Adenocarcinoma of the Prostate: Biopsy to Whole Mount

Prostatome: a combined anatomical and disease based MRI atlas of the prostate

PURPOSE

In this work, the authors introduce a novel framework, the anatomically constrained registration (AnCoR) scheme and apply it to create a fused anatomic-disease atlas of the prostate which the authors refer to as the prostatome. The prostatome combines a MRI based anatomic and a histology based disease atlas. Statistical imaging atlases allow for the integration of information across multiple scales and imaging modalities into a single canonical representation, in turn enabling a fused anatomical-disease representation which may facilitate the characterization of disease appearance relative to anatomic structures. While statistical atlases have been extensively developed and studied for the brain, approaches that have attempted to combine pathology and imaging data for study of prostate pathology are not extant. This works seeks to address this gap.

METHODS

The AnCoR framework optimizes a scoring function composed of two surface (prostate and central gland) misalignment measures and one intensity-based similarity term. This ensures the correct mapping of anatomic regions into the atlas, even when regional MRI intensities are inconsistent or highly variable between subjects. The framework allows for creation of an anatomic imaging and a disease atlas, while enabling their fusion into the anatomic imaging-disease atlas. The atlas presented here was constructed using 83 subjects with biopsy confirmed cancer who had pre-operative MRI (collected at two institutions) followed by radical prostatectomy. The imaging atlas results from mapping thein vivo MRI into the canonical space, while the anatomic regions serve as domain constraints. Elastic co-registration MRI and corresponding ex vivo histology provides "ground truth" mapping of cancer extent on in vivo imaging for 23 subjects.

RESULTS

AnCoR was evaluated relative to alternative construction strategies that use either MRI intensities or the prostate surface alone for registration. The AnCoR framework yielded a central gland Dice similarity coefficient (DSC) of 90%, and prostate DSC of 88%, while the misalignment of the urethra and verumontanum was found to be 3.45 mm, and 4.73 mm, respectively, which were measured to be significantly smaller compared to the alternative strategies. As might have been anticipated from our limited cohort of biopsy confirmed cancers, the disease atlas showed that most of the tumor extent was limited to the peripheral zone. Moreover, central gland tumors were typically larger in size, possibly because they are only discernible at a much later stage.

CONCLUSIONS

The authors presented the AnCoR framework to explicitly model anatomic constraints for the construction of a fused anatomic imaging-disease atlas. The framework was applied to constructing a preliminary version of an anatomic-disease atlas of the prostate, the prostatome. The prostatome could facilitate the quantitative characterization of gland morphology and imaging features of prostate cancer. These techniques, may be applied on a large sample size data set to create a fully developed prostatome that could serve as a spatial prior for targeted biopsies by urologists. Additionally, the AnCoR framework could allow for incorporation of complementary imaging and molecular data, thereby enabling their careful correlation for population based radio-omics studies.

Oncological outcomes in patients potentially eligible for active surveillance who underwent radical prostatectomy

OBJECTIVE

To determine whether there are differences in the oncological outcomes after radical prostatectomy (adverse pathology and biochemical recurrence) based on clinical selection criteria used in two active surveillance (AS) protocols.

MATERIAL AND METHODS

442 patients diagnosed with localized prostate cancer (CP) underwent radical prostatectomy at our institution between August 2003 and December 2009. We selected patients with low-risk CP, which could have been included in an AS program. Patients were divided into two groups: group i, those who met the most strict surveillance criteria described by Epstein (PSAD<.15; T1/T2a;<2 positive core, Gleason≤6,<50% involvement of the core) and group ii, those meeting the more open criteria described by Klotz (PSA≤10 or<15 at age 70, Gleason≤6 or<7 [3+4] in over 70 years). We compared both groups to determine differences in pathological stage, positive surgical margins and biochemical recurrence after radical prostatectomy.

RESULTS

Of the 442 patients 48% (213 patients) had low-risk PC, and become potential candidates for an AS program. Of the patients operated on 17% (76 patients) met the criteria for AS as of Epstein's and 48% (213 patients) according to Klotz. Comparing patients in both groups there were no statistically significant differences in the presence of pT3 (7.9% vs 10.8%) P=.55, positive margins (22.4% vs. 28.3%) P=.41, nor in biochemical recurrence at 3 years (5.3% vs 5.6%) P=.86.

