Page 5 - The Contemporary Role of Conventional Imaging for Staging, Re-staging, and Monitoring Prostate Cancer: Impact on Management

Advances in molecular imaging techniques with
Restaging Upon PSA Recurrence
After Loco-Regional Therapies
outine PSA measurement following local definitive
Rtherapy is an effective tool for identifying men
with disease recurrence. Determining the extent of
recurrence, localized versus metastatic, is critical when
planning further management. Salvage treatment
may alter the patient’s quality of life and expose them
to high morbidity, sometimes without altering the
overall course of disease. Imaging should help to better
select patients for salvage treatment and avoid futile
treatment.
Imaging Modalities in the Setting of
Biochemical Recurrence
Ruling-out metastatic disease
pon biochemical recurrence (BCR) after local
Utreatment, cancer metastases can be located within
the prostate after radiation therapy, in the prostate
fossa after radical prostatectomy (RP), in regional
(N1) and/or non-regional lymph nodes, or as distant
deposits mainly in the bone (M1). Unfortunately,
the currently available imaging techniques have
limitations in this setting. Minimizing overtreatment
may improve quality of life for patients considering
the toxicities associated with salvage therapies. Studies
have shown that patients who underwent salvage
radical prostatectomy with lymph node dissection
after radiotherapy (RT) had 16-21% lymph node
positivity. 14,15
Ruling-in local relapse
Multiparametric MRI (mpMRI) of the pelvis is the most
efficient imaging modality to diagnose local recurrence
after radical prostatectomy or radiotherapy. In a cohort
of 473 patients undergoing mpMRI prior to salvage RT
after RP at a PSA of 0.2 to 0.5 ng/mL, approximately
50% of patients had an identifiable lesion. The location
of lesions were as follows: 26% vesicourethral, 28%
seminal vesical bed/prostatic fossa, 7% lymph nodes
and 1% in the bone. In this study, mpMRI was useful
in the early salvage RT setting, improving the c-index
of the original Stephenson nomogram from 0.71 to
0.77 for PSA recurrence, and 0.66 to 0.77 for metastasis
(improved accuracy). A negative pelvic mpMRI in
the context of postoperative rising PSA indicates an
increased risk of a “distant” source of that PSA. 16
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the use of novel tracers such as PSMA binders and
fluciclovine will provide new options to identify
patients with distant metastases after biochemical
recurrence following local treatments. In a meta-
analysis of 8 studies, PSMA PET detected sites of
recurrence in 50% of patients with restaging PSA levels
of 0.20-0.49 ng/mL; and 53% with restaging levels
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of 0.50-0.99 ng/mL. Because the FDA has already
approved 11C-choline and 18F-fluciclovine for patients
with recurrent disease after RP, it is expected that these
tracers (including PSMA binders) will probably be
recommended based on their superior performance
compared to conventional techniques. However,
limited accessibility outside of clinical trials currently
prevents their integration into Canada practices at this
time.
Guidance for Imaging Use for Re-Staging
number of uro-oncology groups have made
A recommendations regarding imaging use in men
with biochemical recurrence (Table 3). Guidance is
provided based on prior disease state and previous
therapy. The PSA parameters defining recurrence vary,
including minimum PSA levels, magnitude of increase,
or PSA doubling time (PSADT) thresholds. In general,
current guidelines recommend bone imaging, and
abdo-pelvic CT or MRI in men who are experiencing
biochemical recurrence after previous definitive local
therapy and when the patient is a candidate for local
salvage therapy.
If the patient is under androgen deprivation therapy
and fulfills the definition of CRPC, chest assessment
by X-Ray or CT is added. It is worth noting that
conventional imaging positivity is much higher in
CRPC patients than at initial staging for the same PSA
levels. For instance, Moreira et al reported a bone scan
positivity in a fifth of patients with PSA levels below
15. Therefore, in CRPC patients, early imaging when
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PSA is between 2 and 10 ng/mL is recommended.