Multidisciplinary therapy for treatment of patients with peritoneal carcinomatosis from gastric cancer

There is no standard treatment for peritoneal carcinomatosis (PC) from gastric cancer.A novel multidisciplinary treatment combining bidirectional chemotherapy [neoadjuvant intraperitoneal-systemic chemotherapy protocol (NIPS)],peritonectomy,hyperthermic intraperitoneal chemoperfusion (HIPEC) and early postoperative intraperitoneal chemotherapy has been developed.In this article,we assess the indications,safety and eff icacy of this treatment,review the relevant studies and introduce our experiences.The aims of NIPS are stage reduction,the eradication of peritoneal free cancer cells,and an increased incidence of complete cytoreduction (CC-0) for PC.A complete response after NIPS was ob-tained in 15 (50%) out of 30 patients with PC.Thus,a signif icantly high incidence of CC-0 can be obtained in patients with a peritoneal cancer index (PCI) ≤ 6.Using a multivariate analysis to examine the survival benef it,CC-0 and NIPS are identified as significant indicators of a good outcome.However,the high morbidity and mortality rates associated with peritonectomy and perioperative chemotherapy make stringent patient selection important.The best indications for multidisciplinary therapy are localized PC (PCI≤6) from resectable gastric cancer that can be completely removed during a peritonectomy.NIPS and complete cytoreduction are essential treatment modalities for improving the survival of patients with PC from gastric cancer.

Pathophysiology of colorectal peritoneal carcinomatosis: Role of the peritoneum

Colorectal cancer(CRC) is the third most common cancer and the fourth most common cause of cancerrelated death worldwide. Besides the lymphatic and haematogenous routes of dissemination,CRC frequently gives rise to transcoelomic spread of tumor cells in the peritoneal cavity,which ultimately leads to peritoneal carcinomatosis(PC). PC is associated with a poor prognosis and bad quality of life for these patients in their terminal stages of disease. A loco-regional treatment modality for PC combining cytoreductive surgery and hyperthermic intraperitoneal peroperative chemotherapy has resulted in promising clinical results. However,this novel approach is associated with significant morbidity and mortality. A comprehensive understanding of the molecular events involved in peritoneal disease spread is paramount in avoiding unnecessary toxicity. The emergence of PC is the result of a molecular crosstalk between cancer cells and host elements,involving several well-defined steps,together known as the peritoneal metastatic cascade. Individual or clumps of tumor cells detach from the primary tumor,gain access to the peritoneal cavity and become susceptible to the regular peritoneal transport. They attach to the distant peritoneum,subsequently invade the subperitoneal space,where angiogenesis sustains proliferation and enables further metastatic growth. These molecular events are not isolated events but rather a continuous and interdependent process. In this manuscript,we review current data regarding the molecular mechanisms underlying the development of colorectal PC,with a special focus on the peritoneum and the role of the surgeon in peritoneal disease spread.

Current status and future strategies of cytoreductive surgery plus intraperitoneal hyperthermic chemotherapy for peritoneal carcinomatosis

This article is to offer a concise review on the use of cytoreductive surgery （CRS） plus intraperitoneal hyperthermic chemotherapy （IPHC） for the treatment of peritoneal carcinomatosis （PC）. Traditionally, PC was treated with systemic chemotherapy alone with very poor response and a median survival of less than 6 too. With the establishment of several phase Ⅱ studies, a new trend has been developed toward the use of CRS plus IPHC as a standard method for treating selected patients with PC, in whom sufficient cytoreduction could be achieved. In spite of the need for more high quality phase Ⅲ studies, there is now a consensus among many surgical oncology experts throughout the world about the use of this new treatment strategy as standard care for colorectal cancer patients with PC. This review summarizes the current status and possible progress in future.

Pathophysiology and biology of peritoneal carcinomatosis

Peritoneal carcinomatosis represents a devastating form of cancer progression with a very poor prognosis.Its complex pathogenesis is represented by a dynamic process comprising several steps.To the best of our knowledge pathogenesis can be partly explained by 3 major molecular pathways: (1) dissemination from the primary tumor;(2) primary tumor of peritoneum;and (3) independent origins of the primary tumor and peritoneal implants.These are not mutually exclusive and combinations of different mechanisms could occur inside a single case.There are still several aspects which need explanation by future studies.A comprehensive understanding of molecular events involved in peritoneal carcinomatosis is of paramount importance and should be systematically pursued not only to identify novel strategies for the prevention of the condition,but also to obtain therapeutic advances,through the identification of surrogate markers of prognosis and development of future molecular targeted therapies.

