두경부 암의 표적 지향적 방사선 치료

김귀언(Gwi Eon Kim) 대한방사선종양학회 2004 대한방사선종양학회지 Vol.22 No.2

종양 발생 과정에 관여되고 있는 분자 생물학적 기전을 직접 공격해 보자고 하는 치료 방침은 암 치료에 있어서 아주 유망한 치료방법의 하나로 인정되고 있다. Epidermal growth factor receptor (EGFR) 수용체에 여러 ligands가 결합하게 되면 발암 단계에서부터 암의 진행 과정과 전이 과정 그리고 방사선에 대한 저항성과 관련된 여러 가지 중요한 신호전달체계를 활성화시킨다. 특히 진행된 두경부 암 환자들에서 EGFR이 과발현 된 경우에는 매우 불량 한 예후를 나타내고 있기 때문에 이러한 signaling pathway의 selective targeting을 위한 많은 임상 시도가 이루어지 고 있다. 현재까지 알려진 표적치료 항암제로는 크게 EGFR에 대한 monoclonal antibody와 tyrosin kinase inhibitors로 대별될 수 있는데 이와 같은 약제들은 여러 xenograft에서 고무적인 실험 결과들이 입증되어 곧 바로 임상 현장에 서 적용되고 있다. 그러나 기대와는 달리 EGFR inhibitor 단독으로 치료한 초기 임상연구 결과들을 보면 극히 소수 의 환자에서만 미미한 효과를 나타내고 있고, 방사선 치료와의 병용치료에서도 괄목할만한 항암 효과를 보여주지 않고 있다. 그럼에도 불구하고 많은 실험적 데이터로부터 여러 가지 생물학적 이점이 밝혀져 있고 또 미래 지향적 인 치료법의 하나로 각광을 받고 있기 때문에 현재 많은 연구자들은 어떤 환자 군에서 이러한 표적 치료가 도움이 될 것이며, 방사선 치료 또는 항암 치료와는 어떤 방식으로 조합할 것인지, 또 그 순서는 어떻게 할 것이며, 또 환 자 선정에 있어 reliable marker는 무엇인지, 어떻게 체내에서 신호 전달체계의 효과적인 차단을 확인할 수 있겠는 지, 또한 multiple targeted therapy가 필요하도록 하는 targeted agent에 대한 intrinsic 또는 acquired resistance의 기전은 무엇인지 등등, 현재 당면하고 있는 많은 문제점을 규명하고자 노력하고 있다. 특히 EGFR-signaling pathway를 표적으로 하는 표적 지향적 방사선 치료를 위한 translation research의 적절한 모델이 되고 있는 두경부 암 환자에 서 이러한 제반 문제점을 해결하기 위해서는 더 많은 임상 연구와 함께 well-integrated laboratory clinical research program이 필요할 것으로 생각된다. 또한 EGFR antagonist 외에도 angiogenic pathway나 cell-cycle pathway를 표적 으로 하는 새로운 약제들이 계속 개발되고 있고 이에 관한 연구가 활발히 진행 중이다. 따라서 이 고찰에서는 두 경부 암 환자에서 이러한 약제들을 방사선 치료와 병용하였을 때의 임상 연구 결과들을 재검토해 보고 부가적으로 EGFR blockade에 따르는 내성 문제 그리고 방사선 치료를 병용하면서 여러 표적을 동시에 차단시키는 multiple-targeted therapy의 개발 현황을 간략히 소개하고자 한다. Purpose: The purpose of this review is to provide an update on novel radiation treatments for head and neck cancer. Recent Findings: Despite the remarkable advances in chemotherapy and radiotherapy techniques, the management of advanced head and neck cancer remains challenging. Epidermal growth factor receptor (EGFR) is an appealing target for novel therapies in head and neck cancer because not only EGFR activation stimulates many important signaling pathways associated with cancer development and progression, and importantly, resistance to radiation. Furthermore, EGFR overexpression is known to be portended for a worse outcome in patients with advanced head and neck cancer. Two categories of compounds designed to abrogate EGFR signaling, such as monoclonal antibodies (Cetuximab) and tyrosine kinase inhibitors (ZD1839 and OSI-774) have been assessed and have been most extensively studied in preclinical models and clinical trials. Additional TKIs in clinical trials include a reversible agent, CI-1033, which blocks activation of all erbB receptors. Encouraging preclinical data for head and neck cancers resulted in rapid translation into the clinic. Results from initial clinical trials show rather surprisingly that only minority of patients benefited from EGFR inhibition as monotherapy or in combination with chemotherapy. In this review, we begin with a brief summary of erbBmediated signal transduction. Subsequently, we present data on prognostic-predictive value of erbB receptor expression in HNC followed by preclinical and clinical data on the role of EGFR antagonists alone or in combination with radiation in the treatment of HNC. Finally, we discuss the emerging thoughts on resistance to EGFR blockade and efforts in the development of multiple-targeted therapy for combination with chemotherapy or radiation. Current challenges for investigators are to determine (1) who will benefit from targeted agents and which agents are most appropriate to combine with radiation and/or chemotherapy, (2) how to sequence these agents with radiation and/or cytotoxic compounds, (3) reliable markers for patient selection and verification of effective blockade of signaling in vivo, and (4) mechanisms behind intrinsic or acquired resistance to targeted agents to facilitate rational development of multi-targeted therapy. Other molecular-targeted approaches in dead and neck cancer were briefly described, including angioenesis inhibitors, farnesyl transferase inhibitors, cell cycle regulators, and gene therapy Summary: Novel targeted therapies are highly appealing in advanced head and neck cancer, and the most promising strategy to use them is a matter of intense investigation.

