scholarly journals PC3 - 219 Evaluation of delayed FDG-PET in differentiating progressive disease from post-treatment radiation effect in brain tumors

2016 ◽  
Vol 43 (S4) ◽  
pp. S23-S23
Author(s):  
R.A. Harrison ◽  
A. Masood ◽  
O. Mawlawi ◽  
D. Schellingerhout ◽  
B.A. Chasen ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Fdg Pet ◽  
Progressive Disease ◽  
Radiation Effect ◽  
Post Treatment ◽  
Delayed Imaging ◽  
Time Points ◽  
Delayed Time ◽  
Time Point

Traditional and advanced magnetic resonance imaging techniques are often unable to differentiate progressive central nervous system neoplasm from post-treatment radiation effect (PTRE). 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) with delayed imaging has been shown to increase the specificity of PET imaging for cerebral neoplasm in small studies. We sought to further evaluate the potential diagnostic benefits of delayed imaging at 5 hours versus standard imaging at 1 hour to differentiate progressive disease (PD) from PTRE in patients with primary or metastatic brain tumors treated with radiation therapy.Ten patients with primary (n=4) and metastatic (n=6) brain tumors were identified, with diagnostic confirmation of PD or PTRE provided by pathology or>3 month clinical and radiographic follow-up. Maximum standard uptake values (SUV) were calculated for suspicious areas of abnormal contrast enhancement (lesion) and compared to contralateral normal appearing brain (background) at both early and delayed time points. Seven patients were classified as having PD and 3 as having PTRE based pathology or clinical/radiographic follow up. The average lesion to background ratio (L/B) at the early time point (1.16+0.50) was significantly different than L/B for the later time point (1.72+1.10), p=0.030. The mean L/B for PD was 2.17+1.01 at the later time point compared to 0.65+0.06 for PTRE (p=0.010). For the earlier time point, L/B for PD was 1.40+0.42, compared to the L/B for PTRE which was 0.61+0.10 (p=0.003).L/B ratios at early and delayed time points successfully differentiated between patients with PD and PTRE, with significantly greater L/B ratios seen at delayed time points. These initial results are promising and further investigation is underway to evaluate the contribution of delayed imaging in differentiating PD from PTRE.

scholarly journals Delayed FDG PET Provides Superior Glioblastoma Conspicuity Compared to Conventional Image Timing

2021 ◽  
Vol 12 ◽  
Author(s):  
Jason Michael Johnson ◽  
Melissa M. Chen ◽  
Eric M. Rohren ◽  
Sujit Prabhu ◽  
Beth Chasen ◽  
...  
Keyword(s):  
Fdg Pet ◽  
Conventional Imaging ◽  
Delayed Imaging ◽  
Time Points ◽  
Non Invasive ◽  
Imaging Time ◽  
Standardized Uptake Values ◽  
Pre Treatment ◽  
True Progression ◽  
Time Point

Background: Glioblastomas are malignant, often incurable brain tumors. Reliable discrimination between recurrent disease and treatment changes is a significant challenge. Prior work has suggested glioblastoma FDG PET conspicuity is improved at delayed time points vs. conventional imaging times. This study aimed to determine the ideal FDG imaging time point in a population of untreated glioblastomas in preparation for future trials involving the non-invasive assessment of true progression vs. pseudoprogression in glioblastoma.Methods: Sixteen pre-treatment adults with suspected glioblastoma received FDG PET at 1, 5, and 8 h post-FDG injection within the 3 days prior to surgery. Maximum standard uptake values were measured at each timepoint for the central enhancing component of the lesion and the contralateral normal-appearing brain.Results: Sixteen patients (nine male) had pathology confirmed IDH-wildtype, glioblastoma. Our results revealed statistically significant improvements in the maximum standardized uptake values and subjective conspicuity of glioblastomas at later time points compared to the conventional (1 h time point). The tumor to background ratio at 1, 5, and 8 h was 1.4 ± 0.4, 1.8 ± 0.5, and 2.1 ± 0.6, respectively. This was statistically significant for the 5 h time point over the 1 h time point (p > 0.001), the 8 h time point over the 1 h time point (p = 0.026), and the 8 h time point over the 5 h time point (p = 0.036).Conclusions: Our findings demonstrate that delayed imaging time point provides superior conspicuity of glioblastoma compared to conventional imaging. Further research based on these results may translate into improvements in the determination of true progression from pseudoprogression.

