Is omentectomy mandatory in the operation for ovarian cancer? Preliminary results in a rat study

Revisiting the Use of Normal Saline for Peritoneal Washing in Ovarian Cancer

The omentum is the predominant site of ovarian cancer metastasis, but it is difficult to remove the omentum in its entirety. There is a critical need for effective approaches that minimize the risk of colonization of preserved omental tissues by occult cancer cells. Normal saline (0.9% sodium chloride) is commonly used to wash the peritoneal cavity during ovarian cancer surgery. The omentum has a prodigious ability to absorb fluid in the peritoneal cavity, but the impact of normal saline on the omentum is poorly understood. In this review article, we discuss why normal saline is not a biocompatible solution, drawing insights from clinical investigations of normal saline in fluid resuscitation and from the cytopathologic evaluation of peritoneal washings. We integrate these insights with the unique biology of the omentum and omental metastasis, highlighting the importance of considering the absorptive ability of the omentum when administering agents into the peritoneal cavity. Furthermore, we describe insights from preclinical studies regarding the mechanisms by which normal saline might render the omentum conducive for colonization by cancer cells. Importantly, we discuss the possibility that the risk of colonization of preserved omental tissues might be minimized by using balanced crystalloid solutions for peritoneal washing.

Normal saline remodels the omentum and stimulates its receptivity for transcoelomic metastasis

The omentum contains immune cell structures called milky spots that are niches for transcoelomic metastasis. It is difficult to remove the omentum completely, and there are no effective strategies to minimize the risk of colonization of preserved omental tissues by cancer cells that circulate in the peritoneal fluid. Normal saline is commonly administered into the peritoneal cavity for diagnostic and intraoperative lavage. Here we show that normal saline, when administered into the peritoneal cavity of mice, is prominently absorbed by the omentum, exfoliates its mesothelium, and induces expression of CX3CL1, the ligand for CX3CR1, within and surrounding the omental vasculature. Studies using CX3CR1-competent and CX3CR1-deficient mice showed that the predominant response in the omentum following saline administration is an accumulation of CX3CR1+ monocytes/macrophages that expand milky spots and promote neoangiogenesis within these niches. Moreover, saline administration promoted the implantation of cancer cells of ovarian and colorectal origin onto the omentum. By contrast, these deleterious effects were not observed following i.p. administration of lactated Ringer's solution. Our findings suggest that normal saline stimulates the receptivity of the omentum for cancer cells and that the risk of colonization can be minimized by using a biocompatible crystalloid for lavage procedures.

CT and MR imaging of the greater omentum: Pictorial essay

The greater omentum is a unique anatomical structure that serves a critical function in the containment of inflammatory and infectious processes within the abdominal cavity. It is also a common site of involvement by metastases, as well as the primary location for various pathologic lesions of clinical significance. Its fibroadipose composition, large size, and position in the most anterior aspect of abdomen allow accurate visualization of the greater omentum on CT and MR images. Careful evaluation of the greater omentum can provide important clues to the diagnosis of the underlying abdominal disorder. The aim of this article is to present the normal appearance of the greater omentum, and the wide spectrum of its pathological features as demonstrated on CT and MRI of the abdomen.

Assessment of prognostic and reproductive outcomes of omentectomy for patients with clinically apparent early-stage (I, II) malignant ovarian germ cell tumours: A multicentre retrospective study

OBJECTIVE

This study assessed the effect of omentectomy on the prognosis and fertility in patients with clinically early-stage (I, II) malignant ovarian germ cell tumours (MOGCT).

DESIGN

A retrospective multicentre study.

SETTING

Four university teaching hospitals in China.

POPULATION

A total of 268 patients with clinically apparent early-stage (I, II) MOGCT.

METHODS

Data were obtained from the medical records. Additionally, the propensity score matching (PSM) algorithm was adopted.

MAIN OUTCOME MEASURES

Prognostic outcomes were disease-free survival (DFS) and overall survival (OS). Fertility outcomes were pregnancy and live birth rates.

