How would you assess apparent cancer progression when CT technique has changed?

Instruction: Calculate what the comparable target measurements establish, explain the remaining uncertainty, and avoid assigning a complete response category from incomplete evidence.

Context: An oncology trial uses RECIST 1.1. The documented baseline target-lesion sum was 80 mm and the nadir was 50 mm. On matched portal venous images, the same reliably measured targets now total 56 mm. An additional arterial phase, absent from the previous study, shows two tiny liver foci that cannot confidently be called new metastases. Non-target disease is unchanged. The oncologist asks whether this is definite progression.

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I would report that the comparable target-lesion sum has increased by 6 mm, or 12%, from its nadir. That does not meet RECIST 1.1 target-lesion progression: the required relative increase has not been reached, even though the absolute increase exceeds 5 mm...

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