European Radiology: Imaging screening value for bone metastases in prostate cancer

It is well known that the detection of metastases is crucial
in determining the appropriate treatment and prognosis of newly diagnosed prostate cancer patients.
Current guidelines from the European Urological Association (EAU) recommend a bone scan (BS) in prostate cancer patients to detect bone metastases and abdominal cross-sectional imaging with lymph node staging to confirm the stage
in patients at intermediate and high risk.
The combination of biopsy results, PSA, and clinical T stage defines the risk group, while radiological T (radT) classification is not formally applied
.

Several studies have shown that the pelvis is the most common site of metastasis, with isolated bone metastases outside the pelvis occurring in only 0-0.
3%.

In addition, bone metastases are predominantly prevalent in high-risk patients, but few studies have reported metastases
in intermediate-risk populations.
This research group recently analyzed the routine use
of whole-body MRI for the detection of bone metastases using current eligibility criteria defined by EAU.
In this study, no bone metastases were found in the adverse risk group, and no extrapelvic bone metastases were found in the absence of pelvic metastases
.
Therefore, MRI of the lumbar spine and pelvis is now used as the standard screening method
for lymph node and bone metastases.

MRI, choline PET/CT, and PSMA PET/CT are superior to BS
in detecting bone metastases.
In the mixed population with untreated and recurrent disease, the overall sensitivity of MRI was 91–97%, PSMA PET-CT 97%, choline PET-CT 87–91%, NaF PET-CT 96%, and BS 79–86%.

Recently, a study published in the journal European Radiology verified the EAU screening criteria for bone metastasis in patients with treatment-naïve prostate cancer, and evaluated the ability and value of radiological T classification to predict bone metastasis, providing reference and technical support
for early clinical and accurate screening of high-risk prostate cancer patients.

This single-center retrospective study included all untreated patients
with untreated intermediate- or high-risk prostate cancer.
All patients underwent MRI scans of the lumbar column (T2Dixon) and pelvis (3DT2w, DWI, and T2 Dixon).

The presence and location
of lymph node and bone metastases are documented according to risk group and radiological (RAD) T stage.
Risk of lymph node metastasis is assessed by odds ratio (OR
).

The study included 390 patients, of whom 68% were high-risk and 32% were unfavorable
intermediate-risk.
In the high-risk group, the rates of regional and non-regional lymph node metastases were 11% and 6%, respectively, and the rate of bone metastases was 10%.

In the unfavorable intermediate-risk group, the rates of regional and non-regional lymph node metastases were 4% and 0.
8%, respectively, and the rate of bone metastases was 0.
8%.

In all patients, 0.
5% of metastases occurred only in the lumbar spine, 4% in the pelvis, and 3% in the pelvis and lumbar spine
.
All patients with bone metastases had radT3-4, and patients with radT3-4 had a fourfold increased risk of lymph node metastases (OR 4.
48, 95% CI: 2.
1 to 9.
5).

Pictured: An 82-year-old patient, cT3/radT4, PSA 108 ng/ml, ISUP 5
.
Solid arrows indicate right ischial body metastases, and dotted arrows indicate regional lymph node metastases
.
a Coronal T2 dixon lipid phase, (b) coronal T2 dixon aqueous phase, (c) axial position DWI b800 s/mm², (d) axial position ADC figure, (e) axis position 3DT2, (f) axis position DWI b800 s/mm²

This study showed that the overall prevalence of bone metastases was 10% in high-risk patients and 0.
8%
in unfavorable intermediate-risk patients.
The low incidence of metastases in the unfavorable intermediate-risk group suggests that too many screening tests in this category of patients result in a large degree of waste
.
In addition, no bone metastases were found in patients with radT1-2 disease in this study, suggesting that radT classification can improve the prediction of bone metastases
.

Original source:

Erik Rud,Daniyal Noor,Kristina Flor Galtung,et al.
Validating the screening criteria for bone metastases in treatment-naïve unfavorable intermediate and high-risk prostate cancer - the prevalence and location of bone- and lymph node metastases.
DOI:10.
1007/s00330-022-08945-7