The Use of Positron Emission Tomography-Computed Tomography in the Early Response Assessment of Nodular Sclerosing Hodgkin Lymphoma: A Case Series

Purpose: Positron Emission Tomography-Computed (PET-CT) is increasingly being incorporated into the management of pediatric lymphomas. Clinical trials are currently using “interim” PET/CT to assess early response and are seeking to establish whether its’ predictive value can successfully be used to direct individual treatments with the purpose of improving outcomes and decreasing treatment-associated toxicities. This review presents three cases of pediatric Hodgkin’s Lymphoma (HL) seen at Cook Children’s Medical Center (CCMC) to demonstrate the role that PET/CT is currently playing in the management of high-risk HL patients. Methods: A literature review was first performed in regards to the current protocol for PET-CT imaging in pediatric malignancies. It was found that the utility of PET-CT in this population is not yet a standard of care but there is support in the literature for its’ use in risk-stratification and treatment modulation. A review of the cases of three pediatric HL patients at CCMC receiving PET-CT imaging during their initial treatment was performed. The clinical decisions made by practitioners were examined to determine whether the PET-CT imaging that was done in addition to standard CT imaging changed treatment decisions among these three patients. This was based on examining whether the radiologic reports from the PET-CT studies provided additional information about treatment response in comparison to the CT imaging that was performed. It was also examined whether this additional information that was provided by the PET-CT studies was used to guide clinical decisions as demonstrated by changes in treatment plans. Results: In each of these three cases, PET-CT imaging provided the practitioner with additional information over the CT imaging alone. Patient 1 was found to have residual bulky disease on CT imaging. The PET-CT imaging provided the additional information that the lesions were not metabolically active. This demonstrated that the malignancy was responding well to the chemotherapy treatment. This patient was able to avoid radiation therapy due to the additional information that the PET-CT imaging provided. Patient 2 also showed residual bulky disease on CT imaging but a marked decrease in metabolic activity on PET-CT imaging similar to patient 1. This patient, however, had such extensive involvement at diagnosis that the protocol they are enrolled on required involved site radiation therapy (ISRT) regardless of PET-CT negativity. This case demonstrates a patient that may have been able to avoid radiation therapy if using PET-CT is the sole standard of treatment response assessment in the future. Patient 3 had one region that was found to still be metabolically active on PET-CT and was subjected to ISRT of this region specifically. Other previously involved regions avoided radiation therapy as they were determined by PET/CT to be responsive to chemotherapy. Conclusions: PET-CT has become a valuable resource in evaluating the response to chemotherapy in this population. PET-CT played a pivotal role in the risk-stratification among these three patients and kept one of them completely off of radiation therapy and allowed the others to receive ISRT and allowed avoidance of full body radiation. It provides a promising means by which pediatric patients with high-risk HL can avoid unnecessary chemotherapy and radiation related toxicities.