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Anal canal

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Anal canal

  1. 1. Carcinoma Anal Canal Dr Pavan Kumar Lachi 24 9 2013
  2. 2. Anatomy of anal region
  3. 3. Anatomy and histology of the anal canal • Definition - the ‘‘surgical’’ anal canal from the anorectal ring (upper portion of the puborectalis/levator complex) at the floor of the pelvis to the anal verge. Appx 4 cm in length The anal verge is the point at which modified squamous epithelium (anoderm) of the anal canal meets hairbearing perianal skin.
  4. 4. Anatomy and histology of the anal canal • The lining of the anal canal is divided into three zones: • Colorectal zone - proximally • Anal transitional zone (ATZ, extending approx. 1 cm upward from dentate line) • Squamous zone (extending distally from the dentate line to the anal verge.
  5. 5. • The colorectal zone - columnar mucosa identical to the distal rectal mucosa. • The ATZ - many epithelial variants, including squamous & colorectal type mucosa - ‘‘ATZ epithelium,’’- 4-9 cell layers including basal, columnar, & cuboidal cells. - Melanocytes and endocrine cells are also occasionally found. • The squamous zone - unkeratinized squamous mucosa without skin appendages. - Melanocytes may also be present.
  6. 6. Anal verge • The perianal skin contains sweat, sebaceous & apocrine glands & is keratinized • The anal margin - perianal skin extending approx. 5- 6cm from the anal verge. • All skin cancers can affect the anal margin .
  7. 7. 1
  8. 8. Epidemology – Anal cancer • Anal cancers are about one-tenth as common as cancers of the rectum. • Cancers arise in the canal 3 to 4 times more frequently than in the perianal skin. • In North America and Western Europe squamous cell cancers - 80% of anal cancers • In Japan only 20% are squamous.
  9. 9. Risk factors of anal cancer Old age Common in female - 1:1.5 – 2 Cigarette smoking – fourfold increase of risk A history of anal intercourse sexually transmitted disease
  10. 10. • HPV infection. • Human immunodefi ciency virus (HIV) • Immunosuppression - tenfold risk is seen in immunosuppressed • Cancer of the cervix, vagina, or vulva • Benign lesions of the anus (such as chronic anal–rectal inflammation)
  11. 11. AIDS defining cancers • Invasive ca cervix • Primary CNS Lymphoma • Kaposi sarcoma
  12. 12. Clinical Presentation • • • • • Bleeding per rectum Perianal pain Pruritus A palpable mass Change in bowel habit
  13. 13. Routes of spread – LOCAL EXTENSION • Sphincter muscles • Perianal connective tissues • Rectum • Perineum • Prostate • • • • • Perineal fossa Perianal skin Pelvic wall Vaginal septum Anal-vaginal fistula is seen in <5% of cases
  14. 14. Lymphatic spread • May occur early in disease • Overall lymph node spread is seen in 25% of cases at diagnosis • Delayed inguinal lymph node metastasis is seen in approximately 10–25% of patients
  15. 15. • Distant metastasis is relatively rare, and extra pelvic metastasis is seen in <10% of patients before treatment Common sites of metastasis include • Liver • Lungs • Extrapelvic lymph nodes
  16. 16. Prognostic factors • • • • • • • Advanced stage at diagnosis Male gender Age ≥65 years Hemoglobin levels ≤10 g/l at presentation Nodal metastasis at presentation Poor performance status Presence of HIV infection or AIDS
  17. 17. Management – Anal Canal Carcinoma • For a long time APR remained the standard of care for anal cancer. Papillon et al • In the early 1960s • Introduced the concept - long-term local control with definitive radiation therapy.
  18. 18. Chemo radiotherapy • Nigro et al. In 1974 • First demonstrated complete pathologic responses to concurrent 5-fluorouracil, Mitomycin C, and Radiation therapy.
  19. 19. Surgery - Indications • Has limited role in the primary treatment of anal cancer • Local excision can be considered only for selected patients with well differentiated early-stage (T1N0M0) • SCC that is <40% circumferential involvement • No sphincter involvement • Abdominal peritoneal resection (APR) is reserved for salvage after primary chemoradiotherapy failure
  20. 20. Radiation therapy - Indications • EBRT with concurrent chemotherapy is the mainstay treatment for localized anal cancer • RT alone can be reserved for stage T1N0M0 disease • Palliation to primary or metastatic foci Techniques • EBRT using three-dimensional conformational RT(3D-CRT) or IMRT • Brachytherapy has no role in the treatment and is associated with high incidence of anal necrosis
  21. 21. UKCCCR Trial • Randomized 585 patients to either radiation therapy (RT)alone or concurrent chemoradiation therapy (CRT) • RT alone used 45 Gy in 20 or 25 fractions over 4–5 weeks
