Significant variability in 10-year cumulative radiation exposure incurred on different surveillance regimens after surgery for pT1 renal cancers: yet another reason to standardize protocols?

Abstract

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: The topic of radiation safety has been hotly debated not only in the mainstream media, but also in the urological literature. Radiation exposure has been examined in urological diseases such as testicular cancer and urinary stone disease, with resultant recommendations for modifying surveillance imaging. Radiation risk with respect to surveillance regimens after RCC surgery has yet to be examined. We consider this largely to be a result of RCC typically affecting older patients in whom cumulative radiation exposure may be less of a consideration. However, current population data emphasize that RCC diagnosis and therapy have an increasing impact upon younger patients with a longer life expectancy after treatment. Therefore, radiation considerations in this cohort of patients may be significant.

Objective: To determine the 10-year cumulative radiation exposure incurred on different surveillance imaging protocols after surgery for pT1 renal cell carcinoma (RCC).

Materials and methods: The PubMed database was queried for surveillance protocols after surgery for RCC. There were two index lesions that were selected: (i) pT1a 3 cm, Fuhrman 2, clear cell and (ii) pT1b 5 cm, Fuhrman 3, clear cell. Exposure for single-phase chest computed tomography (CT), abdominal CT and chest X-ray were 7, 8 and 0.1 mSV, respectively. Calculations assumed biphasic CT scans, negative surgical margins and an Eastern Cooperative Oncology Group status of ≤1.

Results: In total, 12 published surveillance regimens were identified. For the first lesion (pT1a, clear cell, Fuhrman 2), we observed significant variability in the proposed regimens, ranging from no imaging to several CT scans of both chest and abdomen. Cumulative incurred radiation exposure for this index patient was in the range 0-102 mSv (mean, 34 mSv). When considering the second tumour (pT1b, clear cell, Fuhrman 3), all studies recommended some form of follow-up imaging, although regimens once again varied from annual chest X-ray to multiple CT scans of chest and abdomen. Cumulative incurred radiation exposure in this scenario was in the range 0.5-450 mSv (mean, 89 mSV).

Conclusions: Surveillance protocols after surgery for early-stage RCC result in widely divergent levels of radiation exposure. Such considerations are increasingly paramount given concerns of radiation-induced secondary malignancies and present another reason to standardize follow-up protocols.