Colorectal cancer (CRC) is one of the major causes of cancer-related deaths. Early detection of tumor relapse is crucial for determining the most appropriate therapeutic management. In clinical practice, computed tomography (CT) is routinely used, but small tumor changes are difficult to visualize, and reliable blood-based prognostic and monitoring biomarkers are urgently needed. The aim of this study was to prospectively validate a gene expression panel (composed of GAPDH, VIL1, CLU, TIMP1, TLN1, LOXL3 and ZEB2) for detecting circulating tumor cells (CTCs) as prognostic and predictive tool in blood samples from 94 metastatic CRC (mCRC) patients. Patients with higher gene panel expression before treatment had a reduced progression-free survival (PFS) and overall-survival (OS) rates compared with patients with low expression (p = 0.003 and p ≤ 0.001, respectively). Patients with increased expression of CTCs markers during treatment presented PFS and OS times of 8.95 and 11.74 months, respectively, compared with 14.41 and 24.7 for patients presenting decreased expression (PFS; p = 0.020; OS; p ≤ 0.001). Patients classified as non-responders by CTCs with treatment, but classified as responders by CT scan, showed significantly shorter survival times (PFS: 8.53 vs. 11.70; OS: 10.37 vs. 24.13; months). In conclusion, our CTCs detection panel demonstrated efficacy for early treatment response assessment in mCRC patients, and with increased reliability compared to CT scan.

Molecular profiling of circulating cell-free DNA (cfDNA) has shown utility for the management of colorectal cancer (CRC). TruSight Tumor 170 (TST170) is a next-generation sequencing (NGS) panel that covers 170 cancer-related genes, including KRAS, which is a key driver gene in CRC. We evaluated the capacity of TST170 to detect gene variants in cfDNA from a retrospective cohort of 20 metastatic CRC patients with known KRAS variants in tumor tissue and in cfDNA previously analyzed by pyrosequencing and BEAMing, respectively. The cfDNA of most of the patients (95%) was successfully sequenced. We frequently detected variants with clinical significance in KRAS (79%, 15/19) and PIK3CA (26%, 5/19) genes. Variants with potential clinical significance were also identified in another 27 cancer genes, such as APC. The type of KRAS variant detected in cfDNA by TST170 showed high concordance with those detected in tumor tissue (77%), and very high concordance with cfDNA analyzed by BEAMing (94%). The variant allele fractions for KRAS obtained in cfDNA by TST170 and BEAMing correlated strongly. This proof-of-principle study indicates that targeted NGS analysis of cfDNA with TST170 could be useful for non-invasive detection of gene variants in metastatic CRC patients, providing an assay that could be easily implemented for detecting somatic alterations in the clinic.

Background: Osteosarcoma is a rare disease, but it is the most frequent malignant bone tumor. Primary treatment consists of preoperative MAP (methotrexate (MTX), doxorubicin and cisplatin) chemotherapy followed by surgery and adjuvant chemotherapy. Pathological response to preoperative chemotherapy is one of the most important prognostic factors, but molecular biomarkers are lacking. Additionally, chemotherapy-induced toxicity might jeopardize treatment completion. We evaluated variants in genes involved in DNA repair and drug metabolism pathways as predictors of response to MAP-based treatment. Material and Methods: Germline polymorphisms in MTHFR, SLC19A1, ABCB1, ABCC2, ABCC3, ERCC1, ERCC2 and GSTP1 genes were determined for association studies in 69 patients diagnosed with localized osteosarcoma who enrolled in the prospective GEIS-33 trial. P-glycoprotein expression in tumor tissue was also analyzed. Results: In the multivariate analysis, the ABCC2 rs2273697 (odds ratio [OR] 12.3, 95% CI 2.3–66.2; p = 0.003) and ERCC2 rs1799793 (OR 9.6, 95% CI 2.1–43.2; p = 0.003) variants were associated with poor pathological response. P-glycoprotein expression did not correlate with pathological response. The ABCB1 rs1128503 (OR 11.4, 95% CI 2.2–58.0; p = 0.003) and ABCC3 rs4793665 (OR 12.0, 95% CI 2.1–70.2; p = 0.006) variants were associated with MTX grade 3–4 hepatotoxicity. Conclusions: Our findings add to the evidence that genetic variants in the ABC transporters and DNA-repair genes may serve as predictive biomarkers for MAP chemotherapy and contribute to treatment personalization.

