This is a limited coverage policy for next generation sequencing (NGS) assays
performed on solid tumor cell free DNA in plasma, from here on called "liquid
biopsies."

**Criteria for Coverage**  
Guardant360 is covered only when **all** of the following conditions are met:

  * Patient has been diagnosed with a recurrent, relapsed, refractory, metastatic, or advanced solid tumor that did not originate from the central nervous system. Patients who would meet all of the indications on the Food and Drug Administration (FDA) label for larotrectinib if they are found to have a neurotrophic receptor tyrosine kinase (NTRK) mutation may be considered to have advanced cancer, **and**
  * Patient has not previously been tested with the Guardant360 test for the same genetic content. For a patient who has been tested previously using Guardant360 for cancer, that patient may not be tested again unless there is clinical evidence that the cancer has evolved wherein testing would be performed for a different genetic content. Specifically, in patients with previously tested cancer, who have evidence of new malignant growth, despite response to a prior targeted therapy, that growth may be considered to be sufficiently genetically different to require additional genetic testing, **and**
  * Patient is untreated for the cancer being tested or the patient is not responding to treatment (e.g. progression or new lesions on treatment), **and**
  * The patient has decided to seek further cancer treatment with the following conditions: 
    * The patient is a candidate for further treatment with a drug that is either FDA-approved for that patient's cancer, or has a National Comprehensive Cancer Network (NCCN) or NCCN 2A recommendation for that patient's cancer, **and**
    * The FDA-approved indication or NCCN recommendation is based upon information about the presence or absence of a genetic biomarker tested for in the Guardant360 assay **and**
  * Tissue-based, comprehensive genomic profiling (CGP) is infeasible (e.g., quantity not sufficient for tissue-based CGP or invasive biopsy is medically contraindicated) or specifically in NSLC Tissue-based CGP has shown no actionable mutations.

If no alteration is detected by Guardant360 or if circulating tumor
deoxyribonucleic acid (ctDNA) is insufficient/not detected, tissue-based
genotyping should be considered.

Other liquid biopsies will be covered for the same indications if they display
similar performance in their intended use applications to Guardant360.

A wide array of cancer treatments have developed, ranging from surgery to
medications. One of the newer approaches to the medical treatment of cancer
has been to use drugs based on genetic features of malignancy. While many
patients will not benefit from genetic testing to select treatment, for those
whose cancers have select biomarkers, the treatment of choice often includes
therapy targeting that specific biomarker or therapy being avoided because of
a biomarker.1-13  
  
In spite of the importance of actionable biomarker identification in cancer,
research has shown that many patients do not receive genetic testing for the
presence of actionable mutations in their cancers, and there are geographic
disparities in testing with patients in rural areas and those receiving care
at community treatment centers being less likely to receive testing.14-16 In
addition, logistical challenges to testing such as adequate tissue and the
availability of any tissue have been identified as barriers to tissue-based
genomic testing.15 Additionally, even among patients whose cancers were
genomically profiled at diagnosis and found to have a mutation for which they
are receiving targeted treatment, resistance to the initial targeted treatment
may emerge. For some patients, the identification of a new mutation, not
present in the original tissue sample and found in the blood, may allow the
selection of a new targeted life-prolonging therapy.17  
  
 **Clinical utility of comprehensive genomic profiling using plasma-based
testing**  
Traditionally, tumor genotyping has been conducted by direct interrogation of
tumor tissue obtained through invasive tissue sampling procedures. This
diagnostic approach, however, is limited by the availability of sufficient
tumor tissue and the ability of patients to undergo invasive procedures. In a
recent study of over 100 community-based oncologists, nearly one-third of non-
small cell lung cancer (NSCLC) patients were not tested for epidermal growth
factor receptor (EGFR) or anaplastic large-cell lymphoma kinase (ALK), over
75% were not tested for ROS1 fusions, and fewer than 10% were tested for all
guideline-recommended alterations.15 These results were similar to a study in
a single academic center where only 58% of non-squamous NSCLC were tested for
EGFR and 40% for ALK fusions, despite 13% of patients undergoing repeat
invasive biopsies to obtain sufficient tissue for genomic testing.18 Tissue
availability was similarly limited in several recent series, some of which
reported that more than 50% of NSCLC patients had insufficient or unobtainable
material for tissue-based CGP.19-21