Immunophenotypical Sequential MRD Assessment in AML for Prediction of Relapse and Definition of Putative Future Intervention Time Points.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3012-3012
Author(s):  
Nicole Feller ◽  
Peter C. Huijgens ◽  
Angele Kelder ◽  
Guus Westra ◽  
Gert Ossenkoppele ◽  
...  
Keyword(s):  
Residual Disease ◽  
Treatment Strategies ◽  
Sampling Period ◽  
High Dose Chemotherapy ◽  
Post Treatment ◽  
High Dose ◽  
Time Points ◽  
Definition Of ◽  
Time Point

Abstract Immunophenotypical assessment of minimal residual disease (MRD) has been shown by us (Feller et al, Leukemia18:1380, 2004) and others (San Miguel et al., Blood98: 1746, 2001, Venditti et al., Blood96: 3948, 2000) to be predictive for clinical outcome in AML both in patients treated with standard chemotherapy (SD) and high dose chemotherapy followed by autologous (AutoTQ) or allogeneic (AlloTQ) transplantation. Directly after consolidation therapy using a cut-off of 0.11% in the high MRD group the risk of relapse was 7.2 fold than in the low MRD group (Feller et al., 2004). Using that cut-off level, in the present study another important issue, i.e. sequential MRD assessments after end of treatment were done to i) prove consistancy of low MRD% in patients that remain in CR, ii) prove the ability to predict relapse using increase of MRD% and iii) assess the minimally required inter-sampling period to make MRD assessment clinically useful. To enable such 124 samples of 33 patients (<60 years) were included: 16 after SD, 8 after AutoTQ and 9 after AlloTQ. All time points refer to post-treatment periods, time point zero reflecting end of therapy. Of 16 patients studied after SD, 15 had MRD <0.11%. Of these, 12 are in CR with a median follow-up of 30.5 (range 9–46) months. In these 12 patients MRD remained consistently <0.11 %, (mean of 3 sequential MRD assessments per patient). Of these 15 patients 3 relapsed after 9, 9 and 26 months, but in these cases the last time point of MRD assessment (still <0.11%) unfortunately was at least 6 months before relapse. One patient who started with MRD>0.11 relapsed within 2 months after that MRD assessment. Of 8 patients studied after AutoTQ, 6 had MRD <0.11%. Of these, 4 are in CR with a follow-up of 6, 15, 40 and 72 months. Again, MRD remained consistently <0.11% (mean of 3 assessments per patient). Of these 6 patients 2 relapsed after 13 and 43 months, with relapse predictable using 3 months assessment intervals. Two patients had >0.11% MRD and relapsed after 5 and 11 months and within 3 months after the last MRD assessment, with no previous sign of forthcoming increase. Of 9 patients studied after AlloTQ, 2 had MRD <0.11%; thet are still in remission after 47 and 53 months. Again, MRD remained consistently <0.11 % (6 and 7 MRD assessments in these 2 patients). Of these 9 patients 2 relapsed too fast to have the opportunity to assess MRD. In addition, 5/9 had MRD >0.11%, of whom 2/5 relapsed after 6 and 7 months which was 4 and 2 months resp., after their last MRD assessment, with no previous sign of forthcoming increase. A remarkable phenomenon was observed in the other 3/5 patients: a large drop in MRD% down to detection level (0.01%) occurred 3–10 months after end of therapy. 2 of these 3 patients are still in CR (at 11 and 33 months), 1/3 relapsed after 26 months, 5 months after last MRD assessment with no previous sign of increase. The unique decrease of MRD% may be speculated to result from graft versus leukemia effects. These results show: 1) consistently low MRD% in sequential MRD assessments during persisting CR; 2) increases of MRD% which consistently predict relapse; 3) a minimally required inter-sampling period of 3 months for patients with MRD <0.11% and probably <3 months for patients with MRD>0.11%; 4) a strong decrease of MRD in part of the allogeneically transplanted patients. Results show the feasibility of sequential post-treatment MRD assessment that ultimately will contribute to design of post-treatment strategies in AML.

