저선량 CT 선별검사 유양성자에 대한 대책

저선량 CT 선별검사를 도입하고자 한다면 우선 검사 양성 판정에 대한 정의부터 해야 한다. 저선량 CT에서 발견되 는 결절은 형태학적으로 4가지로 분류한다^31,32: 1군) 내부에 양성을 시사하는 석회화를 포함한 양성 결절, 2군) 5 mm 미만의 크기로 너무 작은 크기 때문에 판정이 불가능한 결절, 3군) 5∼10 mm의 고형결절(solid nodule), 5 mm를 초과하는 간유리음영결절(ground-glass opacity nodule, GGO) 및 고형 부분(고형 부분 5 mm이하)을 포함한 간유리음영결절(partly solid GGO), 4군) 10 mm를 초과하는 고형 결절, 고형 부분(고형 부분 5 mm 초과)을 포함한 간유리음영결절, 성장하는 결절, 고형 부분이 성장하는 간유리음영결절, 기관지 폐쇄를 유발하여 폐의 허탈을 초래하 는 결절(Table 1). 1군 결절이 폐암일 확률은 거의 없다. 2군 결절이 폐암일 확률은 1% 미만으로 추적검사가 필요하 며, 3군 결절이 폐암일 확률은 6∼28%, 4군 결절이 폐암일 확률은 33∼64%에 달한다^12,31-33.

저선량 CT 검사 유양성자에 대한 대책은 각 국가의 각 전문가 집단마다 여러 가지가 보고되고 있는데 전문가들의 합의에 근거한 제안들이며 각 제안들은 대동소이하다. 여기에서는 대한흉부영상의학회에서 결절의 분류에 따른 대책 을 제시한 것을 소개한다(Table 2)³².

10. 결론

대규모 대조군 연구에서 저선량 흉부 CT 촬영군이 흉부 방사선 촬영군에 비하여 낮은 폐암 사망률과 전체 사망률을 보인다는 것이 입증됨으로써 저선량 CT 선별검사에 대한 관심이 급증하고 있다. 그러나 저선량 CT 선별검사는 단순 히 매년 CT를 촬영한다는 의미보다는 더 복잡한 난제를 포함하고 있는데, 촬영 장비와 판독의 질관리, 발견된 결절의

Category Definition

Category 1 (benign nodule) Nodules containing fat or with a benign pattern calcification

Category 2* (non-significant small nodule) Any nodule, smaller than category 3 and no characteristics of category 1 Category 3* (intermediate nodule requiring 5 mm＜solid nodule≤10 mm

growth evaluation) Part-solid nodule (solid portion≤5 mm) 5 mm＜pure ground-glass nodule Category 4* (potentially malignant nodule 10 mm＜solid nodule

requiring diagnostic work-up) Part-solid nodule (solid portion＞5 mm) Nodules showing interval growth^†

Part-solid nodules showing solid portion growth^‡

Part-solid nodules or pure ground-glass nodules showing increasing internal attenuation over follow-ups Table 1. Pulmonary nodule classification detected on screening CT

Category Management protocol*

Category 1 (benign nodule) Negative test

Category 2^† (non-significant small nodule) Follow-up low dose CT after 12 months to determine the nodules interval growth

Category 3^† (intermediate nodule requiring Baseline detected nodule: follow-up low dose CT after 3 months to evaluate growth evaluation) nodules’ interval growth → If no growth, additional follow-up CT after 6∼9

months to reevaluate nodule’ interval growth

Interval detected nodule: follow-up low dose CT after 6-8 weeks to evaluate nodules’ interval growth → If no growth, additional follow-up CT after 6∼9 months to reevaluate nodule’ interval growth

Category 4 (potentially malignant nodule Further management decision should be determined following the requiring diagnostic work-up) multidisciplinary team assessment

*Management protocol covers both the baseline-detected nodules and the interval detected nodules.

†Solid nodules can be considered benign (category 1) if they are stable over at least 2 years’ follow-up period irrespective of the size. In the case of part-solid nodules or pure ground glass nodules, there has been no sufficient evidence to determine any specific follow-up duration to confirm their benignity yet.

Adapated from the article of Lee et al. (J Korean Soc Radiol 2012;67:349-65)³². Table 2. Management protocol according to nodule classification

침습적, 비침습적 진단 과정의 정도 관리, 비용-효과적 측면에서의 선별검사 대상군 설정, 검사 참여자들의 정신 건강학적 문제, 위양성과 위음성률을 낮추기 위하여 필수적인 결절 판별의 기술적 진보, 검사 주기와 검사 지속 기간 등 매우 복잡한 문제는 여러 전문가들이 다학제적으로 풀어가야 할 문제들이다.

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