Even when successful, tissue acquisition procedures pose a significant
morbidity and mortality risk to Medicare patients. In a recent report, 19% of
all lung tissue acquisition procedures resulted in a serious adverse event,22
while the National Lung Cancer Screening Trial reported 1-2% mortality rates
in their cohorts.23 The FDA has also specifically approved a medication for
patients who have cancer (cancer type unspecified on the label) for which
there is a high risk associated with surgical resection.24 Given the high
rates of inadequate genotyping described above, plasma-based CGP can provide
an opportunity for non- and under-genotyped patients to benefit from therapy
matched to a genetic biomarker. Early studies suggested that plasma-based CGP
can identify potential genomic targets in both the first and second lines,
with response rates similar to those of patients identified using tissue-based
CGP and tissue-based CoDX.20, 21, 25-27

It has been shown that the region of DNA sequenced is important, since
alterations may occur outside the sequenced region or involve complex
alterations (e.g. indels, copy number alterations, or rearrangements) that are
not detectable by certain tests.28 Newer techniques such as next-generation
sequencing (NGS), offer the possibility of not only increased analytical
sensitivity but also the ability to detect a broader range of genomic
alterations.29

While the evidence appears most developed for clinically actionable targets in
NSCLC, targeted therapy for cancer has been recommended for a number of other
cancers as well. Genetic biomarkers associated with specific guideline
recommended targeted therapies for a number of conditions is summarized below
in Table 1. These guidelines are updated frequently, so new genes not listed
in the table may also become part of guideline-consensus recommendations.

**Table 1**

Non-small cell lung cancer6 | EGFR  
BRAF  
MET  
HER2 / ERBB2  
ALK  
ROS1  
RET  
MET  
KRAS  
---|---  
Colorectal 3,10 | KRAS  
NRAS  
BRAF  
Breast2 | HER2 / ERBB2  
BRCA1  
BRCA2  
Endometrial13  | HER2 / ERBB2  
Gastric and Gastroesophageal4 | HER2 / ERBB2  
Gastrointestinal Stromal Tumor11 | KIT  
PDGFRA  
BRAF  
Melanoma5 | BRAF  
KIT  
Ovarian7 | BRCA1  
BRCA2  
Pancreatic8 | BRCA1  
BRCA2  
Prostate9 | BRCA1  
BRCA2  
Thyroid12 | BRAF  
RET  
Chordoma1 | EGFR  
  


Additionally, there are now medications, which are FDA approved for cancers
based on the presence of genetic mutations regardless of the tissue of origin.

**Microsatellite instability**  
Microsatellite instability structures are composed of a repeated nucleotide
sequences that emerge due to defects in mismatch repair during DNA
replication.30 The importance of them in cancer, is that Microsatellite
Instability High (MSI-H) tumors have been found to respond to immunotherapy,
31 and one immunotherapy drug, pembrolizumab, now has an FDA indication for
the treatment of patients with unresectable or metastatic, MSI-H solid
tumors.32

**NTRK**  
The tropomyosin receptor kinase (TRK) receptor family is family of
transmembrane proteins, some of which are encoded by the NTRK1, NTRK, and
NTRK3 genes. Of these, Guardant360 tests for NTRK1 mutations including
fusions. Fusions in the NTRK genes lead to chimeric TRK proteins, which have
oncogenic potential, and have been viewed as a potential therapeutic target
for cancer.33

Larotrectinib, a TRK inhibitor, has received FDA approval for NTRK positive
(without a known resistance mutation) tumors in patients with metastatic
disease or where surgical resection is likely to result in severe morbidity,
and who have no satisfactory alternative treatments or that have progressed
following treatment.24

**Guardant360 **  
Guardant360 is a comprehensive genomic profiling test that identifies
mutations in 73 genetic mutations. It has demonstrated targeted therapy
response rates similar to tissue-detected genomic targets in numerous
published NSCLC studies. 20,21,25-28 In addition to sequencing accuracy,
research has been done evaluating the ability of the test to identify
actionable mutations across cancers originating in a number of organ systems.

In a study by Rozenblum et al., tissue biopsies from 101 advanced NSCLC
patients were tested locally for EGFR mutations and ALK fusions.34 Tissue-
based CGP identified 15 EGFR and ALK alterations missed locally but could only
be performed in 82 of the 101 (81%) patients because of tissue exhaustion.
Guardant360 was used in the 19 remaining patients and two (11%) additional
sensitizing EGFR mutations were found that had been missed with local tissue
genotyping. In addition, alterations including MET amplification, ERBB2 (HER2)
mutation, and two RET fusions were also identified (missed with local non-CGP
genotyping), for a total of 6 driver alterations in 19 patients (32%). Thus,
Guardant360 changed treatment in 32% of patients with insufficient samples
for tissue-based CGP, with five receiving matched therapy. These five patients
achieved a 60% objective response rate and 100% disease control rate.