scholarly journals The Role of Dual-Phase FDG PET/CT in the Diagnosis and Follow-Up of Brain Tumors

2020 ◽  
Vol 215 (4) ◽  
pp. 985-996 ◽  
Author(s):  
Can Özütemiz ◽  
Elizabeth C. Neil ◽  
Manoj Tanwar ◽  
Nathan T. Rubin ◽  
Kerem Ozturk ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Fdg Pet ◽  
Dual Phase ◽  
Pet Ct ◽  
Fdg Pet Ct

scholarly journals Tumour Relapse Prediction Using Multiparametric MR Data Recorded during Follow-Up of GBM Patients

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Adrian Ion-Margineanu ◽  
Sofie Van Cauter ◽  
Diana M. Sima ◽  
Frederik Maes ◽  
Stefaan W. Van Gool ◽  
...  
Keyword(s):  
Adjuvant Therapy ◽  
Random Forests ◽  
Feature Vector ◽  
Tumour Progression ◽  
Ensemble Classifiers ◽  
Radiological Criteria ◽  
Time Points ◽  
Relapse Prediction ◽  
Time Point

Purpose. We have focused on finding a classifier that best discriminates between tumour progression and regression based on multiparametric MR data retrieved from follow-up GBM patients.Materials and Methods. Multiparametric MR data consisting of conventional and advanced MRI (perfusion, diffusion, and spectroscopy) were acquired from 29 GBM patients treated with adjuvant therapy after surgery over a period of several months. A 27-feature vector was built for each time point, although not all features could be obtained at all time points due to missing data or quality issues. We tested classifiers using LOPO method on complete and imputed data. We measure the performance by computing BER for each time point and wBER for all time points.Results. If we train random forests, LogitBoost, or RobustBoost on data with complete features, we can differentiate between tumour progression and regression with 100% accuracy, one time point (i.e., about 1 month) earlier than the date when doctors had put a label (progressive or responsive) according to established radiological criteria. We obtain the same result when training the same classifiers solely on complete perfusion data.Conclusions. Our findings suggest that ensemble classifiers (i.e., random forests and boost classifiers) show promising results in predicting tumour progression earlier than established radiological criteria and should be further investigated.

Prognostic Value of Minimal Residual Disease (MRD) Detection in Adult Acute Lymphoblastic Leukemia (ALL) – HYPER-CVAD Protocol

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4870-4870
Author(s):  
Nikolaos Tsagarakis ◽  
Nektaria Kentrou ◽  
Mirsini Pergaminou ◽  
Theodore Marinakis ◽  
Stefanos I Papadhimitriou ◽  
...  
Keyword(s):  
Maintenance Therapy ◽  
Induction Therapy ◽  
Treatment Time ◽  
Lymphoblastic Leukemia ◽  
Treatment Protocol ◽  
Disease Free Survival ◽  
Consolidation Therapy ◽  
Time Points ◽  
Time Point