Design and Dose Distribution of Docking Applicator for an Intraoperative Radiation Therapy

추성실,김귀언,노준규,Chu, Sung-Sil,Kim, Gwi-Eon,Loh, John-Kyu The Korean Society for Radiation Oncology 1991 Radiation Oncology Journal Vol.9 No.2

수술중 방사선치료법 (Intraoperative Radiation Therapy)은 외과적으로 개복된 상태에서 종양이나 장기를 절제한후 비가시적 또한 육안적 암세포를 전자선등으로 직접 조사 치료하는 방법으로서 일시에 다량의 방사선량을종양부위에 집중적으로 조사할 수 있으며 정상장기나 조직을 방사선 조사 범위로부터 차단함으로 방사선 손상을 격감 시킬 수 있는 장점을 갖고 있다. 본 연세암쎈터 치료방사선과에서는 1986년 2월부터 현재까지 십여명의 위암환자를 대상으로 수술중 방사선치료를 시 행하여 좋은 결과를 얻었으나 치료절차상 많은 어려운점 이 야기되어왔다. 그중에서도 방사선치료실(LINAC room)내에서 수술을 시행함에 따른 수술기구, 응급처치 장치, 조명 및 감시장치 등이 완벽하게 준비되여져 야 하며 치료실내를 $2\sim3$일 동안 자외선과 소독약으로 완전히 제독 하여야 함으로 그기간동안 많은 방사선치료 환자들이 한명의 IORT환자를 위하여 치료를 중단하여 야 하는 어려움이 있었다. 본 연세 암쎈터에서는 콜리메터 접속기구(collimator holder)와 투명 조사통(Acrylic cone)으로 구성된 조립형 조사기구(Docking Applicator)를 고안 제작하여 수술과 방사선 치료를 각각 해당 장소에서 시 행할 수 있었다. 즉 tORT 환자의 개복수술은 수술실에서 시 행하되 다만 가볍고 투명하며 외부 공기와 차단된 투명 조사기구(Acrylic cone)를 종양 부위에 조준고정 시켜 봉합하고 방사선 치료실로 이송된후 선형가속기의 방사구에 장착된 콜리메터 접속기와 접합시킴으로서 많은 문제점을 해결할 수 있었다. 조립조사 기구는 치료부위를 잘 관찰할 수 있고 쉽게 결합할 수 있도록 가벼운 아크릴과 Mylafilm으로 구성 제작하였으며 콜리메터 접속기는 종양 부위에 균일한 선량분포와 누출선량을 줄이기 위하여 스텐레스 강철로 구성제작하였다. 직경이 8cm이고 길이가 30cm인 접합형 조사기구를 사용하여 12MeV 전자선을 조사하였을때 $90\%$의 등선량곡선이 5 mm 정도 확장 되었으며 조사통 가장자리의 선량이 약 $6\%$ 증가하였다. 조사 통밖 의 누출 선량은 위치에 따라 출력선량의 $3\sim5\%$가 측정되었고 심부 백분율은 기준조사통에 의한 것과 유사하였다. 조사통의 모양과 크기는 종양범위에 알맞도록 원형, 사각형 또는 오각형 등으로 제작하였으며 $1\sim2$ cm의 금속띠를 이용 조절하므로서 최적한 선량분포를 얻을수 있었고 콜리메터의 차폐 금속편을 이용하여 조사통밖의 누출선량을 최대한으로 줄일 수 있었다. A docking intraoperative electron beam applicator system, which is easily docking in the collimator for a linear accelerator after setting a sterilized transparent cone on the tumor bearing area in the operation room, has been designed to optimize dose distribution and to improve the efficiency of radiation treatment method with linear accelerator. This applicator system consisted of collimator holder with shielded metals and docking cone with transparent acrylic