Up to date, there isn’t current method or parameter that allows identifying long survivors in treatment with immunotherapy (IT) in a simple and accessible way. We made a prospective study of the usefulness of quantifying circulating tumor cells (CTCs) and CTCs/PDL1+ in patients treated with immunotherapy.
Patients, diagnosed with non-small cell lung cancer and in second-line treatment with IT were analyzed prospectively. CTCs from peripheral blood samples were isolated by double density gradient and immunomagnetic separation with AutoMACS equipment (M.Biotec). Quantification of CTCs was performed by Cytometry and Confocal Microscopy. The combination of both methodologies allows greater sensitivity and specificity. Samples were acquired in a MACSQuant cytometer (M.Biotec) and TCS SP5 Confocal Microscope (Leica).Data analysis was performed using MACSQuantify and LASF Lite. Determination of CTCs was made at the beginning of the treatment and every 3 months and up to 12 months during IT, together with radiological evaluation in each extraction. We selected those patients who had no progression of the disease for at least 12 months.
Determination of CTCs alone did not allow us to obtain any pattern of recurrence or response. However, we were able to identify 7 patients in the group of long survivors (> 12 months of treatment with IT) using the marker PDL1. The study of their CTCs showed that none of them had circulating CTCs+/PD-L1+. Two of these patients were PDL1+ in tissue sample but negative CTC/PDL1 in blood. We also observed the presence of non-tumor WBC (white blood cells)/PDL1+, but their meaning is not clear in patients with relapse. To emphasize, another patient PDL1 + in tissue, CTC/PDL1+ in serum and low number of WBC, showed positive imaging (PET) of the progression of the disease and its CTC number increased in later determinations.
The absence of circulating CTCs/PDL1 + can predict a sustained response to long-term IT. Isolated CTCs without quantifying their associated expression of PDL1 are not associated with a particular pattern nor appear to be useful in identifying long survivors. WBCs that express PDL1 were associated with the appearance of relapse. Larger studies are needed to validate our results.
Clinical trial identification
Legal entity responsible for the study
Hospital Universitario Puerta de Hierro Majadahonda.
Has not received any funding.
All authors have declared no conflicts of interest.