Survival Rate of Colorectal Cancer Patients Receiving Chemotherapy based on Tumor Location and K-Ras Gene Mutation Status: A Systematic Review

The incidence of early-onset colorectal cancer (EOCRC) is rapidly increasing worldwide in decade when screening of colorectal cancer (CRC) is more prevalent. The clinicopathological and molecular characteristics of EOCRC have not yet been clarified. This study aims to evaluate clinicopathological and molecular features among EOCRC and late-onset colorectal cancer (LOCRC) patients according to different tumor locations. We identified CRC patients from a prospectively maintained CRC database between January 2015 and December 2018. The clinicopathological and molecular characteristics including dMMR, mutation of PIK3CA, BRAF and KRAS were compared between EOCRC and LOCRC. The relationships according to different tumor locations were assessed. Totally 4468 patients were analyzed in this study. Compared to LOCRC patients, EOCRC patients were more likely to have status of dMMR (OR, 2.52; P < 0.001), regardless of tumor location. EOCRC patients were more likely to be detected with mutation of PIK3CA (OR, 1.24; P = 0.041), which only tended to exist in the left-side colon (OR, 1.51; P = 0.06), but not in the right-side colon or rectum. No significant difference was found for BRAF or KRAS mutation, but mutation of KRAS was more frequently found in left-side colon (OR, 1.34; P = 0.04) among EOCRC patients. Status of dMMR, mutation of PIK3CA, BRAF and KRAS was different between EOCRC and LOCRC patients according to different tumor locations, which implied that EOCRC might be a unique subgroup of CRC patients. Further investigations of molecular and genetic differences should be performed to help define new diagnosing and therapeutical strategies for EOCRC patients.

Objective To investigate the association between KRAS gene mutations and clinico-pathological characteristics and prognosis of colorectal cancer (CRC) patients. Methods The retrospective case-control study was conducted. The clinicophathological data of 315 patients who underwent radical resection of CRC in the Yangpu Hospital Affiliated to Tongji University between January 2007 and July 2011 were collected. Next-generation sequencing was performed to identify KRAS gene mutations from surgical specimens. Observation indicators: (1) detection of KRAS gene; (2) association between KRAS gene mutations and clinicopathological characteristics of CRC patients; (3) follow-up and survival situations; (4) multivariate analysis of KRAS gene mutations in the prognosis of CRC patients. Follow-up using outpatient examination and telephone interview was performed to detect postoperative overall survival up to August 2016. Comparisons of count data were analyzed using the chi-square test. Measurement data with skewed distribution were described as M (interquartile range), and comparison between groups was analyzed using the nonparametric test. The survival rate was calculated using the Kaplan-Meier method, and survival was compared using the Log-rank test. The multivariate analysis was done using the COX regression model. Results (1) Detection of KRAS gene: all the 315 patients finished gene detection of surgical specimens, including 172 in wide-type mutations and 143 in mutant-type mutations (mutations at codon 12 and 13 of KRAS exon 2 and other mutant points were respectively detected in 80, 24 and 40 patients, and 1 patient had simultaneous mutations at codon 12 and 13 of KRAS exon 2; missense and nonsense mutations were respectively detected in 141 and 2 patients). The major point mutations were at p. G12D and p. G13D. (2) Association between KRAS gene mutations and clinicophathological characteristics of CRC patients: tumors located in the proximal colon, distal colon and rectum were respectively detected in 34, 48, 90 patients with wild-type mutation and in 44, 27, 72 patients with mutant-type mutation, with a statistically significant difference (χ2=0.038, P<0.05). (3) Follow-up and survival situation: 315 patients were followed up for 3-115 months, with a median time of 78 months. The postoperative overall survival rate was 41.0% in 172 patients with wild-type KRAS mutations, 27.4% in 80 patients with KRAS codon 12 mutations, 26.3% in 24 patients with KRAS codon 13 mutations and 48.2% in 40 patients with other KRAS mutations, showing a statistically significant difference (χ2=0.040, P<0.05). (4) Multivariate analysis of KRAS gene mutations in the prognosis of CRC patients: the results of multivariate analysis showed that mutations at codon 12 of KRAS exon 2 was an independent factor affecting poor prognosis of CRC patients (Hazard ratio=1.543, 95% confidence interval: 1.050-2.265, P<0.05). Conclusions Most KRAS mutations of CRC patients are at codon 12 and 13 of KRAS exon 2, and the major point mutations are at p. G12D and p. G13D. KRAS gene mutations may be associated with tumor location. Mutations at codon 12 of KRAS exon 2 is an independent factor affecting poor prognosis of CRC patients. Key words: Colonic neoplasms; Rectal neoplasms; KRAS gene; Genetic mutations; Surgical procedures, operative; Prognosis

