Routine scans for lymphoma produce minimal radiation-related cancer mortality risk

Abstract

17508 Background: Recent concern regarding the risks of cancer and cancer-related death due to radiation from computed tomography (CT) scans (Brenner, NEJM 2007) is accompanied by increased use of 18FDG positron emission tomography (PET) scans in lymphoma (Cheson, JCO 2007). We compared the radiation-related lifetime cancer mortality risks (LCMR) associated with CT and PET scans for staging and monitoring of non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL) with the probability of cancer death during this monitoring period. Methods: Using NCCN Guidelines for HL and NHL, we determined the number of scans a patient would undergo in the 5 years after diagnosis. We utilized published estimates of the cumulative organ-specific radiation doses from full-body CT scans (Brenner, Radiology 2004) and PET (Brix, J Nucl Med 2005), and calculated the lifetime cancer mortality risk (LCMR) associated with scans, using sex-, age-, and organ-dependent cancer risks per 0.1Gy provided by the Biological Effects of Ionizing Radiations VII report. Site-specific cancer risks were summed to yield the overall LCMR as described by Brenner (Med Phys 2001). To provide a comparator for the LCMRs, Surveillance, Epidemiology, and End Results data were used to identify cases between 1973 and 2004 and calculate cumulative probability of cancer death (CPCD) for the specified cohorts. Results: Since LCMR depends on gender and age at exposure, the table shows the LCMRs for CT and PET scans and CPCD for lymphoma subtypes by age at diagnosis. LCMRs were lower for males, were markedly less than the CPCD at 5-years for most lymphoma patients, but become relevant for younger women with HL undergoing CTs given their low risk of cancer death. Although PET scans are not recommended for lymphoma surveillance, they have a reduced LCMR due to less radiation exposure. Conclusions: While the LCMR from scans is small compared to cancer-related deaths for most individuals, these data should be discussed with patients in formulating plans for surveillance following lymphoma therapy. Lymphoma Subtype (Age at Diagnosis) LCMR from CT * LCMR from PET * 5-year Cumulative Probability of Cancer Death Males Females Males Females Males Females NHL (70 yrs) 0.58 0.80 0.33 0.42 46% 42% FL (70 yrs) 0.58 0.80 0.33 0.42 30% 27% DLBCL (70 yrs) 0.58 0.80 0.33 0.42 55% 53% HL (20 yrs) 1.27 1.95 0.61 0.83 13% 8% HL (80 yrs) 0.35 0.47 0.21 0.27 68% 61% * deaths per 100 persons exposed to the cumulative radiation dose associated with scans at 5 years No significant financial relationships to disclose.