Detection of KRAS mutations in circulating tumour DNA from plasma and urine of patients with colorectal cancer

BACKGROUND

Circulating tumour DNA (ctDNA) is very useful for purposes of cancer genetics; however, it has some limitations. Recently, ctDNA in body fluids, such as urine, sputum, and pleural effusion, has been investigated. The aim of this study was to evaluate the quantity of ctDNA derived from urine (trans-renal ctDNA) and the accuracy of KRAS mutation detection in relation to disease stage in colorectal cancer.

METHODS

Urine, plasma, and tissue samples were collected from consecutively resected colorectal cancer patients. DNA was extracted from each sample and the quantity was determined. From each DNA sample, KRAS mutations were detected using droplet digital PCR.

RESULTS

200 patients participated and KRAS mutations were detected in 84 patients (42.0%) from tumour tissue. The concentration of trans-renal ctDNA (trtDNA) was significantly lower than that of plasma; however, there was no significant difference between the sensitivity using ctDNA and that using trtDNA (29.8% VS 33.3%, p = 0.62). Concordance between these two tests was only 17.5%. Combination analysis (ctDNA + trtDNA) improved the sensitivity to 53.6%, and sensitivity was significantly higher than that of corresponding single assays (p = 0.003). In early cancer stages, trtDNA had greater sensitivity for detecting KRAS mutations than ctDNA (37.7% vs. 21.3%, p = 0.047). Conversely, it was less useful for advanced cancer stages (21.7% vs. 52.2%, p = 0.07). Notably, KRAS mutations were detected using ctDNA or trtDNA in 12 of 116 (10.3%) patients who had no KRAS mutations in their tissue samples.

CONCLUSIONS

trtDNA and ctDNA have equal potential and combination analysis significantly improved the sensitivity.

Prognostic Role of the Platelet-to-Lymphocyte Ratio for Patients With Metastatic Colorectal Cancer Treated With Aflibercept

BACKGROUND/AIM

The efficacy of aflibercept plus 5-fluorouracil, leucovorin and irinotecan (FOLFIRI) therapy has been demonstrated in patients with metastatic colorectal cancer (mCRC) in global and Japanese clinical trials. However, a practical biomarker to predict its efficacy is lacking.

PATIENTS AND METHODS

This was a single-institution retrospective study of 21 patients with mCRC consecutively treated with aflibercept plus FOLFIRI from March 2018 to July 2019. We investigated the association and predictive value of pretreatment blood inflammation and immune-based scores, including the neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio (PLR), and lymphocyte-monocyte ratio, using their median values as cut-offs, in regard to disease control (DC), progression-free (PFS), and overall (OS) survival.

RESULTS

The number of patients in each treatment line of aflibercept was as follows: Second, 14 (66.7%); third, four (19.0%); fourth, two (9.5%); eighth, one (4.8%). The median number of aflibercept treatment courses was seven (range=2-17). The median follow-up time was 391 days. In univariate analysis, patients with DC had a significantly lower PLR than those without DC. Only the PLR was significantly negatively associated with PFS, but not with OS. Multivariate analysis showed a significantly poor prognostic impact of a high PLR on PFS (hazard ratio=10.28; p=0.003).

CONCLUSION

A low pretreatment PLR might be a predictor of aflibercept efficacy in patients with mCRC and may be clinically useful for selecting patient responders.

Elevated serum carcinoembryonic antigen level after curative surgery is a prognostic biomarker of stage II-III colorectal cancer

BACKGROUND

High preoperative carcinoembryonic antigen (CEA) is a well-known risk factor for stage II-III colorectal cancer (CRC); however, in most cases, cancer does not recur. Conversely, postoperative CEA (post-CEA) is occasionally measured, and high post-CEA patients often develop recurrence; however, the clinical significance of post-CEA testing is unknown. The purpose of this study was to determine whether post-CEA elevation might indicate a poor prognosis for stage II-III CRC patients who underwent curative surgery.

PATIENTS AND METHODS

482 patients with pathological stage II-III CRC were included. Univariate and multivariate analyses were performed to evaluate post-CEA levels.

RESULTS

Multivariate analysis showed that elevated post-CEA (hazard ratio (HR): 3.14, P < 0.001), pathological lymph node metastasis (pN+), and pathological T4 (pT4) are associated with poor recurrence-free survival (RFS), and that elevated post-CEA (HR: 3.12; P = 0.002), pN+, pT4, age >70, and smoking are independently associated with poor overall survival. Subgroup analysis among stage III patients, in combination with the risk classification of the International Duration Evaluation of Adjuvant Chemotherapy (IDEA) study, showed that elevated post-CEA is a significant indicator of poor prognosis for RFS in both low-risk (73.8% vs. 21.2%, P < 0.001) and high-risk (49.9% vs. 25.0%, P = 0.04) groups.

CONCLUSIONS

Post-surgical CEA elevation is independently associated with poor prognosis in stage II-III CRC. Adding post-CEA levels to the IDEA risk classification may provide a more reliable indicator of the need for individualized surveillance and adjuvant chemotherapeutic strategies.