Objective To analyze the correlation between K-ras gene mutation and clinicopathological characteristics and prognosis of colorectal cancer patients with different primary sites. Methods The clinical and pathological records of 69 patients who were pathologically confirmed as colorectal cancer and tested K-ras gene status at Wuxi People's Hospital Affiliated to Nanjing Medical University between May 2007 and August 2017 were adopted. The correlation between clinicopathological characteristics and prognosis of colorectal cancer patients with different primary sites and K-ras gene mutation status were retrospectively analyzed. And the patients were visited to adopt the prognosis data and perform the Kaplan-Meier survival analysis. Results The K-ras mutation rate was 50.7% (35/69), including 40.0% (12/30) in left-side colon cancer, 73.3% (11/15) in right-side colon cancer and 50.0% (12/24) in rectal cancer. The mutation rate of K-ras gene in patients ≥ 60 years old [61.5% (24/39) vs. 36.7% (11/30), χ2 = 4.197, P = 0.041] or serum CA19-9 raising up abnormally was conspicuously high [65.6% (19/29) vs. 37.5% (15/40), χ2 = 5.486, P = 0.019]. Other clinicopathological characteristics, such as gender, lesion location, histological classification, TNM stage, serum CEA expression, clinical features had no correlation with K-ras gene mutation status (all P > 0.05). And no relationship was found between prognosis and overall survival of colorectal cancer patients with different primary sites and K-ras gene mutation status (χ2 = 0.001, P = 0.997; χ2 = 0.583, P = 0.445). In general, the 5-year survival rate of left-side colon cancer patients was highest (76.9%), followed by rectal cancer (69.7%), and right-side colon cancer was lowest (31.3%). The primary site of colorectal cancer was related to the overall survival of patients (χ2 = 11.004, P = 0.004). Conclusions K-ras gene mutation in colorectal cancer is closely related to age and serum CA19-9 levels of the patients. The prognosis of left-side colon cancer is best, rectal cancer second, and right-side colon cancer poorest. Whether K-ras gene mutation is the prognostic factor of colorectal cancer is not clear. Testing the K-ras gene status and serum tumor index expression, distinguish the primary site and age group will provide the theory basis and promote the clinical targeted therapy and improve the survival of colorectal cancer patients. Key words: Intestinal neoplasms; Genes, ras; Pathology, clinical; Prognosis

The aim of this study was to evaluate the influence of cellular immunity parameters on overall survival of colorectal and gastric cancer patients after surgery. The parameters of cellular immunity (CD3+, CD4+, CD8+, CD20+, and CD16+) were determined by immunofluorescence method. Cox regression analysis showed no impact of the estimated preoperative and postoperative parameters of cellular immunity on overall survival of colorectal cancer patients and similarly of gastric cancer patients in stage II. However, the analysis showed that the survival of colorectal and gastric cancer patients in stage III depended on immunological parameters determined before surgery: CD3+ (P=0.007 and P=0.007, respectively), CD4+ (P=0.021 and P=0.011, respectively), and CD8+ (P=0.047 and P=0.007) counts. Only the survival of colorectal cancer patients depended on natural killer cell number (P=0.009). Kaplan-Meier analysis showed that patients with stage III colorectal and gastric cancer had better survival rates when absolute number of CD3+ lymphocytes, determined before surgery, was greater than 0.8 x 10(9)/L, CD4+--greater than 0.25 x 10(9)/L, CD8+--greater than 0.3 x 10(9)/L. Colorectal cancer patient survived longer when the number of natural killer cells CD16+ was more than 0.25 x 10(9)/L. This study suggests that higher levels of the absolute number of lymphocyte subsets before surgery have a beneficial effect on overall survival of gastric and colorectal cancer patients in stage III.

