Because of the peculiar mechanism of action of immune checkpoint inhibitors (ICIs), evaluation of the radiologic response to them in solid tumors presents many challenges. We aimed to compare evaluation of the first response to nivolumab by means of CT-based criteria with respect to 18 F-FDG PET response criteria in non-small cell lung cancer (NSCLC) patients. Methods: Seventy-two patients with advanced NSCLC were recruited in a single-institution ancillary trial within the expanded-access program (NCT02475382) for nivolumab. Patients underwent CT and 18 F-FDG PET at baseline and after 4 cycles (the first evaluation). In cases of progressive disease, an additional evaluation was performed after 2 further cycles to confirm progression. We evaluated the treatment response on CT using RECIST 1.1 and the immune-related response criteria (irRC) and on 18 F-FDG PET using PERCIST and immunotherapy-modified PERCIST. The concordance between CT-and PET-based criteria and the capability of each method to predict overall survival were evaluated. Results: Forty-eight of 72 patients were evaluable for a first response assessment with both PET-and CT-based criteria. We observed low concordance between CT-and PET-based criteria (κ-value of 0.346 and 0.355 between PERCIST and imPERCIST and RECIST, respectively. κ-value of 0.128 and 0.198 between PERCIST and imPERCIST and irRC, respectively). Regarding overall survival, irRC could more reliably distinguish responders from nonresponders. However, thanks to the prognostic value of partial metabolic response assessed by both PERCIST and immunotherapy-modified PERCIST, PET-based response maintained prognostic significance in patients classified as having progressive disease on the basis of irRC. Conclusion: Even though the present study did not support the routine use of 18 F-FDG PET in the general population of NSCLC patients treated with ICIs, the findings suggest that metabolic response assessment has added prognostic value, potentially improving therapeutic decision making.

In the last decades, in addition to conventional imaging techniques and magnetic resonance imaging (MRI), 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) has been shown to be relevant in the detection and management of breast cancer recurrence in doubtful cases in selected groups of patients. While there are no conclusive data indicating that imaging tests, including FDG PET/CT, produce a survival benefit in asymptomatic patients, FDG PET/CT can be useful for identifying the site of relapse when traditional imaging methods are equivocal or conflicting and for identifying or confirming isolated loco-regional relapse or isolated metastatic lesions. The present narrative review deals with the potential role of FDG PET in these clinical settings by comparing its accuracy and impact with conventional imaging modalities such as CT, ultrasound, bone scan, 18F-sodium fluoride PET/CT (18F-NaF PET/CT) as well as MRI. Patient-focused perspectives in terms of patients’ satisfaction and acceptability are also discussed.

Purpose To assess the presence and pattern of incidental interstitial lung alterations suspicious of COVID-19 on fluorine-18-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT) ([18F]FDG PET/CT) in asymptomatic oncological patients during the period of active COVID-19 in a country with high prevalence of the virus. Methods This is a multi-center retrospective observational study involving 59 Italian centers. We retrospectively reviewed the prevalence of interstitial pneumonia detected during the COVID period (between March 16 and 27, 2020) and compared to a pre-COVID period (January–February 2020) and a control time (in 2019). The diagnosis of interstitial pneumonia was done considering lung alterations of CT of PET. Results Overall, [18F]FDG PET/CT was performed on 4008 patients in the COVID period, 19,267 in the pre-COVID period, and 5513 in the control period. The rate of interstitial pneumonia suspicious for COVID-19 was significantly higher during the COVID period (7.1%) compared with that found in the pre-COVID (5.35%) and control periods (5.15%) (p < 0.001). Instead, no significant difference among pre-COVID and control periods was present. The prevalence of interstitial pneumonia detected at PET/CT was directly associated with geographic virus diffusion, with the higher rate in Northern Italy. Among 284 interstitial pneumonia detected during COVID period, 169 (59%) were FDG-avid (average SUVmax of 4.1). Conclusions A significant increase of interstitial pneumonia incidentally detected with [18F]FDG PET/CT has been demonstrated during the COVID-19 pandemic. A majority of interstitial pneumonia were FDG-avid. Our results underlined the importance of paying attention to incidental CT findings of pneumonia detected at PET/CT, and these reports might help to recognize early COVID-19 cases guiding the subsequent management.

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