Liquid biopsy: another tool towards tailored therapy in colorectal cancer
Authors: N. Tarazona, A. Cervantes
Journal: Annals of Oncology (2017)

Colorectal cancer (CRC) is an important public health issue, being the second leading cause of cancer death worldwide [1.Ferlay J. Steliarova-Foucher E. Lortet-Tieulent J. et al.Cancer incidence and mortality patterns in Europe: estimates for 40 countries in 2012.Eur J Cancer. 2013; 49: 1374-1403Abstract Full Text Full Text PDF PubMed Scopus (4112) Google Scholar, 2.Ferlay J. Soerjomataram I. Dikshit R. et al.Cancer incidence and mortality worldwide: sources, methods and major patterns in GLOBOCAN 2012.Int J Cancer. 2015; 136: E359-E386Crossref PubMed Scopus (21344) Google Scholar]. Although the prognosis of patients with CRC has improved during the past decades, almost half of all CRC patients with localized disease will relapse after initial treatment. Even so, the median survival time for patients with metastatic CRC (mCRC) is about 30 months [3.Labianca R. Nordlinger B. Beretta G.D. et al.Early colon cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up.Ann Oncol. 2013; 24: vi64-vi72Abstract Full Text Full Text PDF PubMed Scopus (657) Google Scholar]. In the last 20 years, the identification of genomic alterations among solid tumours has led to a better understanding of the molecular basis of cancer. The detection of genetic changes has meant that we can now introduce a personalized approach to each patient, whereby we undertake precision medicine of a gold standard to improve patient outcomes [4.van Cutsem E. Cervantes A. Adam R. et al.ESMO consensus guidelines for the management of patients with metastatic colorectal cancer.Ann Oncol. 2016; 27: 1386-1422Abstract Full Text Full Text PDF PubMed Scopus (2085) Google Scholar]. The recognition of predictive and prognostic biomarkers could help to identify patients at high risk of relapse and establish potential therapeutic strategies to optimize adjuvant treatment in early stages. In the metastatic setting, pinpointing genomic aberrations that could arise from either clonal evolution after therapy or tumour heterogeneity may provide specific targets for more effective treatments. We are currently aware of the heterogeneity between tumours and particularly of heterogeneity within an individual tumour [5.Gerlinger M. Rowan A.J. Horswell S. et al.Intratumor heterogeneity and branched evolution revealed by multiregion sequencing.N Engl J Med. 2012; 366: 883-892Crossref PubMed Scopus (5749) Google Scholar]. Although tumour tissue remains the cornerstone to diagnose and to characterize the somatic genomic features of a single tumour for a tailored treatment strategy, it might not reflect the actual molecular profiling of the tumour owing to intratumour and interlesional heterogeneity. There is therefore a clear need to overcome the restrictions of tumour tissue genotyping and we cannot consider a single tumour biopsy as representative of the whole genomic landscape. Since Mandel and Métais described for the first time the presence of fragments of cell-free acids in human blood in 1948 [6.Mandel P. Metais P. Les acides nucléiques du plasma sanguin chez Ihomne.C R Seances Soc Biol Fil. 1948; 142: 241-243PubMed Google Scholar], many studies have focused on the implementation of circulating tumour DNA (ctDNA) in decision-making in patients diagnosed with cancer. ctDNA can be detected in the plasma or serum of patients with different types of cancer [7.Bettegowda C. Sausen M. Leary R.J. et al.Detection of circulating tumor DNA in early- and late-stage human malignancies.Sci Transl Med. 2014; 6: 224ra24Crossref PubMed Scopus (2989) Google Scholar] acting as a potential non-invasive procedure to identify molecular profiling for cancer identification and treatment. Liquid biopsies therefore provide, in a simple and non-invasive way, relevant information about the presence of tumour in the organism even when it is macroscopically undetectable by conventional imaging techniques [8.Tie J. Wang Y. Tomasetti C. et al.Circulating tumor DNA analysis detects minimal residual disease and predicts recurrence