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We read with interest the recent work of Chew et al 1 and we would like to share some original data that might implement the concept of immune activation as a consequence of Yttrium90 transarterial radioembolisation (Y90TARE) in hepatocellular carcinoma (HCC). In this study,1 Y90TARE was shown to mediate a significant increase in activated T and NK cells at the site of the tumour and in the peripheral blood of patients with HCC. The increase in these cell populations, particularly T cells expressing specific homing receptors (CCR5 and CXCR6), is associated with local tumour control.
In our study, we monitored immune phenotypes in the blood (figure 1A) of intermediate-advanced HCC patients (n=49) with preserved hepatic function, undergoing Y90TARE treatment during a 2-year period in our centre (table 1).
We observed that tumour irradiation causes an altered adaptive and innate immune response, including an increased frequency of activated CD3+ T cells and CD8+ subsets, regulatory T cells (Treg) and inflammatory (PD-L1+ and HLA-DR+) monocyte populations (online supplemental figure). The immunomodulatory effect peaked 1 month after treatment and decreased significantly at 3 and 6 months, indicating the short-term nature of Y90TARE-induced immunomodulation (figure 1B).
The CD4+ and CD8+ T cells had higher expressions of the proliferative Ki67 and cytotoxic granzyme B markers post-treatment, suggesting an increase in activated immune effector T cells in peripheral blood (figure 1C and online supplemental figure).
Notably, CD8+ cells recognising HBV/HCV peptides were also increased, thereby indicating a rise in circulating antigens and possibly tumour-specific T lymphocytes in patients with virus-derived HCC2 after tumour irradiation (figure 1D). Nonetheless, a significant proportion of Y90TARE-induced CD4+ and CD8+ T cells expressed high levels of the inhibitory checkpoints markers PD-1 and LAG3 (figure 1E) and produced no IFN-γ despite their activation status3 (online supplemental figure). Post-Y90TARE, there were elevated levels of effector T lymphocytes and a reduced frequency of central and effector memory T cells (online supplemental figure). This depicts a dysfunctional and self-extinguishing immune response with the potential to exert immediate antitumour activity, but lacking the functional properties for long-term lasting tumour-specific T cells.4 Indeed, while the CD4+Ki67+GZB+LAG3+T cell subset was significantly higher in patients reaching tumour response compared with stable or progressing patients (figure 1F), no subset was associated with long-term disease control, as measured by time-to-progression (figure 1G). This suggests that the potent immune boosting effect caused by tumour irradiation does not affect long-term clinical outcomes.
It is still unclear as to whether the dysfunctional phenotype of Y90TARE-induced T cells is due to suboptimal immune priming by locoregional radiation or to the immune status of patients with virus-related HCC. It is tempting to speculate that these T-cell defects may instead result from the ‘molecular scar of chronicity’, which characterises the exhausted T-cell repertoire of patients with chronic viral disease and HCC.5 6 Nevertheless, the timely delivery of immune checkpoint inhibitors (ICIs) may restore the antitumour immune responses of immune checkpoint-expressing T cells in the blood of Y90TARE-treated patients with HCC.
Furthermore, as Y90TARE-induced T cells are short lived, possibly due to PD-1 and LAG3 expression, the provision of multiple immune ICIs could enhance long-term antitumour immunological memory.7 8 On the other hand, the peak of T cells expressing immune checkpoints detected 1 month after Y90TARE could be the potential period for ICIs to be administered to enhance both the immunological and clinical efficacy of irradiation treatment.
In conclusion, in the expanding debate on combination strategies for a personalised HCC treatment,9 10 our results suggest that Y90TARE treatment, followed by administration of PD-1 and LAG3 inhibitors after 1 month, represents a promising combination to induce optimal immune-mediated disease control in patients with HCC.
Patient consent for publication
This study involves human participants and was approved by Comitato Etico Istituto Nazionale Tumori Milano Study number INT 110/13. Approval date 28 October 2014. Participants gave informed consent to participate in the study before taking part.
English language editing was provided by Editage (www.editage.com).
Contributors LR and VM contributed to study design, results interpretation and manuscript preparation. SB and DC contributed to data retrieval and interpretation. LB, CCam and CCas performed immunological analyses. PF and LL performed statistical analyses.
Funding This research received nonprofit grants from Associazione Italiana per la Ricerca sul Cancro (number CC IG-15192) and Ministero della Salute (number 52/RF-2010-2312620).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.