The following article features coverage from the American Society of Hematology 2020 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Using a combination of techniques, researchers were able to precisely quantify the number of chimeric antigen receptor (CAR) T cells in circulation and distinguish patients who responded to therapy from those who did not.

The study findings were presented at the virtual 62nd American Society of Hematology (ASH) Annual Meeting and Exposition.

Study presenter Chiara Monfrini, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy, explained that studies have shown that CAR T-cell engraftment and in vivo expansion have a “crucial” impact on disease response.

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“For these reasons, it’s of relevance to develop a standardized approach for monitoring the expansion and the persistence of CAR T cells,” for CAR-T products, she said. She added that is it specifically relevant in the case where cells are undetectable by flow cytometry.

The study researchers used flow cytometry to analyze samples from 36 patients treated with either tisagenlecleucel (tiso-cel) or axicabtagene ciloleucel (axi-cel). Overall, 25 patients had diffuse large B-cell lymphoma and 11 had primary mediastinal large B-cell lymphoma. A total of 16 patients achieved a complete response and 6 experienced a partial response.

At day 14, flow cytometry was able to distinguish patients who achieved a complete response from those who did not (P <.05).

Among samples from 15 patients taken at time points after infusion, digital droplet polymerase chain reaction (PCR) and flow cytometry were correlated (r, 0.85; P <.001). However, when only a low number of CAR-positive cells were measured by flow cytometry, discordance was seen.

“In this cases, digital droplet PCR helped us clarify these low count results by flow [cytometry],” said Monfrini.

“We conclude that our digital droplet PCR method allows a sensitive detection of both the tiso-cel and axi-cel products,” said Monfrini. “Digital droplet PCR has the ability to quantify low amounts of the CAR vector, and it’s possible to combine our novel molecular assay and flow cytometry to obtain a precise enumeration of commercial anti-CD19 CAR T-cell products.”

Disclosures: Some of the presenters disclosed financial relationships with the pharmaceutical industry and/or the medical device industry. For a full list of disclosures, please refer to the presentation abstract.

Read more of Cancer Therapy Advisor‘s coverage of the ASH 2020 meeting by visiting the conference page.


Monfrini C, Aragona V, Magni M, et al. A novel method for molecular enumeration of circulating tisa-cel and axi-cel in lymphoma patients. Presented at: the 62nd American Society of Hematology (ASH) Annual Meeting and Exposition; December 5-8, 2020. Abstract 198.