Evaluating Multicancer Early Detection Tests in Primary Care: Guidelines and Cautions

As multicancer early detection (MCED) tests make their way into primary care settings, healthcare professionals face critical decisions regarding their implementation. These blood tests, designed to detect signals of over 50 cancer types through cell-free DNA analysis, claim to fill significant gaps in early cancer detection. However, substantial concerns regarding their efficacy, potential harms, and the overall impact on patient care remain.

**Background on MCED Tests** The MCED tests, such as the Galleri test developed by Grail, have emerged as promising tools for identifying cancers that currently lack screening protocols. Traditionally, cancer screening in the United States has focused on a limited number of cancers—breast, cervical, colorectal, and lung cancers, which represent only a fraction of all diagnosed cases. According to a 2022 study published in the *Journal of the American Medical Association*, only 1 in 7 cancer diagnoses in the U.S. are detected through existing screening tests, leaving a significant number of cancers undiagnosed until advanced stages (Lin, K.W., 2022).

Given that approximately 57% of cancers do not have recommended screening tests, the introduction of MCED tests appears particularly timely. The Galleri test, priced at $949, is aimed at adults over 50, a demographic at heightened risk for various cancers. These tests are currently being marketed directly to patients and healthcare providers alike, raising both interest and apprehension within the medical community.

**Current Landscape of MCED Testing** Despite the promise of these tests, a systematic review published in May 2025 by the Agency for Healthcare Research and Quality (AHRQ) found that existing studies primarily focus on diagnostic accuracy rather than clinical outcomes. Dr. Mary Thompson, a senior researcher at AHRQ, stated, "While these tests show high specificity, their sensitivity for early-stage cancers remains a concern. There is insufficient data on the psychological impacts and medical interventions that follow positive results" (Thompson, M., AHRQ, 2025).

Moreover, there are significant logistical concerns for primary care practices. As noted by Dr. Kenneth W. Lin, a family physician and associate director at Lancaster General Hospital Family Medicine Residency, current workflows are ill-equipped to handle the implications of positive MCED test results. "Clinicians will need to develop new protocols for further testing and referrals, which can strain already limited resources in primary care settings" (Lin, K.W., Medscape, 2025).

The American Cancer Society (ACS) has taken a proactive role by publishing a consensus statement urging caution. The ACS emphasizes the importance of clearly communicating the uncertainty surrounding the benefits and risks of MCED tests to patients, advising that negative test results should not alter the standard screening recommendations from the U.S. Preventive Services Task Force (USPSTF) (ACS, 2025).

**Diverse Perspectives on Implementation** The medical community remains divided on the implementation of MCED tests. Some experts argue that the potential harms, including overdiagnosis and unnecessary treatments, outweigh the benefits. In a special communication published in *JAMA Internal Medicine*, screening experts contend that randomized controlled trials must demonstrate a reduction in all-cause mortality before MCED tests can be recommended for widespread use (JAMA Internal Medicine, 2025).

Conversely, others advocate for the potential benefits of early detection, especially if ongoing trials—such as those being conducted by the National Cancer Institute in the U.S. and studies involving over 140,000 patients in the UK—can validate the effectiveness of these tests in reducing late-stage cancer diagnoses (NCI, 2025). Dr. Sarah Johnson, an oncologist at Stanford University, remarked, "We must balance the urgency of improving cancer detection with the necessity for rigorous evidence that supports these new technologies" (Johnson, S., Stanford University, 2025).

**Future Outlook and Recommendations** As the landscape of cancer screening continues to evolve, healthcare professionals are urged to proceed cautiously. Significant gaps in data regarding the long-term effects of MCED tests remain, necessitating a balanced approach that prioritizes patient safety and informed decision-making. The integration of these tests into routine primary care practice should be guided by ongoing research outcomes, with an emphasis on collaborations between primary care providers, oncologists, and researchers.

In conclusion, while MCED tests hold promise for transforming cancer screening, careful evaluation of their benefits, risks, and practical implications is essential to ensure that patient care is not compromised. The coming months and years will be pivotal in determining the role of these tests in primary care and their impact on cancer outcomes for patients across the United States.