[68Ga]Ga-tilmanocept PET/CT lymphoscintigraphy for sentinel lymph node detection in early-stage oral cavity carcinoma
European Journal of Nuclear Medicine and Molecular Imaging
sentinel lymph node (SLN) procedure is routinely performed for nodal
staging in several malignancies, including early-stage oral cancer. In
oral cancer, the SLN imaging procedure usually consists of peritumoral
injections with a [99mTc]Tc-labelled radiotracer followed by dynamic and planar lymphoscintigraphy and SPECT/CT [1, 2].
A frequently discussed limitation of this procedure in oral cancer
arises in situations where SLNs are located in close vicinity of the
radiotracer injection site. Due to the limited resolution of
conventional scintigraphy and SPECT/CT, injection site activity can hide
adjacent SLNs and hamper discrimination between injection site and SLNs
(shine-through phenomenon), potentially resulting in false-negative SLN
procedure outcomes [3, 4].
PET/CT lymphoscintigraphy may offer a solution, as it provides superior
spatial resolution compared with conventional scintigraphy and SPECT/CT
[4, 5]. Here, we present the first within-patient comparison between PET/CT lymphoscintigraphy using [68Ga]Ga-tilmanocept (10 MBq; 15 min post-injection) and SPECT/CT with [99mTc]Tc-tilmanocept (74 MBq; 2 h post-injection)
in a cT1N0 tongue cancer patient, both acquired on the day before
surgery. Maximum intensity projection images (MIP) of PET (D)
demonstrate its superior resolution compared with SPECT (H).
Furthermore, two separate lymph vessels can be identified on PET/CT
lymphoscintigraphy (D), which are not visualized on SPECT/CT (H). Also
note that the activity in a SLN in level Ib on the right site is better
visible on axial (A), sagittal (B), and coronal (C) PET/CT
lymphoscintigraphic images compared with corresponding SPECT/CT
reconstructions (E,F,G). Surgically, five SLNs were localized and
harvested (level Ib, 3x level IIa and level III), using a conventional
gammaprobe. Histopathological assessment showed metastasis in one SLN
located in level IIa. Complementary neck dissection of level I-IV showed
no additional lymphatic metastasis (Figure 1).