We aimed to identify common mCRC profiles associated with a discordant mutational status of RAS between the standard of care (SoC) tumour tissue tests and ctDNA tests to understand ctDNA detection and improve treatment responses. This was a multicentre, retrospective and prospective study. A total of 366 Spanish mCRC patients were independently recruited. BEAMing ddPCR technology was employed to detect ctDNA RAS mutations, and logistic regression analyses were performed to investigate clinicopathological factors associated with discordance. The highest concordance ratios were observed in profiles with multiple metastatic sites when the liver was present (89.7%; 95% CI 84.8–93.2), profiles with synchronous disease without primary tumour resection (90.2%; 95% CI 83.6–94.3) and profiles with mCRC originating in the left colon (91.3%; 95% CI 85.0–95.0). Metachronous disease originating in the right colon (OR = 6.1; 95% CI 1.7–26.5; p-value = 0.006) or rectum (OR = 5.0; 95% CI 1.5–17.8; p-value = 0.009) showed the highest probability of discrepancies. Primary tumour resection and a higher frequency of single metastases in the peritoneum or lungs in these patients were associated with reduced plasmatic mutation allele fractions (MAFs) and an increased probability of showing false-negative genotypes. Additional testing of patients with mCRC originating in the right colon or rectum with a single non-mutated ctDNA test is advised before the choice of therapy.

4068 Background: HER2 status is a predictive biomarker to response to trastuzumab in metastatic gastric adenocarcinomas. However, relatively little is known about the role of HER2 and HER3 in the non-metastatic disease in European population. Methods: Immunohistochemical expression of HER2 was analyzed using DAKO-HercepTest™ and gene amplification using DAKO-DuoCISH kit; both were scored according to published criteria. HER3 expressión was analyzed using HER3 clon DAK-H3-ICHER3 HER2 patients with 0-1+ were classified as HER2 negative, patients with 2+ and negative DuoCISH as equivocal and 3+ or 2+ with positive DuoCISH as positive. HER3 pts were classified as negative if 0-1+ or positive 2-3+ by two independent observers. Six subtypes according to HER2 and HER3 status were defined. Relationship between this classification and the clinicopathological characteristics and survival was analyzed retrospectively. Results: 106 pts diagnosed between Jan-2007 and Jun-2014 were analyzed. Subtype distribution was: HER2-HER3 (-) (56.6%), HER2 equivocal/HER3 (–) 9 pts (8.5%), HER2 (-) HER3 (+) (15.1%), HER2 equivocal HER3 (+) (6.6%), HER2 (+) HER3 (-) (7.5%) and HER2 (+) HER3 (+) (5.7%). HER2 had a significant association with HER3 (p = 0.018). Strong or moderate HER2 expression was associated with intestinal differentiation (p = 0.020) while tumors with strong or moderate HER2 expression or high HER3 expression were associated with lower grade (p = 0.050). Patients with low expression of HER2 and HER3 had a better specific overall survival ( > 85%) than those with HER3 overexpression (66.7-68.6%). Patients with strong or moderate HER2 expression without HER3 expression tumors had the worse survival (50%). Conclusions: Our algorithm based in HER2 and HER3 status proposes a classification in 6 groups with clinicopathologic and prognostic correlates. Overexpression of HER3 is a frequent phenomenon in early gastric cancer that modulates the adverse prognosis associated with HER2 overexpression. Patients with HER3 overexpression have an intermediate prognosis between patients with isolated HER2 overexpression and those who lack both drivers.