A more recent study examined the clinical implications of using plasma-based
testing in addition to tissue-based testing in 128 patients with NSCLC.35 Of
these 55 were found to have a therapeutically targetable mutation. Of these
55, only 31 had this mutation found in tissue and plasma, though not
necessarily the same actionable mutation(s) in each testing method. For 16
patients, the mutation was found in tissue only, and for 8 it was found in
plasma only. To further assess whether the selection of targeted therapy based
on the detection of low allele frequency mutations that Guardant360 is able
to identify has a clinical benefit, the authors assessed the depth of response
to targeted mutations identified in plasma-based testing. A total of 42
patients received a targeted therapy consistent with the plasma-based testing,
12 of whom had that mutation also detectable in tissue-based testing as well.
Of this 42, there were 36 (85.7%) who achieved a response of stable disease,
partial response, or complete response.

The ability of Guardant 360 to identify actionable mutations in multiple
types of cancer, including NSCLC, gastric cancer, and melanoma, was examined
in 194 patients with metastatic cancer but no availability of tissue for NGS-
based genotyping.25 Actionable mutations were found in the majority of
patients, but the study also evaluated treatment response when the patients
were given therapy matching a genetic mutation in the test. In the group with
NSCLC, 15 received matched therapy, and 13 of them responded to the therapy.
Among those with gastric cancer, a total of nine received matched therapy, and
6 responded to treatment, with one of those six have a complete response (a
patient with an ERBB2 amplification). Only 2 patients with melanoma received
matched therapy, and one responded to this treatment.

Guardant360 has been validated recently across genetic mutation types (single
nucleotide variants, indels, fusions, and copy number amplifications) and a
range of specific actionable mutations in a study using orthogonal tissue and
plasma-based methods.36, 37 Analytical performance of Guardant360 is
summarized in the table below.



**Mutation Type**

|

**LOD95**

|

**Sensitivity**

|

**Positive Predictive Value**  
  
---|---|---|---  
  
**SNVs**

|

>0.25%  
0.05 - 0.25%

|

100%  
63.8%

|

99.2%  
96.3%  
  
**Indels**

|

>0.20%  
0.05 -0.20%

|

100%  
67.8%

|

98.2%  
98.2%  
  
**Fusions**

|

>0.20%  
0.05-0.20%

|

95%  
83%

|

100%  
100%  
  
**CNAs**

|

2.24-2.76 copies

|

95%

|

100%  
  


Additionally, the study assessed the detection rate of tumor DNA using
Guardant360 from 10,585 patients with more than 20 different cancers.
Detection rate was >60% for nearly all cancers and around 80-90% for NSCLC,
breast cancer, colorectal cancer, prostate cancer, gastroesophageal cancer,
and gynecologic cancer. For primary CNS malignancies the detection rate was
less 50%.

While MolDX initially covered the Guardant360 assay for the selection of
targeted therapy in NSCLC, the assay tests for the presence of mutations in
over 70 genes and Microsatellite Instability (MSI). More recent research
looking beyond NSCLC has shown that the analytical and clinical performance of
the Guardant360 assay varies little between mutation type and tissue origin,
with the exception of malignancies arising in the central nervous system.36,
37

**Guardant360  Test Description and Intended Use**  
Guardant360 analyzes tumor-derived cell-free DNA (also known as ctDNA) to
detect somatic alterations, though it also reports germline alterations.

Guardant360 detects the following classes of alterations:

  * Base pair substitutions (also known as SNVs)
  * Small (20 bp) and large (>20 bp) indels
  * Copy number amplifications (CNAs)
  * Fusions
  * Microsatellite Instability

The analytical performance characteristics of Guardant360 are similar across
mutation types, specific actionable mutations, and tissue types, except
primary CNS cancers.



Level of Evidence  
Quality: Moderate  
Strength: Limited  
Weight: Limited

The clinical utility of Guardant360 testing for patients with advanced cancer
at diagnosis or at progression, as defined in the intended use above, is quite
promising. At present, the assay appears to have similar performance to detect
mutations regardless of the tissue of origin or mutation type.

While tissue-based testing remains the preferred tool to test for actionable
mutations in cancer, for patients in whom obtaining this tissue is not
feasible, liquid biopsy with Guardant360 represents an alternative which may
allow more patients to get potentially effective cancer treatment.