cylinder, A number of technical innovations have been used in the design of this system, this dooking cone gives a improving latral dose coverage at therapeutic volume. The position of $90\%$ isodose curve under suface of 8 cm diameter cone was extended $4\sim7$ mm at 12 MeV electron and the isodose measurements beneath the cone wall showed hot spots as great as $106\%$ for acrylic cone. The leakage radiation dose to tissues outside the cone wall was reduced as $3\sim5\%$ of output dose. A comprehensive set of dosimetric characteristics of the intraoperative radiation therapy applicator system is presented.

고 강도 차폐벽돌을 이용한 방사선치료실의 차폐설계

서창옥,김귀언,추성실,Suh Chang Ok,Kim Gwi Eon,Chu Sung Sil 한국의학물리학회 2004 의학물리 Vol.15 No.4

According to developing high energy linear accelerators and treatment methods, like (3 dimensional conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT), many radiotherapy centers are replacing older linear accelerators with new higher technical machines. This often presents a shielding problem as the designed shield for the existing rooms is not adequate for the higher technical machines. Additional shielding in limited existing space becomes necessary. We are replacing older brachytherapy room with new higher technical linear accelerator for IMRT. This room is not adequate for the IMRT machine without additional shielding design. The logical development of optimum structural shielding designs with concrete and high density shielding blocks are presented. We obtained following results by comparison between the pre-calculating values and actual survey of completed LINAC installation. High density shielding blocks have more powerful radiation protection about 2 times.

비인강암에서 방사선 구강 건조증 발생 감소를 위한 3차원 입체조형치료

임지훈,김귀언,금기창,서창옥,이상욱,박희철,조재호,이상훈,장세경,노준규,Lim Jihoon,Kim Gwi Eon,Keum Ki Chang,Suh Chang Ok,Lee Sang-wook,Park Hee Chul,Cho Jae Ho,Lee Sang Hoon,Chang Sei Kyung,Loh Juhn Kyu 대한방사선종양학회 2000 대한방사선종양학회지 Vol.18 No.1