Optimizing outcomes for patients with gastric cancer peritoneal carcinomatosis

Peritoneal carcinomatosis (PC) from gastric cancer has traditionally been considered a terminal progression of the disease and is associated with poor survival out-comes. Positive peritoneal cytology similarly worsens the survival of patients with gastric cancer and treatment options for these patients have been limited. Recent ad-vances in multimodality treatment regimens have led to innovative ways to care for and treat patients with this disease burden. One of these advances has been to use neoadjuvant therapy to try and convert patients with positivecytologyorlow-volume PC to negative cytolo-gy with no evidence of active peritoneal disease.These strategies include the use of neoadjuvant systemic chemotherapy alone,using neoadjuvant laparoscopic heated intraper itoneal chemotherapy(NLHIPEC)after systemic chemotherapy,or using neoadjuvant intra-peritoneal and systemic chemother apy(NIPS)in a bi-dir ectional manner. For patients with higher volume PC,cytoreductive surgery (CRS) and hyperthermic intrape-ritoneal chemotherapy(HIPEC)have been mainstays of treatment. When used together, CRS and HIPEC can improve overall outcomes in properly selected patients,but overall survival outcomes remain unacceptably low.The extent of peritoneal disease, commonly measured by the peritoneal carcinomatosis index (PCI), and the com-pleteness of cytor eduction,has been shown to greatly impact outcomes in patients undergoing CRS and HIPEC.The uses of NLHIPEC and NLHIPEC plus NIPS have both been shown to decrease the PCI and thus increase the opportunity for complete cytoreduction. Newer therapies like pressurized intraperitoneal aerosol chemother apy and immunotherapy, such as catumaxomab, along with improved systemic chemotherapeutic regimens, are being explored with great interest.There is exciting progress being made in the management of PC from gastric can-cer and its’ treatment is no longer futile.

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in treatment of gastric cancer with peritoneal carcinomatosis

Although gastric cancer with peritoneal carcinomatosis is associated with poor prognosis and is generally treated with palliative systemic therapy, recent studies have shown that cytoreductive surgery（CRS） and hyperthermic intraperitoneal chemotherapy（HIPEC） may prove to be an efficacious treatment option. In addition to reviewing the natural history of gastric cancer with peritoneal carcinomatosis, this mini-review examines literature on the efficacy of CRS and HIPEC as compared to chemotherapy and surgical options. Both randomized and nonrandomized studies were summarized with the emphasis focused on overall survival. In summary, CRS and HIPEC are indeed a promising treatment option for gastric cancer with peritoneal carcinomatosis and large randomized clinical trials are warranted.

Current treatment options for colon cancer peritoneal carcinomatosis

Peritoneal carcinomatosis(PC),the dissemination of cancer cells throughout the lining of the abdominal cavity,is the second most common presentation of colon cancer distant metastasis.Despite remarkable advances in cytotoxic chemotherapy and targeted therapy for colon cancer over the last 15 years,it has been repeatedly shown that these therapies remain ineffective for colon cancer PC.Recently,there has been a rapid accumulation of reports that cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy(CRS-HIPEC) prolongs the life of colon cancer PC patients.Here,we will review the clinical presentation,the mechanisms of disease progression,and current treatment options for colon cancer PC,with a focus on the benefits and limitations of CRSHIPEC.

