Multi-cancer early detection — screening that catches what standard tests miss

The Galleri test by GRAIL is a multi-cancer early detection (MCED) blood test. It analyzes patterns of DNA methylation in cell-free DNA circulating in the bloodstream. Cancer cells shed DNA with characteristic methylation patterns; the test uses machine learning to detect these signals and predict the tissue of origin when a positive result occurs.

The test screens for signals of more than 50 cancer types, including many for which no standard screening currently exists — pancreatic, ovarian, esophageal, gastric, and others. For these cancers, late-stage diagnosis is common because the disease is often asymptomatic until advanced. MCED testing is an attempt to shift detection earlier.

Important nuance: Galleri is not FDA-approved. It's available as a laboratory-developed test (LDT) through the GRAIL pipeline. Sensitivity varies by cancer type and stage — higher for some cancers, lower for others, and substantially higher at later stages than at early stages. The test is intended to complement, not replace, standard screening like mammograms, colonoscopies, and Pap smears.

A positive Galleri result is not a cancer diagnosis. It's a signal that warrants further workup, typically with imaging directed at the predicted tissue of origin. A negative result is reassuring but not definitive — some cancers will be missed. HealifyNow provides the clinical context: helping you understand whether the test is appropriate for you, what a result actually means, and what the next steps look like in either direction.

Cell-free DNA. When cells die anywhere in the body (normal turnover, immune activity, or disease), small DNA fragments enter the bloodstream. Cancer cells shed DNA at higher rates and with characteristic methylation patterns.

Methylation analysis. The Galleri test sequences cell-free DNA and analyzes methylation patterns at specific genomic sites. Cancer methylation signatures differ from normal tissue methylation in characteristic ways.

Machine learning classification. Algorithms trained on tens of thousands of samples with known cancer status classify the methylation pattern as cancer signal detected or not. If detected, additional algorithms predict the cancer signal origin (tissue type).

Sensitivity and specificity. Galleri's overall sensitivity is moderate — roughly 50% across all stages and cancer types. Sensitivity is higher for later-stage and certain cancer types, lower for early-stage and certain other cancer types. Specificity is high (>99%) — meaning false positives are rare.

Follow-up imaging. A positive result is followed by directed imaging (CT, MRI, PET) based on the predicted tissue of origin. Most positive results are followed up within 4-8 weeks. A workup may confirm a cancer (allowing earlier intervention) or may identify a non-cancer cause of the signal.

Step 1 — Initial consultation. 30-minute video visit with a clinician to discuss your situation, family history, current standard screening status, and whether MCED testing makes sense for you. We're honest if we don't think it's appropriate.

Step 2 — Test order. If we proceed, we order the Galleri test through GRAIL's pipeline. You schedule a single blood draw at a participating phlebotomy site.

Step 3 — Results. Results typically return in 10-14 business days. Two possibilities: "no cancer signal detected" (the large majority of results) or "cancer signal detected" with a prediction of cancer signal origin.

Step 4 — Follow-up. Negative result: continue standard screening, discuss whether to repeat MCED annually. Positive result: coordinated follow-up with directed imaging through your healthcare system. We support this transition.

Step 5 — Future testing. MCED is intended as an annual screening tool, similar to other annual checks. Insurance generally doesn't cover Galleri — pricing is transparent.