For most cancers, intensive surveillance after treatment has not been shown to improve survival, and there is growing concern about radiation exposure from routine imaging, according to Crystal Denlinger, MD, Assistant Professor, Fox Chase Cancer Center, Philadelphia, who chairs the NCCN Guidelines Panel for Survivorship. At the NCCN 19th Annual Conference, Dr. Denlinger outlined the recommendations for surveillance for several tumor types.
Based on results from a US cohort of 31,462 patients undergoing diagnostic imaging with CT scans, recurrent imaging appears to convey more than a 1% risk of radiation-induced cancers in a small percentage of patients.1 In the 7% of patients within this cohort whose risk of cancer was increased by 1% or more due to radiation exposure, the majority had a history of malignancy, yet 30% of this group did not have evidence of active disease. “Our zeal for imaging may actually increase cancer risk in some patients exposed to frequent surveillance imaging tests,” Dr. Denlinger said.
The data on the topic are relatively weak, however, because few randomized studies and few recent studies on the most effective modalities have been performed to inform surveillance strategies, according to Dr. Denlinger.
Although many patients and their families view regular surveillance as a mark of good practice and patients yearn to hear the words “cancer free,” testing can also induce anxiety. In addition, false-positive results can trigger additional testing, and this can increase radiation exposure and costs.
As a general rule, less is more, Dr. Denlinger maintained, because most recurrences are detected on clinical examination or by the presence of symptoms, not by imaging tests or blood-based markers. Regardless of how they are picked up, recurrences are rarely cured.
Discussions with patients regarding the risks and benefits of routine imaging tests and laboratory studies are important for defining and adhering to optimal surveillance strategies (see inset), she said.
Dr. Denlinger has disclosed that she has received grants or research support from Astex Pharmaceuticals, Bayer HealthCare, ImClone Systems Incorporated, MedImmune Inc., Merrimack Pharmaceuticals, OncoMed Pharmaceuticals, and Pfizer Inc., and has served as a scientific advisor for Eli Lilly and Company.
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