Kidney dosimetry in [177Lu]Lu-DOTA-TATE therapy based on multiple small VOIs

PURPOSE

The aim was to investigate the use of multiple small VOIs for kidney dosimetry in [177Lu]Lu-DOTA-TATE therapy.

METHOD

The study was based on patient and simulated SPECT images in anthropomorphic geometries. Images were reconstructed using two reconstruction programs (local LundaDose and commercial Hermia) using OS-EM with and without resolution recovery (RR). Five small VOIs were placed to determine the average activity concentration (AC) in each kidney. The study consisted of three steps: (i) determination of the number of iterations for AC convergence based on simulated images; (ii) determination of recovery-coefficients (RCs) for 2 mL VOIs using a separate set of simulated images; (iii) assessment of operator variability in AC estimates for simulated and patient images. Five operators placed the VOIs, using for guidance: a) SPECT/CT with RR, b) SPECT/CT without RR, and c) CT only. For simulated images, time-integrated ACs (TIACs) were evaluated. For patient images, estimated ACs were compared with results of a previous method based on whole-kidney VOIs.

RESULTS

Eight iterations and ten subsets were sufficient for both programs and reconstruction settings. Mean RCs (mean ± SD) with RR were 1.03 ± 0.02 (LundaDose) and 1.10 ± 0.03 (Hermia), and without RR 0.91 ± 0.03 (LundaDose) and 0.94 ± 0.03 (Hermia). Most stable and accurate estimates of the AC were obtained using five 2-mL VOIs guided by SPECT/CT with RR, applying them to images without RR, and including an explicit RC for recovery correction.

CONCLUSION

The small VOI method based on five 2-mL VOIs was found efficient and sufficiently accurate for kidney dosimetry in [177Lu]Lu-DOTA-TATE therapy.

Nephrotoxicity and hematotoxicity one year after four cycles of peptide receptor radionuclide therapy (PRRT) and its impact on future treatment planning. A retrospective analysis

INTRODUCTION

Nephro- and hematotoxicity after peptide receptor radionuclide therapy (PRRT) have been described in multiple studies with heterogeneous cumulative activities, number of cycles or radiolabelled peptides. Though highly differentiated metastasized neuroendocrine tumours (NET) have long progression free survival, they may progress. We analysed long-term side effects in a homogenous treatment schedule in PRRT-patients and their impact on future oncologic treatment in case of progression.

METHODS

From our database 89/384 patients receiving the same PRRT (Lu-177-DOTATATE or Y-90-DOTATOC) 4 times every 10 to 12 weeks and a follow-up at 12 months were analysed. One patient had three and 11 patients had two times four PRRT-cycles resulting in 102 cases. eGFR, Hb, WBC and platelets before the first and one year after the fourth therapy cycle were compared. eGFR-Grading was done according to chronic kidney disease classification (CKD) and grading of hematotoxicity according to Common Terminology Criteria for Adverse Events (CTCAE). Impact of age, gender, cumulative activity, type of PRRT on long-term-toxicity was also assessed.

RESULTS

eGFR grade 1-2 dropped from 87/102 at the baseline to 71 cases at follow-up (p<0.001). Before treatment grade 3a was found in 13, grade 3b in 2 cases, and at follow-up grade 3a in 25, grade 3b in 5, and grade 4 in 1 case. Anaemia prior to PRRT and at follow-up was grade 0 in 63 versus 48 (p<0.001), grade 1 in 36 versus 48, and grade 2 in three versus six cases. In white blood cell count and platelets, there were no significant changes in grading occurring. Subgroup analysis revealed that only in the age group 65 and older was there a higher incidence for anaemia (p=0.006). CONCLUSIóN: In roughly 20% of cases an increase in grading of nephro- or hematotoxicity is observed. In those patients, except in one, toxicity findings were mild or moderate one year after completion of four cycles of PRRT with either Y-90- or Lu-177-SST-analogues. In terms of safety, PRRT has no critical impact on further oncologic treatment options in the case of disease progression.

Theragnostics in Neuroendocrine Tumors

Several studies have demonstrated the effectiveness of somatostatin receptor (SSTR)-targeted imaging for diagnosis, staging, evaluating the possibility of treatment with cold somatostatin analogs, as well peptide receptor radionuclide therapy (PRRT), and evaluation of treatment response. PET with ⁶⁸Ga-labeled somatostatin analogs provides excellent sensitivity and specificity for diagnosing and staging neuroendocrine tumors (NETs). Metabolic imaging with PET with fludeoxyglucose ¹⁸F/computed tomography (CT) complements the molecular imaging with ⁶⁸Ga-SSTR PET/CT toward a personalized therapy in NET patients. The documented response rate of PRRT in NET summing up complete response, partial response, minor response, and stable disease is 70% to 80%.