Dual time point imaging in locally advanced head and neck cancer to assess residual nodal disease after chemoradiotherapy.

BACKGROUND: FDG-PET/CT has a high negative predictive value to detect residual nodal disease in patients with locally advanced squamous cell head and neck cancer after completing concurrent chemoradiotherapy (CCRT). However, the positive predictive value remains suboptimal due to inflammation after radiotherapy, generating unnecessary further investigations and possibly even surgery. We report the results of a preplanned secondary end point of the ECLYPS study regarding the potential advantages of dual time point FDG-PET/CT imaging (DTPI) in this setting. Standardized dedicated head and neck FDG-PET/CT images were obtained 12 weeks after CCRT at 60 and 120 min after tracer administration. We performed a semiquantitative assessment of lymph nodes, and the retention index (RI) was explored to optimize diagnostic performance. The reference standard was histology, negative FDG-PET/CT at 1 year, or > 2 years of clinical follow-up. The time-dependent area under the receiver operator characteristics (AUROC) curves was calculated. RESULTS: In total, 102 subjects were eligible for analysis. SUV values increased in malignant nodes (median SUV1 = 2.6 vs. SUV2 = 2.7; P = 0.04) but not in benign nodes (median SUV1 = 1.8 vs. SUV2 = 1.7; P = 0.28). In benign nodes, RI was negative although highly variable (median RI = - 2.6; IQR 21.2), while in malignant nodes RI was positive (median RI = 12.3; IQR 37.2) and significantly higher (P = 0.018) compared to benign nodes. A combined threshold (SUV1 ≥ 2.2 + RI ≥ 3%) significantly reduced the amount of false-positive cases by 53% (P = 0.02) resulting in an increased specificity (90.8% vs. 80.5%) and PPV (52.9% vs. 37.0%), while sensitivity (60.0% vs. 66.7%) and NPV remained comparably high (92.9% vs. 93.3%). However, AUROC, as overall measure of benefit in diagnostic accuracy, did not significantly improve (P = 0.62). In HPV-related disease (n = 32), there was no significant difference between SUV1, SUV2, and RI in malignant and benign nodes, yet this subgroup was small. CONCLUSIONS: DTPI did not improve the overall diagnostic accuracy of FDG-PET/CT to detect residual disease 12 weeks after chemoradiation. Due to differences in tracer kinetics between malignant and benign nodes, DTPI improved the specificity, but at the expense of a loss in sensitivity, albeit minimal. Since false negatives at the 12 weeks PET/CT are mainly due to minimal residual disease, DTPI is not able to significantly improve sensitivity, but repeat scanning at a later time (e.g. after 12 months) could possibly solve this problem. Further study is required in HPV-associated disease.

Quantification of 18F-fluorodeoxyglucose uptake to detect residual nodal disease in locally advanced head and neck squamous cell carcinoma after chemoradiotherapy: results from the ECLYPS study.

BACKGROUND: The Hopkins criteria were introduced for nodal response evaluation after therapy in head and neck cancer, but its superiority over quantification is not yet confirmed. METHODS: SUVbody weight thresholds and lesion-to-background ratios were explored in a prospective multicenter study of standardized FDG-PET/CT 12 weeks after CRT in newly diagnosed locally advanced head and neck squamous cell carcinoma (LAHNSCC) patients (ECLYPS). Reference standard was histology, negative FDG-PET/CT at 12 months after treatment or ≥ 2 years of negative follow-up. Area under the receiver operator characteristics curves (AUROC) were estimated and obtained thresholds were validated in an independent cohort of HNSCC patients (n = 127). RESULTS: In ECLYPS, 124 patients were available for quantification. With a median follow-up of 20.4 months, 23 (18.5%) nodal neck recurrences were observed. A SUV70 threshold of 2.2 (AUROC = 0.89; sensitivity = 79.7%; specificity = 80.8%) was identified as optimal metric to identify nodal recurrence within 1 year after therapy. For lesion-to-background ratios, an SUV50/SUVliver threshold of 0.96 (AUROC = 0.89; sensitivity = 79.7%; specificity = 82.8%) had the best performance. Compared with Hopkins criteria (AUROC = 0.81), SUV70 and SUV50/SUVliver provided a borderline significant (p = 0.040 and p = 0.094, respectively) improvement. Validation of thresholds yielded similar AUROC values (SUV70 = 0.93, SUV50/SUVliver = 0.95), and were comparable to the Hopkins score (AUROC = 0.91; not statistically significant). CONCLUSION: FDG quantification detects nodal relapse in LAHNSCC patients. When using EARL standardized PET acquisitions and reconstruction, absolute SUV metrics (SUV70 threshold 2.2) prove robust, yet ratios (SUV50/SUVliver, threshold 0.96) may be more useful in routine clinical care. In this setting, the diagnostic value of quantification is comparable to the Hopkins criteria. TRIAL REGISTRATION: US National Library for Medicine, NCT01179360. Registered 11 August 2010, https://clinicaltrials.gov/ct2/show/NCT01179360.

