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

Background: We evaluated how comprehensive assessment of coronary artery lesions and their hemodynamic relevance by means of hybrid positron emission tomography (PET) and computed tomography (CT) imaging would affect decision-making in coronary artery bypass surgery (CABG), compared with using invasive coronary angiography (ICA) alone.Methods: After undergoing ICA, 27 patients (21 men and 6 women; mean SD age, 66 � 10 years) planned for cardiac surgery were scheduled for myocardial perfusion stress/rest evaluation with [13N]ammonia PET and CT coronary angiography. Only ICA was available to the surgeon. Postoperatively, the performed CABG was compared with the hypothetical strategy based on hybrid PET/CT findings (regional coronary flow reserve [CFR], myocardial perfusion defects). Procedures included CABG (n = 18) alone, CABG combined with valve replacement (n = 6), and CABG combined with isolated valve replacement (n = 3). A total of 56 bypass grafts (28 venous and 28 arterial) and 66 distal anastomoses were placed.Results: CT evaluation showed 93% concordance (66/71) with ICA regarding significant stenoses, with sensitivity, specificity, positive predictive value, and negative predictive value of 93.1%, 98.7%, 94.4%, and 98.4%, respectively. In the PET scan, 16 patients had 1 ischemic region, and 12 patients had 1 scar region, including 5 patients who presented with mixed conditions (scar and ischemia). One patient had a completely normal myocardium. Compared with the performed surgery, PET/CT fusion evaluation showed that of the performed anastomoses, 48% had documented ischemia (with a CFR <2 in 86%), 38% were nonischemic (although a CFR value <2 was found in 78%), and 14% had scar tissue (fixed perfusion defect).Conclusions: Although <50% of bypasses were placed to areas with myocardial ischemia, the CFR was low in the majority of nonischemic regions, a finding that may have important prognostic relevance. PET/CT fusion imaging could potentially influence planning for CABG and provide incremental prognostic information.

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Imaging Assessment of Tumor Response in the Era of Immunotherapy

Diagnostics ◽

10.3390/diagnostics11061041 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1041

Author(s):

Jun Nakata ◽

Kayako Isohashi ◽

Yoshihiro Oka ◽

Hiroko Nakajima ◽

Soyoko Morimoto ◽

...

Keyword(s):

Positron Emission Tomography ◽

Solid Tumors ◽

False Positive ◽

Progressive Disease ◽

Tumor Response ◽

Metabolic Response ◽

Evaluation Criteria ◽

Emission Tomography ◽

Response Criteria ◽

Positron Emission

Assessment of tumor response during treatment is one of the most important purposes of imaging. Before the appearance of immunotherapy, response evaluation criteria in solid tumors (RECIST) and positron emission tomography response criteria in solid tumors (PERCIST) were, respectively, the established morphologic and metabolic response criteria, and cessation of treatment was recommended when progressive disease was detected according to these criteria. However, various types of immunotherapy have been developed over the past 20 years, which show novel false positive findings on images, as well as distinct response patterns from conventional therapies. Antitumor immune response itself causes 18F-fluorodeoxyglucose (FDG) uptake in tumor sites, known as “flare phenomenon”, so that positron emission tomography using FDG can no longer accurately identify remaining tumors. Furthermore, tumors often initially increase, followed by stability or decrease resulting from immunotherapy, which is called “pseudoprogression”, so that progressive disease cannot be confirmed by computed tomography or magnetic resonance imaging at a single time point. As a result, neither RECIST nor PERCIST can accurately predict the response to immunotherapy, and therefore several new response criteria fixed for immunotherapy have been proposed. However, these criteria are still controversial, and also require months for response confirmation. The establishment of optimal response criteria and the development of new imaging technologies other than FDG are therefore urgently needed. In this review, we summarize the false positive images and the revision of response criteria for each immunotherapy, in order to avoid discontinuation of a truly effective immunotherapy.

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