Problematic analysis of pseudoprogressions:
Fig. 10: Problematic analysis of pseudoprogressions
At conventional imaging:
Pseudoprogression: self-limited enhancing lesions that spontaneously stabilize and resolve without treatment.
True progression. During the first 12 weeks after RT+QT or RT alone:
- New enhancement outside radiation field
- Pathologic confirmations of progressive disease
- Subependymal enhancement
With conventional techniques,
in most cases it is not possible to differentiate pseudoprogression and true progression.
Fig. 11: At conventional imaging
At DWI:
Pseudoprogression: higher ADC values in treatment related changes
True progression: lower ADC values
Fig. 12: DWI differentiating pseudoprogression and true progression
ADC values may differentiate between true progression and pseudoprogression. Tumor recurrence usually presents with lower ADC values (mean & minimum).
Due to tumor heterogeneity,
DWI as a single ROI measure is inadequate.
Articles applied Voxel-wise analysis with ADC histograms analysis or parametric response.
However,
this advances analysis are NOT incorporated into clinical practice.
IMPORTANT!!! New enhancing lesion with DWI restriction...
think true progression.
Fig. 13: New enhancing lesion with DWI restriction ... think true progression
At DSC perfusion MRI:
Cerebral blodd volume (rCBV) elevated in malignant gliomas and relatively low in pseudoprogression.
Some estudies conclude that speficific relative thresholds are helpful:
- rCBV ratio thresholds ranging from 1.2 to 2.0 for pseudoprogression (low rCBV)
- rCBV>2.5 for recurrent disease (high rCBV)
Fig. 14: rCBV threshold values for pseudoprogression and recurrent disease
Variations in rCBV in respect to previous tumor:
- ⇓ 41% pseudoprogression
- ⇑ 21% disease progression
Hence,
>5% ⇑ in rCBV after treatment predicts poor survival
There is a conflicting evidence for the ability of rCBV to distinguish pseudoprogression from true progression.
Overlap results derived from coexistence of tumor with treatment-related enhancement.
Fig. 15: Variations of rCBV in respecto to previous tumor
Fig. 16: Importance of rCBV distinguishing pseudoprogression and true progression
At DCE perfusion MRI:
This perfusion technique allows "quantitative" and "semiquantitative" evaluation of enhancing tumor.
Ktrans and iAUC are better imaging markers than Ve and Kep,
and are significantly higher in the recurrent group.
Fig. 17: Ktrans and iAUC relatively higher in recurrent tumors
Semiquantitative analysis: curves of enhancing SI(signal intensity)/time
iAUC: reflects the degree of early leakage of contrast agent into the EES.
Depends on the hypervascularity and neoangiogenesis.
INCREASES IN TUMORS.
fAUC: HIGHER IN PSEUDOPROGRESSION. A measure of contrast retention within EES.
Reflecfs increased EES associated with ⇓ cellularity and more tissue damage.
Fig. 18: Semiquantitative analysis: curves of enhancing SI/time
Fig. 19: Different curves of enhancing SI/time in pseudoprogression and recurrent disease