PET/CT and the Response to Immunotherapy in Lung Cancer

Abstract

Objective: In the recent years, the introduction of immune checkpoint inhibitors has significantly changed the outcome of patients affected by lung cancer and cutaneous melanoma. Although the clinical advantages, the selection of patients and the evaluation of response to immunotherapy remain unclear. The immune-related Response Evaluation Criteria in Solid Tumor (irRECIST) was proposed as an update of the RECIST criteria for the assessment of response to immunotherapy. However, morphological images cannot predict the early response to therapy that represents a challenge in clinical practice. 18F-FDG PET/CT before and after immunotherapy has an indeterminate role, demonstrating ambiguous results due to inflammatory effects secondary to the activation of immune system. The aim of the present review was to analyze the role of PET/CT as a guide for immunotherapy, by analyzing the current status and future perspectives. Methods: A literature search was made in order to select all papers that discussed about the role of PET/CT with FDG or other tracers in the evaluation or the prediction of response to immunotherapy in lung cancer patients. Results: Many papers are now available. Many clinical trials have demonstrated the efficacy of immunotherapy in lung cancer patients. FDG PET/CT can be used for the prediction of response to immunotherapy, while its utility for the evaluation of response is not still clearly reported. Moreover, the standardization of FDG PET/CT interpretation is missing and different criteria, such as information, have been investigated until now. Conclusions: The utility of FDG PET/CT for patients with lung cancer undergoing immunotherapies, is still preliminary and not well addresses. New agents for PET are promising, but large clinical trials are mandatory.

Modern radiopharmaceuticals for lung cancer imaging with positron emission tomography/computed tomography scan: A systematic review

“…From these, it is obvious that 18F-FAMT-PET can be another technique of LAT1 molecular imaging. 11 C-labeled Methionine is another amino-acid PET tracer which has been used in several human tumor imaging tests.…”

“…The practicability of 18 F-FDG-PET and 11 C-MET-PET for the assessment of therapeutic response after stereotactic radiotherapy (SRT) in lung cancer was examined. 18 F-FDG-PET and 11 C-MET-PET were conducted 1 week before and up to 8 months after SRT in nine patients. Standard uptake value (SUV) of 18 F-FDG-PET and 11 C-MET-PET after SRT altered consistently, and the addition of 11 C-MET-PET did not confer any new information.…”

“…Standard uptake value (SUV) of 18 F-FDG-PET and 11 C-MET-PET after SRT altered consistently, and the addition of 11 C-MET-PET did not confer any new information. 2 The usefulness of 11 C-MET-PET in the evaluation of prognosis and chemotherapy response is not enough examined in lung cancer patients. Moreover, PET tracers which are combined with tyrosine derivatives like 2-18F-fluoro-L-tyrosine ( 18 F-FET) and 3-123I-iodoα-methyl-L-tyrosine ( 123 I-IMT) have been analyzed.…”

“…123 I-IMT as well as 18 F-FET was found to be transported selectively by human LAT1 which is expressed in normal cells. It is still vague in human malignant tumors if 11 C-MET, 18 F-FET, and 123 I-IMT are connected strongly with the amino-acid transporters like LAT1. 2 The uptake of the 18 F-FAMT is closely connected with the expression of LAT1 in lung cancer patients.…”

“…For validation of the above, further investigation is needed. Huang 3 concluded that apart from 18 F-FLT, PET tracers may have significance as potential biomarkers of DNA synthesis like: 18F-(fluoroarabinofuranosyl) cytosine, 11 C-labeled nucleosides, such as 11 C-methionine, 11 C-flumazenil, and 11 C-4DST.…”