Polyvinyl alcohol increased growth, migration, invasion, and sphere size in the PK-8 pancreatic ductal adenocarcinoma cell line

Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer used in eye drops, embolization particles, and artificial cartilage. It has also been shown to cause expansion of functional multipotent self-renewing hematopoietic stem cells under serum-free conditions. In this study, we examined the effects of PVA on human pancreatic ductal adenocarcinoma (PDAC) cell lines using 2-dimensional (2D) and 3D-cultures with serum-free medium. In the 2D-culture, PVA-treatment induced an aggregated colony-like appearance in PDAC cells. It increased the growth of PK-8 cells in a dose-dependent manner as well as significantly increasing migration and invasion abilities. qRT-PCR showed an increase in α2 integrin and a decrease in matrix metalloprotease levels in PVA-treated PK-8 cells. Through qRT-PCR analysis, β1 integrin expression at the mRNA level was found to be decreased; however, it was unaltered at the protein level when assessed using FACS analysis.

PVA further induced mesenchymal to epithelial transition-like alterations, including increased E-cadherin and decreased Vimentin and N-cadherin expression. Four cancer stem cell (CSC) markers were higher in PVA-treated PK-8 cells compared to controls. In 3D-culture, PVA-treated PK-8 cells showed a rod-like appearance with larger sphere size and higher growth ability. qRT-PCR showed that CSC markers did not increase and 2 of 4 drug transporters had decreased in PVA-treated PK-8 cells. These findings suggest that PVA increases the growth, migration, invasion, and sphere size of PK-8 cells, but does not increase the proportion of pancreatic CSCs under 3D-culture conditions with serum-free medium.

Systemic Chemotherapy is a Promising Treatment Option for Patients with Colonic Stents: A Review

Approximately 10% of patients with colorectal cancer (CRC) develop malignant large bowel obstruction (MLBO) at diagnosis. Furthermore, for 35% of patients with MLBO, curative primary tumor resection is unfeasible because of locally advanced disease and comorbidities. The practice of placing a self-expandable metallic stent (SEMS) has dramatically increased as an effective palliative treatment. Recent advances in systemic chemotherapy for metastatic CRC have significantly contributed to prolonging patients' prognosis and expanding the indications. However, the safety and efficacy of systemic chemotherapy in patients with SEMS have not been established. This review outlines the current status of this relatively new therapeutic strategy and future perspectives. Some reports on this topic have demonstrated that 1) systemic chemotherapy and the addition of molecular targeted agents contribute to prolonged survival in patients with SEMS; 2) delayed SEMS-related complications are a major concern, and this requires strict patient monitoring; however, primary tumor control by chemotherapy might result in decreased complications, especially regarding re-obstruction; and 3) using bevacizumab could be a risk factor for SEMS-related perforation, which may be lethal. Although this relatively new approach for unresectable stage IV obstructive CRC requires a well-planned clinical trial, this therapy could be promising for patients who are unideal candidates for emergency surgery and require immediate systemic chemotherapy.

[A Case of Peritoneal Dissemination of Colorectal Cancer in Which Conversion Surgery Could Be Performed after Reduction with CAPOX/Bevacizumab]

A woman in her 60s underwent lower endoscopy due to a positive fecal occult blood test. A type 2 tumor was found in the cecum, and a biopsy resulted in the diagnosis of adenocarcinoma(tub2). Contrast-enhanced CT showed an enlarged paracolonic lymph node but no distant metastasis, so the patient underwent a laparoscopic-assisted ileocolic resection and D3 lymph node dissection for cecum cancer. The pathology was pT3, pN2b, pM0, pStage Ⅲc, and 12 courses of FOLFOX were administered as adjuvant chemotherapy. Twenty-four months after the completion of adjuvant chemotherapy, an elevated CEA was observed, and a PET-CT was performed, which showed multiple peritoneal disseminated nodules with FDG accumulation. Based on this finding, CAPOX/bevacizumab therapy was introduced, and on completion of 4 courses, the PET-CT showed a decrease in the size of the nodules and the disappearance of FDG accumulation. Based on this, the patient underwent resection. A peritoneal dissemination resection and bilateral ovariectomy were laparoscopically performed, and the patient is currently under observation. In patients with metastatic recurrence of peritoneal dissemination who underwent complete resection, treatment with CAPOX/bevacizumab may allow for disease control and provide a long-term prognosis.

Does the diameter of colonic stent influence the outcomes in bridge-to-surgery patients with malignant large bowel obstruction?

PURPOSE

This study investigated the short- and long-term outcomes of 18- and 22-mm-diameter self-expandable metallic stent (SEMS) as a bridge to surgery (BTS) in patients with malignant large bowel obstruction (MLBO).

METHODS

Sixty-nine pathological stage II and III colorectal cancer patients who underwent BTS were included in this multi-institutional retrospective study. Patients were divided into two groups regarding the diameter of SEMS: an 18-mm group (n = 30) and a 22-mm group (n = 39).