Cytoreduction and hyperthermic intraperitoneal chemotherapy in the treatment of peritoneal carcinomatosis from pseudomixoma peritonei

AIM： To investigate the most important aspects of hyperthermic intraperitoneal chemotherapy （HIPEC） that has been accepted as the standard treatment for pseudomyxoma peritonei （PMP）, with special regard to morbidity, overall survival （OS） and disease free survival （DFS） over 10 years. METHODS： Fifty-three patients affected by PMP underwent cytoreduction （CCR） and HIPEC with a ＂semi-closed＂ abdomen technique in our institution. The peritonectomy procedure and completeness of CCR were classified according to Sugarbaker criteria. Preoperative evaluation always included thoracic and abdominal CT scan to stage peritoneal disease and exclude distant metastases. Fifty-one patients in our series were treated with a protocol based on administration of cisplatinum 100 mg/m^2 plus mitomycin C 16 mg/m^2, at a temperature of 41.5℃ for 60 min. Anastomoses were always performed at the end of HIPEC. The mean duration of surgery was 12 h including HIPEC. Continuous monitoring of hepatic and renal functions and hydroelectrolytic balance was performed in the postoperative period. RESULTS： Twenty-four patients presented with postoperative complications： surgical morbidity was observed in 16 patients and 6 patients were reoperated. All complications were successfully treated and no postoperative deaths were observed. Risk factors for postoperative morbidity were considered to be gender, age, body surface, duration of surgery,Peritoneal Cancer Index （PCI） and tumor residual value （CC score）. No statistically significant correlation was found during the multivariate analysis： only the CC score was statistically significant. The OS in our experience was 81.8%, with a DFS of 80% at 5 years and of 70% at 10 years. CONCLUSION： In our experience, even if HIPEC combined with cytoreductive surgery involves a high risk of morbidity, postoperative complications can be resolved favorably in most cases with correct patient selection and adequate postoperative care, thus minimizing mortality. The association of CCR and HIPEC can be considered as the standard treatment for PNP. The OS and DFS results confirm the validity of this combined approach for the treatment of this rare neoplasm. The impact of preoperative chemotherapy on OS, in our opinion, is due to a major aggressiveness of tumors in treated patients.

Current role of hyperthermic intraperitoneal chemotherapy in the treatment of peritoneal carcinomatosis from colorectal cancer

Peritoneal carcinomatosis is one of the most common routes of dissemination of colorectal cancer (CRC). It is encountered in 7% of patients at primary surgery, while it develops in about 4% to 19% of patients after curative surgery and in up to 44% of patients with recurrent CRC. Peritoneal involvement from colorectal malignancies has been considered traditionally as a manifestation of terminal disease, due to limited response to conventional surgical and chemotherapeutic treatments. In the past few years the introduction of cytoreductive surgery combined with hyperthermic intraperitoneal chemoperfusion has shown promising results in selected patients. Currently, the surgical management of peritoneal surface malignancies of colonic origin with this combined locoregional therapy has resulted in a signif icant improvement in survival of these patients. However, further controlled studies will help to standardize indications and the technique of this locoregional therapy in order to achieve an improvement of morbidity and mortality rates.

Gastric peritoneal carcinomatosis-a retrospective review

AIM To characterize patients with gastric peritoneal carcinomatosis(PC) and their typical clinical and treatment course with palliative systemic chemotherapy as the current standard of care.METHODS We performed a retrospective electronic chart review of all patients with gastric adenocarcinoma with PC diagnosed at initial metastatic presentation between January 2010 and December 2014 in a single tertiary referral centre.RESULTS We studied a total of 271 patients with a median age of 63.8 years and median follow-up duration of 5.1 mo. The majority(n = 217, 80.1%) had the peritoneum as the only site of metastasis at initial presentation. Palliative systemic chemotherapy was eventually planned for 175(64.6%) of our patients at initial presentation, of which 171 were initiated on it. Choice of first-line regime was in accordance with the National Comprehensive Cancer Network Guidelines for Gastric Cancer Treatment. Thesepatients underwent a median of one line of chemotherapy, completing a median of six cycles in total. Chemotherapy disruption due to unplanned hospitalizations occurred in 114(66.7%), while cessation of chemotherapy occurred in 157(91.8%), with 42 cessations primarily attributable to PC-related complications. Patients who had initiation of systemic chemotherapy had a significantly better median overall survival than those who did not(10.9 mo vs 1.6 mo, P < 0.001). Of patients who had initiation of systemic chemotherapy, those who experienced any disruptions to chemotherapy due to unplanned hospitalizations had a significantly worse median overall survival compared to those who did not(8.7 mo vs 14.6 mo, P < 0.001).CONCLUSION Gastric PC carries a grim prognosis with a clinical course fraught with disease-related complications which may attenuate any survival benefit which palliative systemic chemotherapy may have to offer. As such, investigational use of regional therapies is warranted and required validation in patients with isolated PC to maximize their survival outcomes in the long run.

