Clinical utility of indium 111-capromab pendetide immunoscintigraphy in the detection of early, recurrent prostate carcinoma after radical prostatectomy

Salvage radiotherapy in the treatment of prostate cancer

For patients undergoing radical prostatectomy for prostate adenocarcinoma, the most common cause of failure is an asymptomatic increase in levels of prostate-specific antigen (PSA). Salvage radiotherapy (RT) to the prostate bed has been used when there is no clinical evidence of metastatic disease. However, this is still not widely accepted because there is currently no consensus on the optimal management of an isolated PSA failure. Salvage RT given in a select group of patients is effective, with a 70% to 80% biochemical response rate and a long-term biochemical control rate as high as 35% to 40%. These data indicate that RT offers a substantial risk of curative salvage of patients who fail radical prostatectomy. Although there is interest in studying investigational modalities (eg, vaccine therapy) among patients with asymptomatic, PSA-detected recurrences after surgery, caution must be applied, and treatment modalities with known curative potential (ie, RT) should be used before noncurative techniques are attempted. This article outlines the rationale, results, and toxicity of salvage RT for an asymptomatic increase in PSA levels, with emphasis on identifying patients with favorable prognostic factors with higher rates of long-term biochemical control with local treatment.

Prostate cancer: radical prostatectomy

Today, more men than ever before are being followed after radical prostatectomy. Prognosis and follow-up should be based on the pathologic specimen. Measurable prostate-specific antigen (PSA) after surgery defines failure, with time to detectable PSA and rate of PSA rise being useful prognostic factors. The natural history of untreated biochemical failure is protracted, a fact to be considered in discussions of adjuvant treatment. Early in disease recurrence, imaging studies to locate residual disease rarely are useful clinically. Both adjuvant and salvage radiation to the prostate bed have benefits and risks, but neither is superior in overall prostate cancer survival. The timing of hormone therapy remains largely empiric. The promise of effective cytotoxic chemotherapy still is greater than its actual benefits, although novel cytostatic agents are being developed. The future management of this disease will improve with better molecular definition of risk and therapeutic response.

Molecular imaging in prostate cancer

Prostate cancer (PCa) is the most common non-cutaneous malignancy in men. New ways to diagnose this cancer in its early stages are needed. Unique genetic and biochemical changes in the cell pave the way for tumors to grow and metastasize. Novel imaging approaches attempt to detect pathological processes in cancer cells at the molecular level. This has led to the establishment and development of the field of molecular imaging. Positron emission tomography (PET), magnetic resonance spectroscopic imaging (MRSI), magnetic resonance imaging (MRI), and radiolabeled antibodies are a few of the modalities that can detect abnormal tumor metabolic processes in the clinical setting. Other imaging techniques are still in their early phase of development but hold promise for the future, including bioluminescence imaging (BLI), measurement of tumor oxygenation, and measurement of uptake of iodine by tumors. These techniques are non-invasive and can spare the patient undue morbidity, while potentially providing early diagnosis, accurate follow-up and, finally, valuable prognostic information.

Variables in predicting survival based on treating "PSA-only" relapse

Prostate cancer recurrence (after prior local treatment) that is detectable only by a rise in serum prostate specific antigen (PSA) level is a very common problem facing clinicians. Given that the majority of contemporary era men with PSA-only or biochemical recurrence are relatively young and otherwise healthy, treatment requires approaches that both improve clinical outcomes and preserve quality of life. Treatment is in one of two broad categories, additional local therapies, termed "salvage" local therapy and systemic therapies. For radical prostatectomy patients, salvage external beam radiotherapy to the prostate bed is commonly employed, being reserved for early biochemical recurrence in men with low risk at distant metastases. For primary radiation patients, salvage radical prostatectomy or cryotherapy can similarly be used for those men felt not to harbor distant metastases. Systemic therapy generally involves hormonal therapy. Traditional hormonal therapy (orchiectomy, luteinizing hormone-releasing hormone agonists, or maximum androgen blockade) is the current mainstay of systemic treatment for biochemical recurrence, although nontraditional approaches, such as antiandrogen monotherapy, are increasingly being used. Variables in predicting survival based on treating PSA relapse is problematic. The condition of biochemical failure has only been recognized in the last decade and few "PSA-era" patients with biochemical recurrence have actually died of disease. Hence, the validation of prediction variables in this setting is just emerging. Early work would suggest that timing of recurrence, Gleason grade, and PSA velocity or doubling time during relapse are important prognostic factors. New data on PSA doubling time will be presented.

Indium-111-capromab pendetide radioimmunoscintigraphy and prognosis for durable biochemical response to salvage radiation therapy in men after failed prostatectomy

PURPOSE

We evaluated the prognostic significance of indium-111 (111In)-capromab pendetide imaging for patients with prostate cancer who underwent salvage radiotherapy (RT) for recurrent disease after prostatectomy.

PATIENTS AND METHODS

Records were reviewed for all men who underwent 111In-capromab pendetide imaging at a single institution from February 1997 through December 1999. We identified 30 eligible men who were radiographically negative for metastatic disease, who had increasing serum prostate-specific antigen (PSA) after primary radical prostatectomy, and who received salvage RT. Clinical interpretations of indium monoclonal antibody (In-mab) scan results were compared with postsalvage RT PSA response.

RESULTS

Using an American Society of Therapeutic Radiation and Oncology definition of PSA failure, in men with a positive scan in at least one location (n = 14), the cumulative 2-year PSA control after salvage RT was 0.38 +/- 0.13 (+/- SE) compared with 0.31 +/- 0.13 for men with a normal antibody scan in and outside the prostate fossa (n = 15; proportional hazard ratio [PHR] = 1.32; 95% confidence interval [CI], 0.52 to 3.36). For men with a positive antibody scan limited to the prostate fossa (n = 9), PSA control at 2 years was 0.13 +/- 0.12 (PHR 1.77; 95% CI, 0.65 to 4.85). The 2-year probability of PSA control after salvage RT for men with positive scan results outside the prostate bed irrespective of In-mab findings in the prostate fossa (n = 5) was 0.60 +/- 0.22 (PHR 0.81; 95% CI, 0.17 to 3.78).

CONCLUSION

In contrast to previous reports, for patients with postprostatectomy biochemical relapse who received salvage RT, presalvage RT In-mab scan findings outside the prostate fossa were not predictive of biochemical control after RT.

Controversies in the systemic management of patients with evidence of biochemical failure following radical prostatectomy

The management of patients with evidence of a detectable prostate-specific antigen (PSA) following prostatectomy is an increasingly common and difficult issue for patients and clinicians alike. In the setting in which biochemical failure is believed representative of early systemic failure, therapeutic options primarily involve the use of hormonal therapy. Extrapolating results of early vs. delayed hormonal therapy from studies of patients with more advanced prostate cancer is problematic. Antiandrogen monotherapy and intermittent androgen deprivation are increasingly popular approaches, although their ultimate utility remains unproven. This patient subset is an optimal one in which to conduct clinical trials to both define the role of hormonal therapy and to investigate novel, non-hormonal approaches. The most appropriate therapeutic intervention for patients with evidence of biochemical failure following radical prostatectomy remains undefined.