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Peter Attia MDPeter Attia MD

181 - Viewing cancer through an evolutionary lens: a radically different approach to treatment

Robert (Bob) Gatenby is a radiologist who specializes in exploring theoretical and experimental models of evolutionary dynamics in cancer and cancer drug resistance. He has developed an adaptive therapy approach for treating cancer which has shown promise in improving survival times with less cumulative drug use. In this episode, Bob explains what brought him into medicine, his search for organizing principles from which to understand cancer, and the mathematical modeling of other complex systems that led him to model the dynamics of tumor cell changes in cancer. He discusses his pilot clinical trial treating metastatic prostate cancer, in which he used an evolutionary game theory model to analyze patient-specific tumor dynamics and determine the on/off cycling of treatment. He describes how altering chemotherapy to maximize the fitness ratio between drug-sensitive and drug-resistant cancer cells can increase patient survival and explains how treatment of metastatic cancer may be improved using adaptive therapy and strategic sequencing of different chemotherapy drugs. We discuss: 00:00:00 - intro 00:00:10 - Bob’s unlikely path to medicine and his disappointment with his medical school experience 00:12:30 - Rethinking the approach to cancer: using first principles and applying mathematical models 00:29:27 - Relating predator prey-models to cancer 00:37:50 - Insights into cancer gathered from ecological models of pests and pesticides 00:47:27 - Bob’s pilot clinical trial: the advantages of adaptive therapy compared to standard prostate cancer treatment 00:55:25 - New avenues of cancer therapy: utilizing drug-sensitive cancer cells to control drug-resistant cancer cells 01:03:29 - The vulnerability of small populations of cancer cells and the problem with a “single strike” treatment approach 01:14:30 - Using a sequence of therapies to make cancer cells more susceptible to targeted treatment 01:25:56 - How immunotherapy fits into the cancer treatment toolkit 01:31:25 - Insights into why cancer spreads, where it metastasizes, and the source-sync trade off of cancer 01:42:45 - Defining Eco- and Evo-indices and how they can be used to make better clinical decisions 01:55:24 - Advantages of early screening for cancer 01:58:36 - Bob’s goals for follow-ups after the success of his prostate cancer trial 02:09:22 - Treatment options for cancer patients who have been told they have “failed therapy” Show notes page: https://peterattiamd.com/robertgatenby/ -------- About: The Peter Attia Drive is a weekly, ultra-deep-dive podcast focusing on maximizing health, longevity, critical thinking…and a few other things. With over 30 million episodes downloaded, it features topics including fasting, ketosis, Alzheimer’s disease, cancer, mental health, and much more. Peter is a physician focusing on the applied science of longevity. His practice deals extensively with nutritional interventions, exercise physiology, sleep physiology, emotional and mental health, and pharmacology to increase lifespan (delay the onset of chronic disease), while simultaneously improving healthspan (quality of life). Learn more: https://peterattiamd.com Subscribe to receive exclusive subscriber-only content: https://peterattiamd.com/subscribe Sign up to receive Peter's email newsletter: https://peterattiamd.com/newsletter Connect with Peter on: Facebook: http://bit.ly/PeterAttiaMDFB Twitter: http://bit.ly/PeterAttiaMDTW Instagram: http://bit.ly/PeterAttiaMDIG Subscribe to The Drive: Apple Podcast: http://bit.ly/TheDriveApplePodcasts Overcast: http://bit.ly/TheDriveOvercast Spotify: http://bit.ly/TheDriveSpotify Google Podcasts: http://bit.ly/TheDriveGoogle

Peter AttiahostRobert Gatenbyguest
Oct 25, 20212h 18mWatch on YouTube ↗

Summaries, chapters, transcripts, and FAQs on this page are made by uListen, not YouTube.

CHAPTERS

  1. 0:02 – 12:32

    Gatenby's Path from Physics to Medicine

    Peter Attia asks about Gatenby's unusual route into medicine. Gatenby describes studying physics at Princeton, turning to medical school out of a wish to help humanity, and finding it more dogmatic than scientific. Attia shares parallel stories of memorization and resistance to math-based thinking.

    • •Gatenby wanted to be a physicist but chose medicine, partly because of the humanitarian spirit of the Vietnam era
    • •He says he hated medical school, which felt like catechism-style rote memorization
    • •He says the scripted answer to why cancers grow, that cancer cells grow faster than normal cells, is wrong
    • •Both men describe medicine's conservatism, including resistance to hand washing and to Attia's antibiotic dosing model
  2. 12:32 – 18:21

    Why Radiology Led Gatenby to a Theoretical Approach to Cancer

    Gatenby explains why he chose radiology and how working at a cancer center left him seeing no organizing principle in the literature. He resolved to build first principles based on evolution and ecology, expressed in mathematics.

