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ORIGINAL ARTICLE  
Year : 2019  |  Volume : 62  |  Issue : 1  |  Page : 36-42
A study of morphological prognostic factors in colorectal cancer and survival analysis


1 Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India
2 Department of Pathology, Government Medical College, Kollam, Kerala, India

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Date of Web Publication31-Jan-2019
 

   Abstract 


Context: Globally, colorectal cancer (CRC) is one of the leading causes of cancer death. Many Asian countries experience an increasing incidence of CRC due to changes in diet and lifestyle. Many pathological prognostic factors other than the tumor-node-metastasis (TNM) staging reflect the biological behavior of tumor tissue and influence the treatment and survival. Aims: The aim is to evaluate: (1) Various morphological prognostic factors of colorectal cancer, (2) the correlation of the prognostic factors with survival, and (3) the prognostic factors with independent prognostic significance. Settings and Design: Descriptive study conducted in a tertiary care center in Kerala. Materials and Methods: Five hundred and eighty-seven resected specimens of CRC received from January 1, 2007 to October 31, 2012 were studied for various morphological prognostic factors. Overall survival and disease-free survival were obtained by Kaplan Meier survival analysis. Cox regression analysis was performed to identify the predictors of survival. Results: CRC incidence was higher in the age group 40–60 years and males were dominant. Rectum was the common site with bleeding per rectum as a common symptom. Predominant tumors had ulcerative gross configuration, size ≤5 cm and were free of transverse, radial margin involvement. Majority of tumors were well-differentiated adenocarcinoma with invasion beyond muscularis propria, without vascular, perineural invasion, and lymph node involvement and were in Stage II. The overall and disease-free 3-year survival rates were 89.1% and 88%, respectively. Among the eight significant factors in univariate analysis, tumor histology, depth of invasion, and perineural invasion were found to have independent prognostic significance in multivariate analysis. Conclusions: In addition to the TNM staging, other morphological prognostic factors should be given importance, while considering the patients for adjuvant therapy to improve the survival rates in CRC.

Keywords: Adjuvant therapy, perineural invasion, prognostic factors, survival, tumor histology

How to cite this article:
Poornakala S, Prema N S. A study of morphological prognostic factors in colorectal cancer and survival analysis. Indian J Pathol Microbiol 2019;62:36-42

How to cite this URL:
Poornakala S, Prema N S. A study of morphological prognostic factors in colorectal cancer and survival analysis. Indian J Pathol Microbiol [serial online] 2019 [cited 2019 Apr 24];62:36-42. Available from: http://www.ijpmonline.org/text.asp?2019/62/1/36/251282





   Introduction Top


Colorectal cancer (CRC) remains a leading cause of morbidity and mortality in many developed countries. Globally, CRC contributes to 8.9% of all cancers and is the third leading cause of cancer death in men and women in the United States.[1],[2] Many Asian countries including Japan and Singapore have experienced 2–4 times increase in incidence of CRC during the past few decades.[3],[4] This could be attributed to changes in dietary habits and lifestyle. In the 2007 World Cancer Research Fund (WCRF) report, obesity, lack of exercise, and high meat consumption were considered as convincing environmental factors to affect CRC risk.[5],[6],[7] Until now, standardized pathological staging systems consider only parameters regarding mural depth and lymph node involvement to predict the likelihood of long-term survival. However, there are modifiers of pathological stage such as serosal penetration, resected margin assessment, tumor grade, histological type, venous invasion, perineural invasion, tumor budding, host-immune response, molecular markers, and so on. These factors may reflect the biological behavior of individual cancer tissue and may correlate with tumor aggressiveness and risk of recurrence.[8] Hence, there is a need for extensive research about the tumor biology which will influence the therapy and survival. The current study intends to evaluate (1) various prognostic factors of CRC, (2) the correlation of the prognostic factors with survival, and (3) the prognostic factors with independent prognostic significance.

Study setting and design

It is a descriptive study conducted at department of pathology in Government Medical College, Trivandrum in Kerala. Ethics committee approval was obtained from the Institute Ethics committee.


   Materials and Methods Top


Five hundred and eighty-seven resected specimens of CRC received in the study setting, from January 1, 2007 to October 31, 2012 were studied for following morphological prognostic factors.

Age: Patients were grouped into those <40 years, more than 60 years, and a separate group between 40 and 60 years.

Sex: Patients were grouped into male and female.