  22. 22. UKCCCR Trial • 5-FU - 1,000 mg/m2, days 1–4 or 750 mg/m2 days 1–5 continuous infusion • Mitomycin C - 12 mg/m2 bolus on day 1 • During the first and last week of Radiotherapy
  23. 23. UKCCCR Trial 70% 60% 50% 40% 30% 20% 10% 0% RT Chemo RT 3 Year local control
  24. 24. UKCCCR Trial • 3-Year local control rates (61 versus 36%, p < 0.001) • Addition of chemotherapy produced a reduction of 46% in local failure (p < 0.0001) • No benefit of OS observed with CRT
  25. 25. Can we skip Mitomycin ?
  26. 26. RTOG 98-11 phase III trial for anal cancer
  27. 27. Radiation Therapy Techniques • Radiation fields should encompass 1. Tumor bed 2. Regional lymph node areas (including inguinal nodes) for locoregional control • The patient should be placed in the supine position • Full bladder • A radio-opaque marker at the anal verge of the edge of the tumor
  28. 28. • 3dCRT - planning using CT simulation with small bowel contrast is highly recommended. • Radiation therapy can be divided into three phases 1. Entire pelvic field 2. Cone-down pelvic field 3. Tumor bed only
  29. 29. Initial radiation fields (AP/PA) to cover the entire pelvis
  30. 30. AP/PA field (whole pelvis) • Superior: Top of S1 • Inferior: The lower of anal verge or tumor with 3 cm margin • Anterior lateral: To include lateral inguinal nodes with 1.5 cm margin, determined by bony landmark or lymphangiogram • Posterior lateral: 1.5 cm lateral to the widest bony margin of the true pelvis
  31. 31. Inguinal node involvement at presentation
  32. 32. • Inguinal lymph nodes are a potential site for metastatic dissemination. • Inguinal involvement is demonstrated to be a poor prognostic factor. • Benefit of prophylactic inguinal irradiation (PII) remains questionable because of the potential serious long-term wound and lower extremity complications.
  33. 33. Cone-down radiation fields (AP/PA) to cover the inferior pelvis
  34. 34. AP/PA field (cone-down pelvis) • Superior: Inferior border of sacroiliac joint • Inferior: same as in the whole-pelvis fi eld • Anterior lateral: same as in the whole-pelvis field • Posterior lateral: same as in the whole-pelvis field
  35. 35. Tumor bed boost field(s) • Primary tumor: gross tumor with 2- to 2.5-cm margin • Lymphadenopathy: gross disease with 2-cm margin
  36. 36. Dose and Treatment Delivery • • • • Conventional fractionation 30.6 Gy to the entire pelvis 14.4 Gy to the inferior pelvis Boost to 54–59.4 Gy to gross tumor, with a 2– 2.5 cm margin is recommended for patients with T3 or T4, N+ patients, or T2 disease with gross residual after 45 Gy.
  37. 37. Anal margin neoplasms Bowen’s disease • Intraepidermal squamous cell carcinoma (SCC) • Represents the extreme end of a spectrum of epithelial dysplastic changes known as anal intraepithelial neoplasia (AIN). • AIN - dysplastic changes of the anal canal epithelium • BD generally implies involvement of the perianal skin • Human papillomavirus (HPV) - etiological agent • HPV 16 found in 60% to 80% of pts with perianal Bowen’s disease.
  38. 38. Anal margin neoplasms Bowen’s disease • May progress to invasive SCC in approximately 2% to 5% of cases . • Presentation - as an asymptomatic or mildly symptomatic scaly, erythematous rash of the perianal area. - Pruritus and burning of the skin are common complaints - May be found incidentally on examination of tissue removed during other anorectal procedures. .
  39. 39. Anal margin neoplasms Bowen’s disease • Diagnosis - by biopsy, and must be distinguished from other conditions of the perianal area, including Paget’s disease, melanoma,& other dermatoses. • Histologic appearance – - atypical epithelial cells involving the full thickness of the epidermis, producing sharp demarcation with the normal dermis. - cells with large haloed hyperchromatic nuclei, so-called ‘‘bowenoid cells,’’ • Rx - cryosurgery, topical 5-fluorouracil (5-FU), argon laser therapy, CO2 laser ablation, and photodynamic therapy . • Rx of choice - WLE - negative microscopic margins.
  40. 40. Anal margin neoplasms Bowen’s disease • Small defects from WLE can be closed primarily or covered by SSGs. • Larger defects may require the use of V-Y, S-shaped, or house-shaped advancement anoplasty . • Careful clinical follow-up of longer than five years is required • Local recurrence has been reported as late as 111 months after surgery
  41. 41. Thank you
  42. 42. Discussion • Response assesment after chemoradiotherapy? • ACT II trail…..inference • Recent NCCN guidelines….regarding surgwery after chemo radiation…..

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