Standardized in vitro mapping with multiple core biopsies of total prostatectomy specimens: localization and prediction of tumour volume and grade

Tissue shrinkage after fixation with formalin injection of prostatectomy specimens

Prostate cancer volume correlates with stage, grade, and progression after prostatectomy. When tumor volume is measured planimetrically, results are multiplied by a correction factor to compensate for tissue shrinkage caused by processing. Injection of formalin into prostatectomy specimens was suggested for improved fixation. Our aim was to investigate how this affects the prostate volume. We studied 142 radical prostatectomy specimens. All prostates were immersed in 10% formalin. In 84 prostates (59%) we also injected 20 ml of formalin before routine fixation. The prostates were weighed unfixed after injection and after final fixation. The specimens were sliced and totally embedded. The transverse diameters of the prostates were measured on unfixed specimens and microscopic sections. The average weight loss after final fixation was 5.8 and 8.6% for formalin-injected specimens and standard-fixed specimens, respectively (p<0.001). However, when total shrinkage was estimated from the transverse diameters, there was no difference related to fixation technique (p=0.59). The average linear shrinkage was 4.5%, corresponding to a volume correction factor of 1.15. We conclude that formalin injection for fixation of prostate tissue does not influence tumor volume calculation compared to conventional fixation.

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.

Carcinoma extent in prostate needle biopsy tissue in the prediction of whole gland tumor volume in a screening population

Increasing prostate tumor volume has been shown to correlate with numerous adverse prognostic indicators for patients with prostate carcinoma The ability to predict tumor volume from pretreatment parameters is potentially critical in the stratification of patients for different management strategies. We assessed the capacity of preoperative variables to predict tumor volume in 100 men diagnosed with prostate cancer in a prostate-specific antigen (PSA)-based screening program. Preoperative information included total serum PSA concentration and needle biopsy tissue variables, including Gleason score, number of positive cores, linear extent of carcinoma in millimeters, greatest percentage of carcinoma (in a single core), total percentage of carcinoma (all cores), presence of perineural invasion, and percentage of high-grade carcinoma. The postoperative end point was total tumor volume in radical prostatectomy tissue, calculated by image analysis. We determined independently significant factors and generated a predictive modelfor whole gland tumor volume. Total tumor volume was related significantly in multivariate analysis to 3 preoperative variables: linear extent of carcinoma, exponential number of positive cores, and serum PSA. A predictive model generated based on these 3 variables accounted for only 65% of the natural deviance of the data owing to data-point scatter for individual patients, suggesting that additional variables are needed to more accurately predict tumor volume. Findings highlight the importance of reporting quantitative measures of tumor amount in prostate needle biopsy specimens; several measures of tumor extent (vs 1 measure) provide maximal information on prostate cancer size.

Assessment of morphometric measurements of prostate carcinoma volume

BACKGROUND

The authors have shown that the primary determinants of prostate carcinoma progression are tumor volume and the percent of the tumor comprised of Gleason Grade 4/5 cells. In the current study the authors evaluated six different techniques for the morphometric measurements of prostate carcinoma volume.

METHODS

A computer-assisted image analysis (NIH Image, developed and maintained by the National Institutes of Health, Bethesda, MD) was used to analyze all 108 step-sectioned prostate specimens obtained between January 1 and December 31, 1997. The authors used the Stanford technique of 0.3-cm step-sections, measuring the volume of the tumor at both 0.3-cm and 0.6-cm intervals. The other 4 methods included the authors' previous method based on an earlier image program, the ellipsoidal method (pi / 6 x width x height x length), an estimation of the square area of the largest tumor, and the maximum tumor dimension (MTD).

RESULTS

The authors first checked the accuracy of NIH Image analysis by measuring 24 circles of widely different sizes. The mean coefficient of variation was 1.7% and the correlation between the mean circle areas measured by the NIH Image software and true circle area essentially was perfect (correlation coefficient [r] = 1 and r(2) = 0.999; P < 0.0001). In comparison with the authors' original computer image program using 0.3-cm step-sections measured by a different observer, r(2) with the NIH Image analysis was 0.93. Using NIH Image only, the 0.6-cm step-section method missed measurable cancers in 16.7% of 108 radical prostatectomies in comparison with the 0.3-cm step-method. The mean tumor volume with the 0.6-cm section method (P < 0.0001) and the ellipsoidal method (P < 0.05) were significantly higher than with the 0.3-cm section method. r(2) from linear regressions using the 0.3-cm step section method as the standard versus the ellipsoidal method was 0.594, and was 0.89 versus the 0.6-cm step-section method, 0.652 versus the square area estimation, and 0. 527 versus the MTD method.

