FDG PET in response evaluation of bulky masses in paediatric Hodgkin's lymphoma (HL) patients enrolled in the Italian AIEOP-LH2004 trial

Prospective Evaluation of Different Methods for Volumetric Analysis on [18F]FDG PET/CT in Pediatric Hodgkin Lymphoma

Rationale: Therapy response evaluation by 18F-fluorodeoxyglucose PET/CT (FDG PET) has become a powerful tool for the discrimination of responders from non-responders in pediatric Hodgkin lymphoma (HL). Recently, volumetric analyses have been regarded as a valuable tool for disease prognostication and biological characterization in cancer. Given the multitude of methods available for volumetric analysis in HL, the AIEOP Hodgkin Lymphoma Study Group has designed a prospective analysis of the Italian cohort enrolled in the EuroNet-PHL-C2 trial. Methods: Primarily, the study aimed to compare the different segmentation techniques used for volumetric assessment in HL patients at baseline (PET1) and during therapy: early (PET2) and late assessment (PET3). Overall, 50 patients and 150 scans were investigated for the current analysis. A dedicated software was used to semi-automatically delineate contours of the lesions by using different threshold methods. More specifically, four methods were applied: (1) fixed 41% threshold of the maximum standardized uptake value (SUVmax) within the respective lymphoma site (V41%), (2) fixed absolute SUV threshold of 2.5 (V2.5); (3) SUVmax(lesion)/SUVmean liver >1.5 (Vliver); (4) adaptive method (AM). All parameters obtained from the different methods were analyzed with respect to response. Results: Among the different methods investigated, the strongest correlation was observed between AM and Vliver (rho > 0.9; p < 0.001 for SUVmean, MTV and TLG at all scan timing), along with V2.5 and AM or Vliver (rho 0.98, p < 0.001 for TLG at baseline; rho > 0.9; p < 0.001 for SUVmean, MTV and TLG at PET2 and PET3, respectively). To determine the best segmentation method, we applied logistic regression and correlated different results with Deauville scores at late evaluation. Logistic regression demonstrated that MTV (metabolic tumor volume) and TLG (total lesion glycolysis) computation according to V2.5 and Vliver significantly correlated to response to treatment (p = 0.01 and 0.04 for MTV and 0.03 and 0.04 for TLG, respectively). SUVmean also resulted in significant correlation as absolute value or variation. Conclusions: The best correlation for volumetric analysis was documented for AM and Vliver, followed by V2.5. The volumetric analyses obtained from V2.5 and Vliver significantly correlated to response to therapy, proving to be preferred thresholds in our pediatric HL cohort.

Can the BMI-based dose regimen be used to reduce injection activity and to obtain a constant image quality in oncological patients by 18F-FDG total-body PET/CT imaging?

PURPOSE

PET image quality is influenced by the patient size according to the current guideline. The study aimed to propose an optimized dose regimen to yield a constant image quality independent of patient habitus to meet the clinical needs.

METHODS

A first patient cohort of 78 consecutive oncological patients (59.7 ± 13.7 years) who underwent a total-body PET/CT scan were retrospectively enrolled to develop the regimen. The patients were randomly distributed in four body mass index (BMI) groups according to the World Health Organization (WHO) criteria. The liver SNR (signal-to-noise ratio, SNR_L) was obtained by manually drawing regions of interest (ROIs) and normalized (SNR_norm) by the product of injected activity and acquisition time. Fits of SNR_norm against different patient-dependent parameters were performed to determine the best correlating parameter and fit method. A qualitative assessment on image quality was performed using a 5-point Likert scale to determine the acceptable threshold of SNR_L. Thus, an optimized regimen was proposed and validated by a second patient cohort consisted of prospectively enrolled 38 oncological patients.

RESULTS

The linear fit showed SNR_norm had the strongest correlation (R² = 0.69) with the BMI than other patient-dependent parameters and fit method. The qualitative assessment indicated a SNR_L value of 14.0 as an acceptable threshold to achieve sufficient image quality. The optimized dose regimen was determined as a quadratic relation with BMI: injected activity (MBq) = 39.2 (MBq)/(- 0.03*BMI + 1.49)². In the validation study, the SNR_L no longer decreased with the increase of BMI. There was no significant difference of the image quality regarding the value of SNR_L between different BMI groups (p > 0.05). In addition, the injected activity was reduced by 75.6 ± 2.9%, 72.1 ± 4.0%, 67.1 ± 4.4%, and 64.8 ± 3.5% compared with the first cohort for the four BMI groups, respectively.

CONCLUSION

The study proposed a quadratic relation between the ¹⁸F-FDG injected activity and the patient's BMI for total-body ¹⁸F-FDG PET imaging. In this regimen, the image quality can maintain in a constant level independent of patient habitus and meet the clinical requirement with a reduced injected activity.

