Evaluation of Electron Boost Fields based on Surgical Clips and Operative Scars in Definitive Breast Irradiation

국문 초록 (Abstract)

목 적: 본 연구에서는 초기 유방암환자에서 보존적 수술 후 전자선을 이용한 추가방사선 조사 시 조사야의 범위 결정에 수술상흔 및 외과적 클립이 미치는 역할을 분석하였으며 이상적인 조사야 범위 결정방법을 제시하였다. 대상 및 방법: 조기 유방암 환자로 병소를 제거한 후 외과적 클립을 4∼7개 삽입한 환자 20명을 대상으로 연구를 시행하였다. 전자선의 치료 에너지를 결정하기 위하여 피부에서부터 흉부벽까지의 거리(SCD)와 병변조직의 가장 뒤쪽에 위치해 있는 클립까지의 거리를 측정하였다. 수술시 삽입된 클립들을 simulation 필름 상에서 연결하여 방사선학적 tumor bed로 정의하였다. 방사선 조사야의 범위는 3가지 방법에 의해 simulation 필름에 그렸다. 임상방사선 조사야(CF)는 수술 상흔 둘레로 3 cm의 여유를 주었고, 외과적방사선 조사야(SF)는 클립주위로 2 cm의 여유를 주었으며, 마지막으로 이상적 방사선조사야(IF)는 수술 상흔과 클립을 모두 포함하여 2 cm의 여유를 주었다. 그려진 조사야들의 면적을 측정하기 위하여 치료계획 컴퓨터에 입력되었고 측정된 면적을 비교하였다. 마지막으로 삽입된 클립들을 CT 상에서 그려 넣었고 클립들의 3차원적인 선량분포를 알아보기 위해 선량체적표를 얻었다. 결 과: SCD와 가장 깊이 삽입된 clip까지의 거리의 평균차이는 0.7±0.56 cm이다. 12명의 환자의 경우 깊이의 차이가 있다. 수술 상흔과 클립들의 평균 위치의 변화는 상방으로 1.7 cm, 하방으로 1.2 cm, 내측으로 1.2cm, 그리고 외측으로 0.9 cm이다. CF의 면적은 20명의 환자 중 6명의 경우 SF보다 크고 IF보다 크다. SF 와 IF의 면적 차이는 15의 환자에서 5%보다 작다. CF 조사야를 이용할 경우 15명의 환자들에 대해 1개 또는 3개의 클립들을 조사야 내에 포함하지 못하고 있다. 또한 클립들의 선량분포를 볼 때 17명의 환자들이 처방선
량의 80% 미만을 받는 즉 선량적으로 부적절한 선량을 받는 클립들이 있었다. 결 론: 수술 상흔을 중심으로 방사선 조사야 범위를 결정 할 경우 병변의 상하 부위를 적절히 포함하지 못하므로 병변 조직의 충분한 선량을 전달하지 못하였다. 외과적 클립만을 이용할 경우는 수술 상흔을 모두 포함하지 못하였다. 따라서 결론적으로 즉 수술 상흔과 외과적 클립을 모두 포함하는 본 기관에서 사용하는 방법으로 전자선 추가 조사야를 그린다면 정상조직의 부작용 및 지리상으로 병변조직의 빠트림을 최소화할수 있을 것이다.

다국어 초록 (Multilingual Abstract)

Purpose: To evaluate the role of surgical clips and scars in determining electron boost field for early stage
breast cancer undergoing conserving surgery and postoperative radiotherapy and to provide an optimal method
in drawing the boost field. Materials and Methods: Twenty patients who had 4∼7 surgical clips in the excision cavity were selected for this study. The depth informations were obtained to determine electron energy by measuring the distance from the skin to chest wall (SCD) and to the clip implanted in the most posterior area of tumor bed. Three different electron fields were outlined on a simulation film. The radiological tumor bed was determined by connecting all the clips implanted during surgery. Clinical field (CF) was drawn by adding 3 cm margin around surgical scar. Surgical field (SF) was drawn by adding 2 cm margin around surgical clips and an ideal field (IF) was outlined by adding 2 cm margin around both scar and clips. These fields were digitized into our planning system to measure the area of each separate field. The areas of the three different electron boost fields were compared. Finally, surgical clips were contoured on axial CT images and dose volume histogram was plotted to investigate 3-dimensional coverage of the clips. Results: The average depth difference between SCD and the maximal clip location was 0.7±0.56 cm. Greater difference of 5 mm or more was seen in 12 patients. The average shift between the borders of scar and clips were 1.7, 1.2, 1.2, and 0.9 cm in superior, inferior, medial, and lateral directions, respectively. The area of the CF was larger than SF and IF in 6/20 patients. In 15/20 patients, the area difference between SF and IF was less than 5%. One to three clips were seen outside the CF in 15/20 patients. In addition, dosimetrically inadequate coverage of clips (less than 80% of prescribed dose) were observed in 17/20 patients when CF was used as the boost field. Conclusion: The electron field determined from clinical scar underestimates the tumor bed in superior-inferior direction significantly and thereby underdosing the tissue at risk. The electron field obtained from surgical clips alone dose not cover the entire scar properly. As a consequence, our technique, which combines the surgical clips and clinical scars in determining electron boost field, was proved to be effective in minimizing the geographical miss as well as normal tissue complications.

목차 (Table of Contents)

• Introduction
• Materials and Methods
• Results
• Discussion

참고문헌 (Reference)

1 "The influence of the boost technique on local control in breast conserving treatment in the EORTC 'boost versus no boost' randomised trial" 72 : 25-33, 2004

2 "Surgical clips in planning the electron boost in breast cancer:a qualitative and quantitative evaluation" 34 : 579-584, 1996

3 "Recurrence rates after treatment of breast cancer with standard radiotherapy with or without additional radiation" 345 : 1378-1387, 2001

4 "Radiation treatment volumes and doses for patients with early stage carcinoma of the breast treated with breast conserving surgery and definitive irradiation" 2 : 82-93, 1992

5 "Primary radiation therapy for early breast cancer:The experience at the Joint Center for Radiation Therapy" 7 : 1549-1552, 1981

6 "Pathologic findings from the national Surgical adjuvant breast project II.Relation of local breast recurrence to multicentricity" 57 : 1717-1724, 1986

7 "Irradiation of the tumor bed alone after lumpectomy in selected patients with early-stage breast cancer treated with breast conserving therapy" 70 : 33-40, 1999

8 "Inaccuracies in using the lumpectomy scar for planning electron boosts in primary breast carcinoma" 30 : 43-48, 1994

9 "Impact of boost technique on outcome in early-stage breast cancer patients treated with breast-conserving therapy" 24 : 26-32, 2001

10 "Impack of a boost dose of 16 Gy on the local control and cosmesis in patients with early breast cancer:the EORTC boost vs no boost trial" 48 : 111-, 2000

11 "High-dose-rate brachytherapy alone versus whole breast radiotherapy with or without tumor bed boost after breast-conserving surgery:seven-year results of a comparative study" 60 : 1173-1181, 2004

12 "Conservative treatment of breast cancer-Where should the booster does go" 399-401,

13 "Computer CT-planning of the electron boost in definitive breast irradiation" 20 : 121-125, 1991

14 "A practical technique for the localization of the tumor volume in definitive irradiation of the breast" 11 : 1215-1220, 1985