Aggressive and indolent non-Hodgkin's lymphoma: response assessment by integrated international workshop criteria.

Until recently, response assessment in patients with lymphoma was primarily performed by computed tomography (CT). Based on CT, International Workshop Criteria (IWC) were developed and widely used. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is a more sensitive and specific imaging technique for the detection of residual disease in lymphoma, and Revised Integrated International Workshop Criteria (IWC + PET) were recently proposed by the members of the International Harmonization Project (IHP), which combine both imaging techniques. We determined whether these new IWC + PET-criteria, can more accurately predict outcome compared to IWC-criteria in aggressive and indolent non-Hodgkin's lymphoma (NHL), and therefore correlated IWC and IWC + PET response with time-to-next-treatment (TNT) in 69 patients with NHL. We demonstrated that IWC + PET-guidelines are highly recommended over IWC-guidelines for patients with potentially-curable and routinely FDG-avid lymphoma. In contrast, no additional value of IWC + PET was demonstrated in a small group of patients with incurable histological subtypes.

Hodgkin lymphoma: Response assessment by revised International Workshop Criteria.

Until recently, response assessment in patients with Hodgkin's lymphoma (HL) was primarily performed by computed tomography (CT). Based on CT, International Workshop Criteria (IWC) were developed and widely used. Fluorodeoxyglucose positron emission tomography (FDG-PET) has a higher sensitivity and specificity compared with that of CT, and Revised International Workshop Criteria (IWC + PET) were recently proposed, which combine both imaging techniques. We determined whether these integrated IWC + PET-criteria can more accurately predict outcome compared with IWC-criteria in 56 patients with HL. Of the original 56 patients, nine patients relapsed and 47 are still in remission after a median follow-up of 9 years. Based on IWC-criteria, 15 patients had a complete remission (CR) after chemotherapy, 20 had complete remission unconfirmed (CRu), 19 had partial remission (PR) and two had stable disease (SD). In comparison, by IWC + PET, 47 had CR, seven had PR and two had SD. For IWC, outcome was not significantly different in patients with CR/CRu compared to PR (P = 0.61), while for IWC + PET criteria, time-to-next-treatment was significantly shorter in patients with PR compared to CR (P = 0.01). Therefore, IWC + PET-guidelines provide a more accurate response classification compared with that of IWC-guidelines, and are the preferred method for response assessment in patients with Hodgkin's lymphoma.

Effect of corticosteroids on 18F-FDG uptake in tumor lesions after chemotherapy.

