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  Indian J Med Microbiol
 

Figure 6: Maximum intensity projection images of pre and post therapy scans (a and b) of a patient with diffuse large B cell lymphoma (DLBCL) showing the focus of persistent fluoro-deoxy-glucose (FDG) uptake in spleen suggestive of positive positron emission tomography/computed tomography (PET/CT) indicating poor prognosis. However maximum standardized uptake value (SUVmax) decreased from 24.0 to 3.1 with a decrease of 82% (higher than the threshold of 66%) suggesting good response to treatment. the patient achieved a complete response (CR) after standard six cycle chemotherapy and was disease free on follow-up of 2 years. This image highlights the role of quantitative analysis in interpreting interim FDG PET/CT studies. It is well known that positive interim FDG PET/CT is highly predictive of inadequate response to chemotherapy with a higher chance for relapse and non-achievement of CR. However, visual analysis is inadequate to predict prognosis if PET/CT is done after two cycles of chemotherapy in patients with DLBCL. Less than 66% reduction in SUVmax from staging to interim PET/CT after two cycles has been suggested as a better poor prognostic indicator than positive scan by visual analysis[9]

Figure 6: Maximum intensity projection images of pre and post therapy scans (a and b) of a patient with diffuse large B cell lymphoma (DLBCL) showing the focus of persistent fluoro-deoxy-glucose (FDG) uptake in spleen suggestive of positive positron emission tomography/computed tomography (PET/CT) indicating poor prognosis. However maximum standardized uptake value (SUV<sub>max</sub>) decreased from 24.0 to 3.1 with a decrease of 82% (higher than the threshold of 66%) suggesting good response to treatment. the patient achieved a complete response (CR) after standard six cycle chemotherapy and was disease free on follow-up of 2 years. This image highlights the role of quantitative analysis in interpreting interim FDG PET/CT studies. It is well known that positive interim FDG PET/CT is highly predictive of inadequate response to chemotherapy with a higher chance for relapse and non-achievement of CR. However, visual analysis is inadequate to predict prognosis if PET/CT is done after two cycles of chemotherapy in patients with DLBCL. Less than 66% reduction in SUV<sub>max</sub> from staging to interim PET/CT after two cycles has been suggested as a better poor prognostic indicator than positive scan by visual analysis<sup>[9]</sup>