Background: We have reported that BRAF V600E mutations and microsatellite instability-high (MSI-H) are more prevalent in a population-based cohort of metastatic colorectal cancer (mCRC) patients than has been reported from clinical trials or hospital-based patient groups. The aim was to explore if other mutations in mCRC differ in prevalence between these cohorts in relation to mismatch repair status and primary tumor location and if presence of bone or brain metastases is associated with any mutations.Material and methods: A population-based cohort of 798 mCRC patients from three regions in Scandinavia was used. Forty-four cancer related genes were investigated in a custom designed Ampliseq hotspot panel. Differences in survival were analyzed using the Kaplan–Meier estimator and the Cox regression analysis.Results: Determination of mutations was possible in 449/501 patients for 40/44 genes. Besides BRAF V600E, seen in 19% of the tumors, none of the other mutations appeared more prevalent than in trial cohorts. BRAF V600E and MSI-H, seen in 8%, were associated with poor prognosis as was right-sided primary tumor location (39%) when compared to left-sided and rectum together; however, in a multivariable regression, only the BRAF mutation retained its statistical significance. No other mutations were associated with poor prognosis. ERBB2 alterations were more common if bone metastases were present at diagnosis (17% vs. 4%, p = .011). No association was found for brain metastases. Fifty-two percent had an alteration that is treatable with an FDA-approved targeted therapy, chiefly by EGFR-inhibitor for RAS wild-type and a check-point inhibitor for MSI-H tumors.Conclusions: Right-sided tumor location, BRAF V600E mutations, but no other investigated mutation, and MSI-H are more commonly seen in an unselected cohort than is reported from clinical patient cohorts, likely because they indicate poor prognosis. Half of the patients have a tumor that is treatable with an already FDA-approved targeted drug for mCRC.

The results of this study demonstrate the potential prognostic and predictive values of KRAS and BRAF gene mutations in patients with colorectal cancer (CRC). It has been proven that KRAS and BRAF mutations are predictive biomarkers for resistance to anti-EGFR monoclonal antibody treatment in patients with metastatic CRC (mCRC). We demonstrated the distribution of KRAS (codons 12, 13 and 61) and BRAF (codon 600) gene mutations in 50 mCRCs using direct sequencing and compared the results with clinicopathological data. KRAS and BRAF mutations were identified in 15 (30%) and 1 (2%) patients, respectively. We identified KRAS mutations in codon 12, 13 and 61 in 73.3% (11/15), 20% (3/15) and 6.67% (1/15) of the positive patients, respectively. The KRAS mutation frequency was significantly higher in tumors located in the ascending colon (p=0.043). Thus, we found that approximately 1/3 of the patients with mCRC had KRAS mutations and the only clinicopathological factor related to this mutation was tumor location. Future studies with larger patient groups should yield more accurate data regarding the molecular mechanism of CRC and the association between KRAS and BRAF mutations and clinicopathological features.

Background:There has been an increasing interest in the role of tumour location in the treatment and prognosis of patients with colorectal cancer (CRC), specifically in the adjuvant setting. Together with genomic data, this has led to the proposal that right-sided and left-sided tumours should be considered as distinct biological and clinical entities. The aim of the present study was to examine the relationship between tumour location, tumour microenvironment, systemic inflammatory response (SIR), adjuvant chemotherapy and survival in patients undergoing potentially curative surgery for stage I–III colon and rectal cancer.Methods:Clinicopathological characteristics were extracted from a prospective database. MMR and BRAF status was determined using immunohistochemistry. The tumour microenvironment was assessed using routine H&E pathological sections. SIR was assessed using modified Glasgow Prognostic Score (mGPS), neutrophil:lymphocyte ratio (NLR), neutrophil:platelet score (NPS) and lymphocyte:monocyte ratio (LMR).Results:Overall, 972 patients were included. The majority were over 65 years (68%), male (55%), TNM stage II/III (82%). In all, 40% of patients had right-sided tumours and 31% had rectal cancers. Right-sided tumour location was associated with older age (P=0.001), deficient MMR (P=0.005), higher T stage (P<0.001), poor tumour differentiation (P<0.001), venous invasion (P=0.021), and high CD3+ within cancer cell nests (P=0.048). Right-sided location was consistently associated with a high SIR, mGPS (P<0.001) and NPS (P<0.001). There was no relationship between tumour location, adjuvant chemotherapy (P=0.632) or cancer-specific survival (CSS; P=0.377). In those 275 patients who received adjuvant chemotherapy, right-sided location was not associated with the MMR status (P=0.509) but was associated with higher T stage (P=0.001), venous invasion (P=0.036), CD3+ at the invasive margin (P=0.033) and CD3+ within cancer nests (P=0.012). There was no relationship between tumour location, SIR or CSS in the adjuvant group.Conclusions:Right-sided tumour location was associated with an elevated tumour lymphocytic infiltrate and an elevated SIR. There was no association between tumour location and survival in the non-adjuvant or adjuvant setting in patients undergoing potentially curative surgery for stage I–III colon and rectal cancer.

