Role of FDG-PET in the Implementation of Involved-Node Radiation Therapy for Hodgkin Lymphoma Patients

Involved-site Radiotherapy Delineation Dilemmas in the Treatment of Adult Hodgkin Lymphoma: Turkish Society for Radiation Oncology Hematological Oncology, Pediatric Oncology and TBI Study Group Case-based Questionnaire Review (TROD 03-005)

AIMS

The International Lymphoma Radiation Oncology Group (ILROG) defined involved-site radiotherapy (ISRT) guidelines. These rules offer a certain variability that allows for autonomous decision-making in diverse clinical settings. However, this flexibility also gives rise to conflicts about the selection of treatment fields in the daily decision-making process. The aim of this study was to show the extent of interobserver variability when ILROG-ISRT recommendations were used in different clinical scenarios.

MATERIALS AND METHODS

The 10-question survey used in our study consisted of two parts (part A and part B) and was prepared by four senior radiation oncologists experienced in the haemato-oncology field. The results were presented by stratifying according to clinical experience (<10 years, ≥10 years). Binomial tests (one-sided) were conducted to assess whether answers for each group and the whole group reached a consensus.

RESULTS

Twenty-six radiation oncologists, 13 of whom had less than 10 years of experience and 13 seniors, participated in the survey. Eighty per cent of respondents thought ILROG did not bring sufficient solutions for all clinical scenarios but offered solutions in some cases. In different case-based scenarios, the consensus among the respondents decreased down to 38%. Senior radiation oncologists were found to have more doubts about the adequacy of current guidelines.

CONCLUSIONS

ILROG guidelines allow for a high degree of variability in real-life clinical scenarios and different interpretation of the recommendations may lead to increased toxicity and recurrences. Therefore, there is a need for refinement in ISRT delineation strategies. On behalf of the Turkish Society for Radiation Oncology Hematological Oncology, Pediatric Oncology and TBI Study Group, we are planning to carry out further educational contouring sessions to detect the interobserver variability in real-life contouring cases.

Modern PET-Guided Radiotherapy Planning and Treatment for Malignant Lymphoma

Malignant lymphoma comprises a broad spectrum of diverse entities originating from different types of lymphocytes. In the last century, successive improvements of treatment possibilities have led to an continuous amelioration of patient prognosis from lethal outcome to high rates of disease control and long-term survivors. PET/CT-based imaging plays a key role in stratification of stage and treatment response. Especially for radiotherapy, an essential treatment modality for lymphoma patients, functional imaging and the reevaluation of disease activity after frontline chemotherapy has led to major improvements regarding size of treatment fields and toxicity. International expert groups like the International Lymphoma Radiation Oncology Group (ILROG) develop guidelines for the optimal use of imaging for treatment planning. The shift from uniform large-field treatment volumes to complex individual setups taking into account biological response-assessments based on functional imaging resulted in a further de-escalation of side effects and modernization of lymphoma treatment. This paper aims to summarize the use of FDG-PET-imaging for radiation therapy planning in malignant lymphoma in the context of historic and future developments, as well as associated limitations and challenges ahead. We will discuss the contemporary standard of care as recommended by international expert guidelines like the ILROG, the national comprehensive cancer network (NCCN), as well as the newly updated German S3-guidelines.

Radiotherapy planning of lymphomas: role of metabolic imaging with PET/CT

Accurate target delineation is an absolute requirement for modern radiotherapy planning. Historically, structural imaging modalities have been used for this purpose, but there is a considerable role for functional imaging with PET/CT to contribute in this area. PET/CT's role in radiotherapy planning is well established and its use is indispensable in the clinical management of the lymphomas, particularly Hodgkin Lymphoma. A crucial use of PET/CT is as a baseline scan for delineation of the initial lymphomatous involvement, since this will determine the contouring of the gross-, clinical- and planning-target volumes (GTV, CTV, PTV). This article reviews the principles of contemporary radiotherapy, examines the evidence for the contribution of PET/CT to radiotherapy planning in lymphoma and the practicalities and challenges of applying this powerful technology to this situation.

The optimal use of PET/CT in the management of lymphoma patients

¹⁸F-fluoro-deoxyglucose positron emission tomography (PET)/computed tomography (CT) scans play an important role in the management of lymphoma patients. They are critical to accurately stage disease and assess its response to therapy. In addition, PET/CT scans enable precise target delineation for radiation therapy planning. In this review, we describe the use of PET/CT scans in lymphoma, with a focus on their role in staging disease, assessing response to therapy, predicting prognosis, and planning RT.

