Modeling prostate cancer distributions

Long-Term Results of a Phase 3 Randomized Prospective Trial of Erectile Tissue-Sparing Intensity-Modulated Radiation Therapy for Men With Clinically Localized Prostate Cancer

PURPOSE

The objective of this study was to determine whether limiting the doses delivered to the penile bulb (PB) and corporal bodies with intensity modulated radiation therapy (IMRT) preserves erectile function compared with standard IMRT in men with prostate cancer.

METHODS AND MATERIALS

A total of 117 patients with low- to intermediate-risk, clinical T1a-T2c prostate adenocarcinoma were enrolled in a single-institution, prospective, single-blind, phase 3 randomized trial. All received definitive IMRT to 74 to 80 Gy in 37 to 40 fractions and standard IMRT (s-IMRT) or erectile tissue-sparing IMRT (ETS-IMRT), which placed additional planning constraints that limited the D90 to the penile bulb and corporal bodies to ≤15 Gy and ≤7 Gy, respectively. Erectile potency was assessed with components of the International Index of Erectile Function and phosphodiesterase type 5 inhibitor (PDE5) medication records.

RESULTS

Sixty-two patients received ETS-IMRT, and 54 received s-IMRT; 1 patient did not receive radiation therapy. Before treatment, all patients reported erectile potency. No patients received androgen deprivation therapy. In the intention-to-treat analysis, treatment arms did not differ in potency preservation at 24 months (37.1% ETS-IMRT vs 31.5% s-IMRT, P = .53). Of 85 evaluable patients with International Index of Erectile Function and PDE5 medication follow-up, erectile potency was seen in 47.9% of patients in the ETS-IMRT arm and 46.0% of patients in the s-IMRT arm (P = .86). PDE5 inhibitors were initiated in 41.7% of ETS-IMRT patients and 35.1% of s-IMRT patients (P = .54). Among all patients enrolled, there was no difference in freedom from biochemical failure between those treated with ETS-IMRT and s-IMRT (5-year 91.8% vs 90.7%, respectively, P = .77), with a median follow-up of 7.4 years. There were no differences in acute or late gastrointestinal or genitourinary toxicity. An unplanned per-protocol analysis demonstrated no differences in potency preservation or secondary endpoints between patients who exceeded erectile tissue-sparing constraints and those who met constraints, although power was limited by attrition and unplanned dosimetric crossover.

CONCLUSIONS

ETS-IMRT that strictly limits dose to the penile bulb and corporal bodies is safe and feasible. Use of this planning technique did not show an effect on potency preservation outcomes at 2 years, though power to detect a difference was limited.

Coupling I-125 permanent implant prostate brachytherapy Monte Carlo dose calculations with radiobiological models

PURPOSE

To investigate the coupling of radiobiological models with patient-specific Monte Carlo (MC) dose calculations for permanent implant prostate brachytherapy (PIPB). To compare radiobiological indices evaluated with different radiobiological models using MC and simulated AAPM TG-43 dose calculations.

METHODS

Three-dimensional dose distributions previously computed using MC techniques with two types of patient models, TG43sim (AAPM TG-43 water-based conditions) and MCDmm (realistic tissues and interseed effects), for 613 PIPB patients are coupled with biological dose and tumour control probability (TCP) models. Two approaches and their extensions are considered to evaluate biological doses, biologically effective dose (BED) and isoeffective dose (IED), as well as two methods to evaluate TCP. Three novel extensions of equivalent uniform biologically effective dose (EUBED) are suggested which consider the spatial distribution of doses within the target volume. Adopted radiobiological model parameter values (α, β, etc) are those suggested by AAPM TG-137, and sensitivity to parameter choice is discussed.

