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Using TIL Assay to Predict Treatment Response in Locally Advanced Rectal Cancer

By: Joseph Fanelli
Posted: Monday, February 25, 2019

Evaluating the function of tumor-infiltrating lymphocytes (TILs) can be done within weeks of a diagnostic biopsy for patients with locally advanced rectal cancer, according to findings published in JCO Precision Oncology. The use of an assay that tests TIL cytotoxicity in this patient population before definitive treatment potentially may alter patient management and clinical decision-making in watch-and-wait approaches, concluded author Joseph Cherng Huei Kong, MS, MBChB, of the Peter MacCallum Cancer Centre, Melbourne, Australia, and colleagues.

“This cytotoxic assay also has the potential to serve as a platform to assist in the additional development of [checkpoint inhibition blockade],” the authors concluded.

Dr. Kong’s team initially focused on 34 consecutive patients, with successful completion of the assay before surgery in 17 patients who underwent full treatment. The researchers evaluated TIL-mediated tumoroid lysis by measuring the mean fluorescence intensity of cell death marker, propidium iodide.

Of the 17 patients, 6 achieved an objective pathologic complete response on final evaluation of the resected specimen after neoadjuvant chemoradiotherapy; these 6 patients were stratified accurately, “with 100% concordance,” 12 to 14 weeks before surgery. “Cytotoxic killing identified the [pathologic compete response] group with a higher mean fluorescence intensity (27,982), compared with the non–[pathologic complete response] cohort (12,428),” they reported. “Assessment of the effectiveness of [checkpoint inhibition blockade] revealed partial restoration of cytotoxicity of TILs with increased PD-1 expression with anti–PD-1 antibody exposure.”

“This study has demonstrated the functional characterization of individual patient-specific TILs against matched primary or metastatic tumor cells,” concluded Dr. Kong and colleagues.

Disclosure: The study authors’ disclosure information can be found at ascopubs.org.



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