Predictive value of positron emission tomography for the prognosis of molecularly targeted therapy in solid tumors

Molecular and functional imaging in cancer-targeted therapy: current applications and future directions

Targeted anticancer drugs block cancer cell growth by interfering with specific signaling pathways vital to carcinogenesis and tumor growth rather than harming all rapidly dividing cells as in cytotoxic chemotherapy. The Response Evaluation Criteria in Solid Tumor (RECIST) system has been used to assess tumor response to therapy via changes in the size of target lesions as measured by calipers, conventional anatomically based imaging modalities such as computed tomography (CT), and magnetic resonance imaging (MRI), and other imaging methods. However, RECIST is sometimes inaccurate in assessing the efficacy of targeted therapy drugs because of the poor correlation between tumor size and treatment-induced tumor necrosis or shrinkage. This approach might also result in delayed identification of response when the therapy does confer a reduction in tumor size. Innovative molecular imaging techniques have rapidly gained importance in the dawning era of targeted therapy as they can visualize, characterize, and quantify biological processes at the cellular, subcellular, or even molecular level rather than at the anatomical level. This review summarizes different targeted cell signaling pathways, various molecular imaging techniques, and developed probes. Moreover, the application of molecular imaging for evaluating treatment response and related clinical outcome is also systematically outlined. In the future, more attention should be paid to promoting the clinical translation of molecular imaging in evaluating the sensitivity to targeted therapy with biocompatible probes. In particular, multimodal imaging technologies incorporating advanced artificial intelligence should be developed to comprehensively and accurately assess cancer-targeted therapy, in addition to RECIST-based methods.

Predictive value of positron emission tomography for the prognosis of immune checkpoint inhibitors (ICIs) in malignant tumors

PURPOSE

This study aimed at investigating the value of applying positron emission tomography (PET) to early predict the effect of immune checkpoint inhibitors (ICIs) in malignant tumors.

METHODS

Electronic databases MEDLINE/PubMed, EMBASE, and Cochrane Library were searched to identify relevant trials. The primary endpoints were progression-free survival (PFS) and overall survival (OS). The results were analyzed utilizing Stata 12.0 statistical software. Subgroup analyses were implemented based on primary tumors, study designs, continents, type of ICIs, evaluation index of PET, and evaluated PET timing.

RESULTS

Fifteen studies incorporating 664 individuals were eligible. Compared with PET nonresponse group, PET response group displayed a significantly prolonged PFS (HR 0.27, 95% CI [0.16, 0.44]; P < 0.001) and OS (HR 0.56, 95% CI [0.48, 0.65]; P < 0.001). Analogical outcomes were obtained in subgroup analyses of PFS in non-small cell lung cancer, prospective, America, ipilimumab, nivolumab/pembrolizumab combined ipilimumab, PET Response Criteria in Solid Tumors (PERCIST), baseline PET and early PET timing arms without heterogeneity; so did OS in melanoma, retrospective, Europe, America, ipilimumab, nivolumab/pembrolizumab, PERCIST, baseline metabolic tissue volume, baseline standard uptake value, and baseline total lesion glycolysis, baseline PET timing, early PET timing and late PET timing arms.

CONCLUSION

Our study demonstrated that PET was a promising approach to early predict the prognosis of ICIs for malignancies.

Early Response Assessment to Targeted Therapy Using 3'-deoxy-3'[(18)F]-Fluorothymidine (18F-FLT) PET/CT in Lung Cancer

Although 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) is a sensitive nuclear medicine modality, specificity for characterizing lung cancer is limited. Tumor proliferation and early response to molecularly targeted therapy could be visualized using 3′-deoxy-3′[(18)F]-fluorothymidine (¹⁸F-FLT) PET/CT. The superiority of ¹⁸F-FLT PET/CT over ¹⁸F-FDG PET/CT in early therapeutic monitoring has been well described in patients after chemotherapy, radiotherapy, and/or chemo/radiotherapy. In thispilot study, we explorethe use of ¹⁸F-FLT PET/CT as an early response evaluation modality in patients with lung cancerand provide specific case studies of patients with small cell lung cancer and non-small cell lung cancer who received novel targeted therapies. Early response for c-MET inhibitor was observed in four weeks and for MDM2 inhibitor in nine days.