PET imaging using the radiotracer ⁶⁸GA-PMSA shows good promise for aiding early detection of lymph-node metastases in patients with recurrent prostate cancer, as researchers in Germany and the U.K. have shown the modality more accurate than morphological imaging—and likely capable of guiding salvage lymphadenectomy.

The study posted June 3 in the Journal of Nuclear Medicine.

Lead author Isabel Rauscher, MD, of Technical University of Munich and colleagues retrospectively analyzed the cases of 48 patients (median age, 71 years) who had recurring prostate cancer and underwent PET/CT or PET/MR with ⁶⁸Ga-PSMA HBED-CC, along with histological review.

They found that lymph-node metastases were caught histologically in 68 of 179 resected anatomical lymph-node fields (38.0 percent).

Specificity of PET and morphological imaging was closely comparable, 97.3 percent and 99.1 percent, respectively.

But the PET technique won handily on sensitivity, correctly detecting lymph-node metastases in 53 of 68 histopathologically proven metastatic lymph-node fields (77.9 percent)—while morphological imaging was positive in only 18 of 67 (26.9 percent).

The authors acknowledge a number of limitations to the study, including a strong selection bias. This may have resulted in the missing of imaging-negative but histology-positive templates and, thus, in the underestimation of the sensitivity of the examined imaging technique.

In their discussion, the authors state that their study shows ⁶⁸Ga-PSMA HBED-CC PET imaging to be a promising method for early detection of lymph-node metastases in patients with biochemical recurrence of prostate cancer after primary treatment.

Its efficacy even at low PSA levels and in small lymph nodes is higher than morphological imaging, they add.

“[I]t could be a promising tool,” Rauscher et al. conclude, “not only for detecting lymph-node metastases but also for guiding salvage therapy.”