Second-look surgery plus hyperthermic intraperitoneal chemotherapy for patients with colorectal cancer at high risk of peritoneal carcinomatosis:Does it really save lives?

The treatment of peritoneal carcinomatosis (PC) of colorectal origin with cytoreductive surgery(CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) has a 5-year recurrence-free or cure rate of at least 16%, so it is no longer labeled as a fatal disease, and offers prolonged survival for patients with a low peritoneal carcinomatosis index. Metachronous PC of colorectal origin is so predictable that there is a model which has been used to successfully determine the individual risk of each patient. Patients at risk are clearly identified; those with the highest risk have small peritoneal nodules present in the first surgery (70% probability of developing PC), ovarian metastases(60%), perforated tumor onset or intraoperative tumor rupture(50%). Current clinical, biological and imaging techniques still lack sufficient sensitivity to diagnose PC in its initial stages, when CRS plus HIPEC has a greater impact and a higher cure rate. Second-look surgery with HIPEC or prophylactic HIPEC at the time of the first intervention have been proposed as means of preventing and/or anticipating clinical or radiological relapse in at-risk patients. Both techniques have shown a significant decrease in peritoneal relapses and should be considered essential weapons in the management of colorectal cancer.

Peritoneal carcinomatosis of colorectal origin

Peritoneal carcinomatosis is,after liver metastases,the second most frequent cause of death in colorectal cancer patients and at the present time,is commonly inserted and treated as a stage Ⅳ tumour.Because there is no published data that outlines the impact of new therapeutic regimens on survival of patients with peritoneal surface diffusion,the story of carcinomatosis can be rewritten in light of a new aggressive approach based on the combination of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.Also if these treatment perhaps allow to obtain better results than standard therapies,we suggest,that a large prospective randomised control trial is needed to compare long-term and progression-free survival under the best available systemic therapy with or without cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

Self-expanding metal stents for the palliation of malignant gastric outlet obstruction in patients with peritoneal carcinomatosis

AIM To evaluate the efficacy of self-expanding metal stents(SEMS) for the palliation of malignant gastric outlet obstruction in patients with and without peritoneal carcinomatosis(PC).METHODS We performed a retrospective analysis of 62 patients who underwent SEMS placement for treatment of malignant gastroduodenal obstruction at our hospital over a six-year period. Stents were deployed through the scope under combined fluoroscopic and endoscopic guidance. Technical success was defined as successful stent placement and expansion. Clinical success was defined as an improvement in the obstructive symptoms and discharge from hospital without additional parenteral nutrition. According to carcinomatosis status, patients were assigned into groups with or without evidence of peritoneal disease.RESULTS In most cases, obstruction was caused by pancreatic(47%) or gastric cancer(23%). Technical success was achieved in 96.8%(60/62), clinical success in 79%(49/62) of all patients. Signs of carcinomatosis were identified in 27 patients(43.5%). The diagnosis was confirmed by pathology or previous operation in 7 patients(11.2%) and suspected by CT, MRI or ultrasound in 20 patients(32.2%). Presence of carcinomatosis was associated with a significantly lower clinical success rate compared to patients with no evidence of peritoneal disease(66.7% vs 88.6%, P = 0.036). There was no significant difference in overall survival between patients with or without PC(median 48 d vs 70 d, P = 0.21), but patients showed significantly longer survival after clinical success of SEMS placement compared to those experiencing clinical failure(median 14.5 d vs 75 d, P = 0.0003).CONCLUSION Given the limited therapeutic options and a clinical success rate of at least 66.7%, we believe that SEMS are a reasonable treatment option in patients with malignant gastric outlet obstruction with peritoneal carcinomatosis.