RESULTS

There was no significant difference in the clinical success rate, but both of the two re-obstructions observed occurred in the 18-mm group. The 18-mm group showed a trend toward a higher incidence of overall postoperative complications (Clavien-Dindo grading ≥ II) than the 22-mm group (33.3% vs. 10.3%, P = 0.061). The 3-year disease-free and overall survival showed no significant differences between the 18- and 22-mm groups (78.2% vs. 68.8%, P = 0.753 and 92.8% vs. 82.1%, P = 0.471, respectively).

CONCLUSION

SEMS of 18 and 22 mm diameter confer statistically equivalent short- and long-term outcomes as a BTS.

Even a partial pathological response is associated with lower relapse rates in patients with operable rectal cancer undergoing neoadjuvant chemotherapy

BACKGROUND

Neoadjuvant chemotherapy to treat locally advanced rectal cancer is an effective therapeutic strategy for the prevention of local recurrence and distant organ metastasis after surgery.

OBJECTIVES

To assess the prognostic significance of histopathological tumor response in rectal cancer patients undergoing neoadjuvant chemotherapy.

METHODS

This study included patients with operable rectal cancer who received neoadjuvant chemotherapy using the FOLFOX regimen (5-fluorouracil, l-leucovorin, and oxaliplatin) in a hospital between February 2012 and November 2017. The main outcome measure was disease-free survival with respect to histopathological response to neoadjuvant chemotherapy in resected specimens.

RESULTS

The median follow-up was 32 months. Of 48 patients treated with neoadjuvant FOLFOX, 24 (50%) were classified as responders, which included two patients with pathological complete response and 22 patients with partial response. The remaining 24 patients (50%) were classified as nonresponders. Responders had a significantly better 3-year disease-free survival than nonresponders (86% vs. 62%, p = .02).

CONCLUSIONS

Patients whose surgical specimens show a pathological complete response or partial response have good oncologic outcomes.

Abstract 710: Exosomal DNA has the potential to detect circulating tumor DNA in patients with colorectal cancer

[Introduction] Exosomes are small vesicles of endosomal origin, which are released by all cell types, and are involved in physiological and pathological processes including cancer progression and metastasis. Exosomes comprise proteins, lipids, and nucleic acids such as RNA and DNA (exoDNA). Circulating exoDNAs harboring mutations are detected in patients with pancreatic or colorectal cancer. [Objective] To evaluate the clinical utility of detecting RAS mutations in exoDNAs of patients with colorectal cancers.

[Methods] We prospectively recruited 25 patients with RAS mutations in cells of their colorectal tissues. Circulating exoDNA was extracted from exosomes in 1 ml of preoperative plasma. Circulating cell-free DNA (ccfDNA) was concurrently extracted from 1 ml of plasma. We identified RAS mutations in exoDNAs and ccfDNAs using droplet digital PCR (ddPCR, Biorad).

[Results] We analyzed the exoDNAs of patients with right-sided (n = 13) and left-sided (n = 12) colon cancers (Stage II, [n = 9]; Stage III, [n = 9], Stage IV, [n = 7]). The median concentrations of exoDNA and ccfDNA were 52.3 ng/ml (32.1-223 ng/ml) and 132 ng/ml (41.3-4333 ng/ml). RAS mutations were detected in exoDNAs of 13 patients (52.0%) and in the ccfDNAs of 5 patients (20%) (P=0.03). The sensitivities of exoDNAs and ccfDNAs were equivalent (57.1%). However, for Stages II and III, the sensitivities of exoDNAs were higher compared with those of ccfDNAs. Notably, the sensitivity of exoDNA of Stage III was 77.8%. RAS mutations were undetectable in ccfDNAs of patients without detectable mutations in exoDNAs. The median mutation allele frequencies of exoDNA and ccfDNAs were 12.1% and 18.0%, respectively.

[Conclusion] Previously reported mutation-detection rates using Stages VI and III ccfDNAs are 90% and 15%, respectively. Here, the sensitivities using ccfDNAs for Stage II or III were low as well. Conversely, the sensitivities using exoDNAs were equivalently high in Stages III and Stage IV. These findings indicate that exoDNA has superior potential for detecting circulating tumor DNA compared with that of ccfDNA

Citation Format: Sho Kuriyama, Takeshi Yamada, Michihiro Koizumi, Seiichi Shinji, Akihisa Matsuda, Ryo Ohta, Goro Takahashi, Masahiro Hotta, Keisuke Hara, Kohki Takeda, Koji Ueda, Hiroshi Yoshida. Exosomal DNA has the potential to detect circulating tumor DNA in patients with colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 710.

Abstract 6015: A newly established neuroendocrine carcinoma cell line from a human ascending colon tumor shows high proliferation and CD133 expression in spherical cancer stem cell-like formation

BACKGROUND: The current incidence of neuroendocrine tumor (NET) is 0.6 cases per 100,000 people, although it has increased 50-fold over the last 35 years and is becoming increasingly clinically important. Neuroendocrine carcinoma (NEC) is a type of malignant NET associated with poor prognoses. However, the molecular basis and clinical characteristics of NEC have not yet been fully investigated due to a lack of patient biopsies to derive cell lines and established cell lines. Here, we report a newly established and characterized NEC cell line (SS-2) derived from a human ascending colon tumor. Furthermore, we investigated the ability of SS-2 cells to form spherical cancer stem cells (CSCs) and express CSC markers.