UNLABELLED: To be a reliable predictor of response, (18)F-FDG uptake should reflect changes in the amount of viable tumor cells. However, (18)F-FDG also accumulates in inflammatory cells. Shortly after treatment, the influx of inflammatory cells in the tumor can therefore interfere with early response evaluation. The aim of this study was to investigate whether this inflammation is suppressed by the administration of corticosteroids and, in turn, can improve the correlation of (18)F-FDG uptake with tumor cell kill. METHODS: Severe combined immunodeficiency mice were inoculated subcutaneously with Daudi cells. When the tumor measured 15 mm, mice were divided in 2 groups treated with 1 single dose of cyclophosphamide, 125 mg/kg (group A) or cyclophosphamide followed by hydrocortisone (0.2 mg/d) for 5 d (group B). The change in (18)F-FDG uptake was evaluated with small-animal PET (5 mice/group) on D+6, D+9, D+13, and D+16 (days after treatment). At each time point, 4 mice per group were sacrificed for quantification of the different tumor cell fractions by flow cytometry and histopathology. Changes in (18)F-FDG uptake were correlated with inflammation and viable tumor cells. RESULTS: Cyclophosphamide administration resulted in a steady reduction in viable cell fraction until D+9 (reduction from baseline, -64%). The viable cell fraction increased again on D+13. A transient influx of inflammatory cells was seen from D+6 to D+13 (peak on D+9, 24% of total cell fraction). After hydrocortisone administration, a similar reduction in the viable cell fraction was seen. The inflammatory response was less pronounced but developed with earlier kinetics (peak on D+6 [15% of total cell fraction], almost resolved on D+9) and consisted primarily of granulocytes instead of mononuclear cells in the absence of corticosteroids. In both groups, a significant reduction in (18)F-FDG uptake was seen until D+6. On D+9, a transient increase in (18)F-FDG uptake was seen in group A, whereas a further decrease was observed in group B. CONCLUSION: After corticosteroid administration, the contribution of inflammatory cells to the (18)F-FDG uptake was less important than that in mice treated with chemotherapy alone. The earlier, but weaker, inflammatory response after corticosteroid administration consists primarily of granulocytes instead of mononuclear cells.

Use of positron emission tomography for response assessment of lymphoma: consensus of the Imaging Subcommittee of International Harmonization Project in Lymphoma.

PURPOSE: To develop guidelines for performing and interpreting positron emission tomography (PET) imaging for treatment assessment in patients with lymphoma both in clinical practice and in clinical trials. METHODS: An International Harmonization Project (IHP) was convened to discuss standardization of clinical trial parameters in lymphoma. An imaging subcommittee developed consensus recommendations based on published PET literature and the collective expertise of its members in the use of PET in lymphoma. Only recommendations subsequently endorsed by all IHP subcommittees were adopted. RECOMMENDATIONS: PET after completion of therapy should be performed at least 3 weeks, and preferably at 6 to 8 weeks, after chemotherapy or chemoimmunotherapy, and 8 to 12 weeks after radiation or chemoradiotherapy. Visual assessment alone is adequate for interpreting PET findings as positive or negative when assessing response after completion of therapy. Mediastinal blood pool activity is recommended as the reference background activity to define PET positivity for a residual mass > or = 2 cm in greatest transverse diameter, regardless of its location. A smaller residual mass or a normal sized lymph node (ie, < or = 1 x 1 cm in diameter) should be considered positive if its activity is above that of the surrounding background. Specific criteria for defining PET positivity in the liver, spleen, lung, and bone marrow are also proposed. Use of attenuation-corrected PET is strongly encouraged. Use of PET for treatment monitoring during a course of therapy should only be done in a clinical trial or as part of a prospective registry.

18FDG PET in oncology: the best and the worst (Review).

The clinical added-value of 18F-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG PET) in the management of oncology patients is increasingly documented. In the present review, we discuss both the benefits and the limitations of 18FDG PET in different cancers. Considering the literature data and our own experience, we also indicate the best clinical approach to optimize the use of metabolic imaging in oncology.

Positron emission tomography with [(18)F]FDG for therapy response monitoring in lymphoma patients.

