Cancer DNA is detectable in blood years before diagnosis

Commercial blood-based cancer tests and “Theranos vibes”

• Commenters joke about a kitchen-counter cancer blood tester backed by VC and a charismatic founder, alluding to Theranos.
• Several existing services are mentioned: multi-marker wellness panels and the Galleri multi‑cancer early detection (MCED) test, costing ~$800–$1,000 and sometimes offered via life insurers or longevity clinics.
• Users who’ve taken Galleri generally value it, but others question affordability, especially for “average families” and outside the US/UK.

Actionability, anxiety, and personal stories

• People ask what one actually does with a positive MCED: see a doctor, then imaging/biopsies/oncology referral.
• Anecdotes: one person uses annual tests after losing a friend to late-stage cancer; another relative had a positive ctDNA‑type result that never led to detectable cancer, causing a year of intense anxiety before the signal disappeared.
• Early-detection promise is emotionally compelling for those with family cancer or Alzheimer’s risk.

Sensitivity, specificity, and overdiagnosis

• Multiple medically informed commenters stress that many people harbor pre‑cancerous clones and low‑level cancer signals that never become clinically relevant.
• The core problem: current ctDNA/MCED tests struggle to balance sensitivity and specificity; at population scale, false positives and detection of indolent lesions could lead to unnecessary imaging, biopsies, surgeries, and even serious complications.
• Some argue “you’re better off not knowing” in many scenarios; others push back, emphasizing lives that might be saved.

Costs, insurers, and health‑system incentives

• One view: insurers avoid paying for early screening despite the ability to detect cancer early; others respond that high test cost, follow‑ups, and unknown net benefit justify caution.
• Debate over whether broad screening would actually save money once you include all negatives and workups.
• US insurance barriers (e.g., difficulty getting PET scans) are contrasted with the idea of universal systems where individuals don’t pay out of pocket.

Technical and research challenges

• Experts describe ctDNA workflows, ultra‑low allele fraction noise, CHIP, and background somatic mutations, noting population‑level utility is still unproven.
• Some see promising roles in post‑treatment relapse monitoring; proactive screening in asymptomatic people is described as “dicier.”
• Others propose massive longitudinal datasets (blood sequencing, imaging, cheap high‑bit sensors) plus ML to extract predictive patterns—acknowledging cost, ethics, and data/consent issues.

Possible futures and study skepticism

• Ideas include tiered non‑invasive screening, better precancer treatments, lifestyle‑targeted interventions, and community‑driven trials.
• One commenter flags that the underlying study may be overhyped: paywalled, unclear false‑positive data, and no independent validation mentioned in the press coverage.