MATERIALS AND METHODS: The SS-2 cell line was derived from a tumor resection of the ascending colon from 59-year old Japanese woman with stage four NEC. The Ki-67 labeling index of the resected tumor was &gt;20% and, thus, the tumor was diagnosed as NEC. The characteristics of SS-2 cells transplanted subcutaneously into nude mice was determined. siRNA suppression of the neuroendocrine marker, INSM-1 was detected in SS-2 cells by western blotting. Additionally, SS-2 cells were seeded onto ultra-low attachment plates to detect sphere-formation and the expression of CSC markers, with confirmation by FACS analysis. Additionally, we compared the effect of commonly-used anti-colorectal chemotherapeutics on SS-2 cells and conventional colorectal cancer cells (Caco-2) using cell viability assay. Statistical analysis was done using Student's t test with P-values &lt; 0.05 considered statistically significant.

RESULTS: Characteristics of the resected tumor were retained in the SS-2 cells and in the xenograft in nude mice. INSM-1 was detected in SS-2 cell lysates and in nuclei of established SS-2 cells. siRNA targeting INSM-1 decreased INSM-1 mRNA levels but did not affect levels of chromogranin A and synaptophysin mRNA. SS-2 cells formed spheres when seeded onto ultra-low attachment plates that expressed higher levels of CD133 compared to SS-2 cells cultured under adherent conditions, which was also confirmed upon FACS analysis. After the addition of oxaliplatin and 5-FU, cell viabilities were higher in SS-2 cells than Caco-2 cells.

CONCLUSION: We established a novel NEC cell line, derived from a human ascending colon tumor, which we transplanted into nude mice. We determined that the CSC marker, CD133 is highly expressed in SS-2 cells, and hence posit that combination therapy of chemotherapeutics together with anti-CSC therapy may have increased efficacy against NEC.

Citation Format: Seiichi Shinji, Norihiko Sasaki, Takeshi Yamada, Michihiro Koizumi, Ryo Ohta, Akihisa Matsuda, Goro Takahashi, Masahiro Hotta, Takuma Iwai, Keisuke Hara, Kohki Takeda, Koji Ueda, Sho Kuriyama, Toshiyuki Ishiwata, Hiroshi Yoshida. A newly established neuroendocrine carcinoma cell line from a human ascending colon tumor shows high proliferation and CD133 expression in spherical cancer stem cell-like formation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6015.

Abstract 6470: Possibility of digital cytology of intraoperative ascites and lavage fluid in patients with colorectal cancer

Introduction: In patients with colorectal cancer, the results of intraoperative peritoneal cytology do not affect the prognosis. One of the reasons is the low sensitivity of peritoneal cytology. Thus, improving the sensitivity of peritoneal cytology may improve the accuracy of prognostic prediction. Digital cytology (dCytology), which detects genetic mutations in ascites or abdominal lavage fluid using digital polymerase chain reaction (PCR), is a new method by which to evaluate peritoneal cytology. In this study, we evaluated the sensitivity and clinical significance of dCytology.

Methods: We included patients with clinical T3-T4 colorectal cancer who underwent surgery from November 2018 to November 2019 in our department. In patients with ascites, ascitic fluid was collected at the start of surgery. In patients without ascites, lavage fluid was collected using 50 mL of physiological saline. Half of the liquid was used for conventional cytology, and the other half was used for dCytology. DNA was extracted from the supernatant and intraperitoneal free cells and from the cancer tissue. Circulating tumor DNA was extracted from the preoperative plasma. Digital PCR was performed on cancer tissue, supernatant DNA, intraperitoneal free cell DNA, and circulating free DNA (cfDNA) using a KRAS multi-probe.

Results: This study included 150 patients, 75 of whom had KRAS mutation in their tissues. Among them, dCytology was positive in 45 patients (60%, pStage I/II/III/IV/recurrence/unresectable: 6/22/23/16/4/4). Thirty patients had right-sided colon cancer, 20 had left-sided colon or upper rectal cancer, 7 had lower rectal cancer, and 4 had recurrent disease. Conventional cytology was positive in 11 of the 45 patients (24%), and dCytology was positive in 7 of the 11 patients. cfDNA was positive in 19 patients, and dCytology was positive in 10 of the 19. Four patients, including two patients with positive dCytology but negative conventional cytology, developed recurrence disease. Two of the four patients developed liver metastasis but no peritoneal dissemination.

Discussion: The sensitivity of dCytology was higher than that of conventional cytology. Our results suggest that tumor cells can exist in the abdominal cavity of patients with colorectal cancer. Interestingly, dCytology was positive even for patients in whom the tumor was not exposed on the outside of the colon wall (T3) and in whom the tumor was not located in the abdominal cavity (Rb).

Citation Format: Koji Ueda, Takeshi Yamada, Michihiro Koizumi, Seiichi Shinji, Akihisa Matsuda, Ryo Ohta, Goro Takahashi, Masahiro Hotta, Kohki Takeda, Keisuke Hara, Sho Kuriyama. Possibility of digital cytology of intraoperative ascites and lavage fluid in patients with colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6470.

