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IMRT for the Treatment of Anal Cancer

IMRT for the Treatment of Anal Cancer. Kristen O’Donnell, MS3 December 12, 2007. Anal Cancer: Just the Facts. Estimated new cases in the US in 2007 4,650 Estimated Deaths 690 Pathology ~80% Squamous cell carcinoma, Other 20% adenocarcinoma or melanoma.

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IMRT for the Treatment of Anal Cancer

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  1. IMRT for the Treatment of Anal Cancer Kristen O’Donnell, MS3 December 12, 2007

  2. Anal Cancer: Just the Facts • Estimated new cases in the US in 2007 • 4,650 • Estimated Deaths • 690 • Pathology • ~80% Squamous cell carcinoma, • Other 20% adenocarcinoma or melanoma. • HPV associated, same pathogenic serotypes as cervical cancer, 16 & 18 (Jemal et al., 2007; Hansen and Roach, 2007)

  3. Anatomy: 3-4 cm anal canal Anal verge to dentate line Lymph node drainage: Perirectal Internal iliac Inguinal nodes Anal Cancer: Just the Facts (Up-to-date; cancerbackup.org)

  4. Staging • T • T0 • Tis • T1 <2 cm • T2 >2 cm but <5 cm • T3 >5 cm • T4 invades adjacent organs • N • N0 • N1 perirectal • N2 unilateral internal iliac or inguinal • N3 perirectal and inguinal and/or bilateral inguinal and/or internal iliac • M • M0 • M1 distant metastases (Hansen and Roach, 2007)

  5. Current Standard is Definitive Chemoradiotherapy for Anal Cancer • Radiotherapy alone vs. Chemoradiotherapy. • 45 Gy alone or w/ concomitant 5-FU and mitomycin • UKCCCR, 1996: 585 epidermoid anal cancer patients with any stage disease randomized • EORTC, 1997: 110 patients with stage IIIA-B anal cancer randomized (UKCCCR, 1996; Bartelink et al., 1997)

  6. EORTC No significant difference in acute toxicity Diarrhea and skin reaction most common Better complete remission rates 54%80% 18% improvement in locoregional control 32% improvement in Colostomy-free survival at 5 years UKCCCR Significantly decreases local recurrence 59% 36% local failure rate, Relative risk of 0.54 Decreases cancer related risk of death after 3 years 39% 28% anal cancer mortality, Relative risk 0.71 No significant overall survival benefit after 3 years Radiotherapy 58% and Chemoradiotherapy 65% Current Standard is Definitive Chemoradiotherapy for Anal Cancer (EORCT, Bartelink et al., 1997)

  7. Current Standard is Definitive Chemoradiotherapy for Anal • Cisplatin and 5-FU chemotherapy with radiation therapy is an alternative regimen • Provides similar locoregional control, colostomy free survival and overall survival to 5-fu and mitomycin with radiotherapy • Causes less toxicity • (Hung et al., 2003) • RTOG 98-11: Standard concomitant 5-FU/mitomycin chemRT vs. Induction with 5-FU/Cisplatin then 5-FU/Cisplatin + RT • Reduced hematologic toxicity • Decreased colostomy free survival • Complicated by induction treatment design • (Gunderson et al., 2006) • Anal Cancer Trial II being conducted in the UK • (Das et al., 2007)

  8. Rates of Locoregional Recurrence with Definitive Chemoradiotherapy • UKCCCR: 36% at 3 years • EORTC: ~32% at 5 years • M.D. Anderson: 14% at 3 years • Study of 167 patients treated with definitive chemoRT for anal cancer. • (Das et al., 2007)

  9. Patterns of Locoregional Recurrence • Das et al. at M.D. Anderson found: • 75% Recurred at anus or rectum • 21% Presacral and/or iliac regions • 5/5 had RT field start at the bottom of the SI joints • 3/5 recurred above RT field, 1/5 marginal, 1/5 recurred both above and within field • 4% (1 patient) Inguinal recurrence • Compared to cited 8-15% risk of inguinal recurrence in studies of patients not receiving inguinal RT. • Locoregional control benefit from RT • RT is very effective at inguinal nodes and iliac nodes with adequate treatment coverage. • Need better local control at primary tumor site. • How will IMRT change these statistics? • (Das et al., 2007)

  10. IMRT • Utilizes detailed beam shaping • Creates unique conformal distributions and sharp dose gradients • Increase the ability to: • Target specific volumes • Limit normal tissue exposure • Use in the treatment of head and neck, prostate and gynecologic cancers.

