肛門癌在台灣也不算常見的疾病, 不過在放射腫瘤科還是經常會遇到, 所以還是要來了解一下!
一. 解剖: 主要分成以下兩種:
1. anal canal cancer: 3-5 cm 長度的管狀結構, 上緣是anal sphincter可以摸到的最上緣以及anorectal ring 的上緣, 下緣是anal verge
2. perianal cancer: anal verge 往外5cm的環狀區域
二. 病理:
1. anal canal cancer: 85-90% SCC, 10-15% adenocarcinoma
2. perianal cancer: 大部分都是SCC
三. 危險因子: HPV, HIV, 以及抽菸
四. 治療方式:
1. anal canal cancer:
(1) locoregional cancer: chemoradiation -> if residual -> salvage operation
(2) metastatic disease: chemotherapy +/- RT
2. perianal cancer:
(1) T1(well or moderately differentiated) or selected T2(沒有侵犯到sphincter) N0M0 => local excision
(2) 除了(1) 之外的 loco regional disease => CRT
(3) metastatic disease: chemotherapy +/- RT
五. 放射治療技術:
1. anal canal cancer: 可以參考 RTOG 0529
(1) Anal cancer, cT2-4N0-3M0, 使用dose painting IMRT + day 1,29 5-FU +MMC, RTOG 0529是想要跟RTOG 9811 (不能使用 IMRT)比, 結果證明 dose painting IMRT 可以降低副作用
(2) CT-sim: RTOG0529 使用兩種姿勢: supine, arm-up, frog-leg position; prone position with bowel displacement
(3) RT volume:
GTVA included the primary anal tumor;
GTVN50 metastatic nodal regions ≤ 3 cm
GTVN54 metastatic nodal regions > 3 cm.
CTV = GTVA+ 2.5 cm; GTVN+ 1 cm
(4) RT dose:
T2N0: 42Gy elective nodal and 50.4Gy anal tumor PTVs / 28Fr
T3-4N0-3: 45Gy elective nodal, 50.4Gy ≤ 3cm or 54Gy > 3cm metastatic nodal and 54Gy anal tumor PTVs / 30Fr
reference:
1. Perez and Brady's radiation oncology 7th
2. NCCN guideline
3. RTOG 0529
4. RTOG 9811
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