Abstract Objective: HYPER-CVAD is an intensive treatment protocol of short duration, for ALL and other lymphoid neoplasms. It is consisted of 8 alternating cycles (parts A and B): in part A (cycles 1, 3, 5, 7) fractionated doses of cyclophosphamide, vincristine, doxorubicin and dexamethazone are administrated, while in part B (cycles 2, 4, 6, 8) high doses of methotrexate and aracytin. The two first cycles compose the induction therapy, while the next 6 cycles constitute the consolidation therapy, followed by two years of maintenance therapy. Protection of CNS is achieved with intradorsal injections, whereas in Ph+ ALL patients, imatinib is also administered. The aim of this study was the clinical evaluation of MRD detection in adult patients with ALL, during chemotherapy with HYPER-CVAD. Patients/Methods: During the period 1999–2008, 30 patients were hospitalized in our hospital for ALL and were treated with HYPER-CVAD therapeutic protocol. Among them, 14/30 (46,7%) were males and 16/30 (53,3%) females (median age 43,5 years, range 16–70). Median follow-up time was 12,8 months (range 0,5–100). ALL of T-origin had 8/30 patients and of B-origin, 22/30 (1 B1-EGIL/pro-B, 17 B2-EGIL/B-common, 4 B3-EGIL/pre-B). Caryotypic analysis and FISH was done in all patients (7/30 bcr/abl+). According to classical prognostic markers of ALL: 21/30 were classified as high, 4/30 as medium and 5/30 low risk, respectively. MRD presence was detected in bone marrow samples, with flow cytometric panels, at three particular treatment time-points: completion of induction therapy (T1), completion of consolidation therapy (T2) and at the end of maintenance therapy (T3). Overall survival (OS) and disease free survival (DFS) were investigated, especially in relation to the influence of MRD presence in (OS) and (DFS), respectively. For statistical analysis, Kaplan-Meier was used. Results: At treatment time-point (T1), MRD was detected in 10/28 (35,7%) patients, at time-point (T2) in 7/23 (30,4%) and at treatment-point (T3) in 9/17 (52,94%). The influence of MRD detection in (OS) was statistically significant (p<0,05) at (T2) and (T3), while in (DFS) the detection of MRD presence in any of the standardized treatment time-points resulted in decreased DFS (T1/p<0,05, T2 and T3/p<0,001). Conclusions: Our results suggest that MRD detection during therapy of adult ALL is a negative prognostic indicator for (OS) and (DFS), the independency of which has to be confirmed after prolonged follow-up time and increased number of cases.

Comparison of PSA, FDG-PET, and Prostate Cancer Working Group 2 (PCWG2) criteria to interpret apparent progression on first post-treatment bone scan.

2012 ◽  
Vol 30 (5_suppl) ◽  
pp. 20-20
Author(s):  
Karen A. Autio ◽  
Josef J. Fox ◽  
Eric Conrad Haupt ◽  
Heiko Schöder ◽  
Howard I. Scher ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Fdg Pet ◽  
Bone Scan ◽  
Bone Lesion ◽  
Early Response ◽  
Post Treatment ◽  
Phase Iii ◽  
Flare Response ◽  
Group 2

20 Background: The risk of prematurely discontinuing effective therapy in patients with metastatic castrate resistant prostate cancer (mCRPC) because of apparent initial progression on bone scan has repercussions for drug development and clinical practice. We evaluated three methods to distinguish disease progression (POD) from non-progressive bone disease or flare response. Methods: The dataset was comprised of men with mCRPC enrolled in contemporary clinical trials using AR-directed or targeted therapy. To be included, a worsened bone scan (increased size, intensity, or number of lesions) at the time of initial follow-up at 8-12 wks (FU1), a concurrently performed FDG-PET and PSA, and a second follow-up bone scan (FU2) > 6 wks after FU1 were required. Pts were evaluated by three methods: 1) PSA-guided approach: POD was defined as a PSA increase >25% from baseline at FU1; for non-progressors, a special category was created for flare response defined as a PSA decline >50% and a FU2 bone scan documenting stability/improvement; 2) FDG-PET approach: POD was defined as a new bone lesion or increase in SUV >10% at FU1; 3) Bone scan only approach: POD was defined by PCWG2 requiring 2 new bone scan lesions at FU1 and 2 additional lesions at FU2. Results: 66 pts registered to trials conducted between 2007-2011 were examined; 38/66 (57.6%) pts had a worsened bone scan at FU1, 23 of whom had a FU2 bone scan and were considered evaluable for this analysis. Conclusions: Over half of mCRPC pts have a worsening bone scan during the first three months of therapy. PCWG2 controls for flare without use of PSA, confirms radiographic POD, and maintains pts on study longer than use of early post-treatment PSA changes. FDG-PET at first assessment appears to identify an identical percentage of progressors as PCWG2 did at the second assessment. PCWG2 is undergoing prospective validation in phase III trials; the use of FDG PET as an early response biomarker is currently under investigation. [Table: see text]