RESULTS

A total of 187 (69.8%) patients underwent omentectomy. Kaplan-Meier analysis showed no significant differences in DFS and OS between the omentectomy and non-omentectomy groups before and after PSM (p > 0.05). Additionally, subgroup analysis stratified by age (<18 and ≥18 years) showed similar results. International Federation of Gynecology and Obstetrics (FIGO) stage was the only risk factor associated with DFS (hazard ratio [HR] 14.71, 95% confidence interval [CI] 4.47-48.38, p < 0.001) and OS (HR 37.36, 95% CI 3.87-361.16, p = 0.002). Pregnancy and live birth rates in the total population were 80.3% and 66.7%, respectively. There were no significant differences between the two groups before and after PSM.

CONCLUSIONS

Omentectomy did not improve survival or affect fertility in patients with clinically apparent early-stage (I, II) MOGCT, regardless of the age. The clinical FIGO stage was an independent risk factor for recurrence and death.

Is omentectomy necessary in the treatment of benign or malignant abdominal pathologies? A systematic review

BACKGROUND

The omentum is an organ that is easily sacrificed during abdominal surgery. The scope of omentectomy and whether a routine omentectomy should be performed are still unknown.

AIM

To review the literature in order to determine the physiological functions of the omentum and the roles it plays in pathological events in order to reveal the necessity for removal and preservation of the omentum.

METHODS

A clinical review of the English language literature based on the MEDLINE (PubMed) database was conducted using the keywords: “abdomen”, “gastrointestinal”, “tumor”, “inflammation”, “omental flap”, “metastasis”, “omentum”, and “omentectomy”. In addition, reports were also identified by systematically reviewing all references in retrieved papers.

RESULTS

The omentum functions as a natural barrier in areas where pathological processes occur in the abdominal cavity. The omentum limits and controls inflammatory and infectious pathologies that occur in the abdomen. It also aids in treatment due to its cellular functions including lymphatic drainage and phagocytosis. It shows similar behavior in tumors, but it cannot cope with increasing tumor burden. The stage of the disease changes due to the tumor mass it tries to control. Therefore, it is considered an indicator of poor prognosis. Due to this feature, the omentum is one of the first organs to be sacrificed during surgical procedures. However, there are many unknowns regarding the role and efficacy of the omentum in cancer.

CONCLUSION

The omentum is a unique organ that limits and controls inflammatory processes, foreign masses, and lesions that develop in the abdominal cavity. Omental flaps can be used in all anatomical areas, including the thorax, abdomen, pelvis, and extremities. The omentum is an organ that deserves the title of the abdominal policeman. It is generally accepted that the omentum should be removed in cases where there is tumor invasion. However, the positive or negative contribution of omental resection in the treatment of abdominal pathologies should be questioned.

Neutrophils facilitate ovarian cancer premetastatic niche formation in the omentum

Metastasis of ovarian cancer frequently involves the omentum and has been described as a passive process that is governed by peritoneal fluid dynamics. Lee et al. show that metastatic tropism of ovarian cancer is actively orchestrated through the induction, by early-stage tumors, of neutrophil influx and chromatin extrusion in the premetastatic omental niche.

Ovarian cancer preferentially metastasizes to the omentum, a fatty tissue characterized by immune structures called milky spots, but the cellular dynamics that direct this tropism are unknown. Here, we identified that neutrophil influx into the omentum is a prerequisite premetastatic step in orthotopic ovarian cancer models. Ovarian tumor–derived inflammatory factors stimulated neutrophils to mobilize and extrude chromatin webs called neutrophil extracellular traps (NETs). NETs were detected in the omentum of ovarian tumor–bearing mice before metastasis and of women with early-stage ovarian cancer. NETs, in turn, bound ovarian cancer cells and promoted metastasis. Omental metastasis was decreased in mice with neutrophil-specific deficiency of peptidylarginine deiminase 4 (PAD4), an enzyme that is essential for NET formation. Blockade of NET formation using a PAD4 pharmacologic inhibitor also decreased omental colonization. Our findings implicate NET formation in rendering the premetastatic omental niche conducive for implantation of ovarian cancer cells and raise the possibility that blockade of NET formation prevents omental metastasis.

