Radiation Therapy Explained: Cancer Advances & Low-Dose Relief for Arthritis/Tendonitis | Dr. Sanjay Mehta Summary

This episode of The Peter Attia Drive podcast, titled "#343 – The evolving role of radiation: advancements in cancer treatment, emerging low-dose treatments for arthritis, tendonitis, and injuries, and addressing misconceptions," features Dr. Sanjay Mehta, a radiation oncologist with over 20 years of experience practicing at St. Joseph's Medical Center in Houston, Texas. Dr. Mehta joins host Peter Attia to discuss the multifaceted world of radiation, from its sophisticated applications in modern cancer therapy to its lesser-known, yet potentially transformative, use in treating inflammatory conditions and injuries with low doses. The conversation delves into the history of radiation, addresses common misconceptions and fears (radiophobia), and explores the significant technological advancements that have reshaped radiation oncology. This episode is highly relevant for anyone interested in cancer treatment options, individuals suffering from chronic inflammatory conditions like arthritis or tendonitis, and those seeking a deeper understanding of radiation's risks and benefits in medicine.

Key Insights / Core Messages

• Radiation oncology has evolved significantly, moving from crude, less targeted methods to highly precise, computer-planned treatments (like IMRT/IGRT) that maximize tumor destruction while minimizing damage to healthy tissues and reducing side effects.
• Breast and prostate cancer treatments commonly involve radiation, often achieving outcomes equivalent to more invasive surgeries (like mastectomy or prostatectomy) but with potentially better quality-of-life profiles regarding side effects like incontinence or cosmesis.
• Low-dose radiation therapy (LDRT) is a widely used and effective treatment in Europe (especially Germany) for benign inflammatory conditions like osteoarthritis, tendonitis, and plantar fasciitis, offering an anti-inflammatory effect comparable to cortisone but often with greater durability.
• Despite its potential and historical use, LDRT is vastly underutilized in the United States, largely due to "radiophobia," lack of physician awareness, and potential economic disincentives within the medical system.
• Understanding radiation requires differentiating between ionizing (higher energy, potential for DNA damage, used in therapy/diagnostics) and non-ionizing (lower energy, like radio/microwaves, generally safe) radiation.
• Concerns about radiation exposure from diagnostic tests (like X-rays, CT scans) are often overblown, especially at the low doses used today; the benefits typically far outweigh the minimal theoretical risks, which are based on debatable models like the Linear No-Threshold (LNT) hypothesis.
• Advancements in genomic testing (like Decipher, Artera) and imaging (PSMA PET) are further personalizing prostate cancer treatment, helping determine the necessity of treatments like androgen deprivation therapy alongside radiation.

Understanding Radiation: Basics, Units, and Safety

Dr. Mehta begins by explaining that radiation is part of the electromagnetic spectrum. Lower energy forms like radio waves and microwaves are "non-ionizing" and cannot damage DNA, debunking fears about cell phones or microwave ovens causing cancer. Higher energy forms, including UV light, X-rays, and gamma rays, are "ionizing," meaning they have enough energy to potentially eject electrons from atoms and damage DNA. This ionizing radiation is used in both diagnostic imaging and radiation therapy.

Radiation dose absorbed by tissue is measured in Grays (Gy), representing joules of energy per kilogram of tissue. Exposure in the air or effective dose to the whole body, considering tissue sensitivity, is often measured in Sieverts (Sv) or millisieverts (mSv). For practical purposes with X-rays, 1 Gy is roughly equivalent to 1 Sv. Background radiation exposure at sea level is about 1-2 mSv per year, potentially double or triple at higher altitudes like Denver. Diagnostic procedures involve low doses: a chest X-ray is less than 1 mSv, a modern mammogram around 1 mSv, and advanced CT scans like a cardiac CTA might range from 1-3 mSv (down significantly from older scanners delivering ~25 mSv). PET/CT scans deliver higher doses, potentially 50-100 mSv.

Dr. Mehta emphasizes the principle of ALARA (As Low As Reasonably Achievable) but argues that the risks associated with these low diagnostic doses are often overstated. He critiques the Linear No-Threshold (LNT) model, the traditional basis for radiation safety regulations, which extrapolates cancer risk linearly from high doses down to zero dose. He suggests evidence points towards a threshold below which risk is negligible, and potentially even a hormetic effect (beneficial adaptation) at very low doses, though this remains controversial. He strongly advises against skipping necessary diagnostic scans like mammograms or dental X-rays due to radiation fears, as the diagnostic benefit vastly outweighs the minimal theoretical risk.

