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Peter Attia MD#62–Keith Flaherty, M.D.: Deep dive into cancer—History, novel treatments, & the exciting future
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CHAPTERS
- 0:04 – 7:41
Why the podcast runs on listener support, and the guest introduction
Peter Attia explains why the show takes no ads and relies on member support, then introduces Dr. Keith Flaherty and previews the episode's topics, from chemotherapy history to liquid biopsies and melanoma.
- •Attia says ads conflict with trust and with his need to be enthusiastic about what he promotes
- •Members get exclusive show notes, AMA access and product deals
- •Flaherty is a physician scientist at Mass General focused on targeted therapies and immunotherapy
- •The episode covers the history of cancer treatment, liquid biopsies, CRISPR, stem cells, vitamin D and melanoma
- 7:41 – 16:43
Boston weather, Flaherty's upbringing and the path into medicine
Attia and Flaherty open with small talk about Northeast climate and Flaherty's moves from Baltimore to Boston. Flaherty then describes growing up with two physician parents and how watching their devotion to their careers drew him to medicine and a wish to help people directly.
- •Flaherty's path ran from Baltimore through Connecticut, Boston and Philadelphia before Mass General
- •His father was an academic cardiologist and later worked in industry; his mother is an academic psychiatrist
- •He wanted to avoid transactional business and help people more directly
- •Seeing his parents' conviction about their work shaped his choice of medicine
- 16:43 – 25:16
Medical education, investigation and the accelerating pace of oncology
Flaherty describes his career as two decades of accelerating change and the need for new skills such as working with computational biologists. Attia criticizes medical school as anti-intellectual, and Flaherty agrees that investigation isn't taught and that medicine teaches the known rather than the frontier.
- •2000-2010 translated molecular insights into medicine; 2010-2020 moved far faster
- •Flaherty tells mentees to learn to talk to bioinformaticians and computational biologists
- •Attia calls medical school one of the most anti-intellectual forms of higher education
- •Clinical medicine is essentially Bayesian reasoning, though recency bias contaminates it
- •Flaherty pitches cancer as a career because the boundary of the unknown is so easy to reach
- 25:16 – 37:14
Why chemotherapy, radiation and surgery hit an asymptote
The two define chemotherapy as drugs found by screening for what kills fast-growing cells, which explains its side effects and its limits. They discuss how little metastatic disease outcomes changed from 1974 to recent years, how cancer cells evolve under selective pressure, and where surgery and radiation reach their limits.
- •Blind screening produced DNA-damaging and microtubule drugs that cure testicular cancer and some leukemias and lymphomas but few others
- •Cancer cells have already survived immune and metabolic pressures, so chemo adds only another insult
- •Radiation is local, and surgery has become safer without changing long-term survival for cancers like pancreatic
- •Metastasis is hard for a cancer cell, so many surgical patients with microscopic spread are still cured
- 37:14 – 45:57
The genome era: drivers, two-hit hypothesis and the hope for an AZT of cancer
Attia sets the scene at the late 1990s, when the genome was nearly sequenced, and asks what was known. Flaherty explains driver mutations, tumor suppressors versus oncogenes, and the two-hit hypothesis. He recounts his own pitch to find cancer equivalents of AZT, drawing on his HIV-era training.
- •In the late 1990s it wasn't known how many true driver mutations a typical cancer needed
- •The two-hit hypothesis involves inherited loss of a tumor suppressor followed by a second hit
- •The Cancer Genome Atlas revealed many epigenetic regulators among drivers, giving cells plasticity
- •Flaherty hoped to catalog activated events and target them with drugs as HIV drugs were targeted
- •Many in the field thought his idea naive given cancer's complexity
- 45:57 – 46:03
Bcr-Abl, imatinib and the first targeted therapy success
Flaherty explains the Bcr-Abl translocation in chronic myelogenous leukemia and how imatinib came from a kinase inhibitor library to show striking responses in a phase one trial. He covers the objection that CML is genetically simple, and the weak durability of responses in accelerated and blast-crisis disease.
- •CML involves a Bcr-Abl fusion that makes normal Abl kinase hyperactive, visible as a chromosomal shift
- •Imatinib came from a Ciba-Geigy kinase inhibitor library, championed by Brian Druker
- •Phase one patients responded consecutively, which Flaherty called an AZT moment
- •Responses in advanced, genetically complex CML were transient
- •Fusion-driven solid tumors later showed deep, durable responses
- 46:03 – 1:07:07
Immunotherapy, checkpoint inhibitors and tumor immune visibility
Attia takes a detour into the immunotherapy era. Flaherty explains why melanoma and kidney cancer are visible to the immune system, how PD-1 and CTLA-4 blockade work, and what MHC antigen presentation is. They also cover how tumors evade immune attack and why some cancers like pancreatic cancer and glioblastoma remain black boxes.
- •Melanoma has a very high mutation burden and heavy T cell infiltrate that predicts outcome
- •Kidney cancer is immunogenic without a high mutation burden, for reasons not yet known
- •CTLA-4 blockade can cause severe gut autoimmunity, and interleukin-2 acts like sepsis in a bottle
- •MHC complexes present protein fragments, and cancers that survive checkpoint therapy dial down MHC expression
- •About 10% of patients get heroic benefit from PD-1 antibodies and about 20% respond
- 1:07:07 – 1:12:03
Epigenetic plasticity and resistance across therapies
Flaherty returns to the Cancer Genome Atlas finding that epigenetic regulators are commonly mutated, letting cancer cells open the genomic blueprint. He explains how melanoma cells that survive BRAF and PD-1 therapy revert toward a neural crest-like state, a theme seen across tumor types.
