MIAMI — Care for a veteran with a new diagnosis of colorectal cancer in 2025 reflects a treatment algorithm that is more precise, more individualized, and more effective than anything available 10 years ago.
The veteran CRC risk profile is not simply the general population’s risk profile in uniform. Veterans are more likely to have common risk factors for colorectal cancer. They also face unique risks for CRC shaped by the physiological and psychological aftermath of military service that general colorectal cancer literature largely ignores.
Burn pit exposure is the most notable example of service-related risk for post-9/11 veterans. Open-air combustion of waste materials, including plastics, metals, medical and human waste, as well as unexploded ordinance generated complex mixtures of volatile organic compounds, dioxins and particulate matter at forward operating bases across Iraq, Afghanistan and the Southwest Asia theater of operations. The PACT Act of 2022 established presumptive service connection for gastrointestinal cancers in veterans with qualifying deployment histories, based on biological evidence of a connection between those cancers and burn pit proximity.
For veterans exposed to ionizing radiation during their service, the “atomic veterans,” colon cancer also is a presumptive condition.
The question of increased CRC risk associated with Agent Orange remains unresolved. The dioxin-containing herbicide used extensively during the Vietnam War is a known Group 1 carcinogen, and the VA has established presumptive service connection for multiple Agent Orange-associated cancers. Colorectal cancer is not among them, though Vietnam-era veterans and their clinicians continue to advocate for its inclusion.
Recent research raised another unique risk factor for veterans, an association between military service and biological aging. Scientists at the University of Miami Miller School of Medicine found that patients with early-onset CRC are biologically approximately 15 years older than their chronological age suggests, a finding attributed to accumulated cellular stress and measured through epigenetic aging clocks.1
“Biological age is an interesting concept, and it leads to the idea of accelerated aging when your biological age exceeds your chronological age,” said study co-author Shria Kumar, MD, assistant professor at the University of Miami Miller School of Medicine.
Being biologically older than one’s chronological age has significant implications. “It sounds pretty theoretical, but actually accelerated aging has been shown to be predictive of time to death and even of multiple cancers,” Kumar said.
For CRC, the study showed that each year of accelerated aging increased the risk of preneoplastic polyps by 16%.
In veterans, combat stress, traumatic brain injury or prolonged toxic exposures are associated with accelerated biological aging,2,3 which may have corresponding implications for when cancer develops and how aggressively it behaves. The interaction between military service and the biological aging mechanisms that drive early-onset CRC has not yet been systematically studied.
Shilpa Murthy, MD, a surgeon at Yale School of Medicine and the VA West Haven Healthcare System, aimed to better understand that relationship. Her Department of Defense-funded research investigates military deployment specifically as an independent risk factor for early-onset CRC mortality in veterans. Her work used machine learning alongside patient narratives to build clinical risk models that capture the full picture of a veteran’s health trajectory, not simply the variables that appear in structured electronic health record fields.4
Murthy’s central clinical observation, that young veterans presenting with CRC tend to have worse outcomes than age-matched civilians, might reflect tumor biology, diagnostic delay, treatment access gaps, or some combination of all three. Her goal was to disentangle those contributing factors, clarify the causes of poor outcomes in younger veterans and identify points of potential intervention.
The Diagnostic Delay
Young veterans with colorectal cancer face a diagnostic delay problem that is well documented in the general population: Symptoms are attributed by both patients and physicians to hemorrhoids, irritable bowel syndrome, anxiety or dietary factors because “they’re too young to have cancer.” Patients under age 50 often wait months or years for a CRC diagnosis.5
For veterans, this delay is compounded by factors related to service. Post-traumatic stress disorder is associated with avoidance of medical care, minimization of physical symptoms and reluctance to engage with healthcare systems that can feel bureaucratic, impersonal or triggering. A veteran who attributes rectal bleeding or persistent abdominal pain to the stress of reintegration rather than to a developing tumor is not making an irrational inference, but it could delay diagnosis by months. Military culture, which prizes stoicism and self-sufficiency, can reinforce that tendency across the veteran population, regardless of PTSD status.6
Primary care providers who see young veterans with GI symptoms face a genuine clinical challenge. While rates are rising, the probability of CRC in a 35-year-old remains low enough that a first encounter rarely triggers a diagnostic colonoscopy. In addition, symptoms often overlap with far more common conditions. Complicating matters, toxic exposure history, deployment history and accelerated biological aging are risk factors that do not appear in standard CRC screening decision tools built without veteran populations in mind.