RESULTS

MCDmm dose calculations can reveal low doses in the prostate target volume, due to tissue heterogeneities or inter-seed effects; considering these low doses in EUBED calculations can lower TCP estimates by up to 70%, with largest differences in patients with calcifications. There are large variations in biological doses and TCPs evaluated over the 613 patient cohort for each radiobiological model considered, reflecting the spectrum of physical doses calculated for these patients with either MCDmm or TG43sim. Depending on the model details, BED, IED and EUBED are, on average, 6.0-9.8%, 7.4-9.2% and 1.8-15% higher, respectively, with TG43sim than MCDmm. TCP estimates computed using MCDmm dose distributions are much lower than expected based on past treatment outcome studies, suggesting a need to re-assess model parameters when evaluating radiobiological indices coupled with heterogeneous tissue model-based dose calculations.

CONCLUSIONS

Cohort average differences in biological dose and TCP estimates between radiobiological models are generally larger than differences for any one radiobiological model evaluated with TG43sim or MCDmm dose calculations. However, heterogeneous tissue dose calculations, like MCDmm, can identify clinically-relevant low dose volumes, e.g., in patients with calcifications, which would otherwise be missed with TG-43. In addition to affecting physical dose distributions, these low dose volumes can largely impact radiobiological dose and TCP estimates, which further motivates the clinical implementation of model-based dose calculations for PIPB.

Methodology to study the three-dimensional spatial distribution of prostate cancer and their dependence on clinical parameters

A methodology to study the relationship between clinical variables [e.g., prostate specific antigen (PSA) or Gleason score] and cancer spatial distribution is described. Three-dimensional (3-D) models of 216 glands are reconstructed from digital images of whole mount histopathological slices. The models are deformed into one prostate model selected as an atlas using a combination of rigid, affine, and B-spline deformable registration techniques. Spatial cancer distribution is assessed by counting the number of tumor occurrences among all glands in a given position of the 3-D registered atlas. Finally, a difference between proportions is used to compare different spatial distributions. As a proof of concept, we compare spatial distributions from patients with PSA greater and less than [Formula: see text] and from patients older and younger than 60 years. Results suggest that prostate cancer has a significant difference in the right zone of the prostate between populations with PSA greater and less than [Formula: see text]. Age does not have any impact in the spatial distribution of the disease. The proposed methodology can help to comprehend prostate cancer by understanding its spatial distribution and how it changes according to clinical parameters. Finally, this methodology can be easily adapted to other organs and pathologies.

Sexual function and the use of medical devices or drugs to optimize potency after prostate brachytherapy

PURPOSE

Prospective evaluation of sexual outcomes after prostate brachytherapy with iodine-125 seeds as monotherapy at a tertiary cancer care center.

METHODS AND MATERIALS

Subjects were 129 men with prostate cancer with I-125 seed implants (prescribed dose, 145 Gy) without supplemental hormonal or external beam radiation therapy. Sexual function, potency, and bother were prospectively assessed at baseline and at 1, 4, 8, and 12 months using validated quality-of-life self-assessment surveys. Postimplant dosimetry values, including dose to 10% of the penile bulb (D10), D20, D33, D50, D75, D90, and penile volume receiving 100% of the prescribed dose (V100) were calculated.

RESULTS

At baseline, 56% of patients recorded having optimal erections; at 1 year, 62% of patients with baseline erectile function maintained optimal potency, 58% of whom with medically prescribed sexual aids or drugs. Variables associated with pretreatment-to-posttreatment decline in potency were time after implant (p = 0.04) and age (p = 0.01). Decline in urinary function may have been related to decline in potency. At 1 year, 69% of potent patients younger than 70 years maintained optimal potency, whereas 31% of patients older than 70 maintained optimal potency (p = 0.02). Diabetes was related to a decline in potency (p = 0.05), but neither smoking nor hypertension were. For patients with optimal potency at baseline, mean sexual bother scores had declined significantly at 1 year (p < 0.01). Sexual potency, sexual function, and sexual bother scores failed to correlate with any dosimetric variable tested.

