What is pseudo-progression and how common is it?

Pseudo-progression is initial apparent tumor growth or new lesions followed by subsequent response, caused by immune cell infiltration into tumors. True pseudo-progression occurs in approximately 3–7% of patients on checkpoint inhibitors; it is more common in melanoma (up to 10%) than other histologies.

When should immunotherapy be continued despite iUPD?

Continue immunotherapy with iUPD if the patient is clinically stable (no significant symptom worsening, no deterioration in PS). Reassess at 4–8 weeks. Convert to iCPD if any category shows further progression; declare clinical benefit if lesions stabilize or regress.

iRECIST Immune Response Evaluation

Apply iRECIST criteria for immunotherapy response assessment, accounting for pseudo-progression with unconfirmed PD (iUPD) requiring confirmation at 4–8 weeks before declaring confirmed PD (iCPD).

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Frequently Asked Questions

What is pseudo-progression and how common is it?

When should immunotherapy be continued despite iUPD?