Can Doctors Detect Cancer with Normal Blood Work?

For many advanced medical tests, it is possible to have normal results even if cancer is present. Conversely, test results outside the normal range do not always indicate illness. This complexity underlines the limitations of relying on lab tests alone to diagnose cancer or other diseases.

Tests and Procedures for Cancer Diagnoses

The misconception that blood tests can definitively diagnose cancer is challenging to dispel. While certain cancers can be detected through blood tests, such as leukemia, many others require more advanced techniques like imaging and biopsies.

New Developments in Cancer Detection: The Galleri Blood Test

The recent introduction of the Galleri blood test from Grail has raised anticipation in the medical community. This innovative test can detect up to 50 different types of cancers, often before symptoms arise and the disease has spread extensively.

The test works by identifying DNA fragments from cancer cells in the bloodstream. It offers a preliminary indication of the type of cancer detected, enabling doctors to take further steps like imaging or biopsies to confirm and treat the condition.

A compelling example involves a patient with ovarian cancer. Typically, this form of cancer is diagnosed only after it has spread, making it difficult to treat effectively. The Galleri test would identify the presence of ovarian cancer, allowing for a CT scan to locate the tumor, followed by a biopsy and subsequent treatment.

Despite its promising capabilities, the Galleri test is not without limitations. It may fail to detect cancers if the tumor is extremely small or does not release DNA fragments into the bloodstream, such as in certain skin cancers. Additionally, the test may produce false positives, where aberrant DNA is mistaken for cancer DNA.

The Galleri test has received FDA approval, and doctors can order it. However, insurance coverage is still pending, with the test currently costing around $1000.

My wife and I chose to give her the Galleri test as part of her Christmas present last year, along with some newly acquired jewelry. Happily, the results were normal, and the jewelry was a thoughtful and beautiful addition to her collection.

Other Blood Tests and Tumor Markers

Beyond the Galleri test, there are other blood tests designed to detect cancer. For instance, leukemias, blood cancers, can be identified through the examination of blood smears. Certain solid organ cancers may also be detectable through blood tests, such as liquid biopsies, which use molecular methods to diagnose cancers.

Tumor marker blood tests are commonly used to screen for the recurrence of cancer in patients with known diagnoses. Prostate-specific antigen (PSA) is one such marker, known to be elevated in cases of prostate cancer.

However, the accuracy of these tests is not absolute. While very high PSA levels often indicate prostate cancer, they can also be elevated due to prostatitis, an inflammation of the prostate gland. Conversely, prostate cancer may not always raise PSA levels, leading to ambiguity.

This highlights the importance of corroborating blood test results with other diagnostic methods such as imaging and biopsies. While blood tests are valuable tools in cancer detection, they should not be seen as standalone diagnostic solutions.