scholarly journals Potential role of post‑treatment follow‑up FDG‑PET CT to detect mandibular osteoradionecrosis: A case report

2017 ◽  
Author(s):  
Masaya Akashi ◽  
Satoshi Wanifuchi ◽  
Junya Kusumoto ◽  
Megumi Kishimoto ◽  
Yasumasa Kakei ◽  
...  
Keyword(s):  
Case Report ◽  
Fdg Pet ◽  
Potential Role ◽  
Post Treatment ◽  
Pet Ct ◽  
Fdg Pet Ct

scholarly journals The Pulmonary Sequalae in Discharged Patients With COVID-19:A Short-term Observational Study

2020 ◽  
Author(s):  
Dehan Liu ◽  
Wanshu Zhang ◽  
Feng Pan ◽  
Lin Li ◽  
Lian Yang ◽  
...  
Keyword(s):  
Chest Ct ◽  
Ct Scans ◽  
Optimal Time ◽  
Imaging Features ◽  
Short Term ◽  
Lung Lesions ◽  
Cumulative Percentage ◽  
Time Points ◽  
Time Point

Abstract Background: A cluster of patients with coronavirus disease 2019 (COVID-19) pneumonia were discharged from hospitals in Wuhan, China. We aimed to determine the cumulative percentage of complete radiological resolution at each time point, to explore the relevant affecting factors, and to describe the chest CT findings at different time points after hospital discharge.Methods: Patients with COVID-19 pneumonia confirmed by RT-PCR who were discharged consecutively from the hospital between 5 February 2020 and 10 March 2020 and who underwent serial chest CT scans on schedule were enrolled. The radiological characteristics of all patients were collected and analysed. The total CT score was the sum of non-GGO involvement determined at discharge. Afterwards, all patients underwent chest CT scans during the 1st, 2nd, and 3rd weeks after discharge. Imaging features and distributions were analysed across different time points.Results: A total of 149 patients who completed all CT scans were evaluated; there were 67 (45.0%) men and 82 (55.0%) women, with a median age of 43 years old (IQR 36-56). The cumulative percentage of complete radiological resolution was 8.1% (12 patients), 41.6% (62), 50.3% (75), and 53% (79) at discharge and during the 1st, 2nd, and 3rd weeks after discharge, respectively. Patients ≤44 years old showed a significantly higher cumulative percentage of complete radiological resolution than patients >44 years old at the 3-week follow-up. The predominant patterns of abnormalities observed at discharge were ground-glass opacity (GGO) (65 [43.6%]), fibrous stripe (45 [30.2%]), and thickening of the adjacent pleura (16 [10.7%]). Lung lesions showed obvious resolution from 2 to 3 weeks after discharge, especially in terms of GGO and fibrous stripe. “Tinted” sign and bronchovascular bundle distortion as two special features were discovered during the evolution.Conclusion: Lung lesions in COVID-19 pneumonia patients can be absorbed completely during short-term follow-up with no sequelae. Three weeks after discharge might be the optimal time point for early radiological estimation.