CONCLUSIONS

The results of the current study support NIH Image as a powerful software program for the morphometric measurement of prostate carcinoma volume. Pathologic processing with 0.3-cm section slices was found to be more accurate for tumor volume than the 0.6-cm section slices. The ellipsoidal method, the square area of the largest tumor, and the MTD all were found to be inferior to computer-assisted image analysis measurements. In certain clinical situations in which only estimates of tumor volume are required, the square area of the largest tumor appears to be the best choice (r(2) 0.652).

Most prostate cancers missed by raising the upper limit of normal prostate-specific antigen for men in their sixties are clinically significant

OBJECTIVES

To evaluate the efficacy of applying an age-specific prostate-specific antigen (PSA) reference range to determine whether prostate biopsies are warranted in men 60 to 69 years of age. We estimated the incidence of clinically significant prostate cancer in men in their sixties with PSA levels of 4.01 to 4.50 ng/mL and normal digital rectal examinations (DRE).

METHODS

We reviewed 203 sextant prostate biopsies of men in their sixties with PSA levels of 4.01 to 4.50 ng/mL and normal DRE. Tumors were considered clinically significant if the cancer on biopsy was poorly differentiated (Gleason score of 7 or more), involved more than one core, or included a single focus measuring more than 3 mm.

RESULTS

The positive biopsy rate was 31.5%. More than 80% of the cancers detected satisfied criteria that almost always predict clinically significant cancer. Thus, among men in their sixties with PSA levels of 4.01 to 4.50 ng/mL and normal DRE, the risk of detecting clinically significant cancer on biopsy was approximately 25%.

CONCLUSIONS

Most nonpalpable cancers detected by sextant biopsies in men 60 to 69 years of age with PSA levels of 4.01 to 4.5 ng/mL are clinically significant. Applying an age-specific PSA reference range that increases the upper limit of normal PSA to 4.5 ng/mL results in the failure to detect a substantial number of clinically significant cancers.

Three-dimensional modeling of biopsy protocols for localized prostate cancer

Prostate cancer is the most common malignant tumor in American men, yet only a small percentage of men will develop clinically significant disease. Needle core biopsies are used to confirm the presence of cancer prior to surgery. While needle core biopsies have shown some ability to predict tumor volume and grade in prostatectomy specimens, for the individual patient they are neither sensitive nor specific enough to guide therapy. In this paper, we describe a system for simulating needle biopsies on three-dimensional models of cancerous prostates reconstructed from serial sections. First we segment the serial sections, delineating tumors and landmarks. Next, we register the sections using a color-merging scheme, and reconstruct the three-dimensional model using modified-shape-based interpolation. The resulting volume can be rendered, and simulated needle core biopsies can be taken from the reconstructed model. We use our system to simulate two different biopsy protocols on a reconstructed prostate specimen.

Minimal criteria for the diagnosis of prostate cancer on needle biopsy

Increased clinical screening of men at risk for prostate cancer, and the realization of the benefits of performing multiple biopsies per prostate, have facilitated early detection of malignancy, while presenting the pathologist with a growing array of diagnostic findings. Interpretation of these findings requires discussion of the minimal criteria required for the diagnosis of cancer on needle biopsy within a wide spectrum of related histologic findings. This spectrum includes small acinar proliferations suspicious for but not diagnostic of cancer, benign mimics of cancer, the preinvasive entity of high-grade prostatic intraepithelial neoplasia, and various treatment effects. Clinical implications of these findings and other prognostic factors are detailed.

Use of repeat sextant and transition zone biopsies for assessing extent of prostate cancer

PURPOSE

Little is known why certain prostate cancers are missed on biopsy. In patients with a needle biopsy diagnosis of cancer it is also unknown whether repeat needle biopsy provides useful information to predict extent of disease.

MATERIALS AND METHODS

In the pathology laboratory we performed sextant and transition zone needle biopsies on 193 radical prostatectomy specimens from men with nonpalpable cancer detected on needle biopsy (stage T1c) using an 18 gauge biopsy gun. Radical prostatectomy specimens were then serially sectioned, totally embedded, mapped and staged.