Comparison Between Biweekly and Weekly Cetuximab in Patients With Metastatic Colorectal Cancer: A Meta-analysis

BACKGROUND/AIM

Although weekly administration of cetuximab is the standard regimen in patients with metastatic colorectal cancer (mCRC), the efficacy and safety of a biweekly regimen is a pending issue. We conducted this meta-analysis to compare the efficacy and safety of a biweekly vs. a weekly regimen of cetuximab in the treatment of mCRC.

PATIENTS AND METHODS

We conducted a comprehensive electronic literature search up to January 2020 to identify studies directly comparing the efficacy and safety of biweekly cetuximab administration and conventional weekly administration in patients with mCRC. We then performed a meta-analysis using random-effects models to calculate risk ratios and mean differences with 95% confidence intervals.

RESULTS

Four studies with a total of 381 patients were included in this meta-analysis. The meta-analysis showed that biweekly administration conferred equivalent efficacy, including objective response rate, disease-control rate, progression-free survival, and overall survival, as well as safety, including skin toxicity, gastrointestinal toxicity, and hematologic toxicity, compared with weekly administration in patients with mCRC.

CONCLUSION

Results from this meta-analysis support the administration of biweekly instead of weekly cetuximab, which is beneficial for both patients and health resources.

Abstract B43: Genetic analysis of circulating tumor cells of colorectal cancer patients captured by multiantibodies technique

Background: Accurate genetic analysis is essential for molecular therapy. Conventionally, DNA derived from tumor tissue has been the source of the gold standard of DNA information in solid tumors including colorectal cancer (CRC). However, it is well known that molecular therapy induces emerging mutations that are not found in primary tumor; thus, real-time monitoring of gene information is ideal. Circulating tumor cells (CTCs) are circulating malignant cells of solid tumor origin that are found in the bloodstream and can be a powerful candidate to play an important role. Capturing a large amount of CTCs improves the accuracy of genetic analysis of DNA derived from CTC (ctcDNA). We used 3 (EpCAM, Her2, Trop2) or 4 (EpCAM, Her2, Trop2, EGFR) antibodies to capture CTCs, and analyzed ctcDNA using next-generation sequencing (NGS).

Methods: Cohort 1: Untreated CRC patients were enrolled. Ten mL of whole blood was collected from each patient. The blood was processed using 3 antibodies (EpCAM, Her2, Trop2) and CTCs were collected. Tumor tissue was also collected from each patient. Tumor tissue DNA and ctcDNA were extracted and analyzed using NGS. Cohort 2: CRC patients, both treated and untreated, were enrolled. Twenty mL of whole blood was collected from each patient. Ten mL of the blood was processed using 3 antibodies (EpCAM, Her2, Trop2), and the remaining 10 mL was processed using 4 antibodies (EpCAM, Her2, Trop2, EGFR). The numbers of collected CTCs were counted and compared.

Results: Cohort 1: We enrolled 34 patients (stage II: n=4, stage III: n=7, stage IV: n=23). Median number of extracted CTC was 34 cells. From tumor tissue DNA, 53 mutations were detected. The most frequent mutation was within TP53 (n=18), followed by mutations in APC (n=13) and KRAS (n=12). From ctcDNA, 16 mutations, including 5 mutations which were not found in tissue DNA, were detected. The most frequent mutation was within TP53 (n=5), followed by mutations in KRAS and APC (n=4 each). Cohort 2: We enrolled 10 patients (stage II: n=1, stage III: n=1, stage IV: n=8). Using 3 antibodies, the median number of collected CTCs was 27 cells (range, 2–112). Using 4 antibodies, the median number of collected CTCs was 33 cells (range, 7–260). There were no statistically significant differences between the 2 groups (p=0.40).

Conclusions: Mutations not detected in primary tumors can be identified in ctcDNA, indicating the potential of CTCs in complementing gene analysis. The technique to capture CTCs using 3 antibodies appears to increase the detection rate and yield of CTCs. However, the present study did not show advantages of the 4-antibodies method, and future studies should investigate the best combination of antibodies to extract more CTCs with higher specificity.

Citation Format: Kohki Takeda, Takeshi Yamada, Michihiro Koizumi, Seiichi Shinji, Akihisa Matsuda, Ryo Ohta, Yasuyuki Yokoyama, Goro Takahashi, Masahiro Hotta, Takuma Iwai, Keisuke Hara, Koji Ueda, Sho Kuriyama, Hiroshi Yoshida. Genetic analysis of circulating tumor cells of colorectal cancer patients captured by multiantibodies technique [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B43.

[Consideration for Prognostic Indicators of Ovarian Metastasis of Colorectal Cancer]

Ovarian metastasis of colorectal cancer is associated with poor prognosis. Recent advances in chemotherapy may improve this prognosis. In this retrospective study, we evaluated indicators of poor prognosis for ovarian metastasis of colorectal cancer. Twenty patients, who were diagnosed with ovarian metastasis of colorectal cancer from April 2000 to December 2017, were enrolled. Oophorectomy was performed in 18 of the 20 patients. Postoperative chemotherapy was provided to 13 patients, and molecular targeting agents were administered in 5 patients. Metastases to other organs besides the ovaries, premenopausal condition, undifferentiated histologic type of the primary tumor, and no resection of ovarian metastases were identified as indicators of poor prognosis. The 3-year survival rate was 15%, and the 5-year survival rate was 0%. In conclusion, oophorectomy can improve the prognosis of patients with ovarian metastasis of colorectal cancer. However, prognostic improvement due to molecular target agents was not shown.