Total tumor burden in lymphoma - an evolving strong prognostic parameter

Total metabolic tumor volume (TMTV), a new parameter extracted from baseline FDG-PET/CT, has been recently proposed by several groups as a prognosticator in lymphomas before first-line treatment. TMTV, the sum of the metabolic volume of each lesion, is an index of the metabolically most active part of the tumor and highly correlates with the total tumor burden. TMTV measurement is obtained from PET images processed with different software and techniques, many being now freely available. In the various lymphoma subtypes where it has been measured, such as diffuse large B-cell lymphoma, Hodgkin lymphoma, Follicular Lymphoma, and Peripheral T-cell lymphoma, TMTV has been reported as a strong predictor of outcome (progression-free survival and overall survival) often outperforming the clinical scores, molecular predictors, and results of interim PET. Combined with these scores, TMTV improves the stratification of the populations into risk groups with different outcomes. TMTV cut-off separating the high-risk from the low-risk population impacts the outcome whatever the technique used for its measurement and an international harmonization is ongoing. TMTV is a unique and easy tool that could replace the surrogate of tumor burden included in the prognostic indexes used in lymphoma and help tailor therapy. Other parameters extracted from the baseline PET may give an information on the dissemination of this total tumor volume such as the maximum distance between the lesions. Trials based on TMTV would probably demonstrate its predictive value.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Impact of positron emission tomography with computed tomography for image-guided radiotherapy

Therapeutic effectiveness in radiotherapy is partly related to correct staging of the disease and then precise therapeutic targeting. Positron emission tomography (PET) allows the stage of many cancers to be determined and therefore is essential before deciding on radiation treatment. The definition of the therapeutic target is essential to obtain correct tumour control and limit side effects. The part of adaptive radiotherapy remains to be defined, but PET by its functional nature makes it possible to define the prognosis of many cancers and to consider radiotherapy adapted to the initial response allowing an increase over the entire metabolic volume, or targeted at a subvolume at risk per dose painting, or with a decrease in the dose in case of good response at interim assessment.

Volume de-escalation in radiation therapy: state of the art and new perspectives

PURPOSE

New RT techniques and data emerging from follow-up for several tumor sites suggest that treatment volume de-escalation may permit to minimize therapy-related side effects and/or obtain better clinical outcomes. Here, we summarize the main evidence about volume de-escalation in RT.

METHOD

The relevant literature from PubMed was reviewed in this article. The ClinicalTrials.gov database was searched for clinical trials related to the specific topic.

RESULTS

In Lymphoma, large-volume techniques (extended- and involved-field RT) are being successfully replaced by involved-site RT and involved-node RT. In head and neck carcinoma, spare a part of elective neck is controversial. In early breast cancer, partial breast irradiation has been established as a treatment option in low-risk patients. In pancreatic cancer stereotactic body radiotherapy may be used to dose escalation. Stereotactic radiosurgery should be the treatment choice for patients with oligometastatic brain disease and a life expectancy of more than 3 months, and it should be considered an alternative to WBRT for patients with multiple brain metastases.

CONCLUSION

Further clinical trials are necessary to improve the identification of suitable patient cohorts and the extent of possible volume de-escalation that does not compromise tumor control.

Limited-Stage Hodgkin Lymphoma: Minimizing Toxicity

Early-stage classic Hodgkin lymphoma has been highly curable using extended-field radiation therapy (RT) alone, combined-modality therapy consisting of chemotherapy and RT, and more recently chemotherapy alone. Radiation therapy either to an extended field (extended-field RT) or to various iterations of an involved field (involved-field RT) is potentially associated with late morbidity and mortality, particularly second primary cancers and cardiovascular complications. Treatment with chemotherapy alone, when possible, can achieve a high cure rate while avoiding these risks. This review describes the evolution of treatment for early-stage classic Hodgkin lymphoma.

The Use of Quantitative Imaging in Radiation Oncology: A Quantitative Imaging Network (QIN) Perspective

Modern radiation therapy is delivered with great precision, in part by relying on high-resolution multidimensional anatomic imaging to define targets in space and time. The development of quantitative imaging (QI) modalities capable of monitoring biologic parameters could provide deeper insight into tumor biology and facilitate more personalized clinical decision-making. The Quantitative Imaging Network (QIN) was established by the National Cancer Institute to advance and validate these QI modalities in the context of oncology clinical trials. In particular, the QIN has significant interest in the application of QI to widen the therapeutic window of radiation therapy. QI modalities have great promise in radiation oncology and will help address significant clinical needs, including finer prognostication, more specific target delineation, reduction of normal tissue toxicity, identification of radioresistant disease, and clearer interpretation of treatment response. Patient-specific QI is being incorporated into radiation treatment design in ways such as dose escalation and adaptive replanning, with the intent of improving outcomes while lessening treatment morbidities. This review discusses the current vision of the QIN, current areas of investigation, and how the QIN hopes to enhance the integration of QI into the practice of radiation oncology.