CONCLUSIONS

Erections firm enough for intercourse can be achieved at 1 year after treatment, but most men will require medical aids to optimize potency. Although younger men were better able to maintain erections firm enough for intercourse than older men, there was no correlation between potency, sexual function, or sexual bother and penile bulb dosimetry.

Statistical 3D Distribution Analysis of Prostate Cancers in Korean Using Digital Processing Techniques

Objectives

Several researchers have shown that three dimensional (3D) distribution analysis of prostate cancer is helpful when initiating needle biopsy procedures. Knowledge regarding the distribution of prostate cancer could enhance understanding of the pathophysiology involved and improve detection of these malignancies. We propose utilizing digital processing techniques to analyze prostate cancer distribution in a 3D setting.

Methods

Pre-made radical prostatectomy sample slices were digitized with a resolution of 76 dpi. Slices of each sample were aligned and registered by deformation algorithm and interpolated for analysis of relative distribution statistics. We analyzed 80 samples saved in electronic medical record and compared the detection rate of preoperative needle biopsies and radical prostatectomies using our 3D analysis technique.

Results

The statistical 3D distribution of prostate cancer was evaluated using a 36-sector process. Results were represented in the following two ways: distribution of a single patient, and statistical distribution of prostate cancers of multiple patients. The overall concordance rate was 62.7% between the two methods; therefore a technique is needed which can raise this percentage.

Conclusions

We suggest using the normalization method to develop a software tool which permits reconstruction of the 3D distribution of prostate cancer from 2D legacy images and reduces the loss of image quality as well. This application will facilitate detection of prostate cancer by aiding in the determination of the most effective clinical position via partial sampling with decreased patient inconvenience.

Limited sampling of radical prostatectomy specimens with excellent preservation of prognostic parameters of prostate cancer

CONTEXT

The widespread use of the serum prostate-specific antigen test has increased the early detection of prostate cancer and consequently reduced grossly definable prostate cancers.

OBJECTIVE

To find the most efficient gross sampling method for radical prostatectomy specimens not only preserving important prognostic factors but also being cost effective.

DESIGN

We initially analyzed clinicopathologic features of the entire prostate sections from 148 radical prostatectomy specimens, which then were used to examine the impact of 5 partial sampling methods on tumor stage, Gleason score, extraprostatic extension, resection margin status, and paraffin block numbers. The methods included submission of (1) alternative slices, (2) alternative slices plus biopsy-positive posterior quarters, (3) every posterior half, (4) every posterior half plus one midanterior half, and (5) alternative slices plus peripheral 3-mm rim of the remaining prostate.

RESULTS

Prostate cancers and their extraprostatic extension and resection margin involvement were commonly located in the right posterior portion of the prostate. Method 5 was most efficient, detecting all cases with extraprostatic extension and resection margin involvement and reducing 25% of paraffin blocks compared with the entire sampling of the prostate. The Gleason scores were retained in most of cases, except reversal of the primary and secondary Gleason grade component in only 2 cases (1%). Only 4 cases (3%) were downstaged within the same T2 stage.

CONCLUSIONS

These results demonstrate that sampling of alternative slices plus peripheral rim of the remaining prostate is the most efficient partial sampling method for radical prostatectomy specimens.

Three-dimensional sonography with needle tracking: role in diagnosis and treatment of prostate cancer

OBJECTIVE

Image-guided prostate biopsy has become routine in medical diagnosis. Although it improves biopsy outcome, it mostly operates in 2 dimensions, therefore lacking presentation of information in the complete 3-dimensional (3D) space. Because prostatic carcinomas are nonuniformly distributed within the prostate gland, it is crucial to accurately guide the needles toward clinically important locations within the 3D volume for both diagnosis and treatment.

METHODS

We reviewed the uses of 3D image-guided needle procedures in prostate cancer diagnosis and cancer therapy as well as their advantages, work flow, and future directions.

