TACE is the treatment of choice for intermediate stage HCC
patients which present the most common stage at time of diagnosis.
Monitoring tumor response to loco-regional therapy with imaging
is important in determining treatment success and in guiding future
therapy. Early identification of treatment failure is also critical in patient
management as further treatment will be mandatory before disease
progression. The European Association for the Study of Liver Disease
(EASL) has recommended the use of lesion enhancement, rather than
change in size, as the standard method to determine treatment response.
The EASL recommended contrast-enhanced multi-phasic CT scan
or contrast-enhanced MRI as the method to monitor tumor response to
TACE.
DW MR imaging is unique in its ability to provide information that
reflects tissue cellularity and the integrity of cellular membranes. With
recent advances in the MR hardware and techniques, DWI has expanded
its applications outside the brain. Thus, the diffusion MRI become
applicable in evaluation of HCC post TACE.
The patients included in this study were 42 patients with 59 HCC.
Follow up by dynamic MRI and diffusion imaging was done 3weeks-
5months post intervention.
We classified the Lesions according to the enhancement pattern in
the DCE MR into 4 groups: "Diffuse enhancement group",
Summary & Conclusion
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"Heterogeneous enhancement group", "Partial nodular enhancement
group" and "Complete response group".
We assessed the lesions according to their signal on T1 & T2WIs,
qualitative assessment of lesion signal on DWI and ADC map,
quantitative diffusion analysis (ADC measurement).
In our study we found that conventional T1WIs and T2WIs signal
are not reliable in the differentiation between necrotic and active tumoral
tissue post TACE.
We found that qualitative DWI and ADC map analysis showed
high sensitivity (83.9%) and low specificity (64.6%), fair PPV (72.2%)
and NPV (78.3%) and overall accuracy of 74.5%. This low specificity is
due to high number of false positive cases (10 lesions of 59 lesion
included in the study) which can be explained by the intralesional
hemorrhage and liquefactive necrosis.
The quantitative diffusion analysis showed significant difference
between the ADC values measured in the active tumoral area and those
measured at necrotic areas with no significant difference between the
areas of active tumoral enhancement in the different groups (diffuse
enhancement group, partial nodular enhancement group and
heterogeneous enhancement group).
ROC analysis was performed for the ADC values showing area
under curve 0.7 and maximum combined sensitivity and specificity of
79% and 69.6% respectively at cutoff ADC value of 1.395mm²/sec.
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The perilesional hypervascularity depicted by dynamic MRI is not
specific only for the recurrent lesions but also occurs in benign conditions
as a result of adjacent inflammation or other non tumorous arterio-portal
shunts, including direct arterioportal fistula or decreased portal venous
flow related to iatrogenically induced portal tract injuries in the territory
of selective TACE.
In our study, we included both the persistent perilesional
parenchymal enhancement and the uniform enhancing marginal
granulation tissue as benign pattern of enhancement which had been
detected in 13 lesion. Theses lesions underwent follow up 3-6 months
later to ensure their benign nature (No progression over time).
We found that DWI is a reliable method in the differentiation
between active tumor residual/recurrence and benign perilesional
enhancement as 84.6% of the proven benign enhancement showed
facilitated diffusion on the qualitative DWIs, with significant difference
noted between the ADC values measured at the benign perilesional
enhancement areas and the areas of active tumoral recurrence. |
