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).