[MRI and staging evaluation of prostate cancer]

Prostate MRI: can we do without DCE sequences in 2013?

Multiparametric MRI (mp-MRI) of the prostate currently provides stable and reproducible performances. The usefulness of dynamic contrast-enhanced (DCE) sequences is currently challenged, as they sometimes only confirm what has already been observed on diffusion-weighted imaging (DWI) and require the additional purchase of a contrast agent. Eliminating these sequences may help accelerate the use of MRI in addition to, or in lieu of, prostate biopsies in selected patients. However, many studies show that these sequences can detect lesions invisible on T2-weighted and diffusion-weighted images, better assess cancer extension and aggressiveness, and finally help detecting recurrence after treatment. We present the various applications of dynamic MRI and discuss the possible consequences of its omission from the current protocol.

[Value of MRI in detection of extracapsular extension in prostate cancer: a prospective study comparing imaging and histology]

OBJECTIVE

To establish MRI's performances for the detection of extracapsular progression of prostate carcinoma, in a single center, analyzing the correlation between MRI imaging and histological analysis of prostate specimen.

METHODS

From February 2008 to June 2012, all the patients selected for prostatectomy had a pre-operative MRI. Diffusion, T2 and dynamic T1 with gadolinium injection sequences were realized on a 1.5T-MRI with external antenna. All imaging data was analyzed by a specialized radiologist. Prostate specimens were histologically analyzed throughout large blades for utmost topographic comparison. The histological TNM was compared to the MRI data. MRI's capacity in determining the existence and the size of extracapsular progression was studied.

RESULTS

One hundred and fifty-eight patients (median age 62 years old, mean PSA 8.6 ng/mL) were included, among which 45% of d'Amico low risk and 55% of intermediate and high risk. Histological results were 63% of pT2 and 37% of pT3. MRI's sensibility and specificity for detecting extracapsular progression were 0.30 and 0.85 respectively (PPV 0.54; NPV 0.67), with a 65% accuracy. In the low risk group, sensibility equaled to 0.16.

CONCLUSION

In our experience, MRI results were not reliable to influence the choice of treatment. It should be executed by expert radiologists, who are still very few.

Evaluation of [(18)F]-choline PET/CT for staging and restaging of prostate cancer

PURPOSE

To evaluate the accuracy of [(18)F]-choline (FCH) positron emission tomography/computed tomography (PET/CT) for staging and restaging of prostate cancer.

METHODS

FCH PET/CT was performed in 111 patients with prostate cancer using 200 MBq FCH: 43 patients [mean age 63 years; mean prostrate specific antigen (PSA) 11.58 microg/l] were examined for initial staging, and 68 patients (mean age 66.4 years) were examined for restaging (mean PSA 10.81 microg/l). FCH PET/CT results were correlated to histopathology, bone scan, morphology as revealed by magnetic resonance imaging (MRI) and CT, PET/CT follow-up and PSA follow-up after therapy.

RESULTS

FCH PET/CT scans at initial staging correctly showed no metastases in 36/38 patients undergoing radical surgery, as confirmed by PSA levels <0.1 microg/l 6 months postoperatively. Lymphadenectomy was performed in 24 of these patients, revealing four false FCH-negative lymph nodes (LN). In one patient, only lymphadenectomy was performed since a FCH-positive LN was confirmed by histology. Four patients showed FCH-positive bone metastases, as proven by bone scan. FCH PET/CT scans at restaging correctly revealed local recurrence in 36 patients. No pathological FCH uptake was observed in 11 patients with biochemical recurrence. Twenty-three patients showed FCH-positive LN. Twenty LN were surgically removed in seven patients. Histopathology verified metastases in all LN, but revealed two additional metastastic, FCH-negative LN. Seventeen patients showed FCH-positive bone metastases, as proven by bone scan or MRI. Sensitivity to detect recurrent disease was 86%.

CONCLUSION

The results obtained using FCH PET/CT scans for initial N-staging were discouraging, especially in terms of its inability to detect small metastases. Recurrent disease can be localized reliably in patients with PSA levels of >2 microg/l.