Purpose : Although using the high energy Photon beam with conventional Parallel-opposed beams radiotherapy for nasopharyngeal carcinoma, radiation-induced xerostomia is a troublesome problem for patients. We conducted this study to explore a new parotid gland sparing technique in 3-D conformal radiotherapy (3-D CRT) in an effort to prevent the radiation-induced xerostomia. Materials and Methods : We peformed three different planning for four clinically node-negative nasopharyngeal cancer patients with different location of tumor(intracranial extension, nasal cavity extension, oropharyngeal extension, parapharyngeal extension), and intercompared the plans. Total prescription dose was 70.2 Gy to the isocenter. For plan-A, 2-D parallel opposing fields, a conventional radiotherapy technique, were employed. For plan-B, 2-D parallel opposing fields were used up until 54 Gy and afterwards 3-D non-coplanar beams were used. For plan-C, the new technique, 54 Gy was delivered by 3-D conformal 3-port beams (AP and both lateral ports with wedge compensator; shielding both superficial lobes of parotid glands at the AP beam using BEV) from the beginning of the treatment and early spinal cord block (at 36 Gy) was peformed. And bilateral posterior necks were treated with electron after 36 Gy. After 54 Gy, non-coplanar beams were used for cone-down plan. We intercompared dose statistics (Dmax, Dmin, Dmean, D95, DO5, V95, VOS, Volume receiving 46 Gy) and dose volume histograms (DVH) of tumor and normal tissues and NTCP values of parotid glands for the above three plans. Results : For all patients, the new technique (plan-C) was comparable or superior to the other plans in target volume isodose distribution and dose statistics and it has more homogenous target volume coverage. The new technique was most superior to the other plans in parotid glands sparing (volume receiving 46 Gy: 100, 98, 69$\%$ for each plan-A, B and C). And it showed the lowest NTCP value of parotid glands in all patients (range of NTCP; 96$\~$100$\%$, 79$\~$99$\%$, 51$\~$72$\%$ for each plan-A, B and C). Conclusion : We conclude that the new technique employing 3-D conformal radiotherapy at the beginning of radiotherapy and cone down using non-coplanar beams with early spinal cord block is highly recommended to spare parotid glands for node-negative nasopharygeal cancer patients.

사골동 종양의 3-차원 입체조형치료 : I. 2차원 치료계획과 3차원 치료계획의 비교분석

이상욱,김귀언,금기창,박희철,조재호,한성욱,이강규,서창옥,홍원표,박인용,Lee Sangwook,Kim Gwi Eon,Keum Ki Chang,Park Hee Chul,Cho Jae Ho,Han Soung Uk,Lee Kang Kyu,Suh Chang Ok,Hong Won Pyo,Park In Yong 대한방사선종양학회 1997 대한방사선종양학회지 Vol.15 No.4

Purpose : This is study of whether 3-D conformal radiotherapy for carcino-mas of the ethmoid sinus were better than those treated with conventional 2-D plan, Materials and Methods : The 3-D conformal treatment Plans were compared with conventional 2-D plans in 4 patients with malignancy of the ethmoid sinus. Isodose distribution, dose statistics, and dose volume histogram of the planning target volume were used to evaluate differences between 2-D and 3-D plans. In addition. the risk of radiation exposure of surrounding normal critical organs are evaluated by means of point dose calculation and dose volume histogram. Results : 3-D conformal treatment plans for each patient that the better tumor coverages by the planning target volume with improved dose homo-geneity, compared to 2-D conventional treatment Plans in the same Patient. On the other hand, the radiation dose distributions to the surrounding nor-mal tissue organs, such as the orbit and optic nerves are not significantly reduced with our technique, but a substantial sparing in the brain stem and optic chiasm for each patient. Conclusion : Our findings represented the potential advantage of 3-D treatment planning for dose homogeniety as well as sparing of the normal tissue surrounding the tumor. However, further investigational studies are required to define the clinical benefit.