RESULTS

Guided procedures for the prostate rely on accurate 3D target identification and needle navigation. This 3D approach has potential for better disease diagnosis and therapy. Additionally, when fusing together different imaging modalities and cancer probability maps obtained from a population of interest, physicians can potentially place biopsy needles and other interventional devices more accurately and efficiently by better targeting regions that are likely to host cancerous tissue.

CONCLUSIONS

With the information from anatomic, metabolic, functional, biochemical, and biomechanical statuses of different regions of the entire gland, prostate cancers will be better diagnosed and treated with improved work flow.

Significance of the craniocaudal distribution of cancer in radical prostatectomy specimens

OBJECTIVES

To examine the differences in the distribution of prostate cancer (PCa) in the craniocaudal dimension and their potential significance.

METHODS

We studied 1253 patients with clinically localized PCa treated with radical prostatectomy (RP) from 1983 to 2000. We analyzed the clinicopathological features according to the craniocaudal distribution (apex, mid, base) of the largest cancer focus.

RESULTS

Of these patients, 456 (36%) had the largest cancer focus in the apex, 728 (58%) in the mid, and 69 (6%) in the base. The cancers in the apex were less invasive than those in the mid or base, as evidenced by the lower frequency of extracapsular extension (27% vs 43%, 52%, respectively) and/or seminal vesicle involvement (5% vs 13%, 20%, respectively). The frequency of the largest cancer focus in the apex has increased significantly over time, from 26% before 1995 to 46% after 1995 (P < 0.001). Serum prostate specific antigen non-progression rate at 10 years for patients with a cancer at the apex was 83%, which was better than 76% and 77% of patients with a cancer at the mid or base (P = 0.029, P = 0.14, respectively).

CONCLUSION

The cancers dominant at the apex are increasing over time and represent half of the patients treated by RP in recent years. These cancers tend to be less aggressive compared to those in the mid or base of the prostate. This knowledge may be useful in understanding the biology of and maximizing the detection of PCa.

Erectile dysfunction after radiotherapy for prostate cancer and radiation dose to the penile structures: A critical review

Erectile dysfunction (ED) is a common sequela after external beam radiotherapy and brachytherapy for prostate cancer. There are several structures in the vicinity of the prostate that are critical to erectile function and that receive a substantial radiation dose: neurovascular bundles (NVBs), internal pudendal arteries (IPAs), accessory pudendal arteries, corpora cavernosa and the penile bulb. Most reports analyzing the correlation between radiation dose to these structures and radiation-induced ED are limited by the small number of patients analyzed in each study. So far, there is no evidence for a role of the NVBs in radiation-induced ED. There are no reports on the IPAs, based on reduced arterial flow in the penis. Several studies show contradicting results on the corpora cavernosa, which house the erectile tissue required for erection. There are contradicting reports on the penile bulb, although studies with more patients tend not to find any correlation. Sparing of the penile bulb to improve potency-preservation is not sufficiently supported by the current literature. If sparing of the penile bulb is achieved by reducing the margin for the apex, an oncological risk is taken, while it is uncertain whether this will improve potency-preservation.

Additional Sampling of Dorsal Apex on Systematic Prostate Biopsy: Impact on Early Detection of Prostate Cancer

OBJECTIVES

To evaluate the significance of additional routine biopsies targeting the dorsal apex (DA) in men undergoing transrectal ultrasound (TRUS)-guided biopsies.

METHODS

This study included 429 patients undergoing TRUS-guided biopsy of the prostate. As a rule, 12 cores were taken from each patient, with 8 cores taken from the peripheral zones, 2 cores from the transition zones, and 2 additional cores from the DA.

RESULTS

Cancer was detected in 150 patients, of whom 97 had positive cores in the DA. Furthermore, cancer was detected only in the DA in 14 patients; that is, the increase in the cancer detection rate by additional sampling from the DA was 9.3%. Significant differences were found in the prostate-specific antigen level, prostate-specific antigen density, digital rectal examination findings, TRUS findings, clinical T stage, and percentage of positive biopsy cores among the 14 men with positive cores in the DA alone (group 1), 83 in the DA and other regions (group 2), and 53 in regions except for the DA (group 3). Of these, radical prostatectomy was performed in 6, 41, and 26 in groups 1, 2, and 3, respectively. No significant differences were found in the several pathologic factors among these groups, and 5 of the 6 patients in group 1 had a tumor volume greater than 0.5 cm3.