RESULTS

The transition zone biopsy by itself was positive in only 2.1% of cases, demonstrating the lack of usefulness for this particular biopsy. Despite cancer on preoperative needle biopsy in all cases, 31% showed no cancer on repeat sextant transition zone biopsy. In a multivariate analysis (variables included radical prostatectomy tumor volume, radical prostatectomy tumor location, prostate gland size and radical prostatectomy grade) decreased tumor volume (p < 0.0001), increased gland size (p = 0.001), and decreased radical prostatectomy grade (p = 0.013) were each independent predictors of absence of tumor on repeat biopsy. A lack of cancer on repeat biopsy correlated with pathological stage: 90% of cases without cancer on repeat biopsy were organ confined versus 66% for cases with a single less than 3 mm. focus of cancer on repeat biopsy versus 58% for cases with more cancer on repeat biopsy. Of 38 men with a preoperative needle biopsy showing less than 3 mm. of cancer on 1 core that was not high grade and with prostate specific antigen 10 or less (men for whom urologists are most likely to repeat biopsy) the presence of cancer on repeat biopsy also correlated with extent of disease at radical prostatectomy. However, of these 38 men 6 of 16 with no cancer on repeat biopsy had moderate tumor (4 with organ confined Gleason score 5 to 6, tumor volume 0.79 to 4.5 cc; 1 with organ confined Gleason score 7, tumor volume 0.18 cc; and with 1 established penetration Gleason score 6, tumor volume 0.53) at radical prostatectomy.

CONCLUSIONS

Although absence of cancer on repeat biopsy correlates with various parameters of extent of disease, there is significant overlap for the individual patient. This study also demonstrates the limits of sextant needle biopsy to evaluate tumor status in patients who elect watchful waiting or less invasive forms of therapy (cryotherapy, interstitial radiotherapy).

The relationship between prostatic intraepithelial neoplasia and prostate cancer: critical issues

PURPOSE

Prostatic intraepithelial neoplasia (PIN) is often considered to be a premalignant lesion and the main precursor of invasive carcinoma of the prostate. We evaluated the evidence for and against PIN as a premalignant lesion and determined guidelines for the clinical management of PIN.

MATERIALS AND METHODS

Literature analysis of histopathological, morphometric, phenotypic and molecular genetic evidence of progression and of clinical findings regarding PIN was done. Literature searches were performed on MEDLINE with relevant key words.

RESULTS

PIN, like prostate cancer, occurs most frequently in the peripheral zone of the prostate and is usually located in close proximity to prostate cancer. The relative PIN and prostate cancer volumes vary inversely. Prostate specific antigen in cases of PIN appears to be intermediate between prostate cancer and normal levels, although this elevation may be explained by concomitant prostate cancer or benign prostatic hyperplasia. Deoxyribonucleic acid ploidy in PIN follows the aneuploid proportion as in the concomitant prostate cancer. Prostate cancer and PIN show evidence of loss of putative tumor suppressor genes on chromosome 8p. The clinical relevance of PIN biopsy findings is based on the association of neoplasia and prostate cancer. High grade PIN in core biopsies without concomitant prostate cancer has a substantial risk for prostate cancer in subsequent biopsies (24 to 73%, up to 100% when the digital rectal examination is suspicious) and should cause further biopsy sampling.

CONCLUSIONS

There is convincing evidence that PIN is a precursor lesion to prostate cancer, with a close association of PIN and prostate cancer in biopsy and prostatectomy specimens. A biopsy finding of high grade PIN necessitates further investigation in patients who are candidates for radical treatment for localized prostate cancer.

Intratumoral heterogeneity in prostate cancer demonstrated by volume-weighted mean nuclear volume

This study was conducted to investigate the degree of heterogeneity of the volume-weighted mean nuclear volume (MNV) calculated from radical prostatectomy specimens, and to evaluate how closely the MNV calculated from transrectal biopsy specimens reflected the overall malignancy. MNV was evaluated using 77 sections of histological specimens from 9 patients who underwent radical prostatectomy at Shizuoka City Hospital between January 1990 and December 1995. The MNV values calculated from radical prostatectomy specimens were compared with those calculated from preoperative transrectal biopsy specimens. MNV was judged to be homogeneous in six cases and heterogeneous in three cases. Of the heterogeneous cases, MNV calculated from the transrectal biopsy specimens was judged to be underestimated in 2 of 3 cases. This study shows that intratumoral heterogeneity of prostate cancer may affect clinical estimates of the grade of malignancy based on the MNV, and indicates the need for a sufficient number of specimens in order to evaluate the MNV by transrectal biopsy.

