ideasIdea
When the blood test is positive, hunt for the lesion with sensitive imaging
A positive blood test tells you cancer is back but not where. Combining whole-body MRI with modern PET tracers may find a single spot that can be zapped.
Patients who are ctDNA-positive but scan-negative are currently given systemic therapy or nothing. Whole-body MRI plus a lineage-appropriate PET tracer (PSMA, somatostatin receptor, FAP or fibroblast-directed imaging) detects lesions well below conventional CT thresholds, which would allow ablative treatment of true oligorecurrence and spare the rest systemic therapy.
Hypothesis
In ctDNA-positive, CT-negative patients, whole-body MRI plus a targeted PET tracer localises disease in at least 40%, and ablation of all detected lesions clears ctDNA in half of those patients.
Rationale
PSMA PET already redefined biochemical recurrence in prostate cancer by finding lesions in patients previously classed as non-localisable, and metastasis-directed therapy in that setting delays systemic treatment.
What would test it
A prospective imaging cohort in ctDNA-positive colorectal and breast cancer measuring localisation rate; if the rate exceeds a pre-set threshold, proceed to a randomised trial of ablation plus systemic therapy versus systemic therapy alone.
Maturity
early clinical
Who has to act
clinic
Cost to try
Medium ($1M to $50M)
Years to first evidence
4
Bottlenecks it attacks
- Dormant cells and minimal residual disease · After a 'successful' treatment, cells can sleep for years then relapse. We can barely detect them and cannot target them.
- Metastasis is understood least and studied last · Metastasis causes about nine in ten cancer deaths but gets a small fraction of research money and almost no trials of its own.