Current Impact of Transrectal Ultrasonography in Prostate Cancer Diagnosis

Aims

We evaluate the diagnostic accuracy of transrectal prostate ultrasonography (TRUS) in prostate cancer (PCa) diagnosis in a group of patients who underwent prostate biopsy in 2008.

Material and Methods

100 patients (mean age 65 years) underwent transrectal prostate biopsy at our center. Indications to biopsy were: suspected malignancy at rectal examination or increase of total PSA and/or PSA velocity and/or PSA density and/or low percentage of free PSA. 10–12 biopsies and additional ones in case of suspected ecographic images in every patient were carried out. We classified the ecographic aspects as: highly suggestive for heteroplasia (focal or widespread hypoechoic area in the peripheral zone), weakly suggestive (small hypoechoic focal alterations), and isohecoic areas.

Results

At ultrasound examination, highly suggestive images were found in 20 patients, weakly suggestive images in 39 patients, and isoechoic images in 41 patients. PCa was diagnosed in 45 patients. 40% of cancers (18 pts) appeared as highly suggestive hypoechoic images, 31% (14 pts) as weakly suggestive, and 29% (13 pts) as isoechoic. 32% was the positive predictive value of isoechoic areas biopsies, 90% of highly suggestive hypoechoic images, and 36% of weakly suggestive images. In the last ones, the diagnosis was often coincidental, i.e. in the opposite lobe, or in a different sextant of the same lobe (serendipity). Detection rate was 60% for prostate volumes ≤50 cc and 24% for volumes >50 cc.

Discussion

The result analysis allowed us to formulate the following considerations: - 60% of currently diagnosed PCa are not detectable by ultrasonography, or there are aspecific ecographic findings - 40% of cancers are detectable by ultrasonography with specific ecographic findings - The clinical value of the hypoechoic focal alterations is similar to isoechoic ones - Detection rate is positively influenced by prostate volume.

Conclusions

The study of hypoechoic and isoechoic bioptised areas shows a significant difference in TRUS accuracy in prostate cancer diagnosis. In this set of patients, prostate volume and transrectal ultrasonographic findings proved to be the most informative variables about PCa risk at the moment of first biopsy at any age.

Small cargo proteins and large aggregates can traverse the Golgi by a common mechanism without leaving the lumen of cisternae

Procollagen (PC)-I aggregates transit through the Golgi complex without leaving the lumen of Golgi cisternae. Based on this evidence, we have proposed that PC-I is transported across the Golgi stacks by the cisternal maturation process. However, most secretory cargoes are small, freely diffusing proteins, thus raising the issue whether they move by a transport mechanism different than that used by PC-I. To address this question we have developed procedures to compare the transport of a small protein, the G protein of the vesicular stomatitis virus (VSVG), with that of the much larger PC-I aggregates in the same cell. Transport was followed using a combination of video and EM, providing high resolution in time and space. Our results reveal that PC-I aggregates and VSVG move synchronously through the Golgi at indistinguishable rapid rates. Additionally, not only PC-I aggregates (as confirmed by ultrarapid cryofixation), but also VSVG, can traverse the stack without leaving the cisternal lumen and without entering Golgi vesicles in functionally relevant amounts. Our findings indicate that a common mechanism independent of anterograde dissociative carriers is responsible for the traffic of small and large secretory cargo across the Golgi stack.

Procollagen traverses the Golgi stack without leaving the lumen of cisternae: evidence for cisternal maturation

Newly synthesized procollagen type I (PC) assembles into 300 nm rigid, rod-like triple helices in the lumen of the endoplasmic reticulum. This oligomeric complex moves to the Golgi and forms large electron-dense aggregates. We have monitored the transport of PC along the secretory pathway. We show that PC moves across the Golgi stacks without ever leaving the lumen of the Golgi cisternae. During transport from the endoplasmic reticulum to the Golgi, PC is found within tubular-saccular structures greater than 300 nm in length. Thus, supermolecular cargoes such as PC do not utilize the conventional vesicle-mediated transport to traverse the Golgi stacks. Our results imply that PC moves in the anterograde direction across the Golgi complex by a process involving progressive maturation of Golgi cisternae.