Evaluation of cumulative radiation burden and associated risk in smouldering multiple myeloma patients monitored using recurrent whole-body low-dose CT imaging.

PURPOSE: To assess the cumulative radiation burden and cancer risk associated with multiple whole-body low-dose computed tomography (WBLDCT) scans in patients with smouldering multiple myeloma (SMM).

METHODS

A cohort of 116 SMM patients who underwent recurrent (n = 2-7) WBLDCT examinations was studied. Patient-specific organ doses were estimated using CT dosimetry software (NCICT) whereas effective doses (ED) were estimated from NCICT and the dose-length product (DLP). Organ-specific and total lifetime-attributable risks (LAR) of cancer incidence were calculated per patient using the BEIR VII methodology.

RESULTS

Cumulative dose to the thyroid reached 66 mGy, whereas cumulative doses to salivary glands and eye lenses/balls exceeded 50 mGy. The median ED per WBLDCT examination was 5.6/4.6 mSv (female) and 5.8/3.4 mSv (male) using NCICT/DLP with the highest cumulative (n = 7) ED being 42.1 mSv. Lung cancer (female) and leukaemia (female/male) were associated with the highest risks related to WBLDCT procedures, with total LAR being 44 % higher in females compared to males. The median LAR per single exposure was 36/25 per 100,000 (female/male) with the median cumulative LAR being 85/58 per 100,000.

CONCLUSION

The theoretical radiogenic risk of cancer induction associated with multiple WBLDCT examinations for the active surveillance of a real-life SMM cohort appears to be two orders of magnitude lower than 10 % of SMM patients, which may progress to symptomatic MM requiring treatment. Dose optimisation is recommended for the WBLDCT protocol, as well as a patient-specific strategy for active SMM surveillance, but further research is needed to evaluate the role of early therapeutic interventions.