Prognostic relevance of an epigenetic biomarker panel in sentinel lymph nodes from colon cancer patients

Abstract

Background: Patients with early colorectal cancer (stages I-II) generally have a good prognosis, but a subgroup of 15-20% experiences relapse and eventually die of disease. Occult metastases have been suggested as a marker for increased risk of recurrence in patients with node-negative disease. Using a previously identified, highly accurate epigenetic biomarker panel for early detection of colorectal tumors, we aimed at evaluating the prognostic value of occult metastases in sentinel lymph nodes of colon cancer patients.

Results: The biomarker panel was analyzed by quantitative methylation-specific PCR in primary tumors and 783 sentinel lymph nodes from 201 patients. The panel status in sentinel lymph nodes showed a strong association with lymph node stage (P = 8.2E-17). Compared with routine lymph node diagnostics, the biomarker panel had a sensitivity of 79% (31/39). Interestingly, among 162 patients with negative lymph nodes from routine diagnostics, 13 (8%) were positive for the biomarker panel. Colon cancer patients with high sentinel lymph node methylation had an inferior prognosis (5-year overall survival P = 3.0E-4; time to recurrence P = 3.1E-4), although not significant. The same trend was observed in multivariate analyses (P = 1.4E-1 and P = 6.7E-2, respectively). Occult sentinel lymph node metastases were not detected in early stage (I-II) colon cancer patients who experienced relapse.

Conclusions: Colon cancer patients with high sentinel lymph node methylation of the analyzed epigenetic biomarker panel had an inferior prognosis, although not significant in multivariate analyses. Occult metastases in TNM stage II patients that experienced relapse were not detected.

Keywords: Biomarkers; DNA methylation; Occult metastases; Prognosis; Relapse; Sentinel lymph nodes.

Fig. 1

Average DNA methylation across the biomarker panel for individual lymph nodes. Controls: mean 0.18; 95% CI [0.13–0.23]. HES negative: mean 0.52; 95% CI [0.40–0.64]. HES positive: mean 10.73; 95% [CI 7.84–13.62]. The red line indicates the scoring threshold (1.0). Abbreviations: CI confidence interval, HES hematoxylin-erythrosin-safranin, PMR percentage methylated reference (methylation value)

Fig. 2

Receiver operating characteristics curve of the ability of the biomarker panel to separate HES-positive from HES-negative lymph nodes from colon cancer patients. Abbreviations: AUC area under the receiver operating characteristics curve, HES hematoxylin-erythrosin-safranin

Fig. 3

Methylation index across the lymph nodes from colon cancer patients. HES-positives include patients for whom one or more of the lymph nodes subjected to methylation analysis were HES-positive. Abbreviation: HES, hematoxylin-erythrosin-safranin

Fig. 4

Methylated lymph nodes are associated with poor patient outcome. a–d Survival analyses for methylation status of colon cancer patients’ lymph nodes. Blue curves represent an unmethylated lymph node status whereas green curves represent a methylated lymph node status in colon cancer patients. a, c Overall survival analysis. b, d Time to recurrence analysis. The plots have been generated using the Kaplan-Meyer method, and P values were calculated by the Wald test