目的：本研究主要在比較兩種直腸劑量參考點對子宮頸癌放射線治療引發之直腸出血後遺症的預測價值。材料與方法：從1992年9月至1997年12月，共有181位在新光及中國醫藥學院附設醫院完成放射治療之子宮頸癌病人（第IB，IIA，IIB，IIIA，IIIB期分別有32，23，102，3，21人)進入分析。所有病人皆存活一年以上，且長期存活者須經至少三年之追蹤檢查。放射治療範圍涵蓋整個子宮，陰道及下腹腔淋巴腺，經照射44Gy至45Gy後，腫瘤期別超過IIB的病人，照野縮小至兩側的子宮旁組織（parametrium），再給與14Gy。高劑量率（HDR）子宮腔內近接治療間隔一週，其中51位病人治療次數3次，每次給予參考點A（Point A）7.2Gy的劑量；另130位病人治療次數4次，每次給予參考點A（Point A）6.0Gy的劑量，每次近接治療時皆以ICRU及傳統方式兩種方法來計算每位病人之直腸劑量，總共之放射治療時間47至90天（中位數60天）。由多變數分析來分析病人本身、近接治療及直腸劑量等可能影響直腸後遺症之因子，以找出發生後遺症之高危險群。結果：181位病患經過38至110個月的追蹤檢查（中位值58個月），45人(24.9% )發生RTOG第一至第四級之直腸後遺症（第一、第二、第三至四級分別有27、13及5人）。直腸後遺症發生的機率與累積之ICRU直腸劑量參考點劑量有較明顯的相關性。多變數分析後發現第IIB-III期（p＝0.002）及累積之ICRU直腸劑量參考點劑量大於20Gy（p＝0.005）為引發直腸後遺症之高危險群。結論：研究結果確定ICRU直腸劑量參考點對預測直腸後遺症的價值，而以傳統方式計算之直腸劑量與直腸後遺症的發生並沒有很好的相關性。本研究建議，在不影響治療結果的前提下，針對直腸後遺症之高危險群，應調整治療計劃，以減少後遺症發生的機率。

Purpose: This study aimed to compare the predictive value of ICRU (International Committee on Radiation Units and Measurements) and conventional rectal reference point with the risk of late rectal sequelae in patients with carcinoma of the uterine cervix treated with high-dose-rate intracavitary brachytherapy (HDRICB). Materials and Methods: From September 1992 to December 1997, 181 cases (32 IB, 23 IIA, 102 IIB, 3IIIA, 2IIIB) who survived more than 12 months after treatment and the long-term survivors should receive a minimum 3 years of follow-up, were entered in our study. Initially, they were treated with 10 MV X-rays for 44 - 45 Gy / 22 - 25 fractions over 4-5 weeks to whole pelvis Radiation dose for patients with FIGO Stage IIB-III bilateral parametrial disease was boosted to 54-58 Gy, with a central shielding. After the completion of whole-pelvis radiotherapy, HDRICB was performed using an Ir-192 remote after loading technique at one-week intervals. Fifty-one patients received three insertions, while 130 patients had four insertions. The prescribed dose for each HDRICB was 7.2 Gy to Point A for three insertions (before July 1995), or 6.0 Gy for four insertions (after July 1995). HDRICB dosimetry was calculated using orthogonal films exposed during each insertion. Doses to both ICRU and conventional rectal reference points were calculated for each patient. The overall duration of treatment ranged from 47-90 days (median, 60). Patient and treatment related factors were evaluated for late rectal complication using logistic regression model. Results: Median follow-up of these patients was 58 months (range: 38-110 months). Forty-five patients (24.9%) had late rectal complications (27 Grade 1, 13 Grade 2, 5 Grade 3-4). The probability of rectal complications shows a better correlation of doseresponse with increasing total brachytherapy ICRU rectal dose. Multivariate logistic regression analysis demonstrated a high risk of late rectal sequelae in patients who had Stage IIB-III disease (p = 0.002, relative risk, 3.66, 95% CI 1.82-6.45) and total ICRU rectal dose greater than 20 Gy (p = 0.005, relative risk, 1.62, 95% CI1.03-3.21). Conclusions: This study confirms the value of ICRU rectal reference point in the prediction of late rectal sequelae. Patients who have Stage IIB-III disease, or a total ICRU rectal dose greater than 20 Gy, have a higher risk of late rectal sequelae.