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22-05-2012 | Genetics | Article

High-throughput sequencing best predicts early leukemia relapse


Free abstract

MedWire News: High-throughput sequencing (HTS) of T-cell receptor (TCR) genes detects early signs of potential relapse in nearly twice as many leukemia patients as does-flow cytometry, the current gold standard for detecting minimal residual disease (MRD), US researchers report.

"The ability to predict disease relapse sooner with high-throughput sequencing would give hematologists the option to treat cancer recurrence earlier, offering a greater chance of survival. Longer term, this technology potentially also could be used to initially diagnose leukemia and lymphoma much earlier than we can today," said senior author Harlan Robins (Fred Hutchinson Cancer Center, Washington, Seattle) in a press statement.

Robins and co-authors explain that clinical management of patients with T-lineage acute lymphoblastic leukemia (T-ALL) is dependent on accurate risk stratification, and several studies have confirmed the importance of assessing MRD ‑ the persistence of a small number of cancer cells post-treatment ‑ to predict clinical outcomes of patients.

For the present study, the researchers compared the effectiveness of HTS versus flow cytometry to detect MRD in 43 patients with T-ALL.

The researchers amplified and sequenced the complementarity-determining region 3 (CDR3) of the TCR genes TCRB and TCRG in samples collected from the patients before, and 29 days after treatment.

As reported in Science Translational Medicine, the pretreatment analysis allowed the researchers to identify unique, recombined TCR-gene sequences representing the patient's clonal, neoplastic T lymphoblasts. These sequences were detected in 31 (72%) patients for TCRB and 27 (63%) patients for TCRG.

The team then examined the ability of HTS to identify the same clonal sequence, used as a marker of MRD, in the post-treatment day 29 sample, and compared their findings to those obtained by flow cytometry.

They found that MRD was detected by both HTS and flow cytometry in 12 (39%) of the 31 patients with clonal TCRB sequences. A further 10 (32%) cases of MRD were detected by HTS, but not by flow cytometry, while no MRD was detected by either technique in the remaining nine (29%) samples.

The researchers note that, of the 10 cases for which HTS did and flow cytometry did not detect MRD, the level of MRD was 10- to 100-fold lower than for the 12 MRD cases detected by both techniques.

"Our research indicates that HTS offers many advantages over flow cytometry," Robins said.

A current limitation of the technique, however, is that it only applies to patients whose tumors have a detectable clonal rearrangement at diagnosis either in the TCRB or TCRG genes.

Even so "since HTS can detect any pre-identified clone and is performed in a centralized lab, it consistently generates reproducible and reliable results regardless of cancer type, using the same process for disease detection and tracking. Furthermore, HTS is highly automated, cost-effective and objective, whereas flow cytometry is more time consuming, relies on the skill of the operator and is therefore subject to human error," Robins concluded.

By Laura Cowen

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