P-217 Chemoradiotherapy with Image-Guided Volumetric Modulated Arc Therapy (IG-VMAT) and Image-Guided Intensity Modulated Radiotherapy (IG-IMRT) to treat Squamous Anal Cancer

Abstract

Introduction: In November 2013, we moved from 3D Conformal Radiotherapy to Image-Guided Intensity Modulated Radiotherapy (IG-IMRT) and Image-Guided Volumetric Modulated Arc Therapy (IG-VMAT) to treat squamous anal cancer.We now report on the early clinical outcomes with these new techniques. Radiotherapy was planned and delivered as per the United Kingdom national guidelines (www. analimrtguidance.co.uk). Methods: The records of patients ( pts) starting radiotherapy treatment for anal squamous cancer with IG-IMRT and IG-VMAT from November 2013 to January 2016 were retrospectively reviewed. IG-IMRT and IG-VMAT were planned using a simultaneous integrated boost technique and treatment accuracy verified daily with cone-beam CT scans. The dose-fractionation schedule used was 50.4 (T1/2) to 53.2 Gy (T3/4) to the primary tumour, 50.4 Gy to involved nodes and 40.04 Gy to the elective nodal volume in 28 daily fractions. Concurrent chemotherapy was used unless contraindicated. Results: Twenty-nine pts (8 males & 21 females) were treated. Median age was 59 years (range 45-86 years). All had histologically proven squamous anal cancer. Stage distribution was: stage I (31%), stage II (27.5%), stage IIIA (17.3%) and stage IIIB (24.2%). Seven pts (24%) had an excision of the primary tumour and a colostomy was needed in 5 pts (17%) before treatment. IG-VMAT was used in 27 pts (93%) and IG-IMRT was used in 2 pts (7%). Concomitant chemotherapy was used in 27 pts (93%) with Mitomycin-C & 5-FU (55.5%) (Mitomycin-C 12mg/m2 D1 & 5FU 1000mg/m2 D1-4 and D29-32) and Mitomycin-C & Capecitabine (33.3%) (Mitomycin 12mg/m2 D1 & Capecitabine 825mg/m2 PO BD on days of radiotherapy) the most common schedules. Two pts (7%) did not receive chemotherapy because of frailty and comorbidity. Twenty-eight pts (96.5%) completed the planned radiotherapy schedule and twenty-one pts (72.4%) completed planned chemotherapy. One patient did not complete chemoradiotherapy due to severe non-fatal chemotherapy toxicity related to dihydropyrimidine dehydrogenase (DPD) deficiency. Toxicity data was graded according to the RTOG scale for dermatological toxicity and the NCI - CTCAE scale for other organ systems. Grade 3/4 dermatological toxicity was seen in 15 pts (55.1%) and Grade 3/4 gastrointestinal toxicity in 1 pt (3.4%). Grade 3/4 haematological toxicity was experienced by 6 pts (20.6%). There was 1 admission with febrile neutropenia following treatment. Median follow-up is 12 months (range 0 - 26 months) and there have been no locoregional recurrences. One patient developed distant metastases and has died. All other patients 28 (96.5%) remain alive and disease free. Conclusion: Our encouraging results indicate that IG-VMAT or IG-IMRT for anal squamous cancer is well tolerated with excellent locoregional disease control and manageable toxicity. These advanced radiotherapy techniques should be considered the standard of care in the treatment of this uncommon cancer.