Treatment of Carcinoma of the Uterine Cervix with High-Dose-Rate Intracavitary Irradiation using Ralstron

서창옥,김귀언,노준규,Suh Chang Ok,Kim Gwi Eon,Loh John J.K. The Korean Society for Radiation Oncology 1990 Radiation Oncology Journal Vol.8 No.2

1979년 5월부터 1981년 12월까지 총 524명의 자궁경부암 환자가 근치적 목적하에 방사선 치료를 받았다. 524명의 환자중, 356명이 코발트 선원을 사용한 원격 조정 아프터로딩 고선량률 강내조사 시스템 (Ralstron)으로써 치료받았으며 168명의 환자는 라듐 선원을 사용한 저선량률 강내 조사를 받았다. 외부조사는 골반부 전체에 총 40-50 Gy가 주어졌으며, 이어서 A지점에 10-13번에 걸쳐 30-39 Gy의 강내 조사를 시행하는 치료지침이 사용되었다. 강내조사는 3 Gy씩, 일주일에 세번 주어졌다. 고선량률 강내조사를 받은 군에서의 5년 실제생존률은 IB기 (N=20)가 $77.6{\%}$, II기 (N=182)가 $68.2{\%}$ 그리고 III기 (N=148)가 $50.9{\%}$였다. 저산량률 강내조사군에서의 5년 생존률은 IB기 (N=22)가 $87.5{\%}$, II기 (N=91)가 $66.3{\%}$, 그리고 III기 (N=52)가 $55.4{\%}$였다. 생존률은 병기에 따라서는 통계학적으로 유의한 차이를 보였지만, 두 강내조사군 간에는 유의한 차이가 없었다. 방사선치료후 내장의 후기 합병증은 고선량률 강내조사 군에서 $3.7{\%}$, 저산량률 강내조사군은 $8.4{\%}$에서 관찰되었다. 그러나 외과적 치료가 필요할 만큼 심한 합병증은 없었다. 방광에서 발생한 합병증의 빈도는 고선량률 강내조사군이 $1.4{\%}$, 저선량률 강내조사군은 $2.4{\%}$였다. 고선량률 강내조사의 시술은 외래 환자에 시행하기에 기술적으로 간단하고 쉬우며 마취가 필요없고, 환자가 매우 잘 견딘다. 담당자에 대한 방사선 피폭도 저선량률 강내조사에 비해 사실상 거의 없다. 고선량률 강내조사의 경우 치료시간이 짧기 때문에 주어진 시간내에 더 많은 환자를 치료할 수 있다. 따라서 많은 환자를 치료해야 되는 암센터의 경우, 고선량률 강내조사 시스템이 훨씬 더 권장되어 진다. 그러나 더욱 향상된 결과를 얻기 위하여, 다른 치료 방식으로 광범위한 연구를 통해, 고선량률 강내조사의 적절한 선량-분할조사 계획과 외부조사와 강내조사의 적절한 배합이 이루어져야 할 것이다. From May 1979 through December 1981 a total of 524 patients with carcinoma of the uterine cervix were treated by radiation therapy with curative intent. Among the 524 patients, 350 were treated with a high-dose-rate (HDR), remote-controlled, afterloading intracavitary irradiation (ICR) system using a cobalt source (Ralstron), and 168 patients received a low-dose-rate (LDR) ICR using a radium source. External beam irradiation with a total dose of 40-50 Gy to the whole pelvis followed by intracavitary irradiation with a total dose of 30-39 Gy in 10-13 fractions to point A was the treatment protocol. ICR was given three times a week with a dose of 3 Gy per fraction. Five-year actuarial survival rates in the HDR-ICR group were $77.6{\%}$ in stage IB (N=20), $68.2{\%}$ in stage II (N=182), and $50.9{\%}$ in stage III (N=148). In LDR-ICR group, 5-year survival rates were $87.5{\%}$ in stage IB (N=22), $66.3{\%}$ in stage II (N=91), and $55.4{\%}$ in stage III (N=52). Survival rates showed a statistically significant difference by stage, but there was no significant difference between the two ICR groups. Late bowel complications after radiotherapy were noted in $3.7{\%}$ of the HDR-ICR group and $8.4{\%}$ of the LDR-ICR group. There was no severe complication requiring surgical management. The incidence of bladder complications was $1.4{\%}$ in the HDR-ICR group and $2.4{\%}$ in the LDR-ICR group. The application of HDR-ICR was technically simple and easily performed on an outpatient basis without anesthesia, and the patients tolerated it very well. Radiation exposure to personnel was virtually nil in contrast to that of LDR-ICR. Within a given period of time, more patients can be treated with HDR-ICR because of the short treatment time. Therefore, the HDR-ICR system is highly recommended for a cancer center, particularly one with a large number of patients to be treated. In order to achieve an improved outcome, however, the optimum dose-fractionation schedule of HDR-ICR and optimum combination of intracavitary irradiation with external beam irradiation should be determined through an extensive protocol.