Peritoneal cancer index is a prognostic indicator of survival in advanced gastric cancer with peritoneal carcinomatosis

Objective The peritoneal cancer index(PCI)has been used for the detailed evaluation of the peritoneal spread in tumors of a gynecologic origin and has been found to be a prognostic indicator of survival.The aim of this study was to identify the significance of the PCI in advanced gastric cancer(AGC)with peritoneal carcinomatosis(PC).Methods From 2010 to 2018,a retrospective analysis was carried out of 60 AGC patients with PC,including 21 patients with a PCI≤13 and 39 with a PCI>13.All patients were treated with both surgery and intraoperative peritoneal hyperthermic chemotherapy(IPHC).The performance status(Karnofsky performance status),age,sex,Borromann’s classification,differentiation,depth of invasion,lymph node metastasis,PCI,extent of gastrectomy,extent of lymph node dissection,and residual tumor volume were retrospectively evaluated and correlated to survival.Results The overall 5-year survival rate was 43%and mean survival was(54.47±4.53)months.The favorable clinical prognostic indicators of survival were Borromann’s classification,differentiation,depth of invasion,PCI,and residual tumor volume on univariate analyses(P<0.05).The Cox proportional regression hazard model showed that only the volume of residual tumor and PCI were associated with postoperative survival.The median survival time was 69.76 months for patients with a PCI≤13 and 39.96 months for patients with a PCI>13.There was a significant difference in survival rate between the two group(P=0.004).Postoperative major morbidity and mortality rates were 23.81%and 4.76%in the PCI≤13 group and 43.59%and 5.12%in the PCI>13 group,respectively.Conclusion The peritoneal spread in advanced gastric cancer with peritoneal carcinomatosis can be assessed in detail using the PCI.It is also a significant prognostic factor of survival and is useful in identifying subgroups.

Intraperitoneal Chemotherapy for Gastric Cancer with Peritoneal Carcinomatosis: Is HIPEC the Only Answer?

Gastric cancer with peritoneal carcinomatosis is notorious for its dismal prognosis. While the pathophysiology of peritoneal dissemination is still controversial, the rapid downhill course is universal. Patients usually suffer abdominal distension, intestinal obstruction and various complications before they succumb after a median of 3 - 6 months. Although not adopted in most international treatment guidelines, intraperitoneal chemotherapy has growing evidence compared with conventional systemic chemotherapy for the treatment of peritoneal carcinomatosis. Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy is well-established for clinical benefit but is technically demanding with substantial treatment-related morbidities and mortality. On the other hand, normothermic intraperitoneal chemotherapy in the form of bidirectional neoadjuvant treatment is promising with various newer chemotherapeutic agents. Regardless of the treatment technique applied, the essential element of success is meticulous patient selection and availability of expertise. Future direction is along the line of personalized treatment with the application of translational science.

Peritoneal carcinomatosis of gastrointestinal tumors: Where are we now?

The peritoneal stromal tissue which provides a rich source of growth factors and chemokines is a favorable environment for tumor proliferation. The pathophysiological mechanism of peritoneal carcinomatosis is an individual sequence consisting of genetic and environmental factors and remains controversial. The natural history of the disease reveals a poor median prognosis of approximately 6 mo; however aggressive surgery and multimodal treatment options can improve oncologic outcomes. Considering peritoneal carcinomatosis as though it is a locoregional disease but not a metastatic process, cytoreductive surgery and and intraperitoneal chemotherapy has been a curative option during recent years. Cytoreductive surgery implies a series of visceral resections and peritonectomy procedures. Although the aim of cytoreductive surgery is to eliminate all macroscopic disease, viable tumor cells may remain in the peritoneal cavity. At that point, intraperitoneal chemotherapy can extend the macroscopic disease elimination to microscopic disease elimination. The successful treatment of peritoneal carcinomatosis requires a comprehensive management plan including proper patient selection, complete resection of all visible disease, perioperative intraperitoneal chemotherapy and postoperative systemic chemotherapy. Surgical and oncologic outcomes are strictly associated with extent of the tumor, completeness of cytoreduction and patientrelated factors as well as multidisciplinary management and experience of the surgical team. In this review, pathophysiology and current management of peritoneal carcinomatosis originating from gastrointestinal tumors are discussed according to the latest literature.