CONCLUSIONS

Additional sampling of biopsy cores from the DA significantly improved the cancer detection rate, particularly for early disease; however, this method does not appear to increase the detection of insignificant cancer. Accordingly, we recommend performing systematic biopsy routinely targeting the DA.

Computer technology in detection and staging of prostate carcinoma: A review

After two decades of increasing interest and research activity, computer-assisted diagnostic approaches are reaching the stage where more routine deployment in clinical practice is becoming a possibility [Kruppinski, E.A., 2004. Computer-aided detection in clinical environment: Benefits and challenges for radiologists. Radiology 231, 7-9]. This is particularly the case in the analysis of mammographic images [Helvie, M.A., Hadjiiski, L., Makariou, E., Chan, H.P., Petrick, N., Sahiner, B., Lo, S.C., Freedman, M., Adler, D., Bailey, J., Blane, C., Hoff, D., Hunt, K., Joynt, L., Klein, K., Paramagul, C., Patterson, S.K., Roubidoux, M.A., 2004. Sensitivity of noncommercial computer-aided detection system for mammographic breast cancer detection: pilot clinical trial. Radiology 231, 208-214] and in the detection of pulmonary nodules [Reeves, A.P., Kostis, W.J., 2000. Computer-aided diagnosis for lung cancer. Radiol. Clin. North Am. 38, 497-509]. However, similar approaches can be applied more widely with the promise of increasing clinical utility in other areas. We review how computer-aided approaches may be applied in the diagnosis and staging of prostatic cancer. The current status of computer technology is reviewed, covering artificial neural networks for detection and staging, computerised biopsy simulation and computer-assisted analysis of ultrasound and magnetic resonance images.

Three-dimensional reconstruction of basal cell carcinomas

BACKGROUND

Basal cell carcinoma (BCC) is the most common type of skin cancer. One of the main problems with BCC is the risk of local recurrence of the tumor after treatment. This is mainly due to its irregular outgrowths, which cannot be detected clinically.

OBJECTIVE

To better understand the tumor morphology and growth pattern of BCC, we tried to develop a method that provides a precise three-dimensional model of the tumor.

METHODS

Because Mohs surgery provides the best overview of the tumor and the tumor margins (both lateral and in depth), the reconstruction was based on slides from Mohs surgery. After digitization and processing of the slides, the tumor was then surrounded by a Mohs surgeon on a computer screen. These selections (lines) were used for a three-dimensional reconstruction of the tumor using MedSurf3D software.

RESULTS

This method allows three-dimensional reconstruction of any given BCC. The MedSurf3D software enables visualization of a three-dimensional model of the tissue, which is removed during the surgical procedure.

CONCLUSIONS

Three-dimensional reconstruction is a fascinating tool that might improve our understanding of the behavior, growth pattern, and tumor morphology of BCCs. This technique might also be useful in other fields of cutaneous oncology, such as the calculation of the tumor volume of melanomas.

Assessment of i-125 prostate implants by tumor bioeffect

PURPOSE

A method of prostate implant dose distribution assessment using a bioeffect model that incorporates a distribution of tumor cell densities is demonstrated. This method provides both a quantitative method of describing implant quality and spatial information related to the location of underdosed regions of the prostate. This model, unlike any other, takes into account the likelihood of finding cancer cells in the underdosed region.

METHODS AND MATERIAL

The prostate volumes of 5 patients were divided into multiple subsections and a unique cell density was assigned to each subsection. The assigned cell density was a function of probability of finding tumor foci in that subsection. The tumor control probability (TCP) for each subsection was then calculated to identify the location of any significantly underdosed part of the prostate. In addition, a single TCP value for the entire prostate was calculated to score the overall quality of the implant.