    • •Radiology appealed to him as a minimal-information puzzle
    • •Reading Cancer Research, he found no framework linking the observations
    • •He compares the need for theory to physics breakthroughs such as Newton and Einstein
    • •He decided cancer must follow Darwinian laws and began writing population dynamic equations
  3. 18:21 – 29:27

    Nonlinearity, Humility, and the Limits of Cancer Modeling

    Gatenby argues that human intuition is linear and fails in nonlinear systems, using Franklin's storm anecdote. He and Attia discuss colleagues' hostility to modeling, comparisons with economics and weather forecasting, and where cancer sits on the chaotic spectrum.

    • •Humans think linearly but cancer involves feedback loops and nonlinear dynamics
    • •Colleagues told him cancer is too complicated to model, which he calls self-defeating
    • •Weather models are a analogy: short-term prediction, then update with new data
    • •Gatenby places cancer at about eight or nine on a ten-point chaos scale
  4. 29:27 – 37:51

    Predator-Prey Models and What Ecologists Know That Oncologists Don't

    Gatenby explains why ecological models appealed to him, then describes simple predator-prey dynamics and how immune-cancer interactions differ. He notes that ecologists ask basic birth and death rate questions cancer biology doesn't, and that pesticide makers must submit resistance management plans while cancer drugs are approved without them.

    • •Treating cancer as an evolving system makes it deterministic rather than magical
    • •Predator-prey cycles are a simple model, and the immune system is an imperfect analogue
    • •Cancer biology often lacks basic birth and death rate data
    • •Pesticides require resistance management plans while cancer drugs do not
  5. 37:51 – 46:23

    Pests and Pesticides: Why Maximum Dose Selects for Resistance

    Using the diamondback moth, Gatenby explains why dumping maximum pesticide breeds resistance, and how integrated pest management works instead. Resistance carries a fitness cost, so leaving sensitive populations alive lets them outcompete resistant ones.

    • •The diamondback moth became resistant to every pesticide used on it
    • •High doses kill the sensitive and free the resistant to expand
    • •Integrated pest management leaves untreated refuges and aims to control rather than eradicate
    • •Resistance machinery has a cost when no drug is present
  6. 46:23 – 55:25

    The Adaptive Therapy Prostate Trial

    Gatenby describes his pilot trial of adaptive therapy with abiraterone in metastatic prostate cancer, compared with standard continuous dosing. Median time to progression was 30 months versus 14, and four patients remained on cycling at five years, which the models linked to a high fitness ratio and a pattern of three cycles.

    • •Treatment was given until PSA fell to 50%, then withdrawn
    • •Median time to progression was 30 months versus 14 for standard of care in a non-randomized comparison
    • •The sensitive-to-resistant fitness ratio was about sevenfold, not the estimated two or three
    • •Patients who had three well-timed cycles seemed to drive resistant cells toward extinction
    • •Delays tied to imaging meant patients were overtreated
  7. 55:25 – 1:03:26

    Extinction Strategies and the Knife-Fight Approach

    Gatenby proposes that after a response, when tumor populations are small, one should strike again rather than wait. He draws on Anthropocene extinctions, notes there is no pharma incentive for off-patent drugs, and Attia asks about antibiotic implications.

    • •Resistant cells that remain after response are likely much less fit without treatment
    • •Extinction usually comes from a sequence of perturbations, not one magic bullet
    • •Off-patent drugs like abiraterone lack commercial sponsors for trials
    • •Evolution-based models are used by the WHO for malaria and tuberculosis treatment planning
  8. 1:03:26 – 1:18:30

    Small Populations, Allee Effects, and Sequencing Therapies

    Gatenby explains why small tumor populations are vulnerable, through stochasticity and Allee effects, and how fragmented tumors after neoadjuvant therapy become islands. He contrasts a single dinosaur-style strike with multi-cause extinctions and discusses why sequencing may beat combining drugs.