Is Omentectomy Mandatory Among Early Stage (I, II) Malignant Ovarian Germ Cell Tumor Patients? A Retrospective Study of 223 Cases

Objective

The aim of the study was to investigate whether omentectomy (OMT) is necessary in the operation for apparently early stage malignant ovarian germ cell tumors (MOGCTs).

Methods and Materials

Searching medical records database of Sun Yat-sen University Cancer Center from January 1, 1966, to November 30, 2015, patients with MOGCTs were identified and their age, year of diagnosis, tumor grade, histologic subtype, International Federation of Gynecology and Obstetrics stage, nodal findings, gross observation of omentum, and performance of OMT were assessed. Overall survivals of patients with or without OMT were compared using Kaplan-Meier survival curves.

Results

A total of 223 MOGCT cases with clinically early stage (stage I and II) disease and with the 3 common histological subtypes of MOGCT were obtained, which include yolk sac tumor (YST), dysgerminoma (DSG), and immature teratoma (IMT). There were 192 stage I cases and 31 stage II cases. Fifty-four patients were diagnosed with YST, 61 with DSG, and 108 with IMT. Omentectomy was performed as part of the initial surgery in 74.0% patients (165/223) and was omitted in 26.0% patients (58/223). Chemotherapy was administered in 88.3% (197/223) of all patients. The median follow-up was 82.0 months. The 10-year overall survival rates of the patients with and without OMT were 90.5% and 98.1%, respectively (P = 0.156). Regarding different stages or histological subtypes, the 10-year survival rates of the 2 groups were 92.0% versus 97.9% (P = 0.324, stage I), 83.2% versus 100% (P = 0.351, stage II), 89.2% versus 100% (P = 0.303, YST), 94.1% versus 100% (P = 0.470, DSG), and 89.4% versus 96.0% (P = 0.405, IMT), respectively.

Conclusions

In conclusion, OMT in patients with clinically early stage MOGCT may not improve patient survival and may be omitted.

A Strategy Using Photodynamic Therapy and Clofibric Acid to Treat Peritoneal Dissemination of Ovarian Cancer

BACKGROUND

The current study examined the effectiveness of concurrent therapy using photodynamic therapy (PDT) and clofibric acid (CA) to treat peritoneal carcinomatosis resulting from ovarian cancer.

MATERIALS AND METHODS

Nude rats were used to create a model of peritoneal carcinomatosis resulting from ovarian cancer and the effectiveness of PDT with 5-aminolevulinic acid methyl ester hydrochloride (methyl-ALA-PDT) was determined. The survival time of rats receiving that therapy was compared to the survival time of a control group. Rats with peritoneal carcinomatosis resulting from ovarian cancer were divided into 3 groups: a group that received debulking surgery (DS) alone, a group that received DS+methyl-ALA-PDT, and a group that received DS+methyl-ALA-PDT+CA. The survival time of the 3 groups was compared. Protoporphyrin, a metabolite of methyl-ALA, produces a photochemical action when activated by light. The level of protoporphyrin (the concentration) that reached organs in the abdomen was measured with HPLC.

RESULTS

Rats receiving methyl- ALA-PDT had a significantly longer survival time compared to the controls. Rats with peritoneal carcinomatosis that received DS+methyl-ALA-PDT+CA had a significantly longer survival time compared to the rats that received DS alone. Some of the rats that received concurrent therapy survived for a prolonged period. Protoporphyrin was highly concentrated in peritoneal metastases, but only small amounts reached major organs in the abdomen. PDT was not found to result in necrosis in the intestines.

CONCLUSIONS

The results indicated that concurrent therapy consisting of PDT with methyl-ALA and CA is effective at treating peritoneal carcinomatosis resulting from ovarian cancer without damaging organs.

Role of omentectomy as part of radical surgery for gastric cancer

Background

A complete omentectomy is recommended as part of radical (sub)total gastrectomy for gastric cancer, but there is little evidence to suggest any survival benefit. The aim of this study was to evaluate the incidence of, and risk factors for, metastases in the greater omentum in patients undergoing gastrectomy for gastric cancer.