Peritoneal Colorectal Carcinomatosis Treated with Cytoreductive Surgery and Perioperative Intraperitoneal Chemotherapy

Background-Aims: Peritoneal colorectal carcinomatosis is a potentially curative disease. The purpose of the study is the retrospective analysis of survival of the patients with peritoneal colorectal carcinomatosis that underwent cytoreductive surgery and perioperative intraperitoneal chemotherapy and the identification of prognostic variables of the disease. Patients-Methods: Patients with primary or recurrent colorectal cancer and peritoneal carcinomatosis were included in the study. Clinical variables were correlated to survival, recurrence, hospital mortality, and morbidity. Results: From 2000-2010, 28 patients underwent 33 cytoreductive operations. The hospital mortality and morbidity rate was 9.1% and 45.5% respectively. The overall 5-year and median survival time was 29.2% and 19 months respectively. The extent of peritoneal carcinomatosis (p = 0.0003) and the completeness of cytoreduction (p = 0.0002) were related to survival. The completeness of cytoreduction (p = 0.003) was the single prognostic variable of survival. The recurrence rate was 42.4% and the use of systemic chemotherapy was identified as the single prognostic variable of recurrence (p = 0.047). Conclusions: Patients with limited extent of peritoneal colorectal carcinomatosis who undergo complete cytoreduction may be offered long-term survival.

Analysis of 154 T4 Colorectal Cancer Patients with Peritoneal Carcinomatosis Treated by Surgery

Objective: The purpose of this study was to observe the factors related to T4 patients who underwent surgery for colorectal cancer (CRC) with peritoneal carcinomatosis. Methods: 154 T4 colorectal cancer patients who underwent surgery in the first Affiliated Hospital of Sun Yat-sen University were included in the study between August, 1994 and December, 2005. Some clinical variables were selected and statistically correlated with prognosis. Results: The overall survival time was 91.7 months at the end of December of 2010 or death. The complete cytoreduction had significant survival benefit than the palliative surgery group. The age, location, histological grade, complete cytoreduction and liver metastasis were associated with overall survival time (OS) according to the univariate analysis (P < 0.05). In addition, Cox multivariate analysis showed that the complete cytoreduction (CCR) and liver metastasis were independent factor influencing survival. Conclusion: Compared with palliative surgery, the incomplete cytoreduction fails to improve patient prognosis. Patients performed completed cytoreduction have a relative good prognosis.

Can hyperthermic intraperitoneal chemotherapy effectively control gastric cancer-associated peritoneal carcinomatosis?

Gastric cancer-associated peritoneal carcinomatosis leads to a poor prognosis and low quality of life. The current systemic chemotherapy processes cannot effectively improve survival. Hyperthermic intraperitoneal chemotherapy (HIPEC) has been used as an alternative treatment to control this disease through recurrence prevention, definitive therapeutic modality, and symptom palliation. Although HIPEC has been demonstrated to yield favorable results mainly in some Asian studies, widespread adoption of this treatment is still debatable before larger prospective randomized controlled clinical trials confirm its effectiveness.

CT Differentiation of Diffuse Malignant Peritoneal Mesothelioma, Tuberculous Peritonitis, and Peritoneal Carcinomatosis

Objective:To investigate the significance of computed tomography findings in diffuse malignant peritoneal mesothelioma(DMPeM),tuberculous peritonitis(TBP),and peritoneal carcinomatosis(PC)to differentiate the three diseases.Methods:The clinical manifestation and computed tomography scans of 147 patients with diffuse malignant peritoneal mesothelioma(n=60),tuberculous peritonitis(n=32),and peritoneal carcinomatosis(n=55)were retrospectively reviewed,while taking into account of ascites,pleural plaques,viscera infiltration;abnormalities in the peritoneum;involvement of the mesentery and omentum;as well as the presence and location of enlarged lymph nodes.Results:There was no significant difference among all three groups in terms of clinical manifestation,peritoneum,omentum,and mesentery involvement,ascites,as well as the presence and location of enlarged lymph nodes.The study found that 95%of DMPeM patients had been exposed to asbestos in the past.The patients showed significant differences in the following aspects:(1)irregular peritoneum thickening,caked omentum thickening,pleural plaques,visceral infiltration,and asbestos exposure were more common in peritoneal mesothelioma patients;(2)nodular peritoneum thickening and visceral metastasis were more common in patients with peritoneal carcinomatosis;(3)smooth peritoneal thickening,pleural effusion,and extraperitoneal tuberculosis were more common in patients with tuberculous peritonitis.Conclusion:A combination of computed tomography findings could improve our ability in differentiating the three diseases.