FDG-PET/CT in the management of lymphomas: current status and future directions

FDG-PET/CT is the current state-of-the-art imaging in lymphoma and plays a central role in treatment decisions. At diagnosis, accurate staging is crucial for appropriate therapy selection: FDG-PET/CT can identify areas of lymphoma missed by CT alone and avoid under-treatment of patients with advanced disease stage who would have been misclassified as having limited stage disease by CT. Particularly in Hodgkin lymphoma, positive interim FDG-PET/CT scans are adversely prognostic for clinical outcomes and can inform PET-adapted treatment strategies, but such data are less consistent in diffuse large B-cell lymphoma. The use of quantitative FDG-PET/CT metrics using metabolic tumour volume, possibly in combination with other biomarkers, may better define prognostic subgroups and thus facilitate better treatment selection. After chemotherapy, FDG-PET/CT response is predictive of outcome and may identify a subgroup who benefit from consolidative radiotherapy. Novel therapies, in particular immunotherapies, exhibit different response patterns than conventional chemotherapy, which has led to modified response criteria that take into account the risk of transient pseudo-progression. In relapsed lymphoma, FDG-PET/CT after second-line therapy and prior to high-dose therapy is also strongly associated with outcome and may be used to guide intensity of salvage therapy in relapsed Hodgkin lymphoma. Currently, FDG-PET/CT has no role in the routine follow-up after complete metabolic response to therapy, but it remains a powerful tool for excluding relapse if patients develop clinical features suggestive of disease relapse. In conclusion, FDG-PET/CT plays major roles in the various phases of management of lymphoma and constitutes a step towards the pursuit of personalized treatment.

CALGB 50604: risk-adapted treatment of nonbulky early-stage Hodgkin lymphoma based on interim PET

A negative interim positron emission tomography/computerized tomography (PET/CT) after 1 to 3 cycles of doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) in patients with newly diagnosed, nonbulky stage I or II Hodgkin lymphoma (HL) predicts a low relapse rate. This phase 2 trial was designed to determine if a population of patients with early-stage disease can be treated with short-course ABVD without radiation therapy (RT) on the basis of a negative interim PET/CT, thereby limiting the risks of treatment. Between 15 May 2010 and 21 February 2013, 164 previously untreated patients with nonbulky stage I/II HL were enrolled, and 149 were included in the final analysis. Patients received 2 cycles of ABVD followed by PET. Deauville scores 1 to 3 were negative (≤ liver uptake) based on central review. PET^- patients received 2 more cycles of ABVD, and PET⁺ patients received 2 cycles of dose-intense bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (escalated BEACOPP) plus 3060-cGy involved-field RT. The primary objective was to determine 3-year progression-free survival (PFS) for the PET^- group. One hundred thirty-five patients (91%) were interim PET^-, and 14 patients (9%) were PET⁺ With median follow-up time of 3.8 years, the estimated 3-year PFS was 91% for the PET^- group and 66% for the PET⁺ group (hazard ratio, 3.84; 95% confidence interval, 1.50-9.84; P = .011). There was 1 death as a result of suicide. Four cycles of ABVD resulted in durable remissions for a majority of patients with early-stage nonbulky HL and a negative interim PET. This trial was registered at www.clinicaltrials.gov as #NCT01132807.

Role of FDG PET-CT in the treatment management of Hodgkin lymphoma

Fluorodeoxyglucose (FDG) positons emission tomography (PET)-computed tomography (CT) is used in many ways at baseline and during the treatment of patients with Hodgkin lymphoma. Many properties of the technique are used in the different steps of patient's management. Initial staging with PET-CT is more accurate than conventional imaging and PET-CT also became the gold standard imaging at the end of treatment with a negative PET-CT mandatory for reaching a complete remission. Early assessment of response by PET-CT is one of the most powerful prognostic factors for progression-free survival of patients with localized and advanced stages and allows guiding treatment. Conversely, previous studies showed that there is no role of FDG PET-CT for the patient's follow-up.