Methods

This was a multicentre prospective cohort study (OMEGA trial) of consecutive patients with gastric cancer undergoing (sub)total gastrectomy with complete en bloc omentectomy and modified D2 lymphadenectomy. After resection, the omentum was separated from the gastrectomy specimen distal to the gastroepiploic vessels and sent separately for pathological examination. The primary endpoint was the presence of metastases in the greater omentum.

Results

Of 100 included patients, five (5·0 per cent) had metastases in the greater omentum. Pathology results showed advanced tumours in all five (pT4b N1 M1, pT4b N2 M1, ypT4a N1 M1, ypT3 N2 M0, ypT3 N3 M0). The resection was microscopically non-radical at the proximal (3) or distal (2) resection margin in all of these patients. Metastases in the greater omentum correlated significantly with a microscopically non-radical resection, tumour expansion in the oesophagus or duodenum, linitis plastica or a proximal gastric tumour with diameter of at least 5 cm, stage III–IV disease and (y)pM1 category.

Conclusion

In resectable gastric cancer, the incidence of metastases in the greater omentum is low, and when present associated with advanced disease and non-radical features. Thus, omentectomy as part of a radical gastrectomy may be omitted. Registration number: NCT02050659 (http://www.clinicaltrials.gov).

Does omentectomy in epithelial ovarian cancer affect survival? An analysis of the Surveillance, Epidemiology, and End Results database

OBJECTIVE

Although omentectomy is part of the staging and treatment of epithelial ovarian cancer (EOC), its performance in a patient with a grossly normal omentum—acknowledging its role in debulking gross tumor deposits—has never been definitively shown to improve survival.

METHODS/MATERIALS

Using Surveillance, Epidemiology, and End Results data from 1998 to 2010, we identified patients with EOC and assessed their age, race, year of diagnosis, tumor grade, histologic subtype, International Federation of Gynecology and Obstetrics stage, lymph node dissection, nodal findings, and performance of omentectomy. We compared disease-specific survival (DSS) based on the presence or absence of omentectomy using log-rank univariate analysis, Cox multivariate analysis, and Kaplan-Meier survival curves.

RESULTS

A total of 20,975 patients with invasive EOC underwent surgical treatment. Initial univariate analysis indicated a lower mean DSS with performance of omentectomy. However, multivariate analysis demonstrated no significant association between DSS and performance of omentectomy (hazard ratio, 0.978; P = 0.506). The DSS was improved if lymphadenectomy was performed (hazard ratio, 0.60; P < 0.001). In recent years, there was a trend toward decreased performance of omentectomy.To look specifically at patients without bulky omental disease, a subset analysis was done looking at patients with stage I-IIIA disease who had had lymphadenectomy performed. There were 5454 patients in the group who underwent an omentectomy and 2404 patients in the group who did not. No difference in DSS was seen between the groups based on performance of omentectomy (P = 0.89). However, the analysis was limited by the lack of Surveillance, Epidemiology, and End Results data on the extent of omentectomy, amount of residual disease, and adjuvant chemotherapy.

CONCLUSIONS

In this analysis, performance of omentectomy in patients with EOC without bulky disease (≤stage IIIA) did not seem to confer improvement in survival. A randomized control trial would be needed to fully address this question.

4-Methylumbelliferone inhibits ovarian cancer growth by suppressing thymidine phosphorylase expression

Background

4-Methylumbelliferone (4-MU), a hyaluronan (HA) synthesis inhibitor, has antitumor activity in cancer cells. However, few studies have focused on its effects on ovarian cancer. The aim of this study was to investigate the effects of 4-MU on ovarian cancer and to elucidate its mechanism of action.

Methods

The HRA human ovarian serous adenocarcinoma cell line was used in this study. The effects of 4-MU on cell proliferation, migration, and invasion were determined by using in vitro assays as well as an in vivo rat peritoneal carcinomatosis model. The expression of HA synthase (HAS), CD44 HA receptor, vascular endothelial growth factor (VEGF), and thymidine phosphorylase (TP) mRNA in HRA cells was analyzed by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR).