Tumor site: It denotes whether the tumor is situated in cecum/ascending colon/transverse colon/descending colon/sigmoid colon/rectum. Cecum, ascending colon, hepatic flexure, and transverse colon were taken together as the right colon. Splenic flexure, descending colon, and sigmoid colon were taken together as the left colon and rectum was considered separately.

Tumor size: Usually, tumor size is noted in three dimensions, namely length, width, and depth. In this study, largest dimension of the tumor was taken, and the median value of tumors included in the study was 5 cm. The patients were grouped as having tumor ≤5 cm or >5 cm.

Gross configuration: Based on the gross configuration, the tumors were classified as exophytic, in which the tumor was protruding from the bowel wall into the lumen, [Figure 1] ulcerative in which the tumor presented as infiltrating ulcer, and annular in which the bowel wall was circumferentially involved.
Figure 1: Exophytic gross configuration

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Transverse margin: When the distance between the closest resected margin and the tumor was <1 cm or any one of the resected margin was grossly or microscopically involved by the tumor, the resected margin involvement was considered positive.

Radial margin: In rectal cancers, the radial margin was considered positive when there was gross involvement or microscopic presence of tumor cells.

Tumor grade: Tumor grading was done based on the degree of differentiation which is assessed by the percentage of gland formation. The tumors were categorized into well differentiated (>95% gland formation), moderately differentiated (50%–95% gland formation), and poorly differentiated (<50% gland formation).

Histology: Histologically, the tumors were categorized as adenocarcinoma, adenocarcinoma + mucin secretion (tumor composed of <50% of mucin), mucinous carcinoma, signet ring cell carcinoma, neuroendocrine carcinoma, and adenocarcinoma with neuroendocrine differentiation.

Vascular invasion: Vascular emboli were searched in the tumor as well as in adjacent tissues.

Neural invasion: Considered when the nerve bundles were infiltrated by the tumor cells.

Depth of penetration: It was categorized as involvement of submucosa, muscularis propria, and beyond muscularis propria.

Serosal penetration: The tumor was considered as perforated the serosa when there was gross perforation or presence of serosal nodules on the free serosal surface or when the adjacent organs were involved or pericolic fat was involved.

Residual tumor: The patients were considered to have residual tumor when they had distant metastasis at the time of diagnosis or when any of the resected margins were involved by the tumor or when there was serosal penetration.

Lymph nodes involved: Categorized as no nodes involved when all the retrieved nodes were negative for tumor or involvement of 1–3 nodes or involvement of ≥4 nodes.

Staging: Patients were grouped into four categories according to the tumor-node-metastasis (TNM) staging as per the American Joint Cancer Committee (AJCC) cancer staging manual 6th edition.

For survival analysis, patients in the year 2007, 2008, and 2009 were considered to obtain a minimum of 3-year survival. Period of follow-up was from the date of surgery to October 2012. Follow-up of the patients was obtained through phone calls, reply postcards, and hospital follow-up registers. Patients who died in the immediate postoperative period and those who died of other medical/surgical illness were excluded from survival analysis. Out of 345 patients, follow-up was obtained for 149 patients of whom 6 were excluded based on exclusion criteria. Finally, 143 patients were considered for survival analysis. The overall survival and disease-free survival were obtained by Kaplan–Meier survival analysis. To calculate the predictors of survival, death of the patients and recurrence in alive patients were considered as adverse events. Out of 143 patients, 52 patients had adverse event and Cox multivariate regression analysis was performed to identify the predictors of survival. P < 0.05 was considered statistically significant.