Mutations in KRAS and BRAF genes were associated with treatment failure from EGF receptor inhibitors in colorectal cancer (CRC) patients. However, whether these mutations were associated with survival in patients not treated with EGF receptor inhibitors remained controversial. Moreover, few data were available in Chinese. Therefore, we aimed to evaluate the impact of KRAS and BRAF mutations on the survival of Chinese CRC patients. CRC patients who underwent surgery between October 2003 and April 2006 were included in this study. They were observed until June 30, 2010 or when death was ascertained by the National Death Registration System. Prospectively collected fresh frozen tumor tissues were used for detection of mutations at codons 12, 13, and 61 of the KRAS gene and exons 11 and 15 of BRAF gene by PCR amplification followed by direct sequencing. Among the 314 patients, KRAS and BRAF mutations were detected in 65 (20.7%) and 12 (3.8%) patients, respectively. KRAS mutations appeared to occur more frequently in females than males (p = 0.039) and in non-smokers (p = 0.039). KRAS and BRAF mutations were significantly associated with the proximal location of cancer (p = 0.017 and 0.001, respectively). In the univariate analysis, KRAS and BRAF mutations were not associated with survival. However, BRAF mutations were associated with a significantly worse overall survival (hazard ratio = 3.91, 95% confidence interval 1.31 to 11.66, p = 0.014) in the multivariate Cox proportional hazard model after adjustment for all direct clincopathological variables. BRAF mutations, but not KRAS mutations, were associated with a worse outcome in Chinese CRC patients.

To examine associations of KRAS mutation with tumor deposit status and overall survival in colorectal cancer (CRC) patients. This retrospective cohort study included patients with incidental CRC diagnosed during 2010-2014 and recorded statuses of KRAS and tumor deposit in the National Cancer Database of the USA. Multivariable logistic regression and time-varying Cox regression analyses were used. We included 45,761 CRC patients with KRAS status (24,027 [52.5%] men, 24,240 [53.0%] < 65years old, 17,338 [37.9%] with KRAS mutation). Adjusted for microsatellite instability, age, pathologic stage and tumor grade, KRAS mutation (versus wild type) was associated with tumor deposit presence (odds ratio = 1.11, 95% CI 1.02-1.20). KRAS mutation was also linked to worse overall survival of CRC patients regardless of tumor deposit status (adjusted Hazard ratio [HR] = 1.20, 95% CI 1.07-1.33 for CRC with tumor deposits, and adjusted HR = 1.24, 95% CI 1.14-1.35 or CRC without) or tumor stage (adjusted HR = 1.32, 95% CI 1.14-1.54 for early-stage and adjusted HR = 1.18, 95% CI 1.10-1.27 for late-stage). Microsatellite instability was associated with better overall survival in CRC without tumor deposit (adjusted HR = 0.89, 95% CI 0.79-0.99), but not in CRC with tumor deposit (adjusted HR = 1.12, 95% CI 0.97-1.30). KRAS mutation is independently associated with tumor deposit presence and a worse overall survival in CRC patients.