간암에서 호흡주기를 고려한 2-차원 방사선 치료 방법과 3-차원 입체조형 치료방법에서 방사선 간염 예측의 비교연구

이상욱,김귀언,정갑수,이창걸,성진실,서창옥,Lee Sang-wook,Kim Gwi Eon,Chung Kap Soo,Lee Chang Geol,Seong Jinsil,Suh Chang Ok 대한방사선종양학회 1998 대한방사선종양학회지 Vol.16 No.4

Purpose : To evaluate influences associated with radiation treatment planning obtained with the patient breathing freely. Materials and Methods : We compared reduction or elimination of planning target volume (PTV) margins with 2-D conventional plan with inclusion of PTV margins associated with breathing with 3-D conformal therapy. The respiratory non gated 3-D conformal treatment plans were compared with respiratory gated conventional 2-D plans in 4 patients with hepatocellular carcinomas. Isodose distribution, dose statistics, and dose volume histogram (DVH) of PTVs were used to evaluate differences between respiratory gated conventional 2-D plans and respiratory non gated 3-D conformal treatment plans. In addition. the risk of radiation exposure of surrounding normal liver and organs are evaluated by means of DVH and normal tissue complication probabilities (NTCPs). Results : The vertical movement of liver ranged 2-3 cm in all patients. We found no difference between respiratory gated 2-D plans and 3-D conformal treatment plans with the patients breathing freely. Treatment planning using DVH analysis of PTV and the normal liver was used for all patients. DVH and calculated NTCP showed no difference in respiratory gated 2-D plans and respiratory non gated 3-D conformal treatment plans. Conclusion : Respiratory gated radiation therapy was very important in hepatic tumors because radiation induced hepatitis was dependent on remaining normal liver volume. Further investigational studies for respiratory gated radiation.

N3(AJCC-UICC) 전이성 경부 임파절의 방사선 및 온열 병행요법

이창걸,김귀언,성진실,서창옥,노준규,김병수,박경란,이종영,홍원표,박정수,김수곤,Lee Chang-Geol,Kim Gwi-Eon,Seong Jin-Sil,Suh Chang-Ok,Loh John-Kyu,Kim Byung-Soo,Park Kyung-Ran,Lee Jong-Young,Hong Won-Pyo,Park Cheong-Soo,Kim Soo-Kon 대한두경부종양학회 1992 대한두경부 종양학회지 Vol.8 No.1

In order to improve the control of large unresectable(>6cm) and fixed N3(TNM-UICC) metastatic neck nodes, local hyperthermia(HT) has been combined with radiation therapty (RT) in Yonsei cancer center. From April 1985 to april 1988, a total of 18 patients of head and neck cancer with metastatic large unresectable and fixed cervical neck nodes who underwent combined RT and HT were analyzed. Of 18 patients, complete response rate was 39% (7 pt.) partial response 39% (7 pt.) and overall response rate was 78%. Acute side effects of these combined modalities were found in 8 patients and which were mainly cutaneous reaction such as erythema, dry and moist desquamation but recovered spontaneously in all patients after treatment. Factors of maximum tumor temperature above $43^{\circ}\C$ and MDF(multiple daily fractionation) showed more favorable response rate but not statistically sinificant. Two year actuarial survival rate of all patients was 35.4%.