CONCLUSIONS

In our series of patients theoretically candidates for inclusion in a program of active surveillance, we found no differences in the percentage of patients with pathological stage pT3, positive margins and biochemical recurrence according to clinical inclusion criteria currently used.

[Comparative study of surgical efficacy in open versus laparoscopic prostatectomy: virtual prostate reconstruction and periprostatic tissue quantification]

INTRODUCTION

The introduction of laparoscopic surgery as a procedure to perform radical prostatectomy needs an objective method to evaluate the suitability of this new surgical procedure. The traditional parameters, including the incidence of positive surgical margins, are useful, but not sufficiently objective. Different authors publish different criteria to define positive surgical margins. In addition, there are some technical problems that may ocur during the processing of the surgical specimen by the pathologist, which can give false positive margins. We have used a computer modeling software in connection to scanned images from serial sections of the whole gland, to determine the percentage of extracapsular tissue that surrounds the prostate glands, removed by both, open retropubic and laparoscopic procedures. This percentage can be considered as an objective parameter which can potentially predict the benefit of surgery in predicting cancer control, as well as the clinical success of the surgical procedure. The correlation with the clinical results in the long term--survival and bioche--mical recurrence--will be useful to validate as a last resort the clinical utility of this parameter in the coming years.

MATERIALS AND METHODS

We had a total of 32 prostate surgical specimens, 15 from patients who underwent open retropubic prostatectomy and 17 from patients who underwent laparoscopic prostatectomy for this study. After surgery and 24 hours formol fixation, serial cuts were taken at 5 mm thickness intervals to make complete sections ("whole mount") of the prostate. An expert uropathologist reviewed all the surgical sections and drew in each tissue cut the prostatic capsule and tumor contours. The serial images of the whole gland and surrounding prostate tissue were scanned to produce digital images, using a computer software to create a file with capsule information and a file with information on the surrounding fibroadipose tissue (extraprostatic). These procedures allowed the reconstruction of a three dimensional tissue model of the prostatic capsule and the surrounding extraprostatic tissue. Two separate point clouds files were generated, with the purpose of representing capsule and extraprostatic tissue models and software algorithms were used to generate differences in point clouds and thereby quantifying the extracapsular tissue coverage dimension, a parameter that we considered indicative of the adequeacy and feasibility of the surgical procedure.

RESULTS

The global percentage of prostate gland surface covered by extracapsular fibroadipose tissue was statistically higher in specimens removed by a laparoscopic procedure when compared to the open retropubic procedure. When a segmental analysis of the gland percentage of coverage was evaluated, it was found this percentage was significantly higher in the apical and inferolateral segments of those glands removed without nerves preservation and in the apical segments of those glands removed with nerves preservation for the laparoscopic prostatectomy.

CONCLUSIONS

In our series. laparoscopic prostatectomy contributed superior extracapsular tissue coverage than retropubic prostatectomy. Similarly laparoscopic prostatectomy produced a superior tissue coverage in inferolateral and apical regions on those glands removed without nerve preservation and in the apical regions of those glands removed with nerve preservation. Therefore, the surgical suitability of this technique, when compared to the retropubic, seems to be higher

Per-Sextant Localization and Staging of Prostate Cancer: Correlation of Imaging Findings with Whole-Mount Step Section Histopathology

OBJECTIVE

The objective of our study was to determine the diagnostic accuracy and interobserver agreement of 1.5-T prostatic MRI for per-sextant tumor localization and staging of prostate cancer as compared with whole-mount step section histopathology.

MATERIALS AND METHODS

Combined endorectal-pelvic phased-array prostatic MRI scans obtained at 1.5 T of 106 patients with biopsy-proven prostate cancer who had undergone radical prostatectomy with whole-mount step section histopathology within 28 days of MRI were retrospectively analyzed by three independent abdominal radiologists (reviewers 1, 2, and 3). Sextants of the prostate (right and left base, middle, and apex) were evaluated for the presence of prostate cancer and extracapsular extension (ECE) using a 5-point confidence scale. Data were statistically analyzed using receiver operating characteristic (ROC) analysis. Interobserver variability was assessed by kappa statistics. For calculation of sensitivity and specificity, data from the 5-point confidence scale were dichotomized into negative (score of 1-3) or positive (score of 4 or 5) findings.