BackgroundThe progression of colorectal cancer (CRC) may differ depending on the location of the tumor and the age of onset of the disease. Previous studies also suggested that the molecular basis of CRC varies with tumor location, which could affect the clinical management of patients. Therefore, we performed survival analysis looking at different age groups and mismatch repair status (MMR) of CRC patients according to primary tumor location in an attempt to identify subgroups of CRC that might help in the prognosis of disease.MethodsA group of 2233 patients operated on to remove their CRC tumors were analyzed (521 with right colon cancer, 740 with left colon cancer and 972 with rectal cancer). The expression of four MMR genes was assessed by immunohistochemistry (IHC), independent of clinical criteria. From the data collected, a predictive model for overall survival (OS) could be constructed for some associations of tumor location and age of onset using Kaplan-Meier, logistic and Cox regression analysis.ResultsWhen tumor location was considered as the lone factor, we found no statistical difference in overall survival (OS) between right cancer (68%), left cancer (67%) or rectal cancer tumor locations (71%) (HR: 1.17, 95%CI (confidence interval): 0.97–1.43, P = 0.057). When age of onset was considered, middle age (40–59 years) and older (60–85 years) patients were found to have higher OS than younger onset cancer (20–39 years) patients (69% vs 71% vs 59%, HR: 1.07, 95% confidence interval (CI): 0.91–1.25, P = 0.008). When both age of onset and tumor location were considered in combination as disease factors, we found that the subgroup of patients with left colon cancer from middle age (69%) and older (67%) aged patients had higher OS than younger (54%) patients (HR: 0.89, 95%CI: 0.68–1.16, P = 0.048). However in patients with right colon cancers, we found no statistical difference is OS between younger, middle age or older grouped patients (60% vs 71% vs 67%, HR: 0.84, 95% CI: 0.61–1.16, P = 0.194). With regard to rectal located cancers, we found that younger (62%) and middle age (68) patients had lower OS than older (77%) patients (HR:1.46, 95%CI: 1.13–1.88, P = 0.004). The rates of deficient MMR (dMMR) was 10.4%. We found no statistical difference in OS stratified by tumor locations. However, right colon cancer patients with dMMR (86%) had higher OS than those with proficient MMR (pMMR) (63%) (HR: 3.01, 95% CI: 1.82–4.97, P<0.001). Left colon cancer patients with dMMR (76%) also had higher OS than those with pMMR (66%) (HR: 1.67, 95% CI: 0.95–2.92, P = 0.01). Oppositely, rectal cancer patients with dMMR (60%) had lower OS than those pMMR (68%) (HR: 0.77, 95% CI: 0.51–1.17, P = 0.04).ConclusionsThese data demonstrate that primary tumor location can be an important factor when considered along with age of onset for the prognosis of CRC. Primary tumor location is also an important factor to evaluate the predictive effect of MMR status for the prognosis of CRC.

557 Background: Clinical trials including CALGB/SWOG 80405 and FIRE-3 reveal differences in overall survival (OS) for metastatic colorectal cancer (mCRC) patients treated with targeted therapy based on primary tumor location. We assessed the impact of tumor location on prognosis in a prospective series of patients with mCRC received FOLFIRI in first-line therapy. Methods: Patients treated with FOLFIRI were consecutively recruited between November 2010 and December 2014. Follow-up information was updated in February 2016 when 77.3% of the patients were deceased. We defined the right-sided colon = cecum to transverse colon, left-sided colon = splenic flexure to sigmoid descending colon, rectum = rectosigmoid plus rectal cancer, respectively. We measured median survival using Kaplan-Meier plots and 2-year survival probability using life tables. Associations between tumor locations and treatment outcomes were estimated using a Cox proportional hazards model. Age and gender were included in adjusted Cox models to estimate the hazard ratio (HR) for death of rectal and left-sided tumors relative to right-sided tumors. Results: Right-sided cancer had a shorter median survival (13.5 vs. 20.4 months) and worse 2-year survival probability (28% vs. 39%) than left-sided and rectal cancers, however the difference was of no statistical significance no matter in unadjusted (HR = 1.002, 95% CI 0.635-1.581) or adjusted models (HR = 1.037, 95% CI 0.657-1.639). Conclusions: mCRC patients with right-sided colon got comparative survival benefit from FOLFIRI in first-line treatment to the left-sided colon and rectum. This result needs to be validated in studies with larger sample size. Clinical trial information: NCT01282658.

