Ash Alizadeh on Cancer Blood Tests and Early Detection

Ash Alizadeh, MD, PhD, a Stanford hematologist-oncologist and physician-scientist, joins The Future of Medicine for a conversation about cancer blood tests, DNA, early detection, and the growing ability to find traces of cancer that traditional scans may not yet reveal.

Alizadeh has helped pioneer approaches that search for tiny amounts of tumor DNA circulating in the bloodstream. In this episode, he explains the science in simple terms: as cells throughout the body die, fragments of their DNA enter the blood. Cancer cells can do the same. The challenge is finding those rare cancer signals amid an enormous amount of normal DNA — what Alizadeh describes as essentially a “needle in a haystack” problem.

The conversation explores two major possibilities for these technologies. One is detecting cancer in people who have not yet been diagnosed. Alizadeh discusses the promise of multi-cancer early detection tests, but also why showing that a test finds cancer sooner is different from proving that screening ultimately helps people live longer. He argues that these approaches may prove particularly useful when focused on people already at higher risk rather than trying to use a single test equally across dozens of cancers.

The second application may be closer to transforming cancer care: looking for molecular residual disease after treatment. Once doctors know the specific DNA changes within a person's tumor, a blood test can search for those same changes later, potentially revealing that cancer remains or is returning before it becomes visible on a scan. Alizadeh discusses how personalized DNA tests are already being studied and used across cancers including bladder, colon, lung, and breast cancer — and how emerging evidence could help doctors decide who needs additional treatment and who may be able to avoid unnecessary therapy.

Together, Alizadeh and host Euan Ashley explore what cancer DNA can tell us, where early detection still falls short, why finding residual disease could change treatment decisions, and what it may take to make cancer monitoring far more precise.

Thank you for listening!

Call to action: If you enjoy The Future of Medicine, subscribe for more conversations with leading scientists shaping the next era of healthcare. Please rate and review the podcast to help others discover these important discussions. Share with friends and colleagues who are curious about how science becomes medicine.