   Results Top


  • Among 587 cases, 308 cases (52.5%) were in the age group of 40–60 years, 33 cases (5.6%) were <40 years, and 246 cases (41.9%) were more than 60 years. Mean age was 58 years with the youngest being 19 years and oldest being 88 years and males predominated accounting to 323 cases (55%)
  • The common presenting symptom was bleeding per rectum (PR) which was observed in 139 cases (23.7%), followed by altered bowel habits and acute presentation. Other presenting symptoms were abdominal pain, mass in the abdomen, fatigue, and weakness
  • Rectum was the common site observed in 269 cases (45.8%) followed by the left colon involvement in 183 cases (31.2%) among colon cancers.
  • 314 cases had tumor size ≤5 cm accounting to 53.5% and 253 (43.1%) cases presented with ulcerative gross configuration
  • Regarding resected margins involvement, 554 cases (94.4%) were free of transverse margin involvement, and among 269 cases of rectal cancer, 187 cases were (69.5%) free of radial margin involvement
  • 472 (80.4%) cases were adenocarcinoma NOS subtype and the proportion of other histology subtypes are shown in [Figure 2]. 401 cases (68.3%) were well differentiated.
  • Vascular and perineural invasion [Figure 3] were observed in 13 (2.2%) and 6 (1%) cases, respectively
  • 392 cases (66.8%) showed invasion beyond muscularis propria and serosal penetration was noted in 146 cases (24.9%)
  • 402 cases (68.5%) were free of residual tumor
  • The number of lymph nodes sampled ranged from 5 to 22. Less than 12 nodes were obtained predominantly in APR and anterior resection specimens. Regarding lymph node involvement, 398 cases did not show lymph node involvement accounting to 67.8%
  • Proportion of cases in different stages are shown in [Figure 4]
  • Survival analysis was done by Kaplan–Meier method in 143 cases, for which follow-up details were obtained. The overall 3-year survival rates were 89.1% whereas 3-year disease-free survival rates were 88% [Table 1] and [Figure 5]
  • Regarding the predictors of survival, Cox univariate analysis showed penetration of serosa, tumor size, histology subtype, grade, perineural invasion, and depth of penetration, number of lymph nodes involved, and staging as significant prognostic factors
  • Tumor histology subtype, depth of invasion, and perineural invasion were found to have independent prognostic significance in multivariate analysis [Table 2].
Figure 2: Proportion of cases in different histology subtype

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Figure 3: Photomicrograph of perineural invasion (×400)

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Figure 4: Proportion of cases in different stages

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Table 1: Disease-free survival

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Figure 5: Kaplan–Meier curve – disease-free survival

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Table 2: Results of Cox regression analysis

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   Discussion Top


AJCC has categorized the various prognostic factors into four categories as follows.[9]

  • Category I includes clinically proven and prognostically important factors. They are local extent of tumor invasion (pT), regional lymph node metastasis (pN), blood or lymphatic vessel invasion, residual tumor, preoperative carcinoembryonic antigen, and radial margin (rectal cancer)
  • Category IIA includes the factors which are extensively studied, prognostically important, but further validation required. It includes histologic grade, microsatellite instability, tumor border configuration, and lymphocytic response
  • Category IIB factors are promising in multiple studies, but insufficient data for conclusive proof which includes histologic type, histologic features of microsatellite instability, and chromosome 18q/deleted in colon cancer gene loss
  • Category III factors are not yet sufficiently studied. DNA content, other molecular genetic markers, perineural invasion, microvessel density, other protein expression, peritumoral fibrosis, and purulent peritumoral inflammatory reaction, foci of neuroendocrine differentiation, proliferation indices, and nucleolar organizing regions are included in this category
  • Category IV factors are well studied and have no prognostic significance, which includes tumor size and gross configuration.


The present study has evaluated various factors in all the four categories and the observations are comparable with various other studies.

The mean age of presentation of our study parallels the observation of Park et al. and Sohn et al. and predominance of rectal tumors parallels the observations made by Rajaganeshan et al.[8],[10],[11] The common presenting symptom of bleeding PR is explained by the predominance of rectal tumors and is the earliest symptom in rectal cancers.

Gross configuration of the tumor was predominantly ulcerative like the observations made by Newland et al.[12] As per the AJCC guidelines, gross configuration of tumor and tumor size are category IV factors, as majority of studies have observed that these factors do not carry prognostic significance. However, recent studies suggest that tumor size carries prognostic significance and influences the survival of the patients.[13],[14] In the current study also, tumor size is a significant factor in univariate analysis.

In the present study, 5.6% of cases showed the involvement of transverse resected margin, of which the predominant cases were in the rectum, similar to the observations made by El-Bolkainy et al.[1] the probable reason could be the difficult anatomy of the rectum. However, in rectum, the radial margin has greater prognostic significance which represents the retroperitoneal or perineal adventitial soft-tissue margin closest to the deepest penetration of tumor. In the present study, radial margin was involved in 14.1% cases of rectal cancers which is comparable with the observations of Stocchi et al.[15] In their study, 14% cases showed clearance <5 mm. Many studies have evaluated radial margin as the most critical factor in predicting the local recurrence in rectal cancers.[16],[17] In the study conducted by North Central Cancer Treatment Group, local recurrence rate was 25% with a free radial margin of <1 mm clearance and was 3% if the clearance was more than 1 cm.[15]