[Effectiveness of Chemoradiotherapy for the Treatment of Local Recurrence in Rectal Cancer-A Case Report]

Chemoradiotherapy(CRT)for locally recurrent rectal cancer can shrink the tumor and permit R0 resection; however, its effectiveness and safety have not been established. Herein, we report a case of a 60s man with locally recurrent rectal cancer invading the surrounding organs who was administered CRT followed by R0 laparoscopic-assisted abdominoperineal resection( APR). Local recurrence was detected 11 months after laparoscopic-assisted low anterior resection(pT3N0M0, pStage Ⅱ). After tumor shrinkage by CRT(capecitabine 3,000mg/day plus 45 Gy/25 Fr), laparoscopic-assisted APR was performed. The pathological findings showed a pathological complete response(pCR). The patient had not experienced recurrent disease at 6 months after the second surgery. CRT may improve the prognosis of patients with locally recurrent rectal cancer, especially those with possibly unresectable tumors.

Establishment and characterization of a novel neuroendocrine carcinoma cell line derived from a human ascending colon tumor

The incidence of rare neuroendocrine tumors (NET) is rapidly increasing. Neuroendocrine carcinoma (NEC) is a NET with poorly differentiated histological features, high proliferative properties and associated poor prognoses. As these carcinomas are so rare and, thus, affect only a small number of patients allowing for few cell lines to be derived from patient biopsies, the histological, immunohistochemical, and clinical characteristics associated with colorectal NEC and NEC in other organs have yet to be clearly defined. Herein, we describe the establishment of a novel NEC cell line (SS‐2) derived from a tumor resection of the ascending colon from a 59‐year‐old Japanese woman. The histological, electron microscopic and immunohistochemical features of chromogranin A (CgA) as well as confirmation of synaptophysin positivity in this tumor were typical of those commonly observed in surgically resected colorectal NEC. Further, the Ki‐67 labeling index of the resected tumor was >20% and, thus, the tumor was diagnosed as an NEC of the ascending colon. The SS‐2 cell line maintained characteristic features to those of the resected tumor, which were further retained following implantation into subcutaneous tissues of nude mice. Additionally, when SS‐2 cells were seeded into ultra‐low attachment plates, they formed spheres that expressed higher levels of the cancer stem cell (CSC) marker CD133 compared to SS‐2 cells cultured under adherent conditions. SS‐2 cells may, therefore, contribute to the current knowledge on midgut NEC biological function while providing a novel platform for examining the effects of colorectal NEC drugs, including CSC.

Analysis of colorectal cancer-related mutations by liquid biopsy: Utility of circulating cell-free DNA and circulating tumor cells

We recruited 56 colorectal cancer patients and compared the mutational spectrum of tumor tissue DNA, circulating cell‐free DNA (ccfDNA) and circulating tumor cell (CTC) DNA (ctcDNA) to evaluate the potential of liquid biopsy to detect heterogeneity of cancer. Tumor tissue DNA, ccfDNA, and ctcDNA were extracted from each patient and analyzed using next‐generation sequencing (NGS) and digital PCR. To maximize yields of CTC, three antibodies were used in the capture process. From 34 untreated patients, 53 mutations were detected in tumor tissue DNA using NGS. Forty‐seven mutations were detected in ccfDNA, including 20 not detected in tissues. Sixteen mutations were detected in ctcDNA, including five not detected in tissues. In 12 patients (35.3%), mutations not found in tumor tissues were detected by liquid biopsy: nine (26.5%) in ccfDNA only and three (8.8%) in ctcDNA only. Combination analysis of the two liquid biopsy samples increased the sensitivity to detect heterogeneity. From 22 stage IV patients with RAS mutations in their primary tumors, RAS mutations were detected in 14 (63.6%) ccfDNA and in eight (36.4%) ctcDNA using digital PCR. Mutations not detected in primary tumors can be identified in ccfDNA and in ctcDNA, indicating the potential of liquid biopsy in complementing gene analysis. Combination analysis improves sensitivity. Sensitivity to detect cancer‐specific mutations is higher in ccfDNA compared with ctcDNA.

Prospective Multicenter Study on the Prognostic and Predictive Impact of Tumor Budding in Stage II Colon Cancer: Results From the SACURA Trial

PURPOSE

The International Union Against Cancer highlighted tumor budding as a tumor-related prognostic factor. International assessment criteria for tumor budding were recently defined by the 2016 International Tumor Budding Consensus Conference (ITBCC2016). This study aimed to clarify the prognostic and predictive values of tumor budding in a randomized controlled trial evaluating the superiority of adjuvant chemotherapy with oral tegafur-uracil over surgery alone for stage II colon cancer (SACURA trial; ClinicalTrials.gov identifier: NCT00392899).

