Fræðigrein

Objective: Colon cancer is the third most common cancer in Iceland. The aim of this study was to analyze the epidemiology and histopathology of colon cancer in Iceland, resection rate and the difference between men and women.

Material and methods: Pathology and autopsy reports for all patients diagnosed with colon cancer between 1955 and 2004 where reviewed. All the histopathology material was re-evaluated. Demographical information and pathological findings were registered. Age-standardized incidence was calculated for both men and women. Gender difference was evaluated. Time trend was evaluated by linear regression.

Results: After re-evaluation 2293 cases remained (1148 males and 1145 females). The incidence increased for men from 7.5, to 22.2/105 and for women from 8.6 to 15.1/105. Most tumors were located in the sigmoid colon (35%). Surgical rate increased from 50% to 85%. Adenocarcinomas where 84% and mucinous adenocarcinoma 7%. Altogether 7% of cases were TNM-stage I, 32% were stage II, 24% stage III, 21% in stage IV and stage was unknown in 16% of cases. Slight gender difference was observed regarding grade, vessel invasion, depth of invasion and anatomic subsite.

Conclusion: Incidence of colon cancer increased considerably, mainly for men. Surgical rate and pathology of colon cancer is similar to that reported elsewhere except that there are somewhat fewer cases in TNM-stage I. Little gender difference was observed in the pathological parameters analysed.

 

Figure 1. Colon cancer in Iceland 1955-2004: distribution by age and gender.

Figure 2. Colon cancer in Iceland 1955-2004: changes in age-standardized incidence (world standard) by gender.

Figure 3. Colon cancer in Iceland 1955-2004: changes in incidence rate within different age groups for males.

Figure 4. Colon cancer in Iceland 1955-2004: changes in incidence rate within different age groups for females.

Figure 5. Age specific incidence of colon cancer in Iceland 1955-2004 for men and women. The figure illustrates the difference between the time periods 1955-1979 and 1980-2004.

 

Table I. Colon cancer in Iceland 1955-2004: number and proportion (%) of cases by anatomical subsite and gender. P-values for gender difference.

 

Anatomical subsite                    Male                Female             All cases           P value

No.                                          1148    (%)      1145    (%)      2293    (%)

Right colon                               522      (45)      554      (48)      1076    (47)      0.06^a

            Coecum                       204      (18)      249      (22)      453      (20)      0.002^b

            Ascending colon           178      (16)      156      (14)      334      (15)

            Hepatic flexure 56        (5)        34        (3)        90        (4)

            Transverse colon          84        (7)        115      (10)      199      (9)

Left colon                                 556      (48)      501      (44)      1057    (46)

            Splenic flexure  35        (3)        38        (3)        73        (3)

            Descending colon         95        (8)        86        (8)        181      (8)

            Sigmoid colon               426      (37)      377      (33)      803      (35)

Colon NOS                              70        (6)        90        (8)        160      (7)                   

 

NOS, not otherwise specified.

^a c² test on gender difference for right vs. left colon, undetermined cases (colon NOS) not included. ^b c² test on gender differences for colon subsites (coecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon), undetermined cases (colon NOS) not included.

 

Table II. Colon cancer in Iceland 1955-2004: macroscopic appearance, annular shape and median and mean tumor size by gender (number and proportion (%) of cases). P value for gender difference.

 

                                                            Male                Female             All cases           P value

No.                                                      1148    (%)      1145    (%)      2293    (%)     

Macroscopic appearance                                                                                              0.52^a

            Polypoid                                   219      (19)      212      (19)      431      (19)     

            Ulcerative                                 653      (57)      651      (57)      1304    (57)

            Ulcerative and polypoid            31        (3)        45        (4)        76        (3)

            Diffusely infiltrative                    2          (0)        1          (0)        3          (0)

            Undetermined                           243      (21)      236      (21)      479      (21)

Annular shape                                                                                                               0.47^a

            Annular                                    310      (27)      326      (28)      636      (28)     

            Other                                       595      (52)      583      (51)      1178    (51)

            Undetermined                           243      (21)      236      (21)      479      (21)

Size                                                                                                                              0.93^b

            Mean in cm; SD                       5.0; 2.4            5.0; 2.6            5.0; 2.5                        Median in cm                            4.5                   4.5                   4.5

            No. of undetermined cases        211      (18)      235      (21)      446      (19)                 

 

SD, standard deviation.

^a c² test on gender differences, undetermined cases not included. ^b Student´s t-test test on gender difference in tumor mean size.