RESULTS

Forty-one patients had ECE (tumor stage T3), and 65 patients had organ-confined disease (stage T2). Of 636 prostatic sextants, 417 were positive for prostate cancer and 135 were positive for ECE at histopathology. For prostate cancer localization, ROC analysis yielded area under the ROC curve (AUC) values ranging from 0.776 +/- 0.023 (SD) to 0.832 +/- 0.027. For the detection of ECE, the AUC values ranged from 0.740 +/- 0.054 to 0.812 +/- 0.045. Interobserver agreement (kappa) ranged from 0.49 to 0.60 for prostate cancer localization and from 0.59 to 0.67 for the detection of ECE.

CONCLUSION

Using the sextant framework, independent observers reach similar accuracy with moderate to substantial agreement for the localization of prostate cancer and ECE by means of MRI of the prostate.

Optimized prostate biopsy via a statistical atlas of cancer spatial distribution

A methodology is presented for constructing a statistical atlas of spatial distribution of prostate cancer from a large patient cohort, and it is used for optimizing needle biopsy. An adaptive-focus deformable model is used for the spatial normalization and registration of 100 prostate histological samples, which were provided by the Center for Prostate Disease Research of the US Department of Defense, resulting in a statistical atlas of spatial distribution of prostate cancer. Based on this atlas, a statistical predictive model was developed to optimize the needle biopsy sites, by maximizing the probability of detecting cancer. Experimental results using cross-validation show that the proposed method can detect cancer with a 99% success rate using seven needles, in these samples.

Characteristics of prostate cancers detected at low PSA levels

BACKGROUND

When age-referenced PSA levels as recommended by Oesterling et al.1 were used as a biopsy criterion, only 25% of the cancers detected in a population based PSA Screening Project were organ-confined. This observation led to the decision to use low PSA levels as the sole indication for biopsy. Since 1995 age-referenced PSA levels of 1.25-3.25 ng/ml have been used in combination with a percentage free PSA cutoff of 18%. This PSA cutoff reduction led to a statistically significant migration to lower pathological stages with a decreased prostate cancer mortality in the years 1996-2001. However, concerns have been raised that screening with low PSA levels may detect clinically insignificant cancers.

MATERIALS AND METHODS

We evaluated prostate cancer patients with low PSA levels in terms of heterogeneity, clinical significance, multifocality, and tumor biology including ploidy and proliferation index.

RESULTS

Concerning heterogeneity the Gleason score of the needle biopsy failed to predict the Gleason score of the radical prostatectomy specimen in nearly 40% of prostate cancer patients; regarding multifocality 65% of patients with low PSA levels showed multifocal lesions and 36% exhibited tetraploid DNA distribution; more than 50% of tetraploid tumors were found in patients with tumor volumes of less than 0.5 cm(3). Ploidy correlated with the Ki-67 proliferation index, but not with tumor volume.

CONCLUSIONS

These results demonstrate that small prostate cancers with low PSA levels and low tumor volumes exhibit all features of prostate cancers with higher tumor volumes and show the characteristics of malignant cancers, i.e., multifocality, tetraploidy, and high proliferative activity.

Contemporary pathology of prostate cancer

In less than 20 years since the introduction of serum PSA and the spring-loaded 18-gauge prostatic biopsy needle, pathologists have adjusted to the limited tissue requirements of narrow needle specimens to apply criteria for diagnosis and grading of prostate cancer, borrowing from lessons learned from radical prostatectomies. Substantial gains have been made during this period in the understanding of precancerous lesions, mimics of malignancy, the criteria for minimal cancer, variants of cancer, and treatment-induced changes. The light microscopic findings remain the criterion standard for diagnosis against which all new techniques should be measured. Numerous findings have proven to be of value, including simple quantitation of histopathologic features, cancer volume, perineural invasion, and others.

