Scholarlink

Purpose <p>Nodal immune flare (NIF) is an immune-related adverse event affecting lymph nodes after lung cancer immunotherapy. Differentiating NIF from lymph node metastasis using [<sup>18</sup>F] fluorodeoxyglucose ([<sup>18</sup>F]FDG) is challenging. This study aimed to evaluate whether [<sup>18</sup>F] fibroblast activation protein inhibitor ([<sup>18</sup>F]FAPI), a novel tracer targeting fibroblast activation protein (FAP), can distinguish NIF from lymph node metastasis after immunotherapy.</p> Methods <p>We retrospectively enrolled 589 lung cancer patients who received immunotherapy and subsequently underwent restaging by [<sup>18</sup>F]FDG PET/CT. Maximum standard uptake value (SUV<sub>max</sub>) and false-positive rates were compared in 21 patients who underwent both [<sup>18</sup>F]FDG and [<sup>18</sup>F]FAPI. Immunohistochemistry for FAP, CD4 + and CD8 + T cells was performed.</p> Results <p>NIF occurred in 37 of 589 patients (6.3%) with a median onset time of 5.0 months. A total of 279 regional lymph nodes showed increased [<sup>18</sup>F]FDG uptake (median SUV<sub>max</sub> 6.5). [<sup>18</sup>F]FDG demonstrated high false-positive rates for NIF (100% per patient, 93.3% per region). However, [<sup>18</sup>F]FAPI SUV<sub>max</sub> in NIF was significantly lower than [<sup>18</sup>F]FDG (1.5 vs. 6.5; <i>P</i> &lt; 0.001), reducing the false-positive rate to 33.3% per patient and 14.1% per region. After immunotherapy, both NIF and lymph node metastases showed prominent infiltration of CD4 + and CD8 + T cells, along with increased [<sup>18</sup>F]FDG uptake (all <i>P</i> &gt; 0.05), indicating that a T-cell dominated inflammatory microenvironment underlies the elevated [<sup>18</sup>F]FDG uptake. In contrast, FAP expression and [<sup>18</sup>F]FAPI uptake were significantly lower in NIF than in lymph node metastases (<i>P</i> &lt; 0.05), suggesting the absence of marked FAP in NIF.</p> Conclusion <p>After immunotherapy in lung cancer, [<sup>18</sup>F]FAPI PET/CT outperforms [<sup>18</sup>F]FDG PET/CT in distinguishing NIF from lymph node metastases, reflecting a T-cell driven inflammatory microenvironment with low FAP expression in NIF.</p> Clinical trial registration <p>the Chinese Clinical Trial Registry: ChiCTR2100044944 (Registered: 1 April 2021, retrospectively registered, <a href="https://www.chictr.org.cn/showprojEN.html?proj=123995">https://www.chictr.org.cn/showprojEN.html?proj=123995</a><i>).</i></p> Graphical Abstract <p></p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

[18F]FAPI PET/CT outperforms [18F]FDG in distinguishing nodal immune flare from lymph node metastases during immunotherapy for lung cancer

  • 期刊论文

  • 发表日期：

    2026年3月23日

查看全文
  • Youcai Li,
  • Fang Wu,
  • Meijuan Zhou,
  • Ziwei Yi,
  • Wanmei Liang,
  • Jing Zhang,
  • Dong Li,
  • Dazhou Li,
  • Shaonan Zhong,
  • Peng Hou,
  • Jie Lv,
  • Miao Ke,
  • Ruiyue Zhao,
  • Shaoyu Liu,
  • Xinqing Lin,
  • Xinlu Wang

摘要

Purpose

Nodal immune flare (NIF) is an immune-related adverse event affecting lymph nodes after lung cancer immunotherapy. Differentiating NIF from lymph node metastasis using [18F] fluorodeoxyglucose ([18F]FDG) is challenging. This study aimed to evaluate whether [18F] fibroblast activation protein inhibitor ([18F]FAPI), a novel tracer targeting fibroblast activation protein (FAP), can distinguish NIF from lymph node metastasis after immunotherapy.

Methods

We retrospectively enrolled 589 lung cancer patients who received immunotherapy and subsequently underwent restaging by [18F]FDG PET/CT. Maximum standard uptake value (SUVmax) and false-positive rates were compared in 21 patients who underwent both [18F]FDG and [18F]FAPI. Immunohistochemistry for FAP, CD4 + and CD8 + T cells was performed.

Results

NIF occurred in 37 of 589 patients (6.3%) with a median onset time of 5.0 months. A total of 279 regional lymph nodes showed increased [18F]FDG uptake (median SUVmax 6.5). [18F]FDG demonstrated high false-positive rates for NIF (100% per patient, 93.3% per region). However, [18F]FAPI SUVmax in NIF was significantly lower than [18F]FDG (1.5 vs. 6.5; P < 0.001), reducing the false-positive rate to 33.3% per patient and 14.1% per region. After immunotherapy, both NIF and lymph node metastases showed prominent infiltration of CD4 + and CD8 + T cells, along with increased [18F]FDG uptake (all P > 0.05), indicating that a T-cell dominated inflammatory microenvironment underlies the elevated [18F]FDG uptake. In contrast, FAP expression and [18F]FAPI uptake were significantly lower in NIF than in lymph node metastases (P < 0.05), suggesting the absence of marked FAP in NIF.

Conclusion

After immunotherapy in lung cancer, [18F]FAPI PET/CT outperforms [18F]FDG PET/CT in distinguishing NIF from lymph node metastases, reflecting a T-cell driven inflammatory microenvironment with low FAP expression in NIF.

Clinical trial registration

the Chinese Clinical Trial Registry: ChiCTR2100044944 (Registered: 1 April 2021, retrospectively registered, https://www.chictr.org.cn/showprojEN.html?proj=123995).

Graphical Abstract