'Vanishing' prostate cancer in radical prostatectomy specimens: incidence and long-term follow-up in 38 cases

DNA comparison between operative and biopsy specimens to investigate stage pT0 after radical prostatectomy

PURPOSE

The aim was to eliminate, by DNA comparison, any identity mismatch between operative and biopsy specimens and to analyse the determinants of all pT0 prostate cancers occurred in a single institution.

METHODS

All prostate pT0 cases in a single institution over 20 years were investigated. None of the patients had been diagnosed after a transurethral resection of the prostate nor had they received neoadjuvant hormonal treatment. The biopsies performed in other centres had been referred for a centralized pathologic re-analysis. DNA analysis was performed in samples from operative and biopsy specimens, and pairs of tissues were blindly constituted. Correct matching was verified in each pair and compared to the original database in order to comment on the occurrence of identity mismatches in the series.

RESULTS

Nineteen patients (0.77 %) had been diagnosed as having pT0 prostate cancer among the 2,462 RP procedures performed over 19 years. The biopsy re-analysis invalidated the initial diagnosis of prostate cancer in one biopsy set performed elsewhere. Among 12 entirely processed cases, the biochemistry procedure evaluated as "very unlikely" the occurrence of an error in tissue identification in the biopsy setting, during the surgical procedure or the pathological analysis. No identification error of tissue samples was established in this first verified pT0 series.

CONCLUSIONS

Although it must be suspected, specimen identification error was not a cause for pT0 prostate cancer. Only after a full pathological and DNA verification, the pT0 stage remains a sole entity, unexplained in most cases.

[Status and medicolegal implications in France pT0 stage of prostate cancer: a study by the CC-AFU]

OBJECTIVE

To assess the frequency, circumstances, and possible medico-legal consequences of the pT0 prostate cancer, defined by the absence of tumor in a radical prostatectomy specimen.

METHODS

Six centers retrospectively identified all cases of pT0 and selectionned those that occurred without prior hormone therapy or prostate resection. Preoperative data, histological report and clinical and biological outcome were analyzed. The lawsuits' registry in pathology were consulted at insurance companies.

RESULTS

Thirty cases of pT0 prostate cancer (0.4%) were reported on 7693 patients. The median age was 63years, PSA 7.4ng/mL. The number of positive preoperative biopsies ranged from one to four for a median tumor length of 1mm (0.3 to 18mm). The biopsy Gleason score was 3+3 for 23 patients, less than 5 for six others and included a contingent of grade 4 in two patients. With a median follow-up of 82months, no clinical or biochemical recurrence was observed. One patient complaint for pT0 prostate was found in the insurances registry.

CONCLUSION

The occurrence of a prostate pT0 called into question all the diagnostic procedures and surgical indication. To avoid a forensic procedure, urologists should inform patients of the possibility of this situation before radical prostatectomy.

[Histological modifications observed in prostate after preserving treatments for prostate cancer and their impact on Gleason score interpretation]

Total prostatectomy remains the main treatment for intermediate risk prostate cancer with a life expectancy greater than 10 years. In other cases non-surgical treatments can be proposed: external radiotherapy (exclusive or combined anti-androgen therapy), brachytherapy with permanent implants, high frequency ultrasounds (HIFU, Ablatherm), cryotherapy or exclusive hormonal treatment. For such patients in case of biological recurrence, prostate biopsies are usually performed in order to affirm the local recurrence. The histological confirmation of persistent tumor is usually required before any treatment: salvage surgery, cryotherapy, and brachytherapy or high intensity focused ultrasound (HIFU). Pathologists must be aware of the histological modifications induced by these different treatments in order to ensure an optimal interpretation of the biopsies. In this review, we describe the modifications observed in the normal prostate and in cancers after these various therapeutic methods, and also after alpha reductase inhibitors proposed as treatment of benign prostate hypertrophy and prostate cancer chemoprevention.