  11. IMRT in anal cancer • New application gaining support • Early studies show reduced toxicity rates with comparable local control and survival statistics. • Area of active study • Radiation Therapy Oncology Group is currently enrolling for a phase II trial (RTOG 0529).

  12. IMRT Dosimetry studies • Chen et al. Conventional AP/ PA pelvic fields vs. Conformal avoidance IMRT planning in 2 patients • Same PTV with IMRT plan assigned dose constraints for femoral heads and external genitalia. • Comparable PTV coverage: • IMRT plan: 97-98% of PTV at 90% prescribed dose • Conventional AP/PA: 94% of PTV at 90% prescribed dose • IMRT spared femoral heads 58-59% vs. 71-72% of prescribed dose and genitalia 55-63% vs. 78-97% with conventional planning (Chen et al. 2005)

  13. IMRT Dosimetry studies • Lin and Ben-Josef Designed 9-field, non-coplanar IMRT plans for 5 patients with anal cancer • Volumes: • GTV=anal tumor and positive nodes • CTV= GVT + inguinal and iliac nodes • PTV=CTV + 5 mm expansion • IMRT planning, • 1° priority=PTV coverage • 2° priority=limiting dose to organs at risk • Utilized Equivalent uniform dose for optimization • (Lin and Ben-Josef, 2007) ASCO Abstract

  14. IMRT Dosimetry studies • Results: • Homogenous dose coverage • 95% of PTV receiving 99% of prescribed dose • IMRT to treat anal cancer should decrease toxicity and has potential to improve local control. • (Lin and Ben-Josef, 2007) ASCO Abstract

  15. Clinical use of IMRT for anal cancer • Single institution study of 17 anal cancer patients treated with definitive chemoRT using IMRT planning. • Comparative dosimetric analysis of 7 patients: IMRT planning vs. 3-D AP/PA planning • Significant reduction in small bowel, bladder and perineum doses • Toxicity • All patients had mild-mod dermatitis • No treatment breaks due to GI or skin toxicity • All GI and bladder toxicities were ≤ grade 2. • EORTC trial showed frequent grade 3 GI and skin toxicity • Hematologic toxicity unchangedslightly worse than rate in RTOG trial (Milano et al., 2005; Bartelink et al., 1997)

  16. Clinical use of IMRT for anal cancer • Single institution study of 17 anal cancer patients treated with definitive chemoRT using IMRT planning • Similar outcomes to standard treatment • 14/17 complete response • 2 year progression free survival 65% • Overall survival 91% • Colostomy free survival 82% • Local control 82% • Distant control 74% (Milano et al., 2005)

  17. Multicenter experience with IMRT for anal cancer • 53 patients treated at three academic medical centers with IMRT and chemotherapy for definitive treatment of anal cancer. • Toxicity • 58% completed treatment without interruption • Improved GI toxicity rates and severity • Grade 3 in 15% with no Grade 4 • RTOG 98-11: 34% of patients had Grade 3 - 4 • Dermatologic, Grade 3 in 38% • Similar to studies with 2-wk treatment breaks • Better than the 48% in RTOG 98-11 • Hematologic toxicities were severe and common • Grade 3 and 4 in 58% of patients as worst • Similar to RTOG 98-11 rates of 60% • (Salama et al., 2007)

  18. Multicenter experience with IMRT for anal cancer • 53 patients treated at three academic medical centers with IMRT and chemotherapy for definitive treatment of anal cancer. • Response • Complete response in 92% • Local recurrence rate 13% @ 18 months • 18-month colostomy free survival 83.7% • 18-month distant recurrence free survival 92.3% • (Salama et al., 2007)

  19. Summary • Dosimetric studies and small clinical trials have shown reduced dosing and toxicity to normal structures with the use of IMRT. • No decreases in treatment effectiveness or local control rates have been detected. • Limited sample sizes and duration of follow-up minimize the ability to detect small variations in local control rates.

  20. Future Studies using IMRT for Anal Cancer • RTOG 0529 • A Phase II Evaluation of Dose-Painted IMRT in Combination with 5-Fluorouracil and Mitomycin-C for Reduction of Acute Morbidity in Carcinoma of the Anal Canal. • 59 patients with histologically-proven, invasive primary squamous, basaloid, or cloacogenic carcinoma of the anal canal; Stage 2-4 and N0-N3 stage. • Currently enrolling

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