Sex Differences in Subsite Incidence of Large-bowel Cancer R. J. STEWART, CH.M., F.R.C.S., F.R.A.C.S., A. W. STEWART, B.SC., P. R. G. TURNBULL, M.B., CH.B., F.R.C,S., WILLIAM H. ISBISTER, M.D., F.R.C.S. (ED.), F.R.A.C.S.
From the Department of Surgery, Wellington Clinical School of Medicine, University oJ Otago, Wellington, New Zealand
Stewart RJ, Stewart AW, Turnbull P R G , Isbister WH. Sex differences in subsite incidence of large-bowel cancer. Dis Colon Rectum 1983; 26:658-660. A review of patients with large-bowel cancer at a major N e w Zealand hospital showed an excess of right-sided colonic tumors in females compared with males. These observations stimulated analysis of the National Cancer Registry registration data for large-bowel cancer for the whole of N e w Zealand in the years 1972 to 1975 (4678 patients). Rates for each site were calculated and age-standardized, using world population figures. T h e findings confirmed that females have a higher incidence of right-sided colonic cancer and males a higher incidence of rectal cancer and showed a significant trend in this direction from the ascending colon toward the rectum. T h e observed differences between males and females suggest differences in the etiology of the tumor and should be taken into account in assessing modalities and outcomes of treatment. [Key words: Colorectal cancer, subsite incidence]
would appear, therefore, that there are real differences in the disease process between males and females. The present study examined the subsite incidence by sex for all New Zealand patients between 1972 and 1975. Materials and Methods A l l data were obtained from the National Cancer Registry of New Zealand (NCR). T h e N C R estimated that the national registration rate was 92 per cent in 1971 and close to 100 per cent by 1974. An account of the activities of the Registry was recently given by Foster. 5 The records of 4678 patients were available for examination. The subsites of both male and female patients were identified and the age-standardized incidence was determined. 6
NEW ZEALANDhas the highest age-adjusted death rate for colorectal cancer in the world. 1 Three hundred patients received their first treatment for histologically proven colorectal cancer in Wellington Hospital between 1968 and 1972. 2 Analysis of the site distribution of these patients showed that the most c o m m o n single colonic site in females was the right colon, whereas the most c o m m o n single site for colonic tumors in males was the sigmoid colon. This has also been noted in a more recent New Zealand study. 3 In addition, an increase in relative risk of development of colonic cancer in females following cholecystectomy (colon 1.67)< ; rectum 5.5X ) has been demonstrated in a case control study of 324 patients. 4 It
Results
The most c o m m o n single subsite for colonic tumors in females was the right colon whereas in males it was found to be the distal left colon. There was no sex difference in subsite incidence at the rectosigmoid junction. The predominant sex in relation to rectal tumors was male (Fig. 1). T h e age-standardized incidence figures show a similar trend (Fig. 2) and, when the female age-standardized incidence is subtracted from the male age-standardized incidence (Table 1), a gradual increase in positivity occurs as the site moves distally in the large bowel. When the difference in incidence was plotted for the two time peri-
Received for publication March 21, 1983. Addressreprint requests to ProfessorIsbister: Department of Surgery, Wellington Clinical School of Medicine, Wellington Hospital, Wellington, New Zealand.
0012-3706/83/1000/0658/$00.95 ~) American Society of Colon and Rectal Surgeons
658
Volume 26
Number 10
659
SEX A N D SUBSITE I N C I D E N C E
NEW ZEALAND 1972-75 TOTAL NUMBERS A
_
NEW ZEALAND1972-75 AGE-STANDARMSEDINCIDENCE/IOO,OOO/YEAR
A
-0.25 -1.4.3
8O
~JJlll~
r
Rectosigmoid junction
91
+ 4.34
91 FIG. 2. Age-standardized incidence of colorectal cancers by subsite-New Zealand 1972 to 73. Intraluminal figures--Males: heavy type; Females: light type. Extraluminal figures--Male/Female differences. NEW ZEALAND POPULATION (two periods) FIG. 1. T o t a l n u m b e r o f p a t i e n t s w i t h c o l o r e c t a l c a n c e r s b y s u b s i t e - New Zealand 1972 to 73. Males: heavy type; Females: light type.
968-71
ods 1968 to 1971 and 1972 to 1975 (Fig. 3), it was found that the female right-sided excess increased with time. A similar but opposite change occurred in relation to the left-sided male excess.
8
Discussion
,,m
T h e findings of a small Wellington survey 2 have been confirmed at a national level for the whole of New Zealand