RECIST Response Criteria in Tigilanol Tiglate Trials: How Tumour Response Is Actually Measured
RECIST 1.1 is the standard framework for measuring tumour response in clinical trials. Here is how it applies — and where it falls short — for intratumoural agents like tigilanol tiglate.
When tigilanol tiglate clinical trial readouts say a tumour "responded," what was actually measured? In most oncology trials, the answer is the Response Evaluation Criteria In Solid Tumours (RECIST) framework — a standardised set of imaging-based rules that converts a complex tumour-burden assessment into a single response category. This article walks through RECIST 1.1, explains where it works well for intratumoural therapies, and flags where it understates or overstates response.
The RECIST 1.1 Categories
RECIST 1.1 was finalised by the EORTC-NCI-NCIC consortium in 2009 (Eisenhauer et al., European Journal of Cancer, 2009) and remains the dominant solid-tumour response framework. The investigator selects up to five "target lesions" at baseline (no more than two per organ), measures their longest diameters, and sums them. Every follow-up imaging assessment compares the new sum to the baseline sum.
Four response categories follow from that comparison. Complete Response (CR) means all target lesions have disappeared. Partial Response (PR) means the sum of target-lesion diameters has decreased by at least 30%. Progressive Disease (PD) means the sum has increased by at least 20% from the smallest sum observed during the trial, or new lesions have appeared. Stable Disease (SD) is everything in between — neither shrinkage large enough to call PR nor growth large enough to call PD.
Target, Non-Target, and New Lesions
Beyond the target lesions, RECIST tracks "non-target lesions" — measurable disease that wasn't selected for serial measurement — and any new lesions that appear during the trial. A subject can be in CR for target lesions but still be classified as PR overall if non-target disease persists, and any unequivocal new lesion overrides target-lesion shrinkage to mandate a PD classification.
This is the source of one common confusion in trial readouts: a press release may report a "50% tumour reduction" at an injected site, but the RECIST overall response for that subject can still be PD if a new lesion appeared elsewhere. The two statements describe different things and both can be true.
Where RECIST Works Well for Tigilanol Tiglate
For an intratumoural agent like tigilanol tiglate, the injected lesion is a target lesion under RECIST. Tigilanol tiglate produces rapid necrosis with measurable tumour-volume reduction; this shows up cleanly on RECIST measurements at the first imaging time-point after injection. Phase I and Phase II human trials run by QBiotics have reported response rates using RECIST 1.1, and the methodology is appropriate for the question being asked: did the injected tumour shrink?
Where RECIST Falls Short
Three structural limitations matter for tigilanol tiglate trials. First, RECIST measures diameter, not necrosis. A tumour that is 90% necrotic but unchanged in diameter is RECIST-stable but biologically responsive. This is a known issue with all locoregional therapies that produce internal tumour death without immediate shrinkage. Second, RECIST does not distinguish injection-site inflammation from progressive disease without expert reader judgment — early post-injection imaging can show apparent enlargement from oedema and inflammatory infiltrate. Third, RECIST is designed for systemic agents that affect all tumours equivalently; an intratumoural agent injected into a single lesion may produce dramatic local response while non-injected lesions follow their natural course, and the overall RECIST classification will reflect the average rather than the local effect.
Alternative Frameworks: mRECIST, iRECIST, and Volumetric Assessment
Several modified frameworks address these limitations. mRECIST (modified RECIST) measures viable, enhancing tumour rather than total diameter — appropriate for therapies that produce internal necrosis. iRECIST (immune RECIST), introduced in 2017, accommodates pseudoprogression — initial enlargement that resolves on subsequent imaging — by requiring confirmation of progressive disease at a second time-point. Volumetric assessment using three-dimensional reconstruction is more sensitive than diameter-based measurement but is not yet a regulatory standard.
Whether tigilanol tiglate trials should adopt mRECIST or iRECIST as primary endpoints is an open question. As we discussed in our piece on MRI as a response biomarker, imaging modalities that visualise tumour necrosis directly may eventually displace diameter-based RECIST in this setting. For now, conventional RECIST 1.1 remains the regulatory reference and is what appears in published trial reports.
Reading a Tigilanol Tiglate Trial Readout
Three numbers usually matter most in a tigilanol tiglate trial report: the objective response rate (ORR = CR + PR / total evaluable), the duration of response (DoR), and the local recurrence rate at injected sites. The ORR captures the question "did the tumour shrink under RECIST?" The DoR captures durability. Local recurrence captures whether the necrotic lesion regrew after initial response. Reading these three numbers together gives a more complete picture than ORR alone.
Distinguishing Pharmaceutical Trials from Supplement Use
All clinical-trial data discussed above refer to pharmaceutical-grade tigilanol tiglate (intratumoural injection) being evaluated for the treatment of specific cancer types. Oral blushwood berry extract dietary supplements — such as those produced by Blushwood Health — are a different product category, are not clinical-trial endpoints, and are not intended to diagnose, treat, cure, or prevent any disease. Readers interested in the supplement category should refer to our supplement overview rather than to RECIST-based pharmaceutical trial data.
Citations
1. Eisenhauer EA et al., New response evaluation criteria in solid tumours: RECIST 1.1, European Journal of Cancer, 2009.
2. Seymour L et al., iRECIST: guidelines for response criteria for use in trials testing immunotherapeutics, Lancet Oncology, 2017.
3. QBiotics Group — Tigilanol Tiglate clinical program, 2026.
4. EORTC RECIST resource site, 2026.
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