To evaluate the prognostic role of BRAF and KRAS mutations after adjustment for microsatellite instability (MSI) in Iranian colorectal cancer (CRC) patients. BRAF and KRAS mutations and MSI status were assessed in 258 Iranian subjects with CRC. Two hundred fifty-eight consecutive stages I-IV CRC patients, who underwent surgical resection of adenocarcinoma from 2012 to 2016, were enrolled in the research. Pyrosequencing and Cast-PCR methods were used to the detection of KRAS and BRAF mutations. Kaplan-Meier and Cox regression were employed to estimate hazard ratios (HR) for the association between BRAF and KRAS mutation and overall survival (OS). KRAS and BRAF mutations were detected in 36 (14%) and 15 (5.8%) cases of 258 patients with CRC, respectively. BRAF mutations that all comprised V600E and KRAS mutations was found in codon 12 and 13 (80.6% and 19.4%), respectively. KRAS mutations were detected in 19 (15.4%) patients of 123 microsatellite stable (MSS) CRC and it is significantly associated with tumor location and metastasis. BRAF and KRAS mutant vs. wild type of BRAF and KRAS, 5-year OS was 73.3% vs. 82.3% and 83.3% vs. 81.5% (long-rank P > 0.05), respectively. KRAS mutant vs. KRAS-wild-type tumors in MSS/MSI-L status CRC patients, 5-year OS was 78.9% vs. 90.4% (long-rank p = 0.046). The present study revealed that BRAF and KRAS mutations were not related to the worse overall survival, while KRAS mutation can be a prognostic factor for overall survival in sporadic microsatellite-stable (MSS) status in Iranian CRC patients.

Background: Colorectal cancer (CRC) remains a global health challenge. Metabolic disorders, including dyslipidemia, have been linked to CRC progression, yet the relationship between lipid profiles, tumor location, and survival outcomes remains controversial. This study investigates the association between blood lipid parameters, tumor localization, and survival in CRC patients. Methods: A retrospective analysis was conducted on 126 CRC patients diagnosed between 2017 and 2024 at Kartal Dr. Lütfi Kırdar City Hospital. Patients with comorbidities affecting lipid metabolism or who were on lipid-lowering drugs were excluded. Clinical, pathological, and lipid data, including total cholesterol (TC), triglycerides (TGs), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and carcinoembryonic antigen (CEA), were analyzed. Tumor location was categorized as right-sided or left-sided. Overall survival (OS) was evaluated with a statistical analysis using Kaplan–Meier and Cox regression models. Results: Higher HDL-C levels and a lower TC/HDL-C ratio were significantly associated with improved OS (p: 0.004 and p: 0.016, respectively). This relationship remained significant in early- and advanced-stage disease (p: 0.04 for HDL-C and p: 0.03 for TC/HDL-C). In patients with tumors located in the right colon, LDL-C levels of 150 mg/dL and below were found to be statistically positively correlated with overall survival, while in patients with tumors located in the left colon, HDL-C levels of 45 mg/dL and above and TC/HDL-C levels of 4.16 and above were found to be statistically positively correlated with overall survival. A multivariate analysis confirmed that age, stage, HDL-C, and TC/HDL-C were independent predictors of OS. Conclusions: Our study highlights the potential role of lipid profiles, particularly HDL-C and the TC/HDL-C ratio, as prognostic factors in CRC. Further research, including molecular and genetic analyses, is needed to better understand the mechanisms underlying the relationship between lipid metabolism and CRC progression.

Associations of positive epidermal growth factor receptor expression and K-RAS gene mutations with various clinicopathological parameters and survival of colorectal carcinoma patients

KRAS mutations have a significant role in the consecutive activation of RAS.RAF.MEK.ERK pathway in colorectal cancer.Approximately 30.35% of sporadic colorectal cancers have KRAS mutation. While the predictive role of KRAS is commonly accepted at the present time, its prognostic role and association with different clinical and histopathological properties are currently unclear and inconsistent. The intent of this study, has been to evaluate the associations between KRAS gene mutations and clinicopathological features and survival times in Turkish colorectal cancer patients. In this study, the file records of 115 metastatic colorectal cancer patients who applied to the Department of Medical Oncology between 2000 and 2011 were monitored; data on clinicopathological features and survival times were collected. DNA.sequencing method with PCR amplification from archival paraffin blocks were used for KRAS mutation status analysis. The associations between KRAS mutation status and clinicopathological features and survival times were compared statistically. While a significant association hadbeen determined between KRAS mutation status and tumor localization, there was no determined significant association with other clinicopathological properties. Similarly, there was no association between KRAS mutation status and survival parameters. As a result, the effect of KRAS mutation status on clinicopathological features, survival time and prognosis is unclear.