유전 가열장치에서 전극의 각도 배열 -온도 분포의 특성 및 임상 적용-

성진실,추성실,김귀언,노준규,양성화,Seong, Jin-Sil,Chu, Sung-Sil,Kim, Gwi-Eon,John, Juhn-Kyu,Yang, Sung-Wha The Korean Society for Radiation Oncology 1989 Radiation Oncology Journal Vol.7 No.2

고주파유전가열 장치는 심부까지도 효과적인 가온이 가능하여 각족 심부암의 치료에 응용되고 있다. 그러나 한쌍의 전극을 평행으로 대칭 배열하는 현재의 방법은 신체의 일측으로 편재되어 있는 병소에는 배열 자체가 불안정할 뿐만 아니라, 노출된 동측 피부표면이 과열되며 종양의 가온 양상도 만족스럽지 못한 경우가 많아서 임상 적응에 난점으로 지적되고 있는 실정이다. 저자들은 상기와 같은 병소를 보다 안전하고_도 효과적으로 가온하기 위하여 두 전극간에 일정한 각도를 이루는 새로운 전극 배열을 시도하였다. 즉, 임상 적용 가능성을 고려한 $60^[\circ},\;90^{\circ}\;및\;120^{\circ}$로 전극을 배열하고 모형 (phantom)에서 가온 실험을 행하여 이같은 각도 배열에서의 온도 분포의 특성을 평가할 수 있었고, 일측에 편재된 병소를 가진 3예의 환자에게 각도 배열로 온열치료를 시행한 결과 환자의 수용성, 부작용 및 온도분포에 있어서 만족할 만한 결과를 얻을 수 있었다. 따라서 저자들이 시도한 전극의 각도배열은 일측에 편재된 병소를 유전 가열 장치로 가온 할 때 평행 배열이라는 한계점을 극복할 수 있는 새로운 방법으로서 매우 고무적으로 생각된다. In capacitive heating device, which considered efficient for deep heating, parallel arrangement of the electrodes is a serious limiting factor in heating for eccentrically located lesions because it causes overheating of the exposed ipsilateral skin surface, the heating pattern is also frequently inappropriate, and the arrangement tends to be unstable due to the patient's gravity. Therefore we attempted an angular arrangement of the electordes to achieve more homogenous and efficient heating for such lesions. In phantom study, both the thermal profile and thermogram established the heating pattern in this unusual angular arrangement of the electrodes at $60^{\circ},\;90^{\circ}\; and\;120^{\circ}$ angles, respectively. An angular arrangement was also clinically applied to 3 patients. The patients' tolerance was good without significant complication and the thermal distribution was satisfactory. In conclusion, this unusual arrangement of electrodes appears to be promising in the clinical application to the eccentrically located lesions.

Adaptive Response to ionizing Radiation Induced by Low Doses of Gamma Rays in Human Lymphoblastoid Cell Lines

성진실,서창옥,김귀언,Seong, Jin-Sil,Suh, Chang-Ok,Kim, Gwi-Eon The Korean Society for Radiation Oncology 1994 대한방사선종양학회지 Vol.12 No.1

When cells are exposed to low doses of a mutagenic or clastogenic agents. they often become less sensitive to the effects of a higher dose administered subsequently. Such adaptive responses were first described in Escherichia coli and mammalian cells to low doses of an alkylating agent. Since most of the studies have been carried out with human lymphocytes, it is urgently necessary to study this effect in different cellular systems. Its relation with inherent cellular radiosensitivity and underlying mechanism also remain to be answered. In this study, adaptive response by 1 cGy of gamma rays was investigated in three human lymphoblastoid cell lines which were derived from ataxia telangiectasia homozygote, ataxia telangiectasia heterozygote, and normal individual. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher dose (50 cGy), The expression of this adaptive response was similar among three cell lines despite of their different radiosensitivity. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the tested cell lines. Therefore it is suggested that the adaptive response can be observed in human lymphoblastoid cell lines, which was first documented through this study. The expression of adaptive response was similar among the cell lines regardless of their radiosensitivity. The elimination of the adaptive response by 3-aminobenzamide is consistent with the proposal that this adaptive response is the result of the induction of a certain chromosomal repair mechanism.