Clinical significance of repeat sextant biopsies in prostate cancer patients

OBJECTIVES

Six random systematic core biopsies (SRSCB) of the prostate is considered by many to represent the standard method of detecting prostate cancer. We sought to evaluate the sensitivity of the transrectal ultrasound (TRU)S-guided needle biopsies in 89 consecutive patients with a history of biopsy-proven prostate cancer. These patients underwent repeat biopsy prior to enrollment in an ongoing, randomized protocol. We also compared the clinical and pathological features of patients with SRSCB-documented prostate carcinoma and negative repeat-sextant biopsy.

METHODS

Our study population consisted of 89 patients enrolled in our randomized, prospective study assessing the effect of androgen deprivation therapy in combination with radical prostatectomy for clinically localized prostate cancer. A comparison was made of the patients' rebiopsy results with initial biopsy. Patients having either a positive or negative rebiopsy were analyzed with respect to grade, T stage, prostate-specific antigen (PSA), PSA density (PSAD), organ-confined rate, and final surgical margin status.

RESULTS

Repeat sextant biopsy was positive for prostate cancer in 71 (80%) patients and negative in 18 (20%) patients. There was no significant difference between patients with a negative or positive rebiopsy with respect to PSA or PSAD. There was a trend toward greater prostate volumes in the negative-rebiopsy group (P = 0.08) and lower clinical stage in the negative rebiopsy (P = 0.025) group. In patients with a negative repeat biopsy, the organ-confined (OC) rate was 77% (14/18 patients), as compared to the positive-rebiopsy group of 56% (40/71 patients) (P = 0.08). Similarly, the margin-positive rate in the negative-rebiopsy group was 17% (3/18 patients), as compared to the positive-rebiopsy group who had a margin-positive rate of 44% (31/71 patients) (P = 0.03).

CONCLUSIONS

In patients with clinically localized disease, the sensitivity of SRSCB in detecting carcinoma is 80%. The results of this study highlight the potential sampling error of the SRSCB and the implication of a negative rebiopsy in patients with clinically significant prostate cancer.

Tissue-shrinkage correction factor in the calculation of prostate cancer volume

Many studies that have calculated prostate cancer volumes from microscopic slides have used correction factors, ranging from 1.22 to 1.5, to compensate for tissue shrinkage during tissue processing. We undertook a study to measure tissue shrinkage directly because our experience suggested less shrinkage than that reported by others. Ten prostatectomy specimens were processed in a uniform manner. Multiple identical linear measurements were taken at four stages of processing: in the fresh state, following fixation, following processing, and from the microscopic slide. Linear shrinkage following fixation was minimal (4.1%) but increased to 14.5% following tissue processing. With rehydration and expansion on the flotation bath, tissues swelled so that net linear tissue shrinkage was 4.3%, and net volumetric tissue shrinkage was 12.4%, which translates into a correction factor for tissue shrinkage of 1.14. The following variables had no statistically significant effect on shrinkage: concentration of formalin, whole-mount versus quadrant sections, thickness of tissue slices, length of time in the alcohol dehydration steps, and temperature of the flotation bath over a range of 35 to 45 degrees C. This study suggests that (a) tissue-shrinkage correction factors that have been used in some previous studies may not be applicable for all laboratories because of interlaboratory variations in tissue-processing procedures or differences in measuring shrinkage; and (b) some calculated tumor volumes that have been used for prognostic thresholds may be high because of inflated tissue-shrinkage correction factors.

Five year follow-up after radical prostatectomy for localized prostate cancer--a study of the impact of different tumor variables on progression

Fifty-one patients with clinically localized prostate cancer stages A and B, who underwent radical prostatectomy have been followed for a minimum of 5 years. The impact of age, stage, capsular penetration, total tumor volume, Gleason score, seminal vesicle invasion and lymph node metastases on progression has been evaluated. Progression free survival was calculated according to the Kaplan-Meier method. Uni- and multivariate analyses were performed according to the Cox proportional hazards model. During the observation period 16 patients (31%) experienced progression. Tumor volume, grade and seminal vesicle invasion emerged as statistically significant predictors of tumor progression in the survival analyses while age at surgery, preoperative stage and different levels of capsular penetration were not statistically significant. The findings in the Cox models were in accordance with those at actuarial survival analyses though tumor volume was the only variable proven to have an independent statistically significant influence on progression.