Weber D C, Nouet P, Kurtz J M, Allal A S
Radiation Oncology Department of the University Hospital, Geneva, Switzerland.
Radiother Oncol. 2001 Apr;59(1):39-43. doi: 10.1016/s0167-8140(01)00334-6.
To measure anal dose during external beam radiotherapy (EBRT) using in vivo dosimetry, to study the difference of measured from prescribed dose values, and to evaluate possible associations of such differences with acute and late skin/mucosal toxicity and anorectal function.
Thirty-one patients with localized anal carcinoma underwent in vivo measurements during the first EBRT session. Themoluminescent dosimeters (TLD) were placed at the center of the anal verge according to a localization protocol. No bolus was used. Patients received a median dose of 39.6 Gy (range: 36-45 Gy) by anteroposterior opposed AP/PA pelvic fields with 6 or 18 MV photons, followed by a median boost dose of 20 Gy (range: 13-24 Gy). Concomitant chemotherapy (CCT), consisting of 1-2 cycles of continuous infusion 5-fluorouracil (5-FU) and bolus mitomycin-C (MMC), was usually administered during the first weeks of the pelvic and boost EBRT courses. Acute and late skin/mucosal reactions were recorded according to the Radiation Therapy Oncology Group (RTOG) toxicity scale. Anal sphincter function was assessed using the Memorial Sloan Kettering Cancer Center (MSKCC) scale.
TLD anal doses differed by a mean of 5.8% (SD: 5.8) in comparison to the central axis prescribed dose. Differences of at least 10% and at least 15% were observed in eight (26%) and three (9.7%) patients, respectively. TLD doses did not significantly correlate with acute or late grade 2-3 skin or mucosal toxicity. However, patients having good-fair MSKCC anal function had a significantly greater mean difference in anal TLD dose (10.5%, SD: 5.9) than patients having excellent function (3.8%, SD: 4.6) (P = 0.004). Prescribed dose values, length of follow-up, and age at diagnosis did not correlate with late sphincter function.
These data show that AP/PA fields using megavoltage photons deliver adequate dose to the anal verge. However, in about one quarter of patients treated with this technique the anal dose varied from the prescribed dose by at least 10%. The observed correlation of TLD values and late sphincter function suggests that direct measurement of the dose delivered to the anal verge might be clinically relevant.
使用体内剂量测定法测量外照射放疗（EBRT）期间的肛管剂量，研究测量剂量与处方剂量值之间的差异，并评估这些差异与急性和晚期皮肤/黏膜毒性以及肛门直肠功能之间可能存在的关联。
31例局部肛管癌患者在首次EBRT疗程期间进行了体内测量。根据定位方案，将热释光剂量计（TLD）放置在肛缘中心。未使用组织等效物。患者通过前后对穿的AP/PA盆腔野，使用6或18MV光子，接受的中位剂量为39.6Gy（范围：36 - 45Gy），随后接受的中位追加剂量为20Gy（范围：13 - 24Gy）。同步化疗（CCT）通常在盆腔和追加EBRT疗程的前几周进行，包括1 - 2个周期的持续输注5 - 氟尿嘧啶（5 - FU）和推注丝裂霉素 - C（MMC）。根据放射肿瘤学组（RTOG）毒性量表记录急性和晚期皮肤/黏膜反应。使用纪念斯隆凯特琳癌症中心（MSKCC）量表评估肛门括约肌功能。
与中心轴处方剂量相比，TLD测量的肛管剂量平均相差5.8%（标准差：5.8）。分别在8例（26%）和3例（9.7%）患者中观察到至少10%和至少15%的差异。TLD剂量与急性或晚期2 - 3级皮肤或黏膜毒性无显著相关性。然而，MSKCC肛门功能为良好 - 中等的患者，其肛管TLD剂量的平均差异（10.5%，标准差：5.9）显著大于功能优秀的患者（3.8%，标准差：4.6）（P = 0.004）。处方剂量值、随访时间和诊断时的年龄与晚期括约肌功能无关。
这些数据表明，使用兆伏级光子的AP/PA野可向肛缘提供足够的剂量。然而，在采用该技术治疗的患者中，约四分之一的患者肛管剂量与处方剂量相差至少10%。观察到的TLD值与晚期括约肌功能的相关性表明，直接测量传递至肛缘的剂量可能具有临床相关性。