PET/CT-Based Response Evaluation in Cancer-a Systematic Review of Design Issues

Positron emission tomography/x-ray computed tomography (PET/CT) has long been discussed as a promising modality for response evaluation in cancer. When designing respective clinical trials, several design issues have to be addressed, especially the number/timing of PET/CT scans, the approach for quantifying metabolic activity, and the final translation of measurements into a rule. It is unclear how well these issues have been tackled in quest of an optimised use of PET/CT in response evaluation. Medline via Ovid and Science Citation Index via Web of Science were systematically searched for articles from 2015 on cancer patients scanned with PET/CT before and during/after treatment. Reports were categorised as being either developmental or evaluative, i.e. focusing on either the establishment or the evaluation of a rule discriminating responders from non-responders. Of 124 included papers, 112 (90 %) were accuracy and/or prognostic studies; the remainder were response-curve studies. No randomised controlled trials were found. Most studies were prospective (62 %) and from single centres (85 %); median number of patients was 38.5 (range 5-354). Most (69 %) of the studies employed only one post-baseline scan. Quantification was mainly based on SUVmax (91 %), while change over time was most frequently used to combine measurements into a rule (79 %). Half of the reports were categorised as developmental, the other half evaluative. Most development studies assessed only one element (35/62, 56 %), most frequently the choice of cut-off points (25/62, 40 %). In summary, the majority of studies did not address the essential open issues in establishing PET/CT for response evaluation. Reasonably sized multicentre studies are needed to systematically compare the many different options when using PET/CT for response evaluation.

Comparison of Hodgkin's Lymphoma in Children and Adolescents. A Twenty Year Experience with MH'96 and LH2004 AIEOP (Italian Association of Pediatric Hematology and Oncology) Protocols

Adolescents and young adults (AYAs) represent a distinct group of patients. The objectives of this study were: To compare adolescent prognosis to that of younger children; to compare the results achieved with the two consecutive protocols in both age groups; to analyze clinical characteristics of children and adolescents. Between 1996 and 2017, 1759 patients aged <18 years were evaluable for the study. Five hundred and sixty patients were treated with the MH’96 protocol and 1199 with the LH2004 protocol. Four hundred and eighty-two were adolescents aged ≥15 years. Patients in both age groups showed very favorable prognoses. In particular, OS improved with the LH2004 protocol, especially in the adolescent group and in the low risk group, where radiation therapy was spared. Adolescent characteristics differed significantly from the children’s according to sex, histology, and the presence of symptoms. Remarkable is the decrease both in mixed cellularity in the children and in low stages in both age groups in the LH2004 protocol with respect to MH’96 protocol. Based on our experience, adopting pediatric protocols for AYA does not compromise patient outcomes.

Outcomes of Refractory and Relapsed Hodgkin Lymphoma With Autologous Stem-Cell Transplantation: A Single Institution Experience

PURPOSE

Hodgkin lymphoma is the most common cancer in children, adolescents, and young adults. Overall survival is approximately 80% to 90%. A subset of these patients has refractory disease or experience disease relapse. Conventional salvage therapies and autologous stem-cell transplantation is usually considered the standard of care for these patients. Our analysis reports outcomes in these patients.

PATIENTS AND METHODS

After institutional review board approval, a retrospective analysis of patients with Hodgkin lymphoma who were up to 18 years of age and who had refractory or relapsed disease at Shaukat Khanum Memorial Cancer Hospital and Research Centre from September 2009 to December 2013 was performed. Patients who underwent high-dose chemotherapy followed by stem-cell rescue were included in this analysis.

RESULTS

A total of 567 patients with Hodgkin lymphoma registered at the hospital. Sixty of the patients (10.6%) had either primary progressive or refractory disease or relapse after finishing with first-line chemotherapy. High-dose chemotherapy followed by stem cell was administered to 25 of these patients (42%). Thirteen patients (40%) had progressive disease (PD), five (22%) had early relapse, and seven (38%) had late relapse. A number of salvage regimens were used, including etoposide, prednisolone, ifosfamide, and cisplatin; dexamethasone, cytarabine, and carboplatin; and gemcitabine plus vinorelbine. Re-evaluation was performed before taking patients to a high dose, and it showed complete response in 17 patients (68%), partial response in six patients (24%), and PD in two patients (8%). Twenty-one patients (84%) are in remission after transplantation, with two patients (8%) having died as a result of disease progression and two patients (2%) having relapsed after treatment. Overall survival is 92% at 4 years, with event-free survival of 80% at 4 years.

CONCLUSION

Our retrospective analysis shows good outcomes in patients who had PD or refractory disease. Disease response before transplantation is important in predicting outcomes.