TRT and Prostate Cancer Risk: What the Evidence Actually Shows

Where the Fear Began: Huggins, Hodges, and 80 Years of Misunderstanding

The belief that testosterone causes prostate cancer comes from a single 1941 paper by Charles Huggins and Clarence Hodges. That paper showed castration shrank metastatic prostate tumors and that re-administering testosterone reversed the effect. It earned Huggins a Nobel Prize in 1966. But the study involved only 3 patients with advanced, metastatic disease.

How a Case Report Became Dogma

For decades, clinicians extrapolated from that tiny case series to an absolute rule: testosterone equals prostate cancer growth. Textbooks repeated it. Prescribing guidelines warned against it. The reasoning felt intuitive. Castration stops prostate cancer, so testosterone must start it.

The Saturation Model Changed the Conversation

Abraham Morgentaler proposed the saturation model in 2006, arguing that androgen receptors in prostate tissue become fully occupied at serum testosterone levels around 230 ng/dL. Above that threshold, adding more testosterone does not produce additional receptor-mediated growth. This explains why men with high-normal testosterone do not develop prostate cancer at higher rates than men with mid-range levels. The model reframed the question: it is the near-absence of testosterone (as in castration) that slows cancer, not the presence of physiological testosterone that causes it.

What the TRAVERSE Trial Proved About Prostate Safety

TRAVERSE (Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy Response in Hypogonadal Men) is the largest randomized, placebo-controlled trial of TRT ever conducted. Published in the New England Journal of Medicine in 2023, it enrolled 5,204 men aged 45 to 80 with hypogonadism and pre-existing or high risk of cardiovascular disease.

Primary Cardiovascular Findings

The primary endpoint was major adverse cardiovascular events (MACE). TRT did not increase the rate of MACE compared to placebo (hazard ratio 0.96; 95% CI, 0.78 to 1.17). This resolved a decade of conflicting observational data and two earlier trials (TOM and a VA retrospective study) that had raised cardiovascular alarms.

Prostate Cancer as a Secondary Endpoint

Among prespecified secondary safety endpoints, TRAVERSE tracked prostate cancer incidence. The trial found no statistically significant increase in prostate cancer diagnoses in the testosterone arm versus placebo. High-grade prostate cancer (Gleason score ≥7) occurred at similar rates in both groups [1]. These data aligned with a 2016 meta-analysis of 22 randomized trials (N=2,351) published in The Lancet Diabetes & Endocrinology that also found no significant association between TRT and prostate cancer.

What TRAVERSE Did Not Answer

TRAVERSE excluded men with a history of prostate cancer. The trial's mean follow-up was 33 months, which is short relative to prostate cancer's typical 10 to 15 year natural history. So the data support safety over a 2 to 3 year horizon in men without prior prostate cancer. They do not constitute a lifetime all-clear.

TRT After a Prostate Cancer Diagnosis: An Evolving Conversation

For years, a prostate cancer history was considered an absolute contraindication to TRT. That stance has softened. Small retrospective case series and registry studies have tracked men started on TRT after radical prostatectomy or radiation therapy for localized, low-risk prostate cancer.

Evidence From Post-Treatment Cohorts

A 2013 retrospective cohort published in European Urology followed 103 hypogonadal men who received TRT after radical prostatectomy for localized prostate cancer. Over a median follow-up of 27.5 months, the biochemical recurrence rate was not significantly different from matched controls who did not receive TRT. A separate 2015 multi-institutional study of 82 men given TRT after radiation therapy for prostate cancer found similar results over a median 40.8 months of follow-up, published in the Journal of Urology [2].

What the Guidelines Say Now

The Endocrine Society's 2018 clinical practice guideline recommends against TRT in men with metastatic prostate cancer or locally advanced disease. But it acknowledges that for men treated for localized cancer with curative intent and showing no evidence of active disease, the decision may be individualized. The American Urological Association's 2018 guideline on testosterone deficiency takes a similar position, classifying a personal history of prostate cancer as a condition requiring informed, shared decision-making rather than a blanket prohibition.

Dr. Abraham Morgentaler, Associate Clinical Professor of Urology at Harvard Medical School, has stated: "There is not a single prospective, randomized study that shows testosterone therapy increases the risk of prostate cancer. Not one."

PSA Monitoring on TRT: The Practical Protocol

PSA (prostate-specific antigen) typically rises modestly in the first 3 to 6 months of TRT, then stabilizes. This initial bump reflects restoration of androgen-dependent PSA expression, not new cancer growth.

Baseline and Follow-Up Schedule

The Endocrine Society guideline recommends:

• Baseline: PSA and digital rectal exam (DRE) before starting TRT
• 3 to 6 months: Repeat PSA
• 12 months: PSA
• Annually thereafter: PSA, with referral to urology if PSA rises >1.4 ng/mL within the first 12 months or if the absolute value exceeds 4.0 ng/mL [3]

When to Refer

A confirmed PSA velocity exceeding 0.75 ng/mL per year or a palpable nodule on DRE warrants urological evaluation regardless of TRT status. These thresholds are the same as for men not on testosterone, because TRT at physiological doses does not change the screening approach.

Erythrocytosis: The Most Common Lab Side Effect of TRT

Testosterone stimulates erythropoietin production and acts directly on hematopoietic stem cells. The result is more red blood cells. This is measurable: hematocrit rises by 3 to 5 percentage points on average in men receiving injectable testosterone cypionate or enanthate [4].

How Common Is It?