- •Epigenetic regulators were found to be driver events commonly across cancer
- •Cancers open up the genetic blueprint to gain plasticity and take on abilities their normal counterparts lack
- •Melanoma cells surviving BRAF and PD-1 therapy resemble neural crest cells
- •Convergent resistance programs appear across very different therapy types
- 1:12:03 – 1:53:54
Defining targeted therapy: HER2, EGFR and the oncogene landscape
Flaherty defines targeted therapy as drugs whose target was known from the start and describes early HER2 and EGFR antibodies. He walks through how tyrosine kinases, chromosomes and genes fit together, then covers P53, RB, growth factor receptors, RAS, PI3 kinase and BRAF, ending with the 2002 BRAF discovery.
- •Early HER2 antibodies alone gave 10-20% response rates but worked with chemotherapy
- •P53 is mutated in about 50% of cancers, but its pathway is almost always disrupted
- •About 25% of cancers have a RAS mutation, 20% a PI3 kinase mutation and 8% a BRAF mutation
- •The 2002 Nature paper found BRAF V600 mutations clustered in the kinase domain, with about 50% of melanomas affected
- •Oncogene addiction means a cancer relies on an activated oncogene for more than one function
- 1:53:54 – 2:06:40
From metastatic to adjuvant therapy: HER2, GIST and BRAF/MEK combinations
Flaherty shows how treating earlier, microscopic disease works better, using adjuvant HER2 antibody, hormonal therapy, imatinib in GIST and BRAF/MEK in melanoma. He explains how melanoma bypasses BRAF through CRAF and why combinations and several biological pillars will be needed.
- •Adjuvant HER2 antibody cuts recurrences by a third to a half and can cure patients
- •Longer adjuvant hormonal therapy works better, suggesting suppression rather than eradication in some patients
- •BRAF inhibitor alone doubled melanoma survival but resistance came through CRAF bypass
- •BRAF/MEK combination in the adjuvant setting prevents relapse by 50%
- •Attia compares stacking drug classes across pillars to HAART for HIV
- 2:06:40 – 2:18:10
Why combination therapies aren't being tested: biotech fragmentation
Attia shares his clinical framework for cancer, and Flaherty explains the obstacle to combining drugs. He says HIV advocacy shaped favorable regulation, but cancer drugs are scattered across small biotechs, so few rational combinations get tested. They also touch on gene therapy and CRISPR as unrealistic for now.
- •Attia's framework is to avoid cancer, detect it early, and use multi-pillar therapies
- •Flaherty says regulators are allies and the problem is drugs sitting in different companies
- •About 60% of cancer pipeline drugs come from small biotechs, and Flaherty says 0.37 of rational combinations of investigational drugs reach trials
- •He thinks quadruplet therapy is needed for complex cancers
- •Gene therapy and CRISPR can't currently reach every cancer cell, so Flaherty doesn't focus on them
- 2:18:10 – 2:25:21
Liquid biopsies and early cancer detection
Flaherty and Attia discuss circulating tumor DNA, exosomes and circulating tumor cells as ways to detect cancer before it presents. Challenges include tissue of origin, which epigenetic lineage mapping may address, and Flaherty also highlights monitoring treatment response.
- •Tumors under a centimeter likely shed DNA, though how small is not mapped
- •A P53 mutation in blood doesn't reveal which organ the cancer is in
- •Circulating tumor cells and epigenetic lineage mapping could identify tissue of origin
- •Liquid biopsies can also monitor therapy and minimal residual disease
- 2:25:21 – 2:41:59
Stem cell therapy, cancer's link to aging, and the vitamin D–sun debate
Attia asks about intravenous stem cell therapy, and Flaherty says wild-type stem cells should follow the rules unless altered. They then discuss why cancer risk rises with age, and the vitamin D, exercise and melanoma sun exposure debate, where Flaherty doesn't advocate more sun.
- •Flaherty thinks wild-type stem cells won't go rogue without significant genetic perturbation
- •Cancer rises with age because of accumulating mutations and failing DNA repair and immune surveillance
- •Flaherty says that if everyone lived to 130 we'd all get cancer, and competing risks mask this late in life
- •He suspects exercise is a confounder in sun and vitamin D studies and suggests sun-safe exercise
- •David Fisher's work links sun-seeking to endorphin release alongside melanocortin
- 2:41:59 – 2:57:28
Bridging academia and industry, diagnostics, and closing thoughts
Attia asks how Flaherty straddles academic research and industry. Flaherty explains his work depends on industry, the importance of companion diagnostics, misalignments such as the RAS-mutant EGFR example, and why clinical investigators belong on company boards. The episode closes with his optimism about the pace of progress.
- •Therapies come from companies, so translational researchers must understand industry constraints
- •Diagnostics are half the precision medicine equation but poorly incentivized
- •Carving RAS-mutant colorectal patients out of an approved EGFR antibody took years
- •Flaherty has co-founded several companies and says translational clinical investigators are missing from boards
- •He ends optimistic that progress in cancer is quickening
