FDG-PET/CTにより算出したtotal tumor burdenを用いた進行期非小細胞肺癌の治療効果判定と長期予後層別化

Prognostic stratification of advanced stage non-small lung cancer using total tumor burden calculated from FDG-PET/CT

非小細胞肺癌（non-small-cell lung cancer：NSCLC）の治療は進行期では積極的な化学療法が施行される傾向にあり^1）2），治療方針決定には正確な治療効果判定および予後予測が必要である。治療効果判定法には通常，形態画像変化による判定法RECIST（response evaluation criteria in solid tumours）が用いられるが^3），近年は免疫チェックポイント阻害薬を使用後に一過性の腫瘍増大（pseudo-progression）を呈する症例もあり形態変化のみでは判定が難しい場合がある^2）。このため腫瘍の形態変化よりも代謝変化が先行する場合を想定し，FDGの集積変化を用いて判定するPET response criteria in solid tumors（PERCIST）の有用性が報告されている^4-6）。

In the diagnosis of therapeutic effect of advanced non-small cell lung cancer（NSCLC）, PERCIST criteria by FDG-PET/CT is useful. In advanced NSCLC, total tumor burden（TTB）that is calculated by summing total lesion glycolysis（TLG）of all lesion could be useful.

The therapeutic effect of twenty-two NSCLC cases were evaluated by FDG-PET/CT and TTB before and after chemotherapy in this study. The initial therapeutic effect was diagnosed by PERCIST and classified into the progressive metabolic disease（PMD）group and the stable metabolic disease（SMD）or partial metabolic response（PMR）group. The PMD group was divided into two subgroups, TTB≧250g and TTB＜250g, based on the value of TTB before treatment. Survival rates were compared among the three groups. The mean survival time was significantly longer in the PMD with TTB＜250g group than PMD with TTB≥250g group, PMR＋SMD group. The overall survival（OS）rate was significantly lower in the PMD group with TTB≥250g than in cases with TTB＜250g. The value of TTB calculated by summing TLG will be a useful index for stratifying the prognosis in the advanced NSCLC.