Complete embedding and close step-sectioning of radical prostatectomy specimens both increase detection of extra-prostatic extension, and correlate with increased disease-free survival by stage of prostate cancer patients

The objectives of this work were to evaluate the efficacy of controlled close step-sectioned and whole-mounted radical prostatectomy specimen processing in prediction of clinical outcome as compared to the traditional processing techniques. Two-hundred and forty nine radical prostatectomy (RP) specimens were whole-mounted and close step-sectioned at caliper-measured 2.2-2.3 mm intervals. A group of 682 radical prostatectomy specimens were partially sampled as control. The RPs were performed during 1993-1999 with a mean follow-up of 29.3 months, pretreatment PSA of 0.1-40, and biopsy Gleason sums of 5-8. Disease-free survival based on biochemical or clinical recurrence and secondary intervention were computed using a Kaplan-Meier analysis. There were no significant differences in age at diagnosis, age at surgery, PSA at diagnosis, or biopsy Gleason between the two groups (P<0.05). Compared with the non-close step-sectioned group, the close step-sectioned group showed higher detection rates of extra-prostatic extension (215 (34.1%) vs, 128 (55.4%), P<0.01), and seminal vesicle invasion (50 (7.6%) vs 35 (14.7%), P<0.01). The close step-sectioned group correlated with greater 3-y disease-free survival in organ-confined (P<0.01) and specimen-confined (P<0.01) cases, over the non-uniform group. The close step-sectioned group showed significantly higher disease-free survival for cases with seminal vesicle invasion (P=0.046). No significant difference in disease-free survival was found for the positive margin group (P=0.39) between the close step-sectioned and non-uniform groups. The close step-sectioned technique correlates with increased disease-free survival rates for organ and specimen confined cases, possibly due to higher detection rates of extra-prostatic extension and seminal vesicle invasion. Close step-sectioning provides better assurance of organ-confined disease, resulting in enhanced prediction of outcome by pathological (TNM) stage.

Radioimmunoguided imaging of prostate cancer foci with histopathological correlation

PURPOSE

We have previously presented a technique that fuses ProstaScint and pelvic CT images for the purpose of designing brachytherapy that targets areas at high risk for treatment failure. We now correlate areas of increased intensity seen on ProstaScint-CT fusion images to biopsy results in a series of 7 patients to evaluate the accuracy of this technique in localizing intraprostatic disease.

METHODS AND MATERIALS

The 7 patients included in this study were evaluated between June 1998 and March 29, 1999 at Metrohealth Medical Center and University Hospitals of Cleveland in Cleveland, Ohio. ProstaScint and CT scans of each patient were obtained before transperineal biopsy and seed implantation. Each patient's prostate gland was biopsied at 12 separate sites determined independently of Prostascint-CT scan results.

RESULTS

When correlated with biopsy results, our method yielded an overall accuracy of 80%: with a sensitivity of 79%, a specificity of 80%, a positive predictive value of 68%, and a negative predictive value of 88%.

CONCLUSION

The image fusion of the pelvic CT scan and ProstaScint scan helped identify foci of adenocarcinoma within the prostate that correlated well with biopsy results. These data may be useful to escalate doses in regions containing tumor by either high-dose rate or low-dose rate brachytherapy, as well as by external beam techniques such as intensity modulated radiotherapy (IMRT).

MR imaging of the prostate and bladder

Magnetic resonance imaging has become an important imaging modality for the male pelvis. Its unparalleled ability to depict soft tissue structures and highlight pathology have made it the best method for determining the extent of many disease processes. This article reviews the use of MR to evaluate diseases of the prostate gland and bladder. In both, the major indication for imaging is the local staging of cancer, and MR is currently the best imaging modality. This article will discuss the critical clinical issues concerning prostate cancer and neoplasms of the bladder, and the contribution of MR imaging.

Evaluating radical prostatectomy specimens: therapeutic and prognostic importance

The pathologic staging of prostate cancer involves determination of the anatomic extent and burden of tumor based on the best available data. Proper examination of radical prostatectomy specimens is critical in determining cancer stage, stratifying patient need for adjuvant treatment, and prediction of patient outcome. Differences exist in methods of handling and sampling specimens, although publication of practice protocols in recent years has led to convergence of opinion. In this report, we evaluate the current aspects of pathologic staging of prostate cancer and assessment of prostatectomy specimens. Recent international agreement on pathologic staging of prostate cancer should allow valid comparisons of surgical treatment from different institutions. The vanishing cancer phenomenon is also briefly discussed.

Utility of preoperative serum prostate-specific antigen concentration and biopsy Gleason score in predicting risk of pelvic lymph node metastases in prostate cancer

OBJECTIVES

To determine the accuracy of the preoperative serum concentration of prostate-specific antigen (PSA) plus the Gleason pathology score of biopsy specimens in predicting the presence of disease in the pelvic lymph nodes in patients with prostate cancer.

