Axumin-based PET/CT scans and detection of recurrent prostate cancer

A new report from a relatively small, single-institution study has provided additional information about the utility of [18F]fluciclovine (Axumin) PET/CT scans in the detection of recurrent prostate cancer after definitive first-line treatment.

The paper by Armstrong et al. from the Huntsman Cancer Institute in Salt Lake City looked at the rates of success in detecting recurrent prostate cancer at specific PSA levels through the use of [18F]fluciclovine PET/CT scans (see also this report in Renal & Urology News). The basic finding was that:

The probability of having positive imaging findings and increasing numbers of suspicious lesions rises with increasing PSA. Utilization of a lower PSA threshold of 0.5 [ng/ml] may allow earlier intervention with salvage therapies in biochemical recurrence. However, using a threshold below 1 [ng/ml]carries a higher risk of negative scans. Employing a higher PSA threshold of 1 to 2 [ng/ml] carries greater sensitivity and specificity and may maximize identifying individuals with early [biochemical recurrence] who may benefit from early intervention, while minimizing negative scans.

The study evaluated data from 115 men who were given [18F]fluciclovine PET/CT scans.

Among these 115 men:

  • 25 men (21.7 percent) had no concerning lesions.
  • 32 men (27.8 percent) had a single lesion.
  • 45 men (39.1 percent) had 2 to 5 lesions
  • 13 men (11.3%) had > 5 suspicious lesions.

When specific PSA thresholds were considered, lesions were detected in

  • 12/22 men (55.5 percent) with a PSA level of < 0.5 ng/ml
  • 24/34 men (70.6 percent) with a PSA level of 0.5 to 2.0 ng/ml
  • 54/59 men with a PSA level of > 2.0 ng/ml

These data seem to suggest that a PSA level of 1.5 ng/ml or thereabouts might be a reasonable threshold at which an [18F]fluciclovine PET/CT scan could be expected to identify a recurrent prostate cancer lesion after first-line therapy with a high degree of accuracy.

There is no information provided about the rates of false positive or false negative scan results in this paper. However, the report in Renal & Urology News does note that, again out of the 115 men given an [18F]fluciclovine PET/CT scan:

79 had undergone a prior computed tomography scan and 94 had undergone bone scans, with negative findings in the majority of them.

Clearly this type of scan can produce more and earlier actionable clinical data than the traditional types of scan for detection of disease recurrence. We are still waiting to see whether the gallium-67 PSMA-based scans can offer even more accurate data.


2 Responses

  1. The point isn’t to find most positive scans. The point is to detect recurrence at very low PSA values at recurrence after primary treatment.

  2. Dear Finn:

    With respect, surely the objective is to identify recurrences as early as possible with a high degree of accuracy, regardless of the number of positive lesions in an individual patient. False negative and false positive scan results are therefore a potential problem.

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