Impact of PET-CT on involved field radiotherapy design for pediatric Hodgkin lymphoma

RS, Janarthinakani M, Prasad K, Patil C, Anoop P, Reddy N, Anumula SK, Roopa SP, Golamari KR, Danthala M, Malipatil B, Rangarajan B, Udupa KS, Nandennavar M, Niraimathi K. Role of Interim PET Scan after 2 Cycles of ABVD in Pediatric Hodgkin Lymphoma: Retrospective Multicenter Study from South India

Introduction Most Indian centers use Adriamycin/Bleomycin/Vinblastine/Dacarba-zine (ABVD) chemotherapy for pediatric Hodgkin lymphoma (pHL). To reduce the late toxicity, robust predictive markers are needed to risk stratify pHL patients, thereby limiting the number of chemotherapy cycles and omitting radiation for low-risk and intensifying treatment for high-risk children.

Objective This study was conducted to analyze the outcome of pHL patients treated with ABVD and various factors predicting the outcome.

Materials and Methods This retrospective study analyzed the outcome of 113 consecutive pHL children treated with ABVD chemotherapy from 11 tertiary care centers in South India from 2009 to 2019.

Results The median duration of follow-up was 2.73 years. The median age was 13 years. B symptoms are seen in 50.5% patients, bulky disease in 23%, and stage IV in 28.3%. Of 113 pHL, 69% had a positron emission tomography (PET) and 31% had computed tomography (CT)-based staging. Stage IV (37.1%) and extranodal involvement (31.2%) were seen more often with PET than with CT staging (8.5 and 2.8%, respectively). Among 64 patients with interim PET scan after two cycles (iPET2), 20.3% did not achieve complete remission (CR) and no factors were significantly associated. The 4-year event-free survival (EFS) rate of the entire cohort was 86%. The 4-year EFS rate was 93% for patients with CR in iPET2 and 52% for patients not achieving CR. The only independent predictor of low EFS was iPET2 response (p < 0.05).

Conclusion Our study confirms the prognostic role of PET scan staging and response assessment. Not achieving CR on the iPET2 scan indicates poor prognosis and warrants clinical trial enrollment for a better outcome.

Italian Multicenter Study on Accuracy of 18F-FDG PET/CT in Assessing Bone Marrow Involvement in Pediatric Hodgkin Lymphoma

INTRODUCTION

The present study investigated the utility of fluorine-18 (¹⁸F) fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in assessing bone marrow involvement (BMI) compared with bone marrow biopsy (BMB) in newly diagnosed pediatric Hodgkin lymphoma (HL).

PATIENTS AND METHODS

A total of 224 pediatric patients with HL underwent ¹⁸F-FDG PET/CT at staging. BMB or follow-up imaging was used as the standard of reference for the evaluation of BMI.

RESULTS

¹⁸F-FDG PET/CT was negative for BMI in 193 cases. Of the 193 patients, the findings for 16 were originally reported as doubtful and later interpreted as negative for BMI, with negative findings on follow-up imaging and BMB. At BMB, 1 of the 16 patients (6.25%) had BMI. Of the 193 patients, 192 (99.48%) had negative BMB findings. Thus, the ¹⁸F-FDG PET/CT findings were truly negative for 192 patients and falsely negative for 1 patient for BMI.

CONCLUSION

¹⁸F-FDG PET/CT showed high diagnostic performance in the evaluation of BMI in pediatric HL. Thus, BMB should be ideally reserved for patients presenting with doubtful ¹⁸F-FDG PET/CT findings for BMI.

Precision Medicine and PET-Computed Tomography in Pediatric Malignancies

Fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) PET-computed tomography (CT) plays a significant role in diagnosis, staging, therapy selection, and therapy assessment of multiple pediatric malignancies and facilitating precision medicine delivery in pediatric patients. In patients with Hodgkin lymphoma, interim fludeoxyglucose ¹⁸F-FDG PET/CT is highly sensitive and specific for predicting survival and multiple trials with FDG PET/CT-based adaptive therapies are currently ongoing. It is superior to iodine-131 metaiodobenzylguanidine (¹³¹I-MIBG) scintigraphy and bone scintigraphy for detecting metastases in neuroblastoma patients and sarcoma patients. It may predict histologic differentiation and neoadjuvant therapy assessment in Wilms tumor.

