Comparison of renal uptake of 68Ga-DOTANOC PET/CT and estimated glomerular filtration rate before and after peptide receptor radionuclide therapy in patients with metastatic neuroendocrine tumours.

BACKGROUND: Ga-DOTA-conjugated peptide PET/CT is used widely for diagnosis and treatment planning in patients with neuroendocrine tumours. As nephrotoxicity is a major limiting factor during peptide receptor radionuclide therapy (PRRT), it is important to evaluate renal function before, during and after treatment. The aim of our study is to compare renal uptake of Ga-DOTANOC and estimated glomerular filtration rate (eGFR) before and after PRRT and to identify any surrogate indicators of renal toxicity.

MATERIALS AND METHODS: We included 64 Ga-DOTANOC PET/CT examinations in 32 patients with metastatic neuroendocrine tumours who underwent Y-DOTATATE therapy between May 2013 and April 2016. An amino acid infusion was used routinely for renal protection. Renal uptake was quantified as mean standardized uptake value (SUVmean) of both kidneys after background subtraction. eGFR was calculated using standard software. The values were compared and evaluation of correlation and agreement between the two parameters was performed.

RESULTS: Our study showed fair agreement between SUVmean of the kidneys on Ga-DOTANOC PET/CT and eGFR (r=0.33) before PRRT and poor agreement between SUVmean of the kidneys and eGFR (r=0.16) after PRRT. As expected, there was a statistically significant difference in eGFR before and after PRRT (mean difference=4.41±9.24 ml/min/1.73 m, P=0.01). On comparison of renal uptake before and after PRRT, the post-PRRT scans showed a statistically significant increase in uptake (SUVmean=-1.25±3.17, P=0.03).

CONCLUSION: Renal quantitative analysis on Ga-DOTANOC PET/CT before and after PRRT showed no significant correlation with the eGFR. However, there was a statistically significant increase in the renal uptake of Ga-DOTANOC, with a higher uptake after PRRT. As a result of this pilot study, we suggest that the higher renal uptake in the post-PRRT scans could be an indicator of early renal dysfunction and could have implications for further cycles of PRRT. Further longitudinal studies and further evaluation of such data across multiple centres are suggested.