated after surgery therefore it will be less radiosensitive than if it had a good blood supply; this is why the biological effect is increased
• Disadvantages:
• Distorts pathological staging
• Slows healing

Pre-Operative Approaches:

• Low Dose : obsolete  20 Gy in 1 Week
• High Dose: 50/60 Gy in 5-8 weeks

Post-Operative Treatment:

• Historically, pelvic fields were used : L5 to perineum; 45 Gy in 4.5 weeks + boost
• Perineum -  The region between the scrotum and the anus in males, and between the posterior vulva junction and the anus in females

Summary of Adjuvant Radiation Therapy:

• Either pre or post operative; radiation therapy appears to improve local control for Stage II and III rectal carcinomas. (some advocate it for Stage I)
• Currently; chemotherapy is added to postoperative radiation treatments
• Radiation Therapy only improves survival if combined with chemotherapy

Role of Radiation Therapy to inoperable Rectal Carcinomas:

• Only 10% of patients achieved local control with Radiation alone
• 20% control with Radiation and Chemo

Current Radiation Therapy Technique:

• Pre-Operative: inferior border should be 3 – 5 cm below known tumor volume
• Post-operatively : include the perineum (we can use a radioopaque marker to locate the perineum on a film in the simulator)
• Superior Border is L4-L5

Dose Considerations:

• 45 – 50 Gy to pelvic field + Boost
• if postoperative : surgical clips can help to define the field
• Use 3 – 4 field techniques

Outcomes:

• Disease that is confined to the rectal wall (mucousa) : 90%  5 year survival
• If patient has One high risk feature - either extension beyond the rectal wall OR positive node : 60 – 90% have 5 years survival
• if patient has Two high risk features the 5 years survival is 30 – 50%

ANAL CARCINOMAS:

Anal Carcinomas:

• 2% of all GI cancers
• associated with HPV(human papillomavirus) - Any of various strains of papovavirus that cause warts, especially of the hands, feet, and genitals, with some strains believed to be a causative factor in cancer of the cervix, vagina, and vulva.
• More common in females except in urban areas that have a high concentration of homosexual males
• Incidence in Anal Carcinoma is increasing (mostly in young males and is 6X more common in unmarried males)
• Increased incidence in both males and females with AIDS

Signs and Symptoms:

• Bleeding
• Pain
• Sensation of mass
• Symptoms are often misdiagnosed as benign conditions (such as hemmorhoids)

Histopathology and Staging:

• Mostly Squamous Cell Carcinomas
• Very  rarely : melanomas, adenocarcinomas, lymphomas
• Size of the primary is the most important clinical indicator

Treatment for Anal Cancer:

• The standard therapy used to be surgical resection, or more rarely EBRT to doses ranging from 45 – 75 Gy.  5 years survival for either is the same (30 – 90% ranging on size and level of lymph node involvement)
• Currently the preferred treatment is : chemoradiation (no surgery).
• Pelvic irradiation plus 5FU and mitomycin yields a 5 years survival of greater than 70% with preservation of function