    • •Detectable tumors contain billions of cells with large heterogeneity
    • •Allee effects mean small groups may fail at angiogenesis, matrix building, and immune evasion
    • •Pediatric leukemia treatment hits immediately with sequential drugs
    • •Combining many drugs yields diminishing returns and added toxicity
    • •The extinction vortex and Heath hen illustrate fragmented populations collapsing
  9. 1:18:30 – 1:25:57

    Chemotherapy, Anti-Angiogenics, and Timing Therapies

    Attia reviews the logic of chemotherapy, anti-VEGF drugs, and cell cycle signaling, and asks how to cycle therapies to maximize the fitness gap. Gatenby comments on the fitness ratio threshold and on defeating fragmented tumors in detail.

    • •Cancer cells have a self-defined fitness function rather than responding to tissue controls
    • •Chemotherapy targets dividing cells, causing side effects in normal tissues
    • •Anti-angiogenic drugs added only modest survival gains
    • •Gatenby guesses the tipping fitness ratio is around five
  10. 1:25:57 – 1:31:24

    Immunotherapy as the Closer and Strategic Sequences

    Gatenby describes immunotherapy as the closest thing to a magic bullet, but suggests using it as a closer when tumors are small and fragmented. He gives an example in which a P53 vaccine preceded unexpectedly high chemotherapy response rates, supporting designed sequences of therapy.

    • •Immunotherapy may work best as a closer against small populations
    • •Cells surviving chemotherapy may be more vulnerable to immunotherapy
    • •A P53 vaccine study was followed by 60 to 70 percent chemotherapy response
    • •Gatenby wants adaptive strategies from one therapy to become vulnerabilities for the next, guided by math models
  11. 1:31:24 – 1:42:46

    Metastasis and the Source-Sink Puzzle

    Attia raises why some cancers metastasize to particular organs and why some primary sites are rarely colonized. Gatenby says he doesn't know, but argues metastasis isn't planned, discusses species introductions and source-sink habitats, and notes how few circulating cells form metastases.

    • •Metastasis can't be planned by an evolving population
    • •Species introduction rules suggest success depends on fit with the local landscape
    • •Source and sink habitats may explain cell flow between regions
    • •Most cells reaching metastatic sites die, with small-population dynamics limiting survival
    • •Gatenby asks why adjuvant therapy isn't optimized as a sequence
  12. 1:42:46 – 1:55:25

    Eco and Evo Indices and Evolution Driven by Environment

    Gatenby argues that tumor evolution is driven by varying local environments rather than random mutation alone, with genes as consequences of evolution. He uses a modern-Darwin-with-a-microarray thought experiment and criticizes in vitro and genetics-heavy approaches, suggesting imaging to map habitats.

    • •Different tumor habitats select different phenotypes and thus genotypes
    • •Beak-seed matching shows phenotype-environment pairing is the logical route to understanding evolution
    • •Cells in a dish no longer face the immune system or angiogenesis, so findings may not translate
    • •Biopsies and circulating DNA give limited snapshots
    • •Landscape ecology satellite methods inspire imaging-based habitat mapping
  13. 1:55:25 – 2:03:11

    Early Screening and Follow-Up Trials

    Attia asks whether the work supports early screening, and Gatenby says smaller populations are more vulnerable but he's not qualified to comment on programs. They then discuss why prostate cancer was chosen, limited uptake of the trial, and low-hanging fruit such as ovarian, small cell lung, and metastatic prostate cancer.

    • •Gatenby is supportive of screening based on intuition, not his own work
    • •Prostate cancer was chosen for its PSA biomarker and a brave oncologist
    • •He has received a tenth rejection of a paper on eliminating resistant cells, and sees little greater interest
    • •He suggests ovarian cancer, small cell lung cancer, and metastatic prostate cancer as promising targets
    • •Androgen deprivation therapy is miserable for men, motivating treatment strategies that allow stopping it
  14. 2:03:11 – 2:18:34

    Hardest Cancers and Options for Patients Told They've Failed Therapy

    Gatenby names glioblastoma as the toughest problem, discusses pancreatic cancer's open questions, and credits a pediatric oncologist running an extinction trial in sarcoma. He then addresses patients who've been told they failed therapy, emphasizing the need for a willing oncologist, and the conversation closes on nonlinear intuition.

    • •Glioblastoma is the cancer Gatenby would be most reluctant to tackle
    • •Pancreatic fibrosis might be a host response or a tumor strategy, which no one knows
    • •Damon Reed is running an extinction therapy trial in metastatic sarcoma
    • •Gatenby cannot prescribe, and offers to share eco-evolutionary thinking with a patient's oncologist
    • •Attia argues crossover trials would be low risk and Gatenby says we could do better with old drugs

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