Molecular Imaging Using PET/CT for Radiation Therapy Planning for Adult Cancers: Current Status and Expanding Applications

Accurate tumor delineation is a priority in radiation therapy (RT). Metabolic imaging has a key and evolving role in target volume selection and delineation. This is especially so for non-small cell lung cancer, squamous cell cancer of the head and neck, and lymphoma, for which positron emission tomography/computed tomography (PET/CT) is complimentary to structural imaging modalities, not only in delineating primary tumors, but also often in revealing previously undiagnosed regional nodal disease. At some sites, PET/CT has been confirmed to enable target size reduction compared with structural imaging alone, with enhanced normal tissue sparing and potentially allowing for dose escalation. These contributions often dramatically affect RT strategies. However, some limitations exist to the use of fluorodeoxyglucose-PET in RT planning, including its relatively poor spatial resolution and partial voluming effects for small tumors. A role is developing for contributions from metabolic imaging to RT planning at other tumor sites and exciting new applications for the use of non-fluorodeoxyglucose metabolic markers for RT planning.

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.

Lymphoma: current status of clinical and preclinical imaging with radiolabeled antibodies

Lymphoma is a complex disease that arises from cells of the immune system with an intricate pathology. While lymphoma may be classified as Hodgkin or non-Hodgkin, each type of tumor is genetically and phenotypically different and highly invasive tissue biopsies are the only method to investigate these differences. Noninvasive imaging strategies, such as immunoPET, can provide a vital insight into disease staging, monitoring treatment response in patients, and dose planning in radioimmunotherapy. ImmunoPET imaging with radiolabeled antibody-based tracers may also assist physicians in optimizing treatment strategies and enhancing patient stratification. Currently, there are two common biomarkers for molecular imaging of lymphoma, CD20 and CD30, both of which have been considered for investigation in preclinical imaging studies. In this review, we examine the current status of both preclinical and clinical imaging of lymphoma using radiolabeled antibodies. Additionally, we briefly investigate the role of radiolabeled antibodies in lymphoma therapy. As radiolabeled antibodies play critical roles in both imaging and therapy of lymphoma, the development of novel antibodies and the discovery of new biomarkers may greatly affect lymphoma imaging and therapy in the future.

Personalized Management Approaches in Lymphoma: Utility of Fluorodeoxyglucose-PET Imaging

PET/computed tomography (CT) imaging has gained a prominent role in the diagnosis and staging of malignancies. In lymphoma the role of PET/CT imaging continues to evolve as the understanding of its use in prognostication and response assessment improves. Currently, many groups are studying the potential function of PET/CT imaging in helping to direct management decisions for treating clinicians. This article summarizes the most up-to-date literature surrounding the topic of PET/CT-adaptive treatment of different lymphoma subjects. Although more studies are necessary to solidify the role of PET/CT, it is clear that this imaging modality holds much promise for the development of response-adaptive treatment algorithms in the future.

Image-guided radiation therapy in lymphoma management

Image-guided radiation therapy (IGRT) is a process of incorporating imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), Positron emission tomography (PET), and ultrasound (US) during radiation therapy (RT) to improve treatment accuracy. It allows real-time or near real-time visualization of anatomical information to ensure that the target is in its position as planned. In addition, changes in tumor volume and location due to organ motion during treatment can be also compensated. IGRT has been gaining popularity and acceptance rapidly in RT over the past 10 years, and many published data have been reported on prostate, bladder, head and neck, and gastrointestinal cancers. However, the role of IGRT in lymphoma management is not well defined as there are only very limited published data currently available. The scope of this paper is to review the current use of IGRT in the management of lymphoma. The technical and clinical aspects of IGRT, lymphoma imaging studies, the current role of IGRT in lymphoma management and future directions will be discussed.

Beyond PET/CT in Hodgkin lymphoma: a comprehensive review of the role of imaging at initial presentation, during follow-up and for assessment of treatment-related complications

Objective

The purpose of this article is to provide a comprehensive review of the role of imaging modalities other than PET/CT in the management of Hodgkin lymphoma (HL). PET/CT is the imaging modality of choice in the management of Hodgkin’s lymphoma (HL). However, imaging modalities other than PET/CT such as plain radiographs, ultrasound, CT, MRI and nuclear imaging can help in various stages of clinical management of HL, including the initial workup and post-treatment surveillance. Both CT and MRI help in detecting recurrences, treatment-related pulmonary, cardiovascular and abdominal complications as well as second malignancies. Familiarity with expected post-treatment changes and complications on surveillance images can help radiologists guide patient management. The purpose of this article is to provide a comprehensive review of the role of imaging modalities other than PET/CT in the management of Hodgkin lymphoma (HL).

Main Messages

• Surveillance of HL patients is usually performed with plain radiographs and CT.

• Follow-up imaging can depict normal post-treatment changes or treatment-related complications.

• Imaging is important for the timely detection of second malignancies in HL patients.