The Evolution of Radiation Oncology: Breast Cancer

Radiation oncology became its own distinct specialty relatively recently, emerging from diagnostic radiology primarily in the 1970s and 80s. Breast cancer treatment provides a prime example of its evolution. Historically, the standard was the radical Halsted mastectomy, a disfiguring surgery removing the breast, lymph nodes, and chest muscles. Landmark studies in the 1980s (like Fisher's NSABP trials) demonstrated that lumpectomy (removing only the tumor) followed by radiation therapy offered equivalent overall survival to mastectomy for early-stage breast cancer. This shifted the paradigm towards breast conservation.

Today, a typical course for early-stage breast cancer post-lumpectomy involves radiation starting 3-4 weeks after surgery. Treatment planning is highly sophisticated: a CT simulation is performed with the patient immobilized in a reproducible position (often using a vacuum-lock bag). 3D computer modeling allows Dr. Mehta and his team (dosimetrists, physicists) to precisely map the target volume (usually the whole breast) and critical nearby organs (heart, lungs). Tangential beams and intensity-modulated radiation therapy (IMRT) shape the dose to conform to the breast while minimizing exposure to the heart and lungs. Daily image guidance (IGRT), using onboard X-rays or CT, ensures millimeter accuracy for each treatment.

The total dose for whole breast radiation is now typically around 40 Gy delivered in 15 daily fractions (about 2.6 Gy/day) over 3 weeks, often followed by a "boost" of ~10 Gy in 5 fractions specifically to the lumpectomy cavity to improve local control. This "hypofractionated" schedule delivers a biologically equivalent dose to older regimens (e.g., 50 Gy in 25 fractions over 5 weeks) but is more convenient. Side effects have dramatically reduced due to increased precision and energy characteristics of modern linear accelerators compared to older cobalt machines. Severe skin reactions (moist desquamation) are now rare; patients typically experience mild redness or sunburn-like effects (Grade 1-2 dermatitis) managed with simple creams, and feel nothing during the 15-minute daily treatments.

Radiation Therapy for Prostate Cancer

Prostate cancer is another major area for radiation therapy, now considered a primary treatment option alongside surgery (radical prostatectomy) for most stages. Historically, radiation was often reserved for patients unfit for surgery, leading to biased outcome data. Modern techniques offer cure rates essentially equivalent to surgery for many patients.

The decision between surgery and radiation often hinges on quality of life considerations. Radiation therapy, particularly with modern precision, has very low rates of long-term incontinence, a significant advantage over surgery for many men. While erectile dysfunction can occur, techniques minimizing dose to the penile bulb help preserve function, though androgen deprivation therapy (ADT), often used concurrently with radiation for higher-risk disease, significantly impacts libido and sexual function.

Risk stratification using Gleason scores, PSA levels, and newer genomic tests (Decipher) or AI-based pathology analysis (Artera) helps tailor treatment. For low-risk (Gleason 6) disease, active surveillance is common, but radiation without ADT is an option some men choose over repeated biopsies or anxiety. For intermediate-risk disease (Gleason 7), ADT was standard with radiation, but genomic/AI tests now allow some favorable intermediate-risk patients (e.g., 3+4 with low scores) to potentially avoid ADT. High-risk disease (Gleason 8-10) typically requires radiation combined with longer-term ADT.

Precision is key in prostate RT. Daily imaging and careful patient preparation (full bladder, empty rectum) help separate the prostate from the bladder and rectum, allowing high doses (e.g., 70-80 Gy) to the prostate while keeping rectal and bladder doses extremely low, minimizing side effects like proctitis or cystitis. Dr. Mehta notes that with meticulous technique, the need for rectal spacers (like SpaceOAR gel) is often reduced. For metastatic disease, radiation plays a vital palliative role for painful bone metastases. Increasingly, for oligometastatic disease (few metastases), stereotactic body radiation therapy (SBRT) to the metastatic sites, sometimes combined with treating the primary prostate tumor, is being used with curative intent or to delay systemic therapy.

