Screening for Cancer with PET and PET/CT: Potential and Limitations
Screening for cancer remains a very emotional and hotly debated issue in contemporary medical practice. An analysis of published data reveals a multitude of opinions based on a limited amount of reliable data. Even for breast cancer screening, which is now widely practiced in the United States and many European countries, there is continuing controversy regarding the appropriate age limits for screening mammography and, in fact, concerning the value of mammography itself. Similarly, there is no agreement as to whether screening for lung or prostate cancer is meaningful as currently practiced. Recommendations and decisions regarding cancer screening should be based on reliable data, not good intention, assumptions, or speculation. Therefore, we first explain the underlying principles and premises of screening and then briefly discuss current controversies regarding screening for breast, prostate, and lung cancers. Recently, some authors advocated CT, PET, or PET/CT for whole-body screening without support from reliable data. We discuss the potential financial, legal, and radiation safety implications associated with whole-body CT or PET cancer screening. We conclude from the available data that neither CT nor PET/CT cancer screening is currently warranted. Far from providing a desirable binary answer (presence of absence of cancer), in nonselected populations the procedures frequently yield equivocal or indeterminate findings that require further evaluation, with associated costs and potential complications. The clinical and statistical relevance of occasionally detected cancers is likely too low to justify population-wide screening efforts with these 2 imaging modalities. Ultimately, the true utility, or lack thereof, of PET and PET/CT for cancer screening can be assessed only in a prospective randomized trial. Because of prohibitive costs and the required length of follow-up, it is unlikely that such a trial will ever be conducted. Rather than spending time and resources on screening studies, medical practitioners should continue using whole-body PET/CT for diagnosing, staging, and restaging cancer and for monitoring treatment effects. Researchers should also investigate the utility of whole-body PET/CT for the surveillance of selected groups of patients who have cancer, who have completed curative treatment, but who remain at high risk for recurrent disease.