FAQ-093: What are LI-RADS treatment response categories?
They are categories reflecting the probability of viability after locoregional treatment.
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FAQ-094: Do the LI-RADS treatment response categories correspond exactly to histological viability?
No, the categories reflect probabilities, they do not correspond to exact histological viability.
For example, noninvasive imaging cannot exclude small foci of live tumor cells. Hence, LR-TR nonviable means there is no evidence of gross viable tumor, but it does not exclude histological viability.
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FAQ-095: What is a treated observation?
An observation that has been treated by locoregional therapies such as radiofrequency ablation, percutaneous ethanol ablation, cryoablation, microwave ablation, transarterial embolization or chemoembolization, doxorubicin-eluting bead chemoembolization, transarterial radioembolization, and external beam radiotherapy.
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FAQ-096: What about observations treated by systemic therapy?
LI-RADS v2018 does not address systemic treatment response assessment.
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FAQ-097: Can I use LI-RADS Treatment Response algorithm in a patient that underwent both locoregional therapy and systemic therapy?
Yes. In patients undergoing systemic therapy, radiologists at their discretion may apply the treatment response algorithm to assess lesions after locoregional therapy. Radiologists may not apply this algorithm to assess the treatment response of other lesions in such patients, however.
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FAQ-098: How do I determine if a treated observation is nonevaluable?
A category of LR-TR Nonevaluable should be assigned if treatment response cannot be meaningfully evaluated due to inappropriate imaging technique or inadequate imaging quality. Do not assign a response category of nonevaluable if image quality is adequate, even if imaging features are difficult to characterize or interpret.
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FAQ-099: What if the arterial phase is inadequate but the portal venous phase shows unequivocal enhancement? Is that Nonevaluable or Equivocal?
Assign a response category of LR-TR Equivocal. Consider immediate repeat imaging or, if needed to ensure an adequate arterial phase, alternative imaging.
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FAQ-100: What is the optimal follow-up interval to assess treatment response?
Optimal follow-up intervals depend on the treatment, institutional guidelines, and reimbursement constraints. In general, follow-up CT or MRI is recommended every 3 months, although initial imaging at 1 month may help after certain treatments.
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FAQ-101: Are there any pitfalls in assessing response too soon after treatment?
Treatment-related changes in parenchymal perfusion may resemble or obscure tumor enhancement, potentially leading to false positive or false negative assessment of viability. This pitfall is particularly relevant for radioembolization or external beam radiation therapy, where lesions may retain APHE and even grow slightly for the first several months after treatment.
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FAQ-102: What should I do if I am unsure about tumor viability versus posttreatment change?
Categorize as LR-TR Equivocal if image quality is adequate.
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FAQ-103: Does LR-TR nonviable exclude microscopic viability?
No. LR-TR nonviable means there is no evidence of gross viable tumor, but small foci of live tumor cells cannot be excluded by noninvasive imaging.
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FAQ-104: How do I distinguish residual tumor from new tumor adjacent to a treated observation?
In contrast to new tumor in adjacent liver, residual tumor usually arises within or at the margin of the treated observation. No single threshold distance from the margin reliably distinguishes a new lesion from a marginal recurrence. Use your judgment to make the distinction and apply the corresponding LI-RADS algorithm (CT/MRI Treatment Response or Diagnostic). Example: a new observation has features indicating de novo origin (e.g., nodule in nodule) and/or excluding metastasis from the treated lesion (e.g., differences in fat, iron, HBP intensity): this should be considered a new tumor.
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FAQ-105: How do I assess the response of tumor in vein to treatment?
This can be challenging. Apply the LI-RADS treatment response criteria as best you can.
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FAQ-106: How do I categorize and report a new tumor in vein that arises adjacent to a treated observation?
The new tumor in vein should be categorized as LR-TIV and reported as “new LR-TIV adjacent to a treated observation”. The treated observation should be categorized and reported as any other treated observation. Rationale: the finding of new tumor in vein should be communicated to the treating physician as LR-TIV, as this new finding can affect the management of the patient, regardless of the treatment response category of the treated observation.
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FAQ-107: Do I need to assess response of each observation if the number of observations is large?
If there are a large number of treated observations with similar posttreatment imaging features and likely representing similar response, you may assess treatment response in aggregate.
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FAQ-108: How do I categorize the treatment response of an observation that completely disappears after treatment?
As nonviable – i.e., LR-TR nonviable.
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FAQ-109: How do I assess the treatment response of an observation that develops along the surgical margin of a resected tumor?
New observations located along the surgical margin should be categorized using the LI-RADS treatment response algorithm as nonevaluable, nonviable, equivocal, or viable.
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FAQ-110: How do I assess an observation that develops remote from the surgical margin of a resected tumor?
An observation that develops remote from the surgical margin after hepatectomy should be categorized using the LI-RADS diagnostic response algorithm as LR-NC, LR-TIV, LR-1, LR-2, LR-3, LR-4, LR-5, or LR-M.