The Testing Imperative
A veteran who navigates the diagnostic delay and receives a CRC diagnosis enters a treatment system that now depends on molecular information to function as intended. Without genomic results, physicians cannot follow the treatment algorithm for CRC, which recommends specific treatments for particular mutations: immunotherapy for MSI-H disease, anti-EGFR therapy with agents such as panitumumab or cetuximab for RAS and BRAF wild-type left-sided metastatic disease, targeted combinations for KRAS G12C-mutated refractory cases, adjuvant aspirin for stage II-III patients with PI3K pathway alterations and more.
And yet, an analysis of data from 25,937 metastatic CRC patients in the Flatiron Health database undertaken by Alexis Leal, MD, and other researchers at the University of Colorado Anschutz Medical School and the Denver VAMC found significant variability in genomic and biomarker testing. Older age, lower area-level educational attainment, treatment in a community setting and geographic location were all independently associated with lower rates of MSI and KRAS testing.7 Other research demonstrated that the emergence of new biomarker-related therapies sharply increased testing rates.
The VA is not passive in the face of these challenges. The National Precision Oncology Program represents an institutional commitment to precision medicine at a scale that most health systems cannot match. In the decade since its founding, the program has provided molecular tests to more than 78,000 veterans and is used by all oncologists in the VA system. The TeleOncology service extends subspecialist access to veterans in areas without an oncologist.
NPOP was built around metastatic solid tumors, the population for which molecular profiling was first established as standard of care. Consequently, stage II-III patients completing curative-intent treatment fall partly outside the traditional NPOP workflow, but guideline-directed care requires molecular testing for these patients. A veteran with stage III colon cancer who completes surgery and adjuvant chemotherapy and is now in surveillance has a more-than-one-in-three probability of carrying a PI3K pathway alteration that makes aspirin very beneficial in reducing the risk of recurrence.
For the VA, rapidly evolving guidelines and the movement of biomarkers to ever-earlier decision points create a new challenge: expanding access to molecular testing to a much broader population of veterans diagnosed with CRC on a consistent and timely basis.
- CM, Yow MV, Kumar S. Biological Age Acceleration and Colonic Polyps in Persons under Age 50. Cancer Prev Res (Phila). 2025 Feb 3;18(2):57-62. doi: 10.1158/1940-6207.CAPR-24-0317. PMID: 39655428; PMCID: PMC11790358.
- Bourassa KJ, Halverson TF, Garrett ME, et al. Demographic characteristics and epigenetic biological aging among post-9/11 veterans: Associations of DunedinPACE with sex, race, and age. Psychiatry Res. 2024;336:115908. doi: 10.1016/j.psychres.2024.115908.
- Bourassa KJ, Garrett ME, Caspi A, et al. Posttraumatic stress disorder, trauma, and accelerated biological aging among post-9/11 veterans. Transl Psychiatry. 2024;14(1):4. Published 2024 Jan. 6. doi: 10.1038/s41398-023-02704-y
- Shilpa S. Murthy Receives $1.1 Million DoD Career Development Award. Yale School of Medicine. Dec. 12, 2025.
- Colorectal Cancer Alliance—Never Too Young Survey Report 2020. 2021.
- Wachen J, Larsen S, Schnurr P. Trauma, PTSD, and Physical Health. PTSD: National Center for PTSD. VA.gov. Updated Aug. 25, 2025.
- Robinson HR, Hu J, Balmaceda NB, et al. Disparities and trends in biomarker testing in metastatic colorectal cancer. J Clin Oncol. Jan. 22, 2024;42 (3). DOI: 10.1200/JCO.2024.42.3_suppl.2
- Latimer H. Biomarker testing in metastatic colorectal cancer (mCRC): 2015-2024 trends in the United States (US) community oncology setting. 2025 ASCO Annual Meeting. E1557. 10.1200/JCO.2025.43.16_suppl.e15573