VA National Precision Oncology Program

By 2015, multiple examples of DNA-based gene alterations that predict drug response were known, including at least 5 in non-small cell lung cancer (NSCLC). The heterogeneity of molecular testing practice patterns and methods of testing in VA along with the increasing number and complexity of molecular tests facilitated launch of a regional precision oncology program based primarily in Veterans Integrated Service Network 1, which provided tumor DNA sequencing through 2 vendors. Advances in DNA sequencing technology, particularly NGS, permit sequencing of multiple genes in clinical tumor samples, using a panel applicable for multiple tumor types. As part of VA contributions to the 2016 White House Cancer Moonshot initiative, the regional program became NPOP with expanded geographic scope, the addition of clinical consultative services, and robust informatics that supports associated research and a learning health care system. NPOP is a component of the VA National Oncology Program Office under the Office of Specialty Care.

Testing

With the launch of NPOP in mid-2016, there was rapid expansion of the number of VA facilities participating, and the number of tumor samples being submitted increased substantially. ⁵ The expansion was facilitated by both central funding for the tumor DNA sequencing and by NPOP-provided training of pathology laboratory staff and oncologists. Today, NPOP is utilized by almost every oncology practice in VA.

NPOP’s initial focus was on lung cancer, specifically advanced-stage nonsquamous NSCLC, which not only is very common in VA, but also has one of the highest number of mutated genes that result in sensitivity to antineoplastic drugs. Recently, metastatic prostate cancer was added as a second focus tumor type. Dashboards are available on the NPOP website to assist care teams in identifying veterans at their facility with either lung or prostate cancer who may be appropriate for testing. Other solid tumors can be sent for testing through NPOP if patients have advanced stage cancer and are medically appropriate for antineoplastic therapy. To date, NPOP has sequenced > 13,000 samples.

Testing options have been added to NPOP in addition to tumor DNA sequencing. The first addition was the so-called liquid biopsy, more properly known as the cell-free DNA (cfDNA) test, a plasma-based high-sensitivity DNA sequencing assay. cfDNA is shed from dying cells and can be captured and sequenced from a plasma sample obtained by standard venipuncture, using a special-purpose sample collection tube. The test is appropriate for patients who do not have an appropriate archival tumor sample or those who cannot have a new biopsy of tumor tissue. Tumor tissue remains the preferred test sample due to a higher sensitivity than that of cfDNA and less susceptibility to false positives, so consideration of a tumor biopsy is appropriate prior to requesting a cfDNA assay. Therapy can greatly impact the sensitivity of cfDNA testing, so patients should be having disease progression at the time of obtaining a blood sample for cfDNA.

Finally, myeloid leukocytic cells accumulate genetic alterations during aging similar to those found in myelodysplasia and acute myeloid leukemia. These myeloid-associated mutations can be detected in both tumor and cfDNA samples and are known as clonal hyperplasia of indeterminate potential (CHIP). CHIP is much more common in the cfDNA. For lung cancer, CHIP-associated gene variants are readily distinguished from lung cancer-associated variants, but that distinction is much more difficult in many other tumor types.