RESULTS

Adequately dosed subsections scored TCP values greater than 0.80. The TCP for underdosed regions fell dramatically particularly in subsections at higher risk of containing tumor cells.

CONCLUSIONS

Despite uncertainties in radiobiological parameters used to calculate the TCP and the distribution of cancer foci through the prostate, the bioeffect model was found to be useful in identifying regions of underdosed prostate that may be at risk of local recurrence due to inadequate dose. Unlike the isodose distribution, the model has the potential to demonstrate that small volumes of tissue underdosed in regions most likely to contain higher numbers of tumor cells may be more significant than larger volumes irradiated to a lower dose but with a lower probability of containing cancer cells.

Prostate implant evaluation using tumour control probability—the effect of input parameters

In this paper, we examine the effect of treatment parameters in a model used to evaluate permanent prostate implants. The model considers the prostate to be composed of 12 sub-sections, each sub-section is assigned a cell density based on the probability of finding cancer foci in that sub-section. Wasted dose as a result of the dose rate from the implant falling below a level adequate to counteract repopulation was found to vary by 2-16% over the range of radiosensitivity and repopulation rates considered. Within the model, applied to five dose distributions, the uncertainty in the tumour control probability (TCP) values calculated for each sub-section as a result of differences in the model parameters, was found to be less than 12% in most cases for the good quality implants. The difference in TCP values was much larger for the poor quality implant. Substituting a heterogeneous distribution of alpha for a single mean value resulted in generally lower TCP values though introducing a cutoff value with a Gaussian distribution had a profound effect on the calculated values. Despite uncertainties in the parameters, the model was able to identify sub-sections at risk of local recurrence but as a result of these uncertainties, the TCP values can only be considered in the relative rather than absolute sense.

The incidence of prostate cancer in men with prostate specific antigen greater than 4.0 ng/ml: a randomized study of 6 versus 12 core transperineal prostate biopsy

PURPOSE

The prostate cancer detection rate in patients with elevated prostate specific antigen (PSA) increases with extended needle biopsy protocols. Transperineal biopsy under transrectal ultrasound guidance is rarely reported, although notable cancer diagnoses are obtained with this technique. We describe the results of 6 and 12 core transperineal biopsy.

MATERIALS AND METHODS

A total of 214 patients with PSA greater than 4.0 ng/ml were prospectively randomized to undergo 6 or 12 core transperineal biopsy. Each group of 107 patients was comparable in terms of clinical characteristics. The procedure was performed on an outpatient basis using local anesthesia. Specimens were obtained with a fan technique with 2 puncture sites slightly above the rectum (1 per lobe) under transrectal ultrasound guidance. Cores were taken from all peripheral areas, including the far lateral aspect of the prostate.

RESULTS

The overall cancer detection rate was 38% and 51% for 6 and 12 core biopsy, respectively. In patients with PSA between 4.1 and 10 ng/ml the cancer detection rate was 30% and 49% for 6 and 12 core biopsy, respectively.

CONCLUSIONS

The 12 core transperineal prostate biopsy is superior to 6 core biopsy. The technique provides optimal prostate cancer diagnosis. About half of the patients with PSA greater than 4.0 ng/ml and a slightly lower percent with PSA between 4.1 and 10 ng/ml have prostate cancer.

Best approach for prostate cancer detection: a prospective study on transperineal versus transrectal six-core prostate biopsy

OBJECTIVES

To compare the efficacy of transperineal versus transrectal six-core prostate biopsy. Transrectal sextant biopsy is the most common method for prostate cancer detection. However, the cancer detection rate with this technique is increasingly considered inadequate. Different prostate biopsy procedures, mainly based on addition of additional transrectal cores to traditional sextant biopsy, have been proposed to increase the cancer diagnosis rate. The efficacy of the transperineal approach has not yet been fully established.