METHODS

The medical records of all patients treated for prostate cancer at eight medical centers from January 1988 to June 1993 were reviewed. There were 932 patients with newly diagnosed prostate cancer for whom all relevant data were available who had undergone pelvic lymphadenectomy with (n = 912) or without (n = 20) radical prostatectomy. The rate of false-negative predictions of metastases based on combined preoperative biopsy Gleason score and serum PSA concentration was analyzed. A multivariate logistic regression analysis was performed to assess the value of preoperative serum PSA and biopsy Gleason scores individually and in combination in predicting pelvic lymph node metastases.

RESULTS

The false-negative rate of metastases was 0% for preoperative PSA concentrations < or = 6 ng/mL and biopsy Gleason scores < or = 5 (n = 142) and 1.0% for PSA concentrations < or = 10 ng/mL and Gleason scores < or = 6 (n = 388). The 95% upper confidence limit for the rate of false negativity at this PSA cut-off level was 2.0%. A combination of preoperative serum PSA levels and biopsy Gleason scores provided the best prediction for the false-negative rates.

CONCLUSIONS

For patients with newly diagnosed prostate cancer who have biopsy Gleason scores < or = 6 and preoperative PSA concentrations < or = 10 ng/mL (42% of our series), a staging pelvic lymphadenectomy appears to be unnecessary. The substantial cost associated with both cross-sectional imaging and staging lymphadenectomy may therefore be avoidable in this group of patients.

Selection of patients for laparoscopic pelvic lymphadenectomy prior to radical prostatectomy: a decision analysis

Indications for laparoscopic pelvic lymphadenectomy prior to radical prostatectomy have not been established. Criteria to predict lymph node metastases were derived from the preoperative evaluations of 164 prostate cancer patients undergoing pelvic lymphadenectomy. Decision analysis was used to determine which criteria would be optimal indicators for laparoscopic pelvic lymphadenectomy prior to intended radical prostatectomy. Besides a digital rectal examination suggesting uncontained tumor, which was the best indication for laparoscopic pelvic lymphadenectomy, the most useful criteria were sonographic tumor volume > or = 3 cc and prostate-specific antigen (PSA) > or = 20 ng/mL. If either parameter was met, the sensitivity for identifying patients with pelvic lymph node metastases was 88 percent and the positive predictive value was 42 percent. When both were met, the sensitivity fell to 47 percent but the positive predictive value increased to 67 percent. A combination of Gleason biopsy score and PSA was the best criterion that was independent of transrectal ultrasonography. Using a PSA > or = 15 ng/mL for tumors with Gleason biopsy score > or = 7 or a PSA > or = 25 ng/mL for tumors with a Gleason biopsy score of 5-6 had a sensitivity of 71 percent and positive predictive value of 48 percent for identifying patients with pelvic lymph node metastases. In selecting patients for laparoscopic pelvic lymphadenectomy prior to radical retropubic prostatectomy, criteria with a positive predictive value greater than 39 percent maximize the utility of laparoscopic pelvic lymphadenectomy. Prior to radical perineal prostatectomy, laparoscopic pelvic lymphadenectomy will identify pelvic lymph node metastases that would otherwise be undetected by prostatectomy alone. The sensitivity of selection criteria, therefore, should be increased, as long as the positive predictive value remains above 20 percent.

Re-evaluation of the need for pelvic lymphadenectomy in low grade prostate cancer

In a series of 166 patients undergoing radical prostatectomy and bilateral pelvic lymph node dissection for clinical stage A and B prostate cancer we found that 83% of patients with lymph node metastases had a final tumour Gleason score > or = 7. Gleason scoring of the pre-operative biopsy demonstrated 3 groups of patients with biopsy scores < or = 5, 6, and > or = 7, and a prevalence of lymph node metastases of 2, 13 and 23% respectively. The pre-operative serum prostate specific antigen (PSA) was of marginal value in predicting either the presence of lymph node metastases or the presence of cancer, since 15% of patients with nodal metastases had normal pre-operative PSA levels, as did 54% of patients with tumour Gleason scores < or = 5. It was concluded that the need for pelvic lymph node dissection in patients with low grade tumours is questionable because of the low prevalence of lymph node metastases, and that the pre-operative biopsy can identify those patients who are at low risk for lymph node metastases.