Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale1-3. Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter4; identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation5,6; analyses timings and patterns of tumour evolution7; describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity8,9; and evaluates a range of more-specialized features of cancer genomes8,10-18.

Propensity score-matched comparison of oncological outcomes between laparoscopic and open distal pancreatic resection

BACKGROUND

Selected studies have reported improved outcomes in laparoscopic compared with open distal pancreatic resection. Concerns regarding failure to achieve proper oncological resection and compromised long-term outcomes remain. This study investigated whether postoperative outcomes and long-term survival after laparoscopic distal pancreatectomy are comparable to those after an open procedure.

METHODS

This retrospective case-control study included patients who underwent distal pancreatectomy for resectable pancreatic adenocarcinoma between 2010 and 2013, identified from the National Cancer Database. Propensity score nearest-neighbour 1 : 1 matching was performed between patients undergoing laparoscopic or open distal pancreatectomy based on all relevant co-variables. The primary outcome was overall survival.

RESULTS

Of 1947 eligible patients, 605 (31·1 per cent) underwent laparoscopic distal pancreatectomy. After propensity score matching, two well balanced groups of 563 patients each were analysed. There was no difference in overall survival at 3 years after laparoscopic versus open distal pancreatectomy (41·6 versus 36·0 per cent; hazard ratio 0·93, 95 per cent c.i. 0·77 to 1·12; P = 0·457). The overall conversion rate was 27·3 per cent (165 of 605). Patients who underwent laparoscopic distal pancreatectomy had outcomes comparable to those of patients who had an open procedure with regard to median time to chemotherapy (50 versus 50 days; P = 0·342), median number of nodes examined (12 versus 12; P = 0·759); 30-day mortality (1·2 versus 0·9 per cent; P = 0·562); 90-day mortality (2·8 versus 3·7 per cent; P = 0·403), 30-day readmission rate (9·6 versus 9·2 per cent; P = 0·838) and positive margin rate (14·9 versus 18·5 per cent; P = 0·110). However, median duration of hospital stay was shorter in the laparoscopic group (6 versus 7 days; P < 0·001).

CONCLUSION

Laparoscopic distal pancreatectomy is an acceptable alternative to open distal pancreatectomy with no detriment to survival.

Rapid and safe learning of robotic gastrectomy for gastric cancer: multidimensional analysis in a comparison with laparoscopic gastrectomy

BACKGROUND

The learning curve of robotic gastrectomy has not yet been evaluated in comparison with the laparoscopic approach. We compared the learning curves of robotic gastrectomy and laparoscopic gastrectomy based on operation time and surgical success.

METHODS

We analyzed 172 robotic and 481 laparoscopic distal gastrectomies performed by single surgeon from May 2003 to April 2009. The operation time was analyzed using a moving average and non-linear regression analysis. Surgical success was evaluated by a cumulative sum plot with a target failure rate of 10%. Surgical failure was defined as laparoscopic or open conversion, insufficient lymph node harvest for staging, resection margin involvement, postoperative morbidity, and mortality.

RESULTS

Moving average and non-linear regression analyses indicated stable state for operation time at 95 and 121 cases in robotic gastrectomy, and 270 and 262 cases in laparoscopic gastrectomy, respectively. The cumulative sum plot identified no cut-off point for surgical success in robotic gastrectomy and 80 cases in laparoscopic gastrectomy. Excluding the initial 148 laparoscopic gastrectomies that were performed before the first robotic gastrectomy, the two groups showed similar number of cases to reach steady state in operation time, and showed no cut-off point in analysis of surgical success.

CONCLUSIONS

The experience of laparoscopic surgery could affect the learning process of robotic gastrectomy. An experienced laparoscopic surgeon requires fewer cases of robotic gastrectomy to reach steady state. Moreover, the surgical outcomes of robotic gastrectomy were satisfactory.

The nonhomologous end joining factor Artemis suppresses multi-tissue tumor formation and prevents loss of heterozygosity

Nonhomologous end joining (NHEJ) is a critical DNA repair pathway, with proposed tumor suppression functions in many tissues. Mutations in the NHEJ factor ARTEMIS cause radiation-sensitive severe combined immunodeficiency in humans and may increase susceptibility to lymphoma in some settings. We now report that deficiency for Artemis (encoded by Dclre1c/Art in mouse) accelerates tumorigenesis in several tissues in a Trp53 heterozygous setting, revealing tumor suppression roles for NHEJ in lymphoid and non-lymphoid cells. We also show that B-lineage lymphomas in these mice undergo loss of Trp53 heterozygosity by allele replacement, but arise by mechanisms distinct from those in Art Trp53 double null mice. These findings demonstrate a general tumor suppression function for NHEJ, and reveal that interplay between NHEJ and Trp53 loss of heterozygosity influences the sequence of multi-hit oncogenesis. We present a model where p53 status at the time of tumor initiation is a key determinant of subsequent oncogenic mechanisms. Because Art deficient mice represent a model for radiation-sensitive severe combined immunodeficiency, our findings suggest that these patients may be at risk for both lymphoid and non-lymphoid cancers.

The presence of colorectal hepatic metastases does not preclude pulmonary metastasectomy

Hepatic metastases due to colorectal carcinoma have often been felt to preclude pulmonary metastasectomy. With the recent advances in surgical options, should patients with both liver and lung metastases be considered for surgical resection? The current study reviews the impact of such aggressive management on disease-free and overall survival (OS). The clinical course of 63 patients presenting with colorectal metastasis to the lung alone (group 1, n = 45) or combined hepatic and lung metastases (group 2, n = 18) were reviewed. All patients underwent complete resection of their lung metastases. Surgical control of hepatic tumor burden was achieved by tumor ablation, intra-arterial therapy, and/or resection. All patients in group 1 and group 2 were available for a mean follow-up of 27 and 24 months, respectively. The presence of hepatic metastases, the resectability of hepatic tumor burden, and the disease-free interval after pulmonary metastasectomy did not significantly influence survival. These findings demonstrate that aggressive surgical management of pulmonary metastases in the presence of liver metastases offers a similar benefit as compared to patients with pulmonary metastases alone. Therefore, hepatic metastatic disease does not preclude an attempt at pulmonary metastasectomy if hepatic metastases can be resected or remains responsive to therapy. Such an approach achieves comparable OS and mean survival when compared to pulmonary metastasectomy alone.

The Presence of Colorectal Hepatic Metastases Does Not Preclude Pulmonary Metastasectomy

Hepatic metastases due to colorectal carcinoma have often been felt to preclude pulmonary metastasectomy. With the recent advances in surgical options, should patients with both liver and lung metastases be considered for surgical resection? The current study reviews the impact of such aggressive management on disease-free and overall survival (OS). The clinical course of 63 patients presenting with colorectal metastasis to the lung alone (group 1, n = 45) or combined hepatic and lung metastases (group 2, n = 18) were reviewed. All patients underwent complete resection of their lung metastases. Surgical control of hepatic tumor burden was achieved by tumor ablation, intra-arterial therapy, and/or resection. All patients in group 1 and group 2 were available for a mean follow-up of 27 and 24 months, respectively. The presence of hepatic metastases, the resectability of hepatic tumor burden, and the disease-free interval after pulmonary metastasectomy did not significantly influence survival. These findings demonstrate that aggressive surgical management of pulmonary metastases in the presence of liver metastases offers a similar benefit as compared to patients with pulmonary metastases alone. Therefore, hepatic metastatic disease does not preclude an attempt at pulmonary metastasectomy if hepatic metastases can be resected or remains responsive to therapy. Such an approach achieves comparable OS and mean survival when compared to pulmonary metastasectomy alone.