Comparison of sequential planar 177Lu-DOTA-TATE dosimetry scans with 68Ga-DOTA-TATE PET/CT images in patients with metastasized neuroendocrine tumours undergoing peptide receptor radionuclide therapy

    loading  Checking for direct PDF access through Ovid

Abstract

Purpose

The aim of the study was to compare sequential 177Lu-DOTA-TATE planar scans (177Lu-DOTA-TATE) in patients with metastasized neuroendocrine tumours (NET) acquired during peptide receptor radionuclide therapy (PRRT) for dosimetry purposes with the pre-therapeutic 68Ga-DOTA-TATE positron emission tomography (PET)/CT (68Ga-DOTA-TATE) maximum intensity projection (MIP) images obtained in the same patients concerning the sensitivity of the different methods.

Methods

A total of 44 patients (59 ± 11 years old) with biopsy-proven NET underwent 68Ga-DOTA-TATE and 177Lu-DOTA-TATE imaging within 7.9 ± 7.5 days between the two examinations. 177Lu-DOTA-TATE planar images were acquired at 0.5, 2, 24, 48 and 72 h post-injection; lesions were given a score from 0 to 4 depending on the uptake of the radiopharmaceutical (0 being lowest and 4 highest). The number of tumour lesions which were identified on 177Lu-DOTA-TATE scans (in relation to the acquisition time after injection of the therapeutic dose as well as with regard to the body region) was compared to those detected on 68Ga-DOTA-TATE studies obtained before PRRT.

Results

A total of 318 lesions were detected; 280 (88%) lesions were concordant. Among the discordant lesions, 29 were 68Ga-DOTA-TATE positive and 177Lu-DOTA-TATE negative, whereas 9 were 68Ga-DOTA-TATE negative and 177Lu-DOTA-TATE positive. The sensitivity, positive predictive value and accuracy for 177Lu-DOTA-TATE as compared to 68Ga-DOTA-TATE were 91, 97 and 88%, respectively. Significantly more lesions were seen on the delayed (72 h) 177Lu-DOTA-TATE images (91%) as compared to the immediate (30 min) images (68%). The highest concordance was observed for bone metastases (97%) and the lowest for head/neck lesions (75%). Concordant lesions (n = 77; mean size 3.8 cm) were significantly larger than discordant lesions (n = 38; mean size 1.6 cm) (p < 0.05). No such significance was found for differences in maximum standardized uptake value (SUVmax). However, concordant liver lesions with a score from 1 to 3 in the 72-h 177Lu-DOTA-TATE scan had a lower SUVmax (n = 23; mean 10.9) than those metastases with a score of 4 (n = 97; mean SUVmax 18) (p < 0.05).

Conclusion

Although 177Lu-DOTA-TATE planar dosimetry scans exhibited a very good sensitivity for the detection of metastases, they failed to pick up 9% of lesions seen on the 68Ga-DOTA-TATE PET/CT. Three-dimensional dosimetry using single photon emission computed tomography/CT could be applied to investigate this issue further. Delayed (72 h) images are most suitable for drawing regions of interest for dosimetric calculations.

Related Topics

    loading  Loading Related Articles