in patients with stage II colon cancer.Sci Transl Med. 2016; 8: 346ra92Crossref PubMed Scopus (802) Google Scholar]. Moreover, it could give relevant information on clonal evolution and molecular mechanisms of resistance to therapy [9.Siravegna G. Mussolin B. Buscarino M. et al.Clonal evolution and resistance to EGFR blockade in the blood of colorectal cancer patients.Nat Med. 2015; 21: 795-801Crossref PubMed Scopus (632) Google Scholar, 10.Pietrantonio F. Vernieri C. Siravegna G. et al.Heterogeneity of acquired resistance to anti-EGFR monoclonal antibodies in patients with metastatic colorectal cancer.Clin Cancer Res. 2017; 23: 2414-2422Crossref PubMed Scopus (127) Google Scholar]. The efficacy of anti-EGFR antibodies for the treatment of mCRC can be determined by the presence of alterations in genes of the EGFR signalling pathway [11.van Cutsem E. Köhne C.H. Láng I. et al.Cetuximab plus irinotecan, fluorouracil, and leucovorin as first-line treatment for metastatic colorectal cancer: updated analysis of overall survival according to tumor KRAS and BRAF mutation status.J Clin Oncol. 2011; 29: 2011-2019Crossref PubMed Scopus (1506) Google Scholar]. Recent studies [12.Grasselli J. Elez E. Caratù G. et al.Concordance of blood- and tumor-based detection of RAS mutations to guide anti-EGFR therapy in metastatic colorectal cancer.Ann Oncol. 2017; 28: 1294-1301Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar, 13.Vidal J. Muinelo L. Dalmases A. et al.Plasma ctDNA RAS mutation analysis for the diagnosis and treatment monitoring of metastatic colorectal cancer patients.Ann Oncol. 2017; 28: 1325-1332Abstract Full Text Full Text PDF PubMed Scopus (222) Google Scholar] indicate the high concordance between the mutational status of RAS in tumour tissue and ctDNA in mCRC patients when comparing standard of care methods to BEAMing digital PCR to establish eligibility for anti-EGFR therapy. Grasselli et al. proved that the feasibility and functionality of ctDNA analysis in 146 patients treated with anti-EGFR monoclonal antibodies in second- or third-line may translate into an alternative tool for anti-EGFR treatment selection [12.Grasselli J. Elez E. Caratù G. et al.Concordance of blood- and tumor-based detection of RAS mutations to guide anti-EGFR therapy in metastatic colorectal cancer.Ann Oncol. 2017; 28: 1294-1301Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar]. Vidal et al. also determined the impact of plasma RAS detection in predicting response to anti-EGFR based therapy [13.Vidal J. Muinelo L. Dalmases A. et al.Plasma ctDNA RAS mutation analysis for the diagnosis and treatment monitoring of metastatic colorectal cancer patients.Ann Oncol. 2017; 28: 1325-1332Abstract Full Text Full Text PDF PubMed Scopus (222) Google Scholar]. Likewise, Tie et al. demonstrated that ctDNA is detectable in a high proportion (98, 1%) of treatment naïve mCRC patients. Early changes in ctDNA during first-line chemotherapy predict the later radiologic response [14.Tie J. Kinde I. Wang Y. et al.Circulating tumor DNA as an early marker of therapeutic response in patients with metastatic colorectal cancer.Ann Oncol. 2015; 26: 1715-1722Abstract Full Text Full Text PDF PubMed Scopus (424) Google Scholar]. In this issue of Annals of Oncology, Normanno et al. report that the concordance of blood- and tumour-based detection of RAS mutations in 97 patients treated with first-line Cetuximab plus FOLFIRI therapy for mCRC was 78.3%. Additionally, the median progression-free survival of RAS mutant and wild-type patients according to tissue (7.9 versus 12.6 months; P = 0.004) and liquid biopsy testing (7.8 versus 13.8 months; P < 0.001) were similar. Comparable data were observed for the median overall survival of RAS mutant and wild-type patients based upon tissue (22.1 versus 35.8 months, P = 0.016) and plasma (19.9 versus 35.8 months; P = 0.013) [15.Normanno N. Esposito Abate R. Lambiase M. et al.RAS testing of liquid biopsy correlates with the outcome of metastatic colorectal cancer patients treated with first-line FOLFIRI plus cetuximab in the CAPRI-GOIM trial.Ann Oncol. 