PATIENTS AND METHODS

Between 2006 and 2010, we enrolled 991 patients from 123 institutions with stage II colon cancer. Tumor budding was diagnosed by central review on the basis of the criteria adopted in the ITBCC2016. We prospectively recorded all clinical and pathologic data, including the budding grade, and performed prognostic analyses after 5 years of completing the patients’ registration.

RESULTS

Of 991 tumors, 376, 331, and 284 were classified as BD1, BD2, and BD3, respectively; the 5-year relapse-free survival (RFS) rate was 90.9%, 85.1%, and 74.4%, respectively (P < .001), and ranged widely in T4 tumors (86.6% to 53.3%). The budding grade significantly correlated with recurrence in the liver, lungs, lymph nodes, and peritoneum (P < .001 to .01). Multivariable analysis revealed that budding and T stage exerted an independent impact on RFS, and on the basis of the Harrell concordance index, these two factors substantially contributed to the improvement of the Cox model for predicting RFS. Both the BD2 and BD3 groups demonstrated greater improvement in the 5-year recurrence rate in the adjuvant chemotherapy group than the surgery-alone group by approximately 5%, but the difference was statistically nonsignificant.

CONCLUSION

Tumor budding grade on the basis of the ITBCC2016 criteria should be routinely evaluated in pathologic practice and could improve the benefit of adjuvant chemotherapy for stage II colon cancer.

Liquid Biopsy for the Management of Patients with Colorectal Cancer

Liquid biopsy is a collective term that refers to the analysis of tumor-derived biomarkers isolated from biological fluids of cancer patients. Recently, many authors reported the usefulness of liquid biopsy for the management of malignancy. Summary and Key Messages: The peripheral blood of cancer patients is a pool of cells and/or cell products derived from the primary or metastatic tumor, including circulating tumor cells (CTCs), circulating free (cf) DNA or RNA, and exosomes containing proteins, nucleic acids, and lipids. CTCs are tumor cells that can be isolated from peripheral blood. Free circulating DNA with a tumor-specific mutation is called circulating tumor DNA (ctDNA). Some patients who undergo curative surgery experience recurrent disease, which can be due to the presence of minimal residual disease (MRD). Thus, MRD indicates a high risk of relapse. Detection of ctDNA or CTC after surgery is a direct proof of MRD. Molecular volume (e.g., the number of CTCs and level of ctDNA) might reflect tumor burden, thus high molecular volume may indicate poor prognosis. The most notable application of liquid biopsy in cancer is to understand spatial and temporal heterogeneities. Heterogeneity is one of the causes of refractoriness and hampers prediction of chemotherapeutic effect. Emerging mutations that are not present in primary tumors but are found in their metastases can be detected in ctDNA. Some colorectal cancer patients with wild-type RAS do not respond to epidermal growth factor receptor blockade. In a subset of these patients, RAS mutation is detected in ctDNA, indicating heterogeneity.

Primary small intestinal volvulus after laparoscopic rectopexy for rectal prolapse

Primary small intestinal volvulus is defined as torsion in the absence of congenital malrotation, band, or postoperative adhesions. Its occurrence as an early postoperative complication is rare. A 40-year-old woman presented with rectal prolapse, and laparoscopic rectopexy was uneventfully performed. She could not have food on the day after surgery. She started oral intake on postoperative day 3 but developed abdominal pain after the meal. Contrast-enhanced CT revealed torsion of the small intestinal mesentery. An emergent laparotomy showed small intestinal volvulus, without congenital malformation or intestinal adhesions. We diagnosed it as primary small intestinal volvulus. The strangulated intestine was resected, and reconstruction was performed. The patient recovered uneventfully after the second surgery. To the best of our knowledge, this is the first report of primary small intestinal volvulus occurring after rectopexy for rectal prolapse. Primary small intestinal volvulus could be a postoperative complication after laparoscopy.

Feasibility of Neoadjuvant FOLFOX Therapy Without Radiotherapy for Baseline Resectable Rectal Cancer

BACKGROUND/AIM

The combination of oxaliplatin, leucovorin and fluorouracil (FOLFOX) has been established as postoperative adjuvant chemotherapy for stage III colon cancer. However, the safety and efficacy of neoadjuvant FOLFOX in patients with rectal cancer are still controversial. This prospective pilot study aimed to evaluate the feasibility of neoadjuvant FOLFOX therapy without radiation for baseline resectable rectal cancer (RC).

PATIENTS AND METHODS

The study included 30 patients with clinical stage II/III RC between February 2012 and December 2015. The patients were treated with six cycles of FOLFOX followed by elective surgery. The primary endpoint was the R0 resection rate. The secondary endpoints were the scheduled treatment completion rate, adverse events, pathological response and the disease-free survival (DFS) rate.

RESULTS

All the patients underwent elective R0 resection after neoadjuvant FOLFOX therapy. The completion rate of the 6-cycle regimen was 93.3% (28/30 patients). Grade 3-4 adverse events occurred in seven patients (23.3%). Pathological complete response was noted in two patients (6.7%). The 3-year DFS rate was 77.5% (95% confidence interval, 61.4%-93.7%).