METHODS

In a prospective study, 107 patients with elevated prostate-specific antigen levels (greater than 4.0 ng/mL) underwent prostate biopsy with six transperineal cores, using a "fan" scheme, plus six transrectal cores, according to the sextant technique. The median prostate-specific antigen level was 8.2 ng/mL (range 4.1 to 240).

RESULTS

The overall cancer detection rate was 40% (43 of 107); prostate cancer was found in 38% (41 of 107) of patients with the transperineal approach and in 32% (34 of 107) of patients with the transrectal approach. Of 43 diagnosed cancers, 41 (95%) were found with the transperineal approach and 34 (79%) with the transrectal approach (P = 0.012). No patient had low-grade cancer (Gleason score 2 to 4), 25 patients had intermediate-grade cancer (Gleason score 5 to 6), and 18 patients had high-grade cancer (Gleason score 7 to 10).

CONCLUSIONS

This is the first report comparing in vivo two different approaches to prostate biopsy. Transperineal biopsy seems superior to transrectal biopsy to detect prostate cancer. Both the transperineal and the transrectal approach should be familiar to the urologist who needs to obtain an adequate cancer detection rate. Transrectal sextant biopsy cannot be considered the standard technique for prostate cancer detection.

Investigating the distribution of prostate cancer using three-dimensional computer simulation

The objective of this work was to investigate the distribution of prostate cancer using three-dimensional (3-D) computer simulation. Two hundred and eighty-one 3-D computer prostate models were constructed from radical prostatectomy specimens. An algorithm was developed which divided each model into 24 symmetrical regions, and it then detected the presence of tumor within an individual region. The distribution rate of prostate cancer was assessed within each region of all 281 prostate models, and the difference between the rates was statistically analyzed using Mantel-Haenszel methodology. There was a statistically significant higher distribution rate of cancer in the posterior half (57.2%) compared to the anterior half ( 40.5%; P=0.001). The base regions (36.8%) had a statistically significant lower distribution rate than either the mid regions (56.3%; P=0.001) or the apical regions (53.5%; P=0.001). The mid regions did have a statistically significant higher distribution rate compared to the apical regions (P=0.032). There was no statistically significant difference between the distribution rate on the left half (48.5%) compared to that on the right half (49.2%; P=0.494). The spatial distribution of prostate cancer can be analyzed using 3-D computer prostate models. The results illustrate that prostate cancer is least commonly located in the anterior half and base regions of the prostate. Through an analysis of the spatial distribution of prostate cancer, we believe that new optimal biopsy strategies and techniques can be developed.

Anterior distribution of Stage T1c nonpalpable tumors in radical prostatectomy specimens

OBJECTIVES

To determine the anatomic patterns of tumor distribution in radical prostatectomy specimens from nonpalpable prostate cancer.

METHODS

Tumor maps directly traced from histologic slides of 62 radical prostatectomy specimens were superimposed by a computer-assisted imaging technique to create an idealized prostate gland at three levels: apex, mid-prostate, and base. To investigate specific patterns of tumor distribution, the sites of tumor in each quadrant were compared according to risk group stratification. The tumor extent was compared with the patterns of positivity in routine sextant biopsies.

RESULTS

Among all patients, the tumor frequency was 85.5% in the mid-gland, 82.3% in the apex, and 48.4% in the base. Analysis by quadrant showed that tumors were significantly denser in the apex to mid-prostate. The primary extent of these tumors appeared to lie predominantly in the anterior half of the gland. Biopsy yields at the apex and mid-prostate appeared low compared with the frequency of cancers at these levels. No patterns specific to the different risk groups were found, but no tumors within the anterior base were found in the low-risk group.

CONCLUSIONS

The primary extent of nonpalpable tumors appeared to lie predominantly in the anterior half of the gland at the apex to mid-prostate levels. Additional biopsy cores taken from more anterior regions of the gland may enhance the detection of nonpalpable cancers further.