TRAINING and EDUCATION
Demystifying the Lab
The Monash University team is now working
on a series of hypothesis-generating clinical trials
in Australia and New Zealand to analyze ctDNA
and mutational changes related to therapy and
tumor progression in patients with myeloma. Dr.
Spencer hopes the results will inform how to best
use this technology in the clinic to help care for
these patients.
Dr. Spencer also predicts that a ctDNA detec-
tion assay could assess if there are any remaining
myeloma cells after treatment, or minimal residual
disease (MRD), which is typically measured by
quantifying certain serum biomarkers or taking an
additional, invasive BM biopsy. However, neither
technique is highly sensitive and each can produce
false-negative results. 4
Tracking Resistance
ctDNA-based liquid biopsies could be useful for
monitoring patients’ response to therapy during and
after treatment and could allow clinicians to adjust
treatment strategy in real time.
In solid tumors, researchers have previously
shown that tracking blood-borne tumor DNA dur-
ing treatment can detect whether a patient’s cancer
is responding to a specific drug and whether tumor
clones have developed resistance mutations to
targeted agents. 5,6 Investigators are now attempting
to extend the use of ctDNA-based blood assays to
hematologic malignancies. 7-9
Dr. Diehn and Ash Alizadeh, MD, PhD, an
associate professor at the Stanford Comprehensive
Cancer Center, evaluated CAPP-Seq (Cancer Per-
sonalized Profiling by Deep Sequencing), a liquid
biopsy technique that sequences for more than 200
lymphoma-relevant genes, in 92 patients with dif-
fuse large B-cell lymphoma (DLBCL). 10
According to their findings, CAPP-Seq pre-
dicted patient outcomes, with all patients who had
detectable ctDNA ultimately experiencing disease
progression despite therapy. In contrast, ctDNA
was undetectable in plasma samples from patients
who were disease-free for at least 24 months after
therapy and in 24 healthy adult participants – dem-
onstrating 100 percent specificity. In addition, “by
simultaneously tracking multiple somatic mutations
in ctDNA, our approach outperformed immuno-
globulin sequencing and radiographic imaging for
the detection of MRD,” the authors reported. When
they evaluated the CAPP-Seq method in a first-in-
human pilot study, the researchers also showed that
they could detect resistance mutations in the blood
of patients treated with the Bruton tyrosine kinase
inhibitor ibrutinib before patients displayed clinical
signs of resistance.
“DLBCL has a high level of ctDNA compared
with the average carcinoma, so it is ideally suited
for ctDNA studies,” Dr. Diehn told ASH Clinical
News. The researchers also found that unlike their
prior analysis of ctDNA in lung cancer, CAPP-Seq
for DLBCL could track approximately 10 times
more mutations, boosting the assay’s sensitivity
10-fold.
Since 2016, the team has followed up their
study with international collaborations that show
CAPP-Seq could be used to risk-stratify patients
with DLBCL and to detect, after a single cycle of
therapy, whether a patient is responding well to a
curative-intent therapy. 11,12
Other scientists, including Dr. Adalsteinsson,
are taking a more holistic approach by sequencing
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ASH Clinical News
all of the ctDNA rather than focusing on specific
genes. 13 While whole-exome sequencing of ctDNA
is too costly for clinical applications, it can define
every alteration present in ctDNA – offering the
opportunity to identify and discover new targetable
mutations.
“For ... hematologic
malignancies, [ctDNA
is] a particularly
unique opportunity
because the blood is
our analyte.”
—ASH ALIZADEH, MD, PhD
Too Early for Early Detection?
The holy grail of liquid biopsy research is developing
a test that can detect tumors before they cause symp-
toms. With this type of test, people could be routinely
screened to identify their risks of developing cancer.
Another team of researchers at Johns Hopkins
University, led by Nickolas Papadopoulos, PhD, ap-
pears to have made progress in this area, according
to a study published in February 2018 in Science. 14
The study examined 1,005 patients whose tumors
had not yet metastasized. Focusing on mutations
within just 16 genes that are often mutated in cancer
– and adding an analysis of eight protein biomark-
ers known to be associated with specific types of
cancer – the test detected 33 to 98 percent of cases,
depending on the tumor type. The test also appeared
to provide reliable results, with sensitivity levels of
69 to 98 percent for tumors for which there is no
approved screening test, including ovarian, liver, and
pancreatic cancers.
In 2017, the gene-sequencing company Grail
reported results from a feasibility study of its liquid
biopsy test (which scans blood samples for muta-
tions in 508 genes). The researchers analyze