Nuclear Medicine in Pediatric and Adolescent Tumors

Nuclear medicine has an important role in the management of many cancers in pediatric age group with multiple imaging modalities and radiopharmaceuticals targeting various biological uptake mechanisms. 18-Flourodeoxyglucose is the radiotracer of choice especially in patients with sarcoma and lymphoma. (18)FDG-PET, for sarcoma and lymphomas, is proved to be superior to conventional imaging in staging and therapy response. Although studies are limited in pediatric population, (18)FDG-PET/CT has found its way through international guidelines. Limitations and strengths of PET imaging must be noticed before adapting PET imaging in clinical protocols. Established new response criteria using multiple parameters derived from (18)FDG-PET would increase the accuracy and repeatability of response evaluation. Current data suggest that I-123 metaiodobenzylguanidine (MIBG) remains the tracer of choice in the evaluation of neuroblastoma (NB) because of its high sensitivity, specificity, diagnostic accuracy, and prognostic value. It is valuable in determining the response to therapy, surveillance for disease recurrence, and in selecting patients for I-131 therapy. SPECT/CT improves the diagnostic accuracy and the interpretation confidence of MIBG scans. (18)FDG-PET/CT is an important complementary to MIBG imaging despite its lack of specificity to NB. It is valuable in cases of negative or inconclusive MIBG scans and when MIBG findings underestimate the disease status as determined from clinical and radiological findings. F-18 DOPA is promising tracer that reflects catecholamine metabolism and is both sensitive and specific. F-18 DOPA scintigraphy provides the advantages of PET/CT imaging with early and short imaging times, high spatial resolution, inherent morphologic correlation with CT, and quantitation. Regulatory and production issues currently limit the tracer's availability. PET/CT with Ga-68 DOTA appears to be useful in NB imaging and may have a unique role in selecting patients for peptide receptor radionuclide therapy with somatostatin analogues. C-11 hydroxyephedrine PET/CT is a specific PET tracer for NB, but the C-11 label that requires an on-site cyclotron production and the high physiologic uptake in the liver and kidneys limit its use. I-124 MIBG is useful for I-131 MIBG pretherapeutic dosimetry planning. Its use for diagnostic imaging as well as the use of F-18 labeled MIBG analogues is currently experimental. PET/MR imaging is emerging and is likely to become an important tool in the evaluation. It provides metabolic and superior morphological data in one imaging session, expediting the diagnosis and lowering the radiation exposure. Radioactive iodines not only detect residual tissue and metastatic disease but also are used in the treatment of differentiated thyroid cancer. However, these are not well documented in pediatric age group like adult patients. Use of radioactivity in pediatric population is very important and strictly controlled because of the possibility of secondary malignities; therefore, management of oncological cases requires detailed literature knowledge. This article aims to review the literature on the use of radionuclide imaging and therapy in pediatric population with thyroid cancer, sarcomas, lymphoma, and NB.

Importance of baseline PET/CT imaging on radiation field design and relapse rates in patients with Hodgkin lymphoma

PURPOSE

This study analyzed the impact of pretreatment positron emission tomography/computed tomography (PET/CT) scans on involved site radiation therapy (ISRT) field design and pattern of relapse among patients with Hodgkin lymphoma (HL).

METHODS AND MATERIALS

Thirty-seven patients with stage I or II HL who received first-line chemotherapy followed by consolidative ISRT to all initial sites of disease were enrolled in an institutional review board-approved outcomes-tracking protocol between January 2009 and December 2014. Patients underwent standard-of-care follow-up. Relapse-free survival (RFS) was evaluated using a Kaplan-Meier analysis and cohort comparisons using a χ2 test.

RESULTS

Thirty-one patients underwent (PET/CT) scans before chemotherapy and 6 did not because of a lack of insurance (n = 2), inpatient chemotherapy administration (n = 2), scheduling conflicts (n = 1), and unknown reasons (n = 1). The median follow-up was 46 months, and the 4-year RFS rate was 92%. Patients without pretreatment PET imaging were more likely to experience disease relapse (4-year RFS, 97% vs. 67%; P = .001). Among the 6 patients who did not receive a baseline PET/CT scan, all 3 recurrences occurred in lymph node regions outside of, but immediately adjacent to, the radiation field.

CONCLUSIONS

Patients with stage I/II HL who receive ISRT without pretreatment PET/CT scans appear to have an increased risk for relapse in adjacent nodal stations just outside the radiation field. A larger cohort with a longer follow-up is needed to confirm these findings.

Current Role of FDG-PET in Pediatric Hodgkin's Lymphoma

Hodgkin's lymphoma is one of the most curable pediatric cancers with long-term survival rates exceeding 90% following intensive treatment. Collaborative group studies worldwide aim on reduction or elimination of radiotherapy to avoid potentially life-limiting late effects especially second cancers and cardiovascular diseases. Large prospective trials have integrated early response FDG-PET scans to identify adequate responders to chemotherapy in whom radiotherapy may safely be omitted. The criteria for interpretation of early response PET have changed during the past years and will be further refined based on trial results. FDG-PET is also systematically used to assess initial disease involvement of pediatric Hodgkin's lymphoma and could replace bone marrow biopsy. This article summarizes the role of FDG-PET in staging and response assessment focusing on large pediatric trials, the criteria for PET interpretation and pitfalls.

