What is the optimal patient selection for combined androgen ablative and radiation therapy? The role of combined modality staging

Innovative Diagnostik in der Früherkennung und beim Staging des lokalisierten Prostatakarzinoms

Prostate cancer is the most common malignancy in males. Men aged 50 years and older are recommended to undergo an annual digital rectal examination (DRE) and determination of prostate-specific antigen (PSA) in serum for early detection. Fortunately, disease-specific mortality continues to decline as a result of advances in screening, staging, and patient awareness. However, about 30% of men with a clinically organ-confined disease show evidence of extracapsular extension or seminal vesicle invasion on pathological analysis. Consequently, there is a need for more accurate diagnostic tools for planning tailored treatment. A variety of modern imaging techniques has been implemented in an attempt to obtain more precise staging, thereby allowing for more detailed counseling, and instituting optimum therapy. This review highlights developments in prostate cancer imaging that may improve staging and treatment planning for prostate cancer patients.

Update on magnetic resonance imaging, ProstaScint, and novel imaging in prostate cancer

PURPOSE OF REVIEW

Despite marked stage migration, approximately a third of patients with clinically organ-confined prostate cancer will have extracapsular extension on pathological analysis. To improve outcomes further, alternative modalities of determining extraprostatic disease must be investigated beyond the current clinical parameters of digital rectal examination, prostate-specific antigen, and Gleason score. In addition, discerning the location of tumor in patients with biochemical recurrence directly affects treatment choice. This review highlights developments in prostate cancer imaging that may improve staging and treatment planning for prostate cancer patients.

RECENT FINDINGS

Magnetic resonance imaging is most useful in the initial evaluation of men with prostate cancer. Its high specificity for the diagnosis of extracapsular extension is tempered by its low sensitivity. Positron emission tomography is used to assess regional and distant metastasis in many malignancies. Investigation into the most appropriate radiotracer for prostate cancer is paramount in any future applicability. The unique role of ProstaScint has been in evaluating patients with biochemical failure and in trying to discern metastasis before definitive therapy. The addition of spectroscopic imaging and nanoparticle infusion may lead to further improvements. Therefore, in differentiating local versus distant recurrence, appropriate interventions with radiotherapy or hormonal manipulation may be instituted.

SUMMARY

Magnetic resonance imaging, ProstaScint, and to some extent positron emission tomography are all relevant imaging modalities for the evaluation of patients with prostate cancer. Current technological advances in each arena are improving the accuracy of diagnosis. Despite their specific limitations, use in the proper clinical setting may provide essential information to improve management decisions and disease outcomes.

Incidence rate and management of prostate carcinoma

The age-standardised incidence of prostate cancer varies more than one hundredfold between the areas with the highest and lowest incidences in the world. In certain areas, in particular the Western countries, the incidence has increased rapidly over the last 20 years. There are several environmental and genetic factors which partly explain these variations, although the incidence probably depends most of all on the extent to which small latent tumours are detected. As the clinical significance of small tumours is uncertain, the value of early diagnosis and early aggressive treatment is controversial. Randomised trials addressing this question have been initiated and will hopefully provide more evidence-based data in a decade from now. Small localised tumours are managed by radical surgery or radiation therapy. In elderly men or men unfit for operation or radiation therapy surveillance is often preferred. For advanced or metastatic prostate cancers androgen deprivation has been the mainstay of treatment since the early 1940s. Recently, several new treatment strategies have evolved but have not yet been introduced into clinical routine.

Imaging prostate cancer

In the detection of prostate cancer, the most important role of imaging is ultrasound-guided prostatic biopsy. In the staging evaluation of prostate cancer, each presently used modality--transrectal US (TRUS), MR imaging, CT, nuclear medicine, and positron emission tomography--has advantages and disadvantages. Evidence-based guidelines on the use of CT and nuclear medicine bone scan, in assessing the risk of distant spread of prostate cancer, are available. There is no consensus and there are no guidelines, however, for the use of imaging in the evaluation of prostate cancer local tumor extent. Results on the value of TRUS vary widely, and prospective multicenter studies suggest that TRUS is no better than digital rectal examination in predicting extracapsular extension. MR imaging offers the most promise for local staging of prostate cancer, but it must resolve problems of reproducible image quality and interobserver variability, and it should prove its efficacy in multicenter trials before it can be recommended for general clinical use. The introduction of MR spectroscopic imaging further expands the value of MR imaging, offering anatomic and metabolic evaluation of prostate cancer.

The role of androgen deprivation in the definitive management of clinically localized prostate cancer treated with radiation therapy

PURPOSE

Multiple studies exploring the use of androgen deprivation given in combination with radiotherapy (RT) for localized prostate cancer have reported significant improvements in the rates of local, regional, and biochemical control (BC). The impact of this therapeutic strategy on overall and cancer specific survival (CSS) has not been established, however. We performed a MEDLINE search of all available studies on this topic to determine if any conclusions could be reached on the efficacy of this treatment approach and the patients most suitable for its application.

MATERIALS AND METHODS

A MEDLINE search was conducted to obtain all articles in the English language on the use of androgen deprivation in combination with RT for the treatment of localized prostate cancer. The medical subject headings (MeSH) used to search the MEDLINE database included: a) prostatic neoplasms; b) prostatic neoplasms/radiotherapy; c) prostatic neoplasms/androgen deprivation; d) hormone therapy; e) English; and f) 1980 to 1998.

RESULTS

A total of 14 retrospective studies were identified that compared some form of androgen deprivation given in combination with RT. Most studies showed significant improvements in various measures of local/regional control and disease-free survival (DFS). Three of four studies that analyzed BC rates showed significant improvements in this endpoint but conflicting results were obtained for overall survival (OS). No study showed an improvement in CSS. Six prospective randomized trials were identified that directly compared RT with or without androgen deprivation. Again, all six studies showed improvements in some measure of local/regional control or DFS but only two studies showed an improvement in OS. One study reported a statistically significant improvement in CSS and another study showed an improvement in the rate of negative biopsies with combined treatment.

CONCLUSIONS

When all available literature on androgen withdrawal given in combination with RT for the definitive treatment of localized prostate cancer was reviewed, no definite conclusions could be reached on the impact of this treatment approach on OS and CSS. However, local/regional control, DFS, and BC were almost uniformly improved with the use of androgen withdrawal suggesting that these impressive early results may translate into improved cure rates. Data from recently initiated and completed randomized trials will be needed, however, to define the impact of this approach on cancer specific mortality and the patients most suitable for it's use.