Radiation Therapy for Brain Tumors

Radiation is crucial for treating both primary brain tumors (like glioblastoma) and, more commonly, metastatic disease (often from lung cancer). Historically, multiple brain metastases were treated with whole brain radiation therapy (WBRT), typically 30 Gy in 10 fractions. While effective for controlling disease, WBRT carries a risk of long-term cognitive decline, particularly affecting hippocampal function (memory). With patients living longer due to better systemic therapies, this side effect became more significant.

The standard of care has shifted towards stereotactic radiosurgery (SRS), using highly focused radiation (like Gamma Knife or LINAC-based SRS) to target individual metastases, sparing the rest of the brain. WBRT is now used less often, but if necessary, techniques like hippocampal-sparing IMRT can mitigate cognitive effects. For aggressive primary tumors like glioblastoma (GBM), radiation (typically 60 Gy after surgery) is standard but prognosis remains poor due to the infiltrative nature of the disease. Proton therapy, which deposits dose at a specific depth (Bragg peak) with no exit dose, offers theoretical advantages in sparing healthy brain tissue, especially in children, but significant survival improvements for GBM haven't yet been clearly demonstrated.

Radiophobia and the History of Radiation Use

Dr. Mehta discusses "radiophobia," the excessive fear of radiation, noting it seems more prevalent in the US than in Europe. He attributes this partly to the Cold War, nuclear accidents (Three Mile Island, Chernobyl), the atomic bombs, and well-publicized historical incidents like the "Radium Girls." These women, working in the 1920s, ingested radium while painting watch dials by licking their brushes; some developed severe jaw necrosis and cancers, fueling public fear, although Dr. Mehta points out that only a small fraction of the workers experienced these severe effects. He also mentions aggressive lobbying by the oil industry against nuclear power contributing to the negative perception. This fear contrasts sharply with the early 20th century when radiation was incorporated into numerous consumer products (lotions, water, "health" tonics) before its dangers were understood.

Low-Dose Radiation Therapy (LDRT): An Underutilized Tool for Inflammation

Perhaps the most revelatory part of the discussion focuses on Low-Dose Radiation Therapy (LDRT) for benign, non-cancerous conditions. Dr. Mehta highlights that LDRT is a routine, well-established treatment in Germany and other parts of Europe for inflammatory conditions, with decades of data supporting its use, yet it's almost unheard of in the US.

The typical application is for conditions like osteoarthritis, tendonitis (Achilles, rotator cuff, tennis elbow), bursitis, plantar fasciitis, and even Dupuytren's contracture or keloids (though fibrosis requires higher doses). The mechanism is primarily anti-inflammatory; the low dose radiation (typically 0.5 Gy per fraction, for a total of 3 Gy over 6 treatments in 2 weeks) is thought to selectively target and eliminate inflammatory cells like macrophages in the treated area, reducing the cytokine storm and subsequent pain and dysfunction. This effect is similar to a cortisone injection but appears to be much more durable, often lasting months or years, based on European data and Dr. Mehta's early experience.

Dr. Mehta shares his personal experience treating his own Achilles tendonitis with LDRT (after trying conventional therapies on the other side) and reports excellent results after a couple of months. He also recounts treating surgeons with debilitating plantar fasciitis who experienced rapid relief, and patients with high hamstring tendinopathy, tennis elbow, and hand/wrist arthritis, often with significant pain reduction and functional improvement. He notes that even systemic inflammatory conditions like rheumatoid or gouty arthritis can benefit from LDRT for localized joint pain relief.

Despite evidence of efficacy and safety (the doses are extremely low, far below cancer-causing thresholds, especially for older patients often affected by arthritis), adoption in the US faces hurdles: deep-seated radiophobia among patients and physicians, lack of awareness and training in residency programs, potential turf battles with orthopedic surgeons or podiatrists, and the lack of large-scale US-based randomized trials (though Medicare and some private insurers are starting to cover it based on European data and ICD codes for osteoarthritis).

Conclusion

Dr. Sanjay Mehta provides a comprehensive and insightful overview of radiation's evolving role in medicine. He illuminates the remarkable progress in radiation oncology, where technology now allows for highly targeted, effective cancer treatments with significantly reduced side effects compared to the past. Furthermore, he sheds light on the compelling, yet largely overlooked, potential of low-dose radiation therapy (LDRT) to safely and effectively treat a wide range of common and often debilitating inflammatory conditions. The discussion underscores the need for greater awareness, education, and research regarding LDRT in the United States, challenging engrained radiophobia and encouraging a more nuanced understanding of radiation's therapeutic benefits across different dose levels and applications.