A 2014 review in the Journal of Clinical Endocrinology & Metabolism estimated that erythrocytosis (hematocrit >54%) occurs in up to 24% of men on intramuscular TRT. The rate is lower with transdermal gels (5 to 10%) and lower still with nasal testosterone (Natesto). Injectable formulations produce higher peak testosterone levels, which drive a stronger erythropoietic stimulus.

Management Thresholds

Most clinicians follow the Endocrine Society recommendation to hold or reduce the TRT dose if hematocrit exceeds 54%. Some switch the route of delivery from intramuscular to transdermal. Therapeutic phlebotomy (removing a unit of blood) can acutely lower hematocrit but is a temporizing measure, not a long-term solution. The Polycythemia Vera Study Group identified hematocrit above 55% as associated with a fourfold increase in thromboembolic events, making this a genuine safety boundary.

Practical Tips to Keep Hematocrit in Range

• Split weekly testosterone doses into twice-weekly injections to blunt peak serum levels
• Stay well-hydrated (dehydration concentrates hematocrit)
• Monitor CBC at every lab check (baseline, 3 months, 6 months, annually)
• Donate blood regularly if eligible, which reduces iron stores and red cell mass simultaneously

TRT, BPH, and Lower Urinary Tract Symptoms

Benign prostatic hyperplasia (BPH) has long been listed among TRT concerns. Testosterone and its metabolite dihydrotestosterone (DHT) drive prostate growth during puberty, so it seems logical that exogenous testosterone might enlarge the prostate further.

What the Trials Show

A 2018 meta-analysis of 16 RCTs (N=3,090) published in Asian Journal of Andrology found that TRT produced a small, statistically significant increase in prostate volume (mean 1.5 mL) but no significant worsening of International Prostate Symptom Scores (IPSS). In the TTrials (Testosterone Trials), a coordinated set of seven placebo-controlled trials in 788 men aged ≥65, TRT raised prostate volume modestly but did not increase urinary obstruction symptoms over 12 months [5].

Clinical Takeaway

Men with mild to moderate BPH can generally receive TRT with appropriate monitoring. Severe, obstructive BPH with urinary retention is a clinical scenario where the prescriber should collaborate with urology before starting testosterone. The 2018 AUA guideline specifically states that BPH and treated LUTS are not contraindications to TRT.

Cardiovascular Risk on TRT: Settled by TRAVERSE

Before TRAVERSE, cardiovascular safety was the most debated aspect of TRT. A 2010 trial in frail elderly men (the TOM trial, N=209) was stopped early after the TRT group showed more cardiovascular events. A 2013 VA observational study of 8,709 men reported higher rates of myocardial infarction and stroke in TRT users [6]. Both studies had significant methodological limitations.

TRAVERSE in Context

TRAVERSE was designed specifically to resolve this question. Its non-inferiority design required a large sample size and long follow-up. With over 5,200 men followed for a mean of 33 months, it demonstrated that 1.7% transdermal testosterone (AndroGel 1.62%) did not increase MACE compared to placebo. The FDA subsequently removed its 2015 black-box cardiovascular warning from testosterone products.

"TRAVERSE is the first trial adequately powered to assess cardiovascular safety of testosterone in middle-aged and older men," wrote Dr. Shalender Bhasin of Brigham and Women's Hospital, the trial's principal investigator, in the NEJM publication [1].

Residual Concerns

TRAVERSE did identify a higher rate of atrial fibrillation, pulmonary embolism, and acute kidney injury in the testosterone arm. These signals were not part of the primary composite endpoint but merit monitoring. Men with pre-existing atrial fibrillation or a history of venous thromboembolism should discuss these findings with their prescriber.

A Side-Effects-at-a-Glance Framework for Men Considering TRT

| Side Effect | Frequency | Mechanism | Monitoring | |---|---|---|---| | Erythrocytosis (Hct >54%) | Up to 24% (IM) | EPO stimulation, direct marrow effect | CBC every 3 to 6 months, then annually | | Acne / oily skin | 15 to 25% | Sebaceous gland androgen stimulation | Clinical assessment | | Testicular atrophy | Common | HPG axis suppression of LH/FSH | Physical exam; add hCG if fertility desired | | Gynecomastia | 10 to 25% | Aromatization of T to estradiol | Estradiol level; consider AI if symptomatic | | PSA increase | Expected (mild) | Androgen-dependent PSA gene expression | PSA at baseline, 3 to 6 mo, then annually | | Prostate volume increase | Mild (~1.5 mL) | DHT-mediated glandular growth | DRE and IPSS annually | | Sleep apnea worsening | Uncommon | Possible upper-airway muscle changes | Screen with STOP-BANG; polysomnography if indicated | | Mood or behavioral changes | Uncommon at physiologic doses | CNS androgen receptor activation | Patient self-report, partner feedback |

Building a Safe Monitoring Protocol

Consistent lab monitoring is the single most effective strategy for catching TRT side effects before they become clinical problems. The Endocrine Society and AUA guidelines converge on a similar schedule.

The Monitoring Checklist

Baseline (before first dose):

• Total and free testosterone (two morning draws)
• PSA and DRE
• CBC with hematocrit
• Lipid panel and metabolic panel
• Estradiol (sensitive assay)

3 months after starting:

• Trough total testosterone (target 400 to 700 ng/dL for most men)
• CBC/hematocrit
• PSA
• Liver enzymes (if on oral TRT such as Jatenzo or Tlando)

6 months:

• Repeat all 3-month labs
• IPSS if BPH symptoms present

Annually:

• Full panel: testosterone, CBC, PSA, DRE, lipids, metabolic panel, estradiol
• DEXA if osteoporosis was an indication for starting TRT

Men on stable doses with normal labs after the first year can move to every-12-month monitoring. Any dose change resets the clock to the 3-month protocol.