Pathological diagnosis of serosal penetration by the tumor, a significant factor in univariate analysis in the present study, is very important because many studies have evaluated it as an independent adverse prognostic factor.[18],[19] Newland et al. found that 5-year survival rate was only 16% in patients with involvement of free serosal surface, whereas 44% survival was found in patients without involvement of free serosal surface.[12] In spite of prognostic significance, It is an underreported parameter because of the practical difficulties associated with the histological assessment. Shepard et al. have described four patterns of local peritoneal involvement which are helpful in the assessment of serosal invasion.[20]

Regarding the tumor grade which denotes the degree of differentiation, majority of the tumors were well differentiated in the present study. This contrasts with the observations made by Inti Zlobec and Lugli and Petersen et al. who observed a predominance of moderately differentiated tumors.[19],[21] The difference may be due to interobserver variability in grading the tumors. As per the AJCC recommendation, a two-tier grading system of low and high grade will reduce the interobserver variation and improves the prognostic significance. Among various histology subtypes, adenocarcinoma without mucin secretion was the common histological subtype observed which is parallel to the observations made by various other studies.[21],[22] In view of prognostic significance, medullary carcinoma is prognostically favorable, whereas signet ring cell carcinoma and small cell carcinoma are prognostically unfavorable.[23],[24] The prognostic value of mucinous carcinoma is controversial.

The diagnosis of venous invasion per se is an indicator of risk for hematogenous metastasis. Incidence of venous invasion is directly related to stage of the tumor and inversely to tumor differentiation. Proportion of cases with vascular invasion in the present study is significantly smaller. The reason could be the predominance of well differentiated and Stage II tumors.

Sternberg et al. observed that the reported incidence of venous invasion in CRC specimens varies between 10% and 89.5%, mainly as a result of interobserver variability and differences in specimen processing and found that the use of elastic-stained serial sections increased the detection of venous invasion in CRC compared to hematoxylin and eosin sections only.[25],[26] Similar to venous invasion, perineural invasion is also an underreported parameter which carries significance in predicting the survival of the patients. Liebig et al. observed perineural invasion as an independent predictor of prognosis and observed that 5-year disease-free survival rate was 56% for Stage III patients, whereas 29% survival rate for node-negative patients with perineural invasion.[27]

The extent of local invasion of tumor is the first component of TNM staging and regional lymph node involvement is the second component of TNM staging. Tumors confined to mucosa and submucosa have better prognosis because of the lesser chances for regional and distant spread. Similarly, the location and extent of lymph node involvement are significant. Survival rate drops if nodes other than those in immediate vicinity (N1) of tumors are involved and the involvement of apical node is particularly a crucial prognostic factor.[28] The depth of invasion and lymph node involvement in the present study parallels the observations of El-Bolkainy et al. and Liang et al. who found that the 5-year survival rate decreased from 92% to 35% when lymph node metastasis occurred and the survival rate was only 19% when N2 nodes were involved.[18] Regarding staging, the predominance of Stage II in the present study parallels the observation of Zlobec and Lugli.[21]

The results of univariate analysis in the present study were comparable to the other studies Newland et al., Han Liang et al., and Cohen et al.[12],[18],[28] Among the factors of independent prognostic significance, though depth of invasion is a clinically proven prognostic factor and is a component of TNM staging, tumor histology is a Category IIB and perineural invasion is a Category III prognostic factor of AJCC guidelines, and these factors play a crucial role in considering the patients for adjuvant therapy.


   Conclusions Top


The present study concludes that many morphological prognostic factors reflect the biological behavior of the tumor and significantly influences the survival of the patients.

The prognostic significance of tumor size, which is presently a Category IV factor needs to be reevaluated in view of the results of recent studies.

Improved techniques and uniform guidelines should be followed for underreported parameters like serosal penetration, venous invasion, and perineural invasion.

Currently, routine use of adjuvant chemotherapy is not recommended for all Stage II disease. However, the American Society of Clinical Oncology recommends adjuvant chemotherapy for Stage II disease with poor prognostic indicators such as inadequately sampled nodes, T4 lesions, perforation, and poorly differentiated histology.[29] Similarly, in view of independent prognostic significance in the current study, the following factors may be given importance in deciding the adjuvant therapy of Stage II disease to improve the survival rates in CRC:

  • Depth of invasion beyond muscularis propria
  • Presence of perineural invasion
  • Unfavorable Histological subtype.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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S Poornakala
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DOI: 10.4103/IJPM.IJPM_91_18

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