2018; 29: 112-118Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar]. These results indicate that liquid biopsies may orient to patient treatment selection similarly to tissue-derived analysis. Consistent with our earlier discussion, the molecular profiling of individuals with CRC could also be evaluated repeatedly during the course of therapy because the use of targeted drugs can alter the genetic landscape of the tumour. Nevertheless, the repeated use of tissue biopsies has inherent risk of complications associated with these procedures. Consequently, ctDNA has been suggested as a solution to overcome that barrier. Siravegna et al. underlined the biological importance of ctDNA as a surrogate biomarker in CRC. The ability of ctDNA to reflect tumour complexity indicates that liquid biopsy appears to be superior to that of tissue biopsy in capturing the heterogeneity of the overall disease. These results reflect the clonal evolution during the treatment and beyond clinical progression and, could provide a molecular explanation for the efficacy of re-challenging with EGFR blockade [9.Siravegna G. Mussolin B. Buscarino M. et al.Clonal evolution and resistance to EGFR blockade in the blood of colorectal cancer patients.Nat Med. 2015; 21: 795-801Crossref PubMed Scopus (632) Google Scholar]. The potential value of liquid biopsies in CRC should not be restricted to metastatic patients. Tie et al. showed the potential to detect ctDNA in early stage colon cancer. They demonstrated that the ctDNA detection of somatic mutations with massively parallel sequencing called safe-sequencing system could be used to identify minimal residual disease and simultaneously patients at risk of cancer relapse. ctDNA detection after stage II colon cancer resection predicted the likelihood of early recurrence after surgery. ctDNA measurements might thus be considered as a biomarker of recurrence in future [8.Tie J. Wang Y. Tomasetti C. et al.Circulating tumor DNA analysis detects minimal residual disease and predicts recurrence in patients with stage II colon cancer.Sci Transl Med. 2016; 8: 346ra92Crossref PubMed Scopus (802) Google Scholar]. Despite the highly attractive concept of liquid biopsy for detecting ctDNA, we should take into account some limitations, such as the limited number of cases studied and the retrospective nature of the published data. Further challenges remain such as designing prospective cohort studies for assessing the emerging role of liquid biopsies; the lack of standardization of the blood collection method or preferable sample type and appropriate storage conditions [16.El Messaoudi S. Rolet F. Mouliere F. Thierry A.R. Circulating cell free DNA: preanalytical considerations.Clin Chim Acta. 2013; 424: 222-230Crossref PubMed Scopus (399) Google Scholar]; defining appropriate ctDNA quantification methods [17.Devonshire A.S. Whale A.S. Gutteridge A. et al.Towards standardisation of cell-free DNA measurement in plasma: controls for extraction efficiency, fragment size bias and quantification.Anal Bioanal Chem. 2014; 406: 6499-6512Crossref PubMed Scopus (218) Google Scholar]; standardizing of ctDNA isolation to increase yield, and optimizing the detection techniques for rare genomic alterations in order to forecast drug resistance. This all sounds promising, but it is still too early to make treatment decisions in CRC according to ctDNA analysis. At least for now, liquid biopsies provide us with the possibility to detect minimal residual disease, to predict response to chemotherapy early in the therapeutic course and to track tumour evolution throughout the course of treatment. Prospective trials are needed to integrate liquid biopsies into the management of CRC patients. In the near future, the clinical uptake in routine practice of liquid biopsies will also be depending on the practical advantages for patients and physicians, the availability of required infrastructures and their cost effectiveness. NT is a recipient of the Rio Hortega Grant (Contract 15/00246). This work was supported by grant PI15/02180 from Fondo de Investigaciones Sanitarias (Instituto de Salud Carlos III) from the Spanish Government and CIBERONC.