Prognostic analysis of salvage esophagectomy after definitive chemoradiotherapy for esophageal squamous cell carcinoma: The importance of lymphadenectomy

ObjectivesThe objective of this study was to review the prognostic factors for increased survival after salvage esophagectomy after definitive chemoradiotherapy for esophageal squamous carcinoma and determine the importance of lymphadenectomy from a prognostic view.MethodsClinical data for all patients from January 1999 to December 2012 who underwent salvage esophagectomy for residual tumor or tumor recurrence after definitive chemoradiotherapy were retrospectively collected. Survival was determined and prognostic factors were analyzed with univariate and multivariate analyses.ResultsSurvival after 1, 3, and 5 years postoperatively was 74.4%, 39.8%, and 29.5%, respectively. The independent predictive factors for increased postoperative survival were tumor recurrence rather than residual tumor as the indication for salvage surgery (P < .001; odds ratio [OR], 0.292); complete tumor resection (P < .001; OR, 4.520); N category (P = .089; OR, 1.304); M category (P = .081; OR, 2.215), and total mediastinal dissection with 15 or more dissected mediastinal lymph nodes (P = .034; OR, 0.546).ConclusionsSalvage indications of recurrence, earlier disease, and complete tumor resection are related to longer survival. The total area of mediastinal dissection with a sufficient number of dissected mediastinal lymph nodes improves survival. Additional neck dissection does not add benefit. The optimal procedure for lymph node dissection in salvage esophagectomy should be established in future studies

Early-Stage Induction of SWI/SNF Mutations during Esophageal Squamous Cell Carcinogenesis

<div><p>The SWI/SNF chromatin remodeling complex is frequently inactivated by somatic mutations of its various components in various types of cancers, and also by aberrant DNA methylation. However, its somatic mutations and aberrant methylation in esophageal squamous cell carcinomas (ESCCs) have not been fully analyzed. In this study, we aimed to clarify in ESCC, what components of the SWI/SNF complex have somatic mutations and aberrant methylation, and when somatic mutations of the SWI/SNF complex occur. Deep sequencing of components of the SWI/SNF complex using a bench-top next generation sequencer revealed that eight of 92 ESCCs (8.7%) had 11 somatic mutations of 7 genes, <i>ARID1A</i>, <i>ARID2</i>, <i>ATRX</i>, <i>PBRM1</i>, <i>SMARCA4</i>, <i>SMARCAL1</i>, and <i>SMARCC1</i>. The <i>SMARCA4</i> mutations were located in the Forkhead (85Ser>Leu) and SNF2 family N-terminal (882Glu>Lys) domains. The <i>PBRM1</i> mutations were located in a bromodomain (80Asn>Ser) and an HMG-box domain (1,377Glu>Lys). For most mutations, their mutant allele frequency was 31–77% (mean 61%) of the fraction of cancer cells in the same samples, indicating that most of the cancer cells in individual ESCC samples had the SWI/SNF mutations on one allele, when present. In addition, a BeadChip array analysis revealed that a component of the SWI/SNF complex, <i>ACTL6B</i>, had aberrant methylation at its promoter CpG island in 18 of 52 ESCCs (34.6%). These results showed that genetic and epigenetic alterations of the SWI/SNF complex are present in ESCCs, and suggested that genetic alterations are induced at an early stage of esophageal squamous cell carcinogenesis.</p></div

The close association between a cancer cell fraction and the mutant allele frequency in the ESCC samples.

<p>(A) The association of a cancer cell fraction and a mutant allele frequency in a cancer sample. Theoretically, in the case that all the cancer cells in an individual cancer sample have a somatic mutation on one allele of a specific gene and allelic imbalance of the region is absent, a mutant allele frequency is expected to be 50% of the cancer cell fraction. (B) The cancer cell fraction of ESCCs. The cancer cell fraction was analyzed using cancer cell fraction markers, <i>TFAP2B, ARHGEF4,</i> and <i>RAPGEFL1,</i> which are specifically methylated in ESCC cells. The mutant allele frequency was calculated using read numbers of sequences with and without somatic mutations. The mutant allele frequency of the five ESCC samples (#85, #89, #94, #127, and #169) was 31–77% (mean 61%) of their cancer cell fraction.</p

Somatic mutations of genes encoding the components of the SWI/SNF complex in ESCCs.

<p>(A) Status of somatic mutations of the SWI/SNF complex in ESCCs. Somatic mutations were analyzed in the 92 ESCCs by an Ion Proton Sequencer. Among the 92 ESCCs, 8 (8.7%) had 11 somatic mutations of 7 genes, <i>ARID1A, ARID2, ATRX, PBRM1, SMARCA4, SMARCAL1</i> and <i>SMARCC1</i>. Filled box indicates the presence of somatic mutations. The presence of these somatic mutations was confirmed by Sanger sequencing. (B) The position of somatic mutations in the components of the SWI/SNF complex. Somatic mutations were located in various functional domains of a mutated component.</p

Aberrant DNA methylation of the components of the SWI/SNF complex in ESCCs.

<p>(A) Status of DNA methylation of the SWI/SNF complex in ESCCs. DNA methylation was analyzed in the 52 ESCCs by an Infinium HumanMethylation450 BeadChip array. Among the 52 ESCCs, 18 (34.6%) had aberrant methylation of <i>ACTL6B</i>. The expression level of each gene in non-cancerous esophagus tissues (n = 8, pooled) is shown in the rightmost of the panel. (B) DNA methylation status of <i>ACTL6B</i> around TSS. Aberrant methylation was induced around TSS of <i>ACTL6B</i>. (C) DNA methylation of <i>ACTL6B</i> in ESCC cell lines. Three ESCC cell lines, KYSE30, KYSE140, and KYSE220, had complete methylation of <i>ACTL6B</i>. (D) Expression levels of <i>ACTL6B</i> in ESCC cell lines and non-cancerous esophageal tissues. <i>ACTL6B</i> was not expressed in ESCC cell lines with its complete methylation (KYSE30, KYSE140, and KYSE220), and was expressed in neuroblastoma cell lines (NB) without its methylation (IMR-32 and KELLY). This supported that <i>ACTL6B</i> methylation could be involved in its silencing in tissues where it is expressed. At the same time, <i>ACTL6B</i> was not expressed in non-cancerous esophageal tissues without its methylation. This suggested that <i>ACTL6B</i> methylation was a passenger in esophageal squamous cell carcinogenesis. DNA methylation status of non-cancerous tissues and cell lines was analyzed by qMSP and an Infinium HumanMethylation450 BeadChip array, respectively. (E) DNA methylation of <i>ACTL6B</i> in non-cancerous esophageal tissues. <i>ACTL6B</i> was not aberrantly methylated in non-cancerous tissues regardless of alcohol/smoking exposure.</p