Radiology: Application of amide proton metastasis-weighted MRI in predicting histological grade of bladder cancer

According to statistics, bladder cancer is one of the most common urinary tract malignancies in the world, which can be divided into high-grade cancer and low-grade cancer, and its prognosis and treatment strategies are significantly different , especially for non-muscle-invasive bladder cancer
.
Transurethral resection of bladder tumours is generally recommended for patients with low-grade non-muscle-invasive bladder cancer, while patients with high-grade non-muscle-invasive or muscle-invasive bladder cancer often require more intensive treatment modalities such as radical cystectomy, systemic chemotherapy, and radiation therapy
。 Therefore, it is of great clinical significance
to accurately assess the histological grade of bladder cancer before surgery.

The reference standard procedure for preoperative grading of bladder cancer is transurethral resection or cystoscopic biopsy
.
However, these procedures are invasive and have the potential to undergrade the cancer
.
Inadequate grading can lead to inadequate treatment, such as incomplete resection, which can further lead to tumor recurrence or metastasis
.

Amide Proton Transfer Weighted (APTw) MRI, a subtype of chemical exchange saturation transfer imaging, is a molecular MRI technique that measures the chemical transfer properties
of amide protons located at a chemical shift of 3.
5 ppm.
APTw values reflect the concentration of moving macromolecules, such as proteins and peptides
.
Previous studies have shown that APTw MRI is helpful in assessing the histological grade of tumors such as gliomas, hepatocellular carcinomas, rectal cancers, and endometrial adenocarcinomas
.
However, studies by APTw MRI in assessing the grade of bladder cancer have not been well established
.

A study published in the journal Radiology explores the potential of amide proton transfer-weighted (APTw) MRI in evaluating the histological grading of bladder cancer and evaluates the value
of APTw MRI in increasing the diagnosis of bladder diffusion-weighted MRI.

The study recruited pathologically confirmed participants with bladder cancer in a university teaching hospital between July 2020 and September 2021, each treated with a lesion greater than 10 mm
.
All participants underwent preoperative multiparametric MRI, including APTw MRI and DWI
.
The mean APTw and apparent diffusion coefficient (ADC) values of the primary tumor are measured independently by two radiologists and a subject operating characteristic curve is generated to assess the diagnostic performance
of these quantitative parameters.

In total, there were 83 participants (mean age, 64 years± 13 [SD]; 72 men) were evaluated
.
Fifty-one had high-grade bladder cancer and 32 had low-grade bladder cancer
.
APTw values were higher for high-grade bladder cancer compared with low-grade bladder cancer (6% [IQR, 4%-12%] vs 2% [IQR, 1%-3%]; P < .
001), ADC values are lower (0.
92 × 10-3 mm 2/sec ± 0.
17 vs 1.
21 × 10-3 mm²/sec ± 0.
25; P <.
001).

APTw and ADC distinguished AUCs for low- and high-grade bladder cancer similarly (both 0.
84; P = .
94).

In addition, the combination of the two techniques improved diagnostic performance (AUC, 0.
93; all P = .
01).

MRI image of a 63-year-old woman with bladder cancer with a tumor 20 mm
long.
Axial position (A) T2-weighted image, (B) diffusion-weighted image (b=1000 sec/mm²), (C) dynamic contrast enhancement image, (D) apparent diffusion coefficient (ADC) image, (E) Amide proton transfer weighted (APTw) image of T2-weighted image fusion, and (F) microscopic image of hematoxylin-eosin staining (original magnification, 3100).

(E) The color bar represents the APTw value
.
Bladder imaging report and data system 2 points
.
The average ADC and APTw values measured by the two radiologists were 1.
11 3 1023^mm2/sec and 2%,
respectively.
Pathologic examination after transurethral resection showed no detrusor invasion, and the histological grade of the lesion was low

This study suggests that amide proton transfer-weighted (APTw) MRI is beneficial in assessing the histological grade of bladder cancer and can provide additional information to improve the diagnostic outcome
of diffusion-weighted MRI.

Original source:

Huanjun J Wang,Qian Cai,Yiping P Huang,et al.
Amide Proton Transfer-weighted MRI in Predicting Histologic Grade of Bladder Cancer.
DOI:10.
1148/radiol.
211804