Radiotherapy in Follicular Lymphoma Staged by 18F-FDG-PET/CT: A German Monocenter Study

PET/CT-based target volume definition in involved-site radiotherapy for treatment of early-stage nodal follicular lymphoma

PURPOSE

Recent advancements in imaging, particularly 18F-fluorodeoxyglucose positron-emission tomography-computed tomography (FDG-PET/CT), have improved the detection of involved lymph nodes, thus influencing staging accuracy and potentially treatment outcomes. This study is a post hoc analysis of the GAZAI trial data to evaluate the impact of FDG-PET/CT versus computed tomography (CT) alone on radiation target volumes for involved-site radiotherapy (IS-RT) in early-stage follicular lymphoma (FL).

METHODS

All patients in the GAZAI trial underwent pretherapeutic FDG-PET/CT examinations, which were subject to central quality control. Lymph nodes with pathological metabolism were assessed for CT morphology. Differential regional involvement and the impact on radiation target volume for IS-RT were compared between PET/CT-based to solely CT-based staging.

RESULTS

In 54 patients with PET-positive lymph nodes after initial surgery, 170 involved lymph nodes were identified in total. FDG-PET/CT identified additionally involved lymph nodes not detected by CT in 61% of the patients, leading to a significant change in radiation treatment fields for 30% of the cohort. Only 58% of all involved lymph nodes exhibited pathological CT morphology. The findings were robust across different Deauville score thresholds and CT morphological metrics.

CONCLUSION

The findings confirm the essential role of FDG-PET/CT in accurately defining the radiation volume for treatment of early-stage follicular lymphomas with radiotherapy. These results support the integration of FDG-PET/CT into the standard diagnostic pathway and its inclusion in the service catalogue of statutory health insurance, emphasizing its importance for optimal treatment planning and the potential impact on patient outcomes.

Duodenal-type follicular lymphoma in 18F-FDG PET/CT imaging: a case report

Follicular lymphoma (FL) is a subtype of non-Hodgkin lymphoma (NHL) that is typically characterized by a slow-growing course. Duodenal-type follicular lymphoma (D-FL) was recently reclassified as a distinct variant. This subtype exhibits unique clinical and biological characteristics, which set it apart from other forms of FL. We report a case of a 36-year-old male patient with multiple, small, gray polypoid lesions in the descending duodenum which were detected by esophagogastroduodenoscopy. The pathological diagnosis was low-grade D-FL. 18F-FDG PET/CT was performed for staging and revealed the pancreas and peripheral lymph nodes were involved by FL, with a clinical IV stage. The patient underwent a bone marrow smear cytology, which revealed no bone marrow abnormalities, and excluded bone marrow involvement. He was treated with six cycles of chemotherapy using the R-CHOP regimen and reached complete remission.

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.