Case of the Month - November

75 year old man with known prostate cancer presents with a rising PSA.

Investigations

MRI of the prostate, pelvis and spine was performed to look for local extension of the prostate cancer beyond the prostate into adjacent organs, to assess local pelvic lymph nodes and search for metastases to the axial skeleton. No abnormal pelvic lymph nodes or axial skeleton metastases were identified.

Left Image:  This is a transverse image from an MRI scan and shows invasion by the prostate tumour into the anterior wall of the rectum.

Middle Image:  This is a coronal MRI image demonstrating involvement of the left seminal vesicle.

Right Image:  A sagittal MRI image showing invasion into the posterior wall of the bladder.  

Discussion

The radiological assessment of prostate cancer utilises different imaging modalities, but may not be necessary in all patients with prostate cancer if the probability of spread beyond the prostate is low. Studies are usually tailored to the individual patients risk of extra prostatic extension and clinical stage. In the case of known metastatic disease, imaging can be used to aid in the detection of metastases and guide treatment.

CT scanning of the abdomen allows the identification of abnormal lymph nodes, both local and distant. It also allows local extension of cancer into adjacent organs to be assessed and can identify skeletal metastases.

Bone scanning is performed to identify skeletal metastases. It is less accurate but more practical than MRI scanning. Once PET scanning becomes available in Christchurch, PET bone scans will be able to be performed using labelled fluoride, with much improved definition compared with conventional scintigraphy.

MRI scanning is the most promising imaging modality for local staging of prostate cancer. It has been shown to improve the local staging of prostate cancer. It can help identify spread of cancer beyond the prostate into the adjacent bladder or seminal vesicles. It can also identify abnormal enlarged pelvic lymph nodes.

The MRI can be extended to include the bony pelvis and spine. MRI is excellent at detecting skeletal metastases as well as enlarged para-aortic lymph nodes. It can be used to further characterise questionable bone scan findings