Whole-body tumor burden in PET/CT expert review

Introduction: PET/CT whole-body tumor burden (WBTB), as a measure for overall burden of cancer, has been shown bear a strong correlation with prognosis. In the last decade, there has been significant progress in WBTB determination because of software advances and the increasing availability of positron-emitting radiopharmaceuticals. However, the determination of tumor burden with PET/CT is still a challenge especially in widespread metastatic disease. Methods: In this non-systematic review, we will discuss the current role of determination of WBTB in cancer such as non-small cell lung cancer, lymphoma, breast cancer, among others and with a variety of radiotracers. Furthermore, we will address imaging techniques and quantification methods available and challenges. Results: Many types of segmentation methods and different thresholds according to tumor types and radiotracers can be applied. These variations may show different WBTB results, but in general, despite variations, WBTB determination for staging purposes in lung cancer, breast cancer, lymphoma, melanoma, prostate cancer and neuroendocrine tumors have shown to bear a strong correlation with patient prognosis. Conclusion: PET/CT whole-body tumor burden has an invaluable potential to assess prognosis. The accelerated radiopharmaceutical development will provide molecules and mechanisms to determine WBTB with advanced imaging qualification tools to further adjust radiotherapeutic doses in oncology. WBTB will most likely only become routinely accessible in clinical practice when fully automated programs become available and standardized.