Results

4-MU administration inhibited the growth of peritoneal tumors and significantly prolonged survival. In vitro experiments showed that 4-MU inhibited HRA cell proliferation in a dose-dependent manner, while it did not affect HRA cell invasion and migration. 4-MU significantly decreased TP mRNA expression in HRA cells. On the other hand, since HAS2, CD44, and VEGF endogenous mRNA expression levels were very low in HRA cells, it was impossible to evaluate the effect of 4-MU treatment.

Conclusions

These results suggest that 4-MU exerts its antitumor effect on ovarian cancer through suppressing TP expression.

Recent insights into the pathophysiology of omental metastases

Although, useful in inflammatory conditions, the greater omentum represents an important site of metastasis in peritoneal carcinomatosis and is therefore frequently removed as a staging or therapeutic tool. Apart from the milky spots, omental adipose stem cells, and adipocytes have recently been identified to play a role in the preferential homing of tumor cells to the omentum. The extent of omentectomy and whether a routine omentectomy should be done are still known unknowns.

Generation of a dual-functioning antitumor immune response in the peritoneal cavity

Tumor cell metastasis to the peritoneal cavity is observed in patients with tumors of peritoneal organs, particularly colon and ovarian tumors. Following release into the peritoneal cavity, tumor cells rapidly attach to the omentum, a tissue consisting of immune aggregates embedded in adipose tissue. Despite their proximity to potential immune effector cells, tumor cells grow aggressively on these immune aggregates. We hypothesized that activation of the immune aggregates would generate a productive antitumor immune response in the peritoneal cavity. We immunized mice i.p. with lethally irradiated cells of the colon adenocarcinoma line Colon38. Immunization resulted in temporary enlargement of immune aggregates, and after challenge with viable Colon38 cells, we did not detect tumor growth on the omentum. When Colon38-immunized mice were challenged with cells from the unrelated breast adenocarcinoma line E0771 or the melanoma line B16, these tumors also did not grow. The nonspecific response was long-lived and not present systemically, highlighting the uniqueness of the peritoneal cavity. Cellular depletions of immune subsets revealed that NK1.1(+) cells were essential in preventing growth of unrelated tumors, whereas NK1.1(+) cells and T cells were essential in preventing Colon38 tumor growth. Collectively, these data demonstrate that the peritoneal cavity has a unique environment capable of eliciting potent specific and nonspecific antitumor immune responses.

IKK-ε coordinates invasion and metastasis of ovarian cancer

Inhibitor of IκB kinases (IKK) are key regulators of NF-κB signaling. Three IKK isoforms-α, β, and ε-have been linked to oncogenesis, yet the precise components of NF-κB signaling in ovarian cancer have not yet been dissected. We surveyed 120 ovarian cancer specimens for IKK-ε expression. Notably, cytoplasmic expression was elevated in metastatic lesions relative to primary tumors (P = 0.03). Therefore, we hypothesized that IKK-ε drives ovarian cancer metastasis. IKK-ε was identified previously as a breast cancer oncogene and was associated with poor clinical outcome in ovarian cancer. We now define an ovarian cancer-specific IKK-ε-regulated gene expression signature using stably expressed short hairpin RNA targeting IKK-ε. Pathway analysis of the signature indicated that IKK-ε regulates expression of genes involved in cell motility and inflammation. We further showed that IKK-ε depletion in metastatic ovarian cancer cell lines decreased growth, adhesion, and invasion. Consistently, human xenografts depleted of IKK-ε in mice showed decreased aggressiveness, whereas overexpression of IKK-ε in a less invasive ovarian cancer cell line increased metastasis in vivo. Taken together, these data provide evidence that IKK-ε is a key coordinator of invasion and metastasis programs in ovarian cancer. Inhibition of IKK-ε signaling thus emerges as a viable therapeutic strategy in women whose ovarian cancer shows aberrant activation of this pathway.