CONCLUSION

Neoadjuvant FOLFOX therapy without radiation is a feasible therapeutic strategy for baseline resectable RC.

Male sex and history of ischemic heart disease are major risk factors for anastomotic leakage after laparoscopic anterior resection in patients with rectal cancer

Background

Anastomotic leakage (AL) is the most serious and common complication of surgery for rectal cancer, and associated risk factors remain unknown despite developments in laparoscopic surgery. The present study aimed to determine risk factors for AL after laparoscopic anterior resection (AR) of rectal cancer.

Methods

This retrospective cohort study extracted information from a prospective database of all consecutive colorectal resections that proceeded at Nippon Medical School Hospital between January 2011 and December 2015 (n = 865). We identified 154 patients with rectal cancer treated by elective laparoscopic AR with anastomosis using primary double-stapling. Clinical variables and comorbidity, habits, and surgery-related variables were assessed by univariate and multivariate analyses to determine preoperative risk factors for clinical AL.

Results

The overall rate of clinical AL was 11.7% (18 of 154 patients), and 5 (27.8%) of 18 patients required revised laparotomy. Data from males were analyzed because AL occurred only in males. Univariate analysis of male patients (n = 100) significantly associated preoperative creatinine values (p = 0.03) and a history of ischemic heart disease (IHD) (p = 0.012) with AL. The frequency of AL tended to increase (p = 0.06) when patients had low AR (p = 0.06) and transanal drainage. Having AL significantly prolonged hospital stays compared with patients without leakage (36.2 vs. 11.1 days; p <  0.01). Multivariate analysis identified a history of IHD (odds ratio [OR], 4.73; 95% confidence interval [CI], 1.27–17.5; p = 0.025] as an independent risk factor for AL.

Conclusions

Male sex and a history of IHD are possible risk factors for AL after elective laparoscopic rectal cancer surgery.

Abstract 4594: Detection of colorectal cancer related gene mutations from CTC and ctDNA

[Background] It is well known that emerging mutations which is not found in the primary tumor exist in metastatic tumor and molecular therapy induce emerging mutation. Liquid biopsy, which includes circulating tumor cell (CTC) and circulating tumor DNA (ctDNA), may help detecting this spatial and temporal heterogeneity. We have reported that emerging KRAS mutation can be detected by using ctDNA (Yamada et al, Cancer Science 2016). However, mutation detection by using CTC has been difficult because enough amount of DNA cannot be extracted from CTC. Currently we have been able to collect more CTC than before, by using a new device which uses 3 antibodies (EpCAM, Her2, Trop2). In this study, we evaluated the potential to detect colorectal cancer (CRC) related gene mutations from CTC, and compared it with ctDNA.

[Methods] Cohort 1: This cohort included untreated CRC patients. Tumor tissue was collected from each patient, either by primary surgery or by colonoscopic biopsy. DNA was extracted from tumor tissue and was analyzed using Next Generation Sequencing (NGS). Ten mL of whole blood was also collected from the same patient. CTC, serum and white blood cell (WBC) was collected by using the CTC recovery machine (Ion Torrent Liquid Biopsy Instrument®). Cytokeratin positive, DAPI positive, CD45 negative cells were defined as CTC. DNA was extracted from each sample (CTC-DNA, ctDNA, WBC-DNA) and was analyzed using NGS. Cohort 2: This cohort included unresectable CRC patients with KRAS mutation in their primary tumor. All patients in this cohort were under treatment or after completion of chemotherapy. CTC and ctDNA was collected in the same method as cohort 1. KRAS mutations of CTC and ctDNA were detected by using digital PCR (dPCR).

[Results] Cohort 1: We enrolled 16 CRC patients (stage II: n=2, stage III: n=2, stage IV: n=12). A total of 30 somatic, hotspot mutations were detected from tumor tissue DNA. The median number of the detected mutation for each patient was 2 (0-4). The most frequent gene mutation was APC, followed by KRAS and TP53. In all patients, CTC was successfully collected. The median number of the CTC was 34 cells (5-94). However, only 6 somatic, mutations were detected from CTC-DNA. Conversely, 16 somatic mutations were detected from ctDNA. Cohort 2: We enrolled 14 stage IV CRC patients with KRAS mutation in their primary tumor. CTC was collected from 9 patients but not from 5 patients. In the 9 patients CTC was collected, the median number of the collected CTC was 26 cells (5-121). By dPCR, KRAS mutation was detected in 2 patients (2/14) from CTC-DNA, and 4 patients (4/14) from ctDNA.

[Conclusions] The new CTC capturing technology using 3 antibodies can improve detection rate and yield of CTC. However, in patients undergoing chemotherapy, the amount of CTC and ctDNA drastically reduces. At present, ctDNA is superior to CTC in potential to detect mutations, and dPCR is more sensitive than NGS to detect mutations.

Citation Format: Kohki Takeda, Takeshi Yamada, Michihiro Koizumi, Seiichi Shinji, Yasuyuki Yokoyama, Goro Takahashi, Masahiro Hotta, Takuma Iwai, Keisuke Hara, Hiroyasu Furuki, Eiji Uchida. Detection of colorectal cancer related gene mutations from CTC and ctDNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4594.