Search for residual prostate cancer on pT0 radical prostatectomy after positive biopsy

Reported incidence of no residual prostate cancer (i.e. pathological stage pT0) on radical prostatectomy ranges from 0.07 to 4.2%. The incidence is higher after neoadjuvant endocrine treatment. The aim of this study was to search for residual cancer on radical prostatectomy (RP) specimens when an initial sampling failed to find the cancer in patients with positive biopsy. Our database of 1,328 consecutive patients whose biopsies and RP specimen were both examined at the Polytechnic University-United Hospitals of the Marche Region between March 1995 and June 2006 was reviewed. The radical prostatectomies were grossly completely sampled and examined with the whole mount technique. We identified eight patients (i.e. 0.6%; three untreated and five hormonally treated preoperatively, i.e. 0.3 and 0.8%, respectively, of the total number of RPs included in the study) with positive biopsy and with no residual cancer in the initial routine histological examination of the RP. The RP of this group of eight was subjected to additional sectioning and evaluation of the paraffin blocks of the prostatectomy, also after block-flipping, immunostaining with an antibody against CAM 5.2, p63, PSA, and alpha-methylacyl-CoA racemase, and DNA specimen identity analysis. There were no cases with a false positive biopsy diagnosis, and cancer was not overlooked or missed in the initial routine histological examination of any of the 8 pT0 RPs. A minute focus of cancer (the diameter was always below 2.0 mm) was found on the additional sections in five. In particular, cancer was found after block-flipping in one of them. In an additional case, cancer was eventually discovered after immunostaining tissue sections for cytokeratin CAM 5.2, for p63 and PSA. In the remaining two cases (one untreated and the other hormonally treated), cancer was not found (0.15% of the 1,328 RPs included in the study); the review of the description of the macroscopic appearance of the RP and of its slides revealed that part of the peripheral zone corresponding to the site of the positive biopsy was missing, i.e. not removed from the patient at the time of the operation at least in one of the two. DNA specimen analysis confirmed the identity of the biopsy and prostatectomy in both. An extensive search for residual cancer reduces the number of pT0 RPs after a positive biopsy from 0.6 to 0.15%. It is recommended to have the needle biopsy reviewed, carefully look again at the radical prostatectomy, do deeper sections and then flip certain paraffin blocks. In addition, atypical foci should be stained for basal cell markers and often AMACR, especially in hormone-treated cases. If a block is missing part of the peripheral zone (capsular incision), this should be commented on. DNA analysis for tissue identity should be performed when the other steps have been taken without finding cancer.

No residual cancer on radical prostatectomy after positive 10-core biopsy: incidence, biopsy findings, and DNA specimen identity analysis

CONTEXT

It is uncertain whether extensive prostate-specific antigen (PSA) testing and extended biopsies currently performed will increase the incidence of no residual cancer on subsequent prostatectomy.

OBJECTIVE

To identify the incidence of cases with no residual cancer on prostatectomy after a positive 10-core biopsy and to review the clinical, biopsy, and prostatectomy findings and the results of specimen identity analysis.

DESIGN

We identified 9 patients with no residual cancer in 1351 consecutive prostatectomies and we reviewed the clinical, biopsy, and prostatectomy data from our institutional database. In 6 cases encountered after 2003, we also performed a polymerase chain reaction-based microsatellite analysis on formalin-fixed tissue to confirm the identity of the biopsies and prostatectomies.

RESULTS

All patients had positive biopsies in 1 or 2 cores: 1 in 7 and 2 in 2 patients (1 each, unilateral and bilateral). Mean total cancer length on biopsy measured 2.5 mm, which represented 1.7% of the total biopsy tissue. Gleason score 6 was found in 8 of 9 patients and 1 patient had Gleason score 9. Patients' age was 60.3 years, preoperative PSA was 6.0 ng/mL, and PSA density was 0.1 (all means). In 6 cases tested for microsatellite identity, the patient identity was confirmed.

CONCLUSIONS

Incidence of no residual cancer on prostatectomy of 0.67% after 10-core positive biopsy is higher than previously reported. In most cases, finding no residual cancer on prostatectomy after exhaustive work-up may indicate minimal patient disease. Microsatellite analysis provides a useful and cost-effective test in establishing specimen identity.