Lymphomas are a heterogeneous group of diseases with differing histopathology, clinical behaviour, response to therapy and outcome. Lymphomas are highly sensitive to chemotherapy and radiotherapy, and the recent developments in treatment have considerably improved clinical outcome. However, there is increasing recognition that this has been at the cost of long-term treatment-related effects in a relatively young patient population. Thus, one of the most challenging aspects in the imaging of lymphoma patients is tailoring the intensity of the treatment to the individual patient. This paper reviews recently published data concerning the use of fluorine-18 fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET) for therapy monitoring in lymphoma patients and highlights the shortcomings and future directions. A temporary strategy for the implementation of [(18)F]FDG-PET in the management of lymphoma patients is proposed.

Prognostic value of pretransplantation positron emission tomography using fluorine 18-fluorodeoxyglucose in patients with aggressive lymphoma treated with high-dose chemotherapy and stem cell transplantation.

The study assessed the prognostic value of fluorine 18-fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) after salvage chemotherapy before high-dose chemotherapy with stem cell transplantation (HDT/SCT) in patients with induction failure or relapsing chemosensitive lymphoma. Retrospective analysis of the clinical and conventional imaging data of 60 patients scheduled for HDT/SCT was performed in parallel with the analysis of the [18F]FDG-PET results. To determine the ability of [18F]FDG-PET to predict clinical outcome, PET images were reread without knowledge of conventional imaging and clinical history. Presence or absence of abnormal [18F]FDG uptake was related to progression-free survival (PFS) and overall survival (OS) using Kaplan-Meier survival analysis. Thirty patients showed a negative [18F]FDG-PET scan before HDT/SCT; 25 of those remained in complete remission, with a median follow-up of 1510 days. Two patients died due to a treatment-related mortality but without evidence of recurrent disease at that time (228-462 days). Only 3 patients had a relapse (median PFS, 1083 days) after a negative [18F]FDG-PET scan. Persistent abnormal [18F]FDG uptake was seen in 30 patients and 26 progressed (median PFS, 402 days); of these 26, 16 died from progressive disease (median OS, 408 days). Four patients are still in complete remission after a positive scan. Comparison between groups indicated a statistically significant association between [18F]FDG-PET findings and PFS (P <.000001) and OS (P <.00002). [18F]FDG-PET has an important prognostic role in the pretransplantation evaluation of patients with lymphoma and enlarges the concept of chemosensitivity used to select patients for HDT/SCT.

[(18)F]FDG PET monitoring of tumour response to chemotherapy: does [(18)F]FDG uptake correlate with the viable tumour cell fraction?

Because metabolic changes induced by chemotherapy precede the morphological changes, fluorine-18 fluorodeoxyglucose positron emission tomography ([(18)F]FDG PET) is thought to predict response to therapy earlier and more accurately than other modalities. To be a reliable predictor of response, changes in tumour [(18)F]FDG uptake should reflect changes in viable cell fraction, but little is known about the contribution of apoptotic and necrotic cancer cells and inflammatory tissue to the [(18)F]FDG signal. In a tumour mouse model we investigated the relation between chemotherapy-induced changes in various tumoral components and tumour uptake and size. SCID mice were subcutaneously inoculated in the right thigh with 5 x 10(6) Daudi cells. When the tumour measured 15-20 mm, Endoxan was given intravenously. At different time points [1-15 days (d1-d15) after the injection of Endoxan], ex vivo autoradiography and histopathology were performed in two mice and [(18)F]FDG uptake in the tumour and tumour size were correlated with the different cell fractions measured with flow cytometry in five mice. At d1/d3, similar reductions in [(18)F]FDG uptake and viable tumoral cell fraction were observed and these reductions preceded changes in tumour size. By d8/d10, [(18)F]FDG uptake had stabilised despite a further reduction in viable tumoral cell fraction. At these time points a major inflammatory response was observed. At d15, an increase in viable tumour cells was again observed and this was accurately predicted by an increase in [(18)F]FDG uptake, while the tumour volume remained unchanged. In contrast with variations in tumour volume, [(18)F]FDG is a good marker for chemotherapy response monitoring. However, optimal timing seems crucial since a transient increase in stromal reaction may result in overestimation of the fraction of viable cells.