背景：盡管轉移性結直腸癌（mCRC）的分子分割取得了進展，但超越 RAS 狀態的治療作用仍然局限於 ERBB2 擴增、BRAF 突變和 MSI-H 患者的有限亞組。因此，有效治療的優化是必要的。抗表皮生長因子受體單克隆抗體的再激發通常是經驗性的，作為晚期治療有一定的益處。我們以前發現在 EGFR 阻斷期間出現在血液中的突變 RAS 和 EGFR 胞外克隆，在抗體退出後下降，從而恢複藥物敏感性基於這一原理，我們設計了 CHRONOS，這是一個多中心的 II 期抗 EGFR 治療試驗，通過監測 RAS 的突變狀態進行再激發，循環腫瘤DNA（CTDNA）中 bra 和 EGFR 的表達。據我們所知，這是第一次液體活檢在 MCRC 中驅動抗 EGFR 再激發治療的介入性臨床試驗。
Background: Despite advances in molecular segmentation of metastatic colorectal cancer (mCRC), beyond RAS status therapeutic actionability remains confined to the limited subgroups of ERBB2 amplified, BRAF mutated and MSI-H patients. Optimization of available treatments is therefore warranted. Rechallenge with anti-EGFR monoclonal antibodies is often empirically used with some benefit as late-line therapy. We previously found that mutant RAS and EGFR ectodomain clones, which emerge in blood during EGFR blockade, decline upon antibody withdrawal leading to regain drug sensitivity. Based on this rationale, we designed CHRONOS, a multicenter phase II trial of anti-EGFR therapy rechallenge guided by monitoring of the mutational status of RAS, BRAF and EGFR in circulating tumor DNA (ctDNA). To our knowledge, this is the first interventional clinical trial of liquid biopsy for driving anti-EGFR rechallenge therapy in mCRC.
方法：符合條件的患者為 PS ECOG 0-2 RAS/BRAF WT MCRC，首先達到客觀反應，然後在任何含抗 EGFR 抗體的治療方案中進展，顯示 RAS，BRAF 和 EGFR 外域 WT 狀態在進展到最後一個無 EGFR 方案後的分子篩選中增加 tDNA。通過 ddpcr 和下一代測序分析 CTDNA 的克隆進化。每兩周靜脈注射 6 毫克/公斤的帕尼托-穆瑪，直至病情進展。主要終點是 RECIST 版本 1.1 的客觀有效率（ORR），獨立中心回顧共有 27 名患者和 6 名應答者被要求宣布研究陽性（冪=85%，I 型誤差=0.05 ) .
Methods: Eligible patients were PS ECOG 0-2 RAS/BRAF WT mCRC having first achieved an objective response and then progression in any treatment line with an anti-EGFR antibody containing regimen, displaying RAS, BRAF and EGFR ectodomain WT status in ctDNA at molecular screening after progression to the last anti-EGFR-free regimen. Clonal evolution in ctDNA was analyzed by ddPCR and next generation sequencing. Panitumumab 6 mg/kg was administered IV every two weeks until progression. The primary endpoint was objective response rate (ORR) by RECIST version 1.1 with independent central review. 27 total patients and 6 responses were required to declare the study positive (power = 85%, type I error = 0.05).
結果：2019 年 8 月 19 日至 2020 年 11 月 6 日，52 例患者通過液體活檢篩查，36 例（69%）中 CTDNA 的 RAS/BRAF/EGFR 突變陰性。其中，27 名患者在 4 個中心登記。中位年齡為 64 歲（42-80 歲）。PS ECOG 分別為 0/50%、1/46%、2/4%。既往 antEGFR 應用於一線的比例為 63%，二線的比例為 15%和大於 22%，既往治療的中位數為 3。觀察到 8/27 應答（2 例未確認）（ORR=30%，95%Cl:12-47%）11/27 穩定（40%，95%Cl:24-59%），8/11 持續>4個月。疾病控製率（PR+SD>4 個月）為 59%（95%Cl:41-78%）。中位無進展生存期為 16 周。中位反應持續時間為 1 周/周（我正在進行），最大毒性等級為 G3，僅限於 19%的皮膚病患者。
Results: Between Aug 19, 2019 and Nov 6, 2020 52 patients were screened by liquid biopsy and 36 (69%) were negative in ctDNA for RAS/BRAF/EGFR mutations. Of these, 27 patients were enrolled in 4 centers. Median age was 64 years (range: 42-80). PS ECOG was 0/50%, 1/46%, 2/4%. Previous anti-EGFR was administered in 1st line in 63%, 2nd in 15% and > 2nd in 22%. Median number of previous treatments was 3. The primary endpoint was met, with 8/27 partial responses (PR) observed (2 unconfirmed) (ORR = 30%, 95% CI: 12-47%). Stable disease (SD) was obtained in 11/27 (40%, 95% CI: 24-59%), lasting > 4 months in 8/11. Disease control rate (PR plus SD > 4 months) was therefore obtained in 16/27 (59%, 95% CI: 41-78%). Median progression-free survival was 16 weeks. Median duration of response was 17 weeks (1 ongoing). Maximal grade toxicity was G3, limited to dermatological and occurring in 19% of patients. ctDNA dynamics were studied in all patients.
結論：液體活檢驅動抗 EGFR 抗體再激發可使三分之一的患者產生更客觀的反應。對血液中腫瘤 DNA 進行基因分型以指導治療可有效地應用於晚期 CRCS 的治療。
Conclusions: Liquid biopsy-driven rechallenge with anti-EGFR antibodies leads to further objective responses in one third of patients. Genotyping tumor DNA in the blood to direct therapy can be effectively incorporated in the management of advanced CRCs.
