Metastatic Prostate Cancer

Richard Tuli and Naomi B. Haas

Background

What % of newly diagnosed prostate cancer pts present with advanced Dz?

~10%–20% of pts present with advanced Dz (local and/or metastatic).

Has the incidence of metastatic prostate cancer changed with the introduction of the PSA?

Yes. The introduction of the PSA into general practice in the early 1990s appears to have decreased the incidence of metastatic prostate cancer; a SEER database analysis showed a 52% decrease in the incidence of metastatic prostate cancer Dx from 1990–1994. (Stephenson RA et al., World J Urol 1997)

How are most cases of metastatic prostate cancer identified?

The majority of metastatic prostate cancer cases are identified by an isolated biochemical (PSA-only) recurrence; a much smaller % of pts are detected by signs/Sx of metastatic Dz.

In what % of pts with advanced prostate cancer are serum PSA values abnl?

~95% of pts with metastatic Dz also have an abnl PSA, which is the most sensitive and specific marker for recurrence.

What is the anticipated natural Hx of prostate cancer after biochemical failure following local therapy?

Following local therapy and subsequent biochemical failure, the median time to development of mets is 8 yrs, and the median time to death is 13 yrs. (Pound CR et al., JAMA 1999)

What are common predictors of a poorer prognosis after biochemical failure following local therapy?

Poor prognostic factors after biochemical failure following local therapy:

Prostate-specific antigen doubling time (PSA-DT) ≤3 mos
Gleason score ≥8
T3b Dz
LN involvement

(D’Amico AV et al., J Urol 2004; Katz MS et al., J Clin Oncol 2004; Stephenson RA et al., JAMA 2004; Zhou P et al., J Clin Oncol 2005)

What are the common sites of mets for prostate cancer?

The most common sites are the bones of the axial skeleton. These lesions are usually osteoblastic but can be lytic as well.

Workup/Staging

What imaging modalities are commonly used for a metastatic workup?

Imaging modalities most commonly used for workup of suspected metastatic prostate cancer include whole body bone scan (technetium-99m bone scintigraphy), CT abdomen/pelvis with contrast, and chest imaging with CXR or CT. X-ray radiographs or MRI should be used if bone scan findings are equivocal.

How accurate are bone scans and CT scans at predicting mets following biochemical failure?

Both bone scan and CT scan are rarely positive until PSA values of ≥30 ng/mL are reached in the absence of prior androgen suppression (AS). These scans are also more likely to be positive with higher PSA velocities. (Cher ML et al., J Urol 1998; Kane CJ et al., Urology 2003)

Are other imaging modalities useful or being investigated to aid in Dx?

Yes. Other imaging modalities under investigation include MRI of the axial skeleton, MRI with endorectal coil, and ProstaScint.

How sensitive and specific is MRI at detecting metastatic Dz?

The role of MRI in this setting has not been thoroughly evaluated. A prospective study of 66 pts with high-risk prostate cancer found the sensitivity/specificity of axial MRI to be 100%/88% compared to bone scan–X-ray sensitivity/specificity of 63%/64% in detecting mets. (Lecouvet FE et al., J Clin Oncol 2007)

What is ProstaScint?

ProstaScint is indium-111 capromab pendetide, which is a radiolabeled monoclonal antibody used to target prostate-specific membrane antigen. It is FDA approved for detecting localized Dz recurrence after radical prostatectomy but not metastatic Dz.

Is ProstaScint useful in diagnosing localized and/or metastatic prostate cancer?

The data are mixed regarding the utility of ProstaScint. Most studies have shown it to have a poor PPV for detecting extraprostatic Dz (Nagda SN et al., Int J Radiat Oncol Biol Phys 2007; Thomas CT et al., J Clin Oncol 2003). B/c its interpretation is confounded by reader experience and the timing of imaging, it is not commonly included as part of the workup for localized or metastatic recurrence.

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