18F-FDG PET-CT imaging versus bone marrow biopsy in pediatric Hodgkin's lymphoma: a quantitative assessment of marrow uptake and novel insights into clinical implications of marrow involvement

OBJECTIVE

To evaluate whether positron emission tomography/computed tomography using fluorine-18 fluoro-deoxyglucose (¹⁸F-FDG PET-CT) predicts bone marrow involvement (BMI) in pediatric Hodgkin's lymphoma (pHL) with sufficient accuracy to supplant routine staging bone marrow biopsy (BMB), and to assess the clinical importance of marrow disease by comparing the prognosis of stage IV HL with BMI versus that without BMI.

METHODS

Data were retrospectively analyzed for all cases of pHL between July 2010 and June 2015 referred for staging ¹⁸F-FDG PET-CT scan and BMB. The reference standard was BMB. Stage IV patients were divided into three groups to compare their progression-free and overall survival: PET+ BMB-, PET+ BMB+, and PET- BMB-.

RESULTS

Of the 784 patients, 83.3% were male and 16.7% female, with age ranging from 2 to 18 years (mean 10.3 years). Among the total cases, 104 (13.3%) had BMI; of these, 100 were detected by PET imaging and 58 by BMB. BMB and ¹⁸F-FDG PET/CT scans were concordant for BMI detection in 728 patients (93%): positive concordance in 54 and negative in 674. Of the 56 discordant cases, four had a false-negative PET scans and were upstaged by BMB, 46 with focal uptake were PET/CT-positive and BMB-negative (not obtained from active sites), and six with diffuse uptake were false-positive on PET due to paraneoplastic marrow activation. The sensitivity, specificity, PPV, and NPV of PET for identifying BMI was 93.6, 94, 53, and 99.4% respectively. On quantitative assessment, mean iBM-SUV_max of bilateral iliac crests was significantly higher in those with BMI versus those without (p < 0.05).

CONCLUSIONS

¹⁸F-FDG PET-CT imaging is more sensitive than BMB for BMI detection in pHL staging. BMB should be limited to those with normal marrow uptake in the presence of poor risk factors or those with diffusely increased uptake to exclude marrow involvement in the background of reactive marrow.

Posttreatment PET/CT Rather Than Interim PET/CT Using Deauville Criteria Predicts Outcome in Pediatric Hodgkin Lymphoma: A Prospective Study Comparing PET/CT with Conventional Imaging

Data about the significance of ¹⁸F-FDG PET at interim assessment and end of treatment in pediatric Hodgkin lymphoma (HL) are limited. Methods: Patients (≤18 y) with HL were prospectively evaluated with contrast-enhanced CT (CECT) and PET combined with low-dose CT (PET/CT) at baseline, after 2 cycles of chemotherapy, and after completion of treatment. Revised International Working Group (RIW) criteria and Deauville 5 point-scale for response assessment by PET/CT were used. All patients received doxorubicin (Adriamycin), bleomycin, vinblastine, dacarbazine chemotherapy along with involved-field radiotherapy (25 Gy) for early stage (IA, IB, and IIA) and advanced stage (IIB-IV) with bulky disease. Results: Of the 57 enrolled patients, median follow-up was 81.6 mo (range, 11-97.5 mo). Treatment decisions were based on CECT. At baseline, PET/CT versus CECT identified 67 more disease sites; 23 patients (40.3%) were upstaged and of them in 9 patients (39%) upstaging would have affected treatment decision; notably none of these patients relapsed. The specificity of interim PET/CT based on RIW criteria (61.5%) and Deauville criteria (91.4%) for predicting relapse was higher than CECT (40.3%) (P = 0.03 and P < 0.0001, respectively). Event-free survival based on interim PET/CT (RIW) response was 93.3 ± 4.1 versus 89.6 ± 3.8 (positive vs. negative scan, respectively; P = 0.44). The specificity of posttreatment PET/CT (Deauville) was 95.7% versus 76.4% by CECT (P = 0.006). Posttreatment PET/CT (Deauville) showed significantly inferior overall survival in patients with positive scan versus negative scan results (66.4 ± 22.5 vs. 94.5 ± 2.0, P = 0.029). Conclusion: Interim PET/CT has better specificity, and use of Deauville criteria further improves it. Escalation of therapy based on interim PET in pediatric HL needs further conclusive evidence to justify its use. Posttreatment PET/CT (Deauville) predicts overall survival and has better specificity in comparison to conventional imaging.

Use of standardized uptake value thresholding for target volume delineation in pediatric Hodgkin lymphoma

PURPOSE

A limitation of [(18)F] 2-fluoro-2-deoxy-d-glucose positron emission tomography (FDGPET) in radiation planning for Hodgkin lymphoma (HL) is significant variability in delineation of tumor volume. One approach to reduce variability is to apply automatic or semiautomatic segmentation methods such as thresholding based on a percent tumor maximum standardized uptake value (SUVmax). Here, we apply various tumor SUVmax thresholds and examine their effects in involved field radiation therapy (IFRT) and involved site radiation therapy (ISRT) target volumes.

