European Radiology: How to distinguish peritumoral abnormalities in enhanced CT after implantation of liver malignant particles?

Hepatocellular carcinoma (HCC) is known to be the most common primary malignancy of the liver and one of the most common cancers worldwide, followed by cholangiocarcinoma
.
In addition, the liver is also one of the most common metastatic organs, with the most common metastases
associated with colorectal, melanoma, and pancreatic cancer.

Iodine-125 radioparticle brachytherapy (BIRS) has a favorable effect
on the safety and efficacy of primary and secondary liver malignancies.
BIRS is able to release high doses of radiation into the tumor in a concentrated manner, while the dose outside the surface of the target volume drops sharply, reducing damage
to surrounding tissues.
Therefore, BIRS can be performed where thermal ablation is exposed to complications or replace external beam radiation therapy (EBRT)
when the relevant dose cannot be reached.
Therefore, BIRS offers another important treatment option
for patients with advanced cancer.

Based on cost availability, particle imaging capabilities, and accuracy of dose assessment, computed tomography (CT) is recommended for routine detection
of BIRS.
At this stage, CT is widely used to detect local progression
.
However, the atypical reinforcement around some particle implanted lesions is often indistinguishable from other lesions, which affects the clinical recognition
of local progression.
To date, there are few
data in the literature on these ambiguous anomalous radiographic changes.

Recently, a study published in the journal European Radiology analyzed the CT manifestations of HCC peritumor parenchyma to distinguish between local progression and benign response, providing a reference for clinical accurate evaluation of the therapeutic effect of lesions
.

This study retrospectively evaluated
enhanced CT images performed with particle implantation surgery between 2006 and 2018.
Hounsfield measured and quantitatively assessed peritumoral parenchymal and recorded and quantified classification, transformation, consequences, and serological indicators
during follow-up.
The Pearson χ2 test was used to analyze statistical differences
.

RSIPR was observed in 201 (69.
3%) of 290 lesions (161 patients; median age, 55 years; Range, 26-79 years), while 53 lesions developed local progression
.
The density of locally progressive lesions is much lower than that of RSIPR (P<0.
001), which does not exhibit equal/high density
in the portal phase or equilibrium phase.
Ring reinforcement of advanced lesions is also very different
from RSIPR.
The local progression rate of lesions with RSIPR was lower than in lesions without RSIPR (14.
9% versus 25.
8%; p = 0.
03), the dose was also different (397.
2 Gy vs 120.
3 Gy, p < 0.
001
).

Figure a A A 73-year-old woman with cholangiocarcinoma who relapses after resection and has undergone particle implantation, After 1 month it manifests as a type I reaction (green arrow) with several illusions (red stars).

Even after the second implantation, at the final follow-up (11 months after the first implantation), the lesion enlarged (orange arrow), manifested as a single low density
in three stages.
b A 78-year-old woman with rectal cancer appears at 5 months with a new oval-shaped protrusion (orange arrow) next to the particle, appearing as a high-density ring that surrounds a low-density

This study found that the characteristics of the described radioactive particle-induced peritumor response were associated
with higher doses and lower rates of local progression.
In addition, its enhancement mode differs from that of locally progressive augmentation, which facilitates identification from the latter on contrast-enhanced CT
.

Original source:

Guanyu Chen,Dechao Jiao,Sheng Peng,et al.
Peritumoral abnormalities on dynamic-enhanced CT after brachytherapy for hepatic malignancies: local progression or benign changes? DOI:10.
1007/s00330-022-09074-x