Theory 01/Oncology /Tumour biology/3 min
Dormancy Is a Plumbing Problem
A dormant metastasis is described as held in check by immunity. It may simply be waiting for blood.
Tumour dormancy is maintained by an angiogenic balance rather than by immune surveillance, so dormant micrometastases should wake when the balance tips toward vessel formation, and anti-angiogenic therapy can paradoxically end dormancy.
01The evidence
- Molecular mechanisms of tumour dormancy have been reviewed with angiogenesis among the candidate maintenance mechanisms, and metastases can remain quiescent for months or years in the tissue they colonised.Toxicology and Applied Pharmacology
- Resistance to anti-angiogenic therapy has been shown to depend on the timing of exposure, which implies that the angiogenic state is a switch rather than a dial and that intervening can move the switch.PMC review
02The tension
Dormancy is usually attributed to immune control: the micrometastasis is held by T cells until it escapes. That account explains some systems and poorly explains why dormancy can last decades, why immunosuppressed patients do not uniformly develop metastases, and why anti-angiogenic drugs sometimes precede rapid regrowth.
03The theory
A small cluster of tumour cells can survive without its own blood supply only up to a diffusion limit. Beyond that it needs vessels, and it cannot make them while the balance of pro- and anti-angiogenic signals favours quiescence.
If that balance is the gate, then dormancy is a vascular state rather than an immune one. Waking is a switch: when the local balance tips, for instance after surgery, inflammation or a change in therapy, vessels form and growth resumes.
The prediction is that the angiogenic ratio should predict relapse timing better than immune markers, and that therapies which shift the ratio, including some anti-angiogenics, should change dormancy duration in both directions.
The clinical consequence is that dormancy should be maintained rather than attacked: a therapy that keeps the ratio stable may be more useful than one that tries to kill dormant cells, which are already not growing.
04What this is not
Those models make T cells the gate. This makes the angiogenic balance the gate, which explains the timing pattern and the paradoxical regrowth after anti-angiogenic treatment.
05Predictions
- P1Angiogenic ratio should predict relapse timing better than immune markers.
- P2Therapies shifting the ratio should change dormancy duration in both directions.
- P3Dormant lesions should be avascular on imaging before they become detectable.
06What would refute it
Relapse predicted by immune escape regardless of vascular state would restore surveillance as the gate.
07What it would change
It would reframe dormancy as a maintenance problem, and change how adjuvant therapy is aimed.
08Evidence base
- Molecular mechanisms underlying tumor dormancyhttps://www.sciencedirect.com/science/article/abs/pii/S0304383510001412
- Resistance to anti-angiogenic therapies and the timing of exposurehttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC7381352/