Assessing Cancer Therapy & Infection

This issue features several topics of critical importance in the field of imaging. The first one discusses the role of 18F-FDG PET/CT imaging in monitoring tumor responses after various therapeutic interventions. Numerous studies have provided the evidence that 18F-FDG PET imaging is more accurate than anatomical imaging for treatment response assessments in a wide range of solid tumors and hematological cancers. These accurate response assessments can be made as early as after the first cycle of chemotherapy.

However, this approach is only slowly infiltrating clinical practice. Several factors account for this delayed translation and acceptance. Standardization efforts have emerged only recently so that ambiguity about 18F-FDG PET response criteria persist. However, recent proposals for such criteria such as PERCIST (Positron Emission tomography Response Criteria in Solid Tumors)¹ will greatly aid in raising the visibility and acceptance of 18F-FDG PET for response assessments. In addition, the harmonization criteria² that define therapeutic responses in lymphoma have been introduced successfully. However, the timing of response assessment needs firm guidelines. I believe that current guidelines are overly conservative and that monitoring should be done as early as possible since late assessments will have limited impact on patient management. It is now up to national and international professional imaging organizations to provide uniform guidelines for treatment response criteria with PET. Following this first step, we need to inform and educate oncologists about such response criteria to make them as relevant as the tumor-size-based Response Criteria in Solid Tumors (RECIST).

SPECT/CT imaging is now a standard imaging modality in nuclear medicine and is used to image a variety of benign and malignant diseases. This modality provides more accurate disease assessments than SPECT imaging alone. In this issue, we’re taking a closer look at SPECT/CT in inflammation and infection imaging. Initial studies promise more accurate assessments of a variety of orthopedic indications, the diabetic foot, post-device implantation such vascular prosthesis or left-ventricular-assist devices, neuroblastoma, fever of unknown origin (FUO) and in post-transplant patients. SPECT/CT imaging reimbursement does not differ from that of SPECT imaging alone. However, interpretation is more laborious and imaging equipment is more expensive. Professional organizations should make every effort to correct this inadequate reimbursement level.

References:

1. Wahl et al; From RECIST to PERCIST: Evolving Considerations for PET response criteria in solid tumors. J Nucl Med 2009; 50 Suppl 1:122S-50S.
2. Cheson et al; Revised response criteria for malignant lymphoma.Cheson et al; J Clin Oncol. 2007 ; 25:579-86