METHODS AND MATERIALS

PET/computed tomography data sets were reviewed for 16 pediatric and young adult patients treated with IFRT. The following percent tumor SUVmax thresholds were applied to the prechemotherapy PET: 15%, 20%, 25%, 30%, 35%, and 40%. Clinical target volumes for IFRT and ISRT plans were manually generated based on these threshold volumes (CTVPET) and compared with clinical target volumes generated using the standard qualitative visual method (CTVQVM). Treatment plans were generated, doses to normal structures were compared, and the optimum threshold, defined as the CTVPET that corresponded to the percent overlap closest to 100% when compared with the CTVQVM, was determined.

RESULTS

On average, there was a 7.6-fold increase in PET volume between 40% and 15% SUVmax. When the 6 SUVmax thresholds were applied in the design of target volumes for IFRT, 2 of 16 patients had a change in treatment volume. There was a 2.4-fold increase in ISRT CTVs generated based on the 15% and 40% SUVmax, which translated into a clinically significant decrease in dose to normal structures when the ISRT plans that were generated using the 15% SUVmax volumes were compared with the 40% SUVmax. In most patients, the optimum threshold was SUVmax 15%.

CONCLUSIONS

Accurate target volume delineation with [(18)F] 2-fluoro-2-deoxy-d-glucose PET in HL is challenging and may require more precise and reproducible segmentation methods as we move toward more conformal therapies.

Value of 18F-FDG PET and PET/CT for evaluation of pediatric malignancies

Successful management of solid tumors in children requires imaging tests for accurate disease detection, characterization, and treatment monitoring. Technologic developments aim toward the creation of integrated imaging approaches that provide a comprehensive diagnosis with a single visit. These integrated diagnostic tests not only are convenient for young patients but also save direct and indirect health-care costs by streamlining procedures, minimizing hospitalizations, and minimizing lost school or work time for children and their parents. (18)F-FDG PET/CT is a highly sensitive and specific imaging modality for whole-body evaluation of pediatric malignancies. However, recent concerns about ionizing radiation exposure have led to a search for alternative imaging methods, such as whole-body MR imaging and PET/MR. As we develop new approaches for tumor staging, it is important to understand current benchmarks. This review article will synthesize the current literature on (18)F-FDG PET/CT for tumor staging in children, summarizing questions that have been solved and providing an outlook on unsolved avenues.

PET/CT-guided treatment planning for paediatric cancer patients: a simulation study of proton and conventional photon therapy

OBJECTIVE

To investigate the impact of including fluorine-18 fludeoxyglucose ((18)F-FDG) positron emission tomography (PET) scanning in the planning of paediatric radiotherapy (RT).

METHODS

Target volumes were first delineated without and subsequently re-delineated with access to (18)F-FDG PET scan information, on duplicate CT sets. RT plans were generated for three-dimensional conformal photon RT (3DCRT) and intensity-modulated proton therapy (IMPT). The results were evaluated by comparison of target volumes, target dose coverage parameters, normal tissue complication probability (NTCP) and estimated risk of secondary cancer (SC).

RESULTS

Considerable deviations between CT- and PET/CT-guided target volumes were seen in 3 out of the 11 patients studied. However, averaging over the whole cohort, CT or PET/CT guidance introduced no significant difference in the shape or size of the target volumes, target dose coverage, irradiated volumes, estimated NTCP or SC risk, neither for IMPT nor 3DCRT.

CONCLUSION

Our results imply that the inclusion of PET/CT scans in the RT planning process could have considerable impact for individual patients. There were no general trends of increasing or decreasing irradiated volumes, suggesting that the long-term morbidity of RT in childhood would on average remain largely unaffected.

ADVANCES IN KNOWLEDGE

(18)F-FDG PET-based RT planning does not systematically change NTCP or SC risk for paediatric cancer patients compared with CT only. 3 out of 11 patients had a distinct change of target volumes when PET-guided planning was introduced. Dice and mismatch metrics are not sufficient to assess the consequences of target volume differences in the context of RT.

The utility of FDG PET in diagnosis and follow-up of lymphoma in childhood

Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) are among the most common malignancies of childhood. (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) can be employed for accurate staging, treatment planning, and response assessment in pediatric patients with lymphomas, taking advantage of the increased FDG uptake of the malignant cells, secondary to their increased metabolic needs. FDG PET has higher sensitivity than other imaging modalities to detect nodular or diffuse lesions and higher sensitivity than bone marrow biopsy to detect bone marrow infiltration. FDG PET consists of an invaluable imaging modality during evaluation and treatment of pediatric lymphomas.