Minimal Residual Disease (MRD) in Childhood Acute Lymphoblastic Leukemia (ALL). Correlation with Prognostic Factors and Outcome

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4848-4848
Author(s):  
Anna Paisiou ◽  
Georgios Paterakis ◽  
Nikolaos Tsagarakis ◽  
Nektaria Kentrou ◽  
Vassilios Papadakis ◽  
...  
Keyword(s):  
High Risk ◽  
Treatment Time ◽  
Residual Disease ◽  
Childhood All ◽  
Time Points ◽  
Standardized Treatment ◽  
Group A ◽  
Group B ◽  
Time Point

Abstract Aim: The aim of this study was the prospective evaluation of MRD during childhood ALL therapy and its correlation with specific prognostic criteria of ALL-BFM 95 protocol and with patient outcome. Patients/Methods: 127 children (49 girls) with ALL were studied during the period 1999–2008. The median age at diagnosis was 9,32 years (range, 0,6–16,48). All patients were diagnosed in the same center and treated uniformly with the ALL-BFM 95 protocol, modified in two therapeutic branches, medium and high risk, as we have published previously. We used three or five colours’ flow cytometric panels for MRD quantification at sequential standardized treatment time-points: at day 15 of induction (T1), at day 33 (T2) of induction, before consolidation (T3), before re-induction (T4), before maintenance (T5), at maintenance completion (T6). Additionally for the high risk patients, 6 more determinations before each consolidation treatment cycle were performed. The median follow-up time was 48,4 months (range, 1,7–110,3). For statistical analysis, descriptive statistics and Kaplan-Meier were used. Results: Immunophenotypical analysis resulted in 119 patients with ALL of B-origin and 8 of T-origin. Median WBC at diagnosis was 10×109/lt, while extra-BM infiltration was found in 9 children. According to ALL-BFM 95 protocol’s criteria: 40 patients were fulfilling the criteria of the standard risk (SR), 61 of medium (MR) and 26 of high risk (HR), respectively, and therapeutically were divided into two groups: A (101 patients, SR+MR) and B (26 patients, HR). MRD was detected in: 59/123 patients at treatment time-point (T1) (39/59 from group A, of which 26/39 with high MRD levels, and 20/59 from group B, all with high MRD levels). In time-point (T2), disease was detected in 19/124: 5/19 from group A (3/5 high MRD levels), 14/19 from group B (11/14 high MRD levels). At treatment-point (T3), 3/127 had detectable disease (all from group B). None of the patients of group A had minimal residual disease at the following time-points, while only 2 patients of group B had persistent presence of MRD. In total, 14/127 children relapsed (4/SR, 2/MR, 8/HR), with significant levels of MRD in 7 (6/7 HR) and 4 (all HR) patients, at time-point (T1) and (T2), respectively. Among all, 114 children survived (CR1: 110, CR2: 4), while 13 children died (9/disease, 4/therapy-related toxicity). Conclusions: Our results suggest that MRD detection in continuous standardized treatment time-points of childhood ALL correlates with shorter disease free (DFS) and overall survival (OS), however in our cohort there was no sufficient evidence of MRD independency as prognostic factor (cox-regression analysis) compared to the classical prognostic criteria of the ALL-BFM 95. The enlargement of the group of patients and the expansion of the follow-up period will lead to more reliable conclusions.

Result of FDG PET-CT Imaging After Immunochemotherapy Induction Is a Powerful and Independent Prognostic Indicator of Outcome for Patients with Follicular Lymphoma: An Analysis From the PRIMA Study

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 855-855 ◽  
Author(s):  
Judith Trotman ◽  
Marion Fournier ◽  
Thierry Lamy ◽  
Jane A Estell ◽  
Anne Sonet ◽  
...  
Keyword(s):  
Follicular Lymphoma ◽  
Fdg Pet ◽  
Cox Model ◽  
Response Assessment ◽  
Post Treatment ◽  
Ct Scans ◽  
Induction Treatment ◽  
Pet Ct ◽  
Fdg Pet Ct

Abstract Abstract 855 Aim: Despite its often indolent clinical course, follicular lymphoma (FL) is a heterogeneous disease. Current criteria for early identification of patients with a poor prognosis are suboptimal - the FLIPI and F2 index are insufficient prognostic markers for individual patients and the limitations of post-treatment conventional response criteria have long been acknowledged. FL shows increased FDG uptake, but unlike DLBCL, minimal data exist about the role of PET-CT in response assessment. We have used the prospective conventional response assessment and 42 month patient follow-up in the PRIMA (Primary Rituximab and Maintenance, Salles et al., ASCO 2010, Abstr#8004) study as a platform for analysis of the utility of PET-CT in FL. Methods: The PRIMA database was interrogated and investigators surveyed to identify PET-CT scans performed during staging and induction response assessment. Single modality PET-only scans were not eligible for inclusion. Local PET interpretation (positive + or negative -) was used to explore associations with patient outcomes. The primary endpoint was PFS from PRIMA registration. Results: 277 PET-CT scans on 160 patients from 40 centres were identified. Baseline patient characteristics did not differ from the overall PRIMA patient population. Positive PET-CT scans were recorded in 119/120 (99%) at diagnosis, 11/33 (33%) interim restaging scans and 32/124 (26%) post induction treatment (R-CHOP or R-CVP). There was significant correlation between PET-CT result and conventional response assessment at the end of immunochemotherapy (p<0.0005). The incidence of post-treatment PET+ increased across the categories of lesser conventional responses, occurring in 8% (4/50) CR, 31% (12/39) CRu, 41% (11/37) PR, 67% (2/3) SD, and 80% (4/5) PD. While 73/91 (80%) of PET- patients were in CR/CRu, given the very high overall response rate on study, 16/33 (48%) of the PET+ population were also in CR/CRu. With a median follow-up of 42 months, a significantly inferior actuarial 3yr PFS was observed in post-treatment PET+ vs. PET- patients (Figure 1): 32% (95% CI 17–48%) vs. 74% (95% CI 63–82%) (log rank p<0.0001, HR 3.5, 95% CI 2.0–6.1), median PFS 19 months (13-35) vs. not reached, (52-NR). Using proportional hazard regression analysis, both conventional response (overall p=0.0002) and PET+ status (HR 2.8 p=0.0007) were significant predictors of inferior PFS. However, the predictive power of conventional response assessment was limited to non-responders: SD/PD vs. CR/CRu (HR 6.5, p<0.0001), and SD/PD vs. PR (HR 5.2, p=0.0009). Comparison of PR vs. CR/CRu was not different (HR 1.2, p=0.5). While PET+ status had a significant negative impact on PFS in both the CR/CRu (HR 2.6, p=0.015) and PR (HR 4.3 p=0.018) patient groups, there was no difference in outcome between CR/CRu vs. PR patients within the PET+ (HR 1.5 p=0.42) and PET- (HR 1.0 p=0.98) subgroups. When only patients randomised for the maintenance element of the PRIMA study were considered, post-treatment PET+ (15/59) remained predictive of 3yr PFS (27 vs. 69%, HR 3.1, p=0.005) in the observation arm, but post-treatment PET+ (9/47) was not significantly associated with an adverse outcome in patients receiving rituximab maintenance (3-year PFS 56 vs. 81%, HR 2.2, p= 0.18). In a multivariate Cox model including responding patients the following factors were negative predictors of PFS: post-treatment PET+ (HR 3.1 p<0.0014); R-CVP induction therapy (HR 2.8, p<0.014); and baseline β2M ≥3 (HR 2.6 p<0.0042), while conventional PR and FLIPI were not. Conclusion: This PRIMA sub-study demonstrates that post-treatment PET-CT is a powerful predictor of PFS that complements conventional response evaluation after first line immunochemotherapy for FL. Patients who are PET- can expect a prolonged PFS whether in conventional CR or PR, but for those remaining PET+, with a median 19 month PFS, the disease cannot be characterized as indolent. Future clinical trials should evaluate an FDG PET-CT response adapted approach focused on improving outcomes for this group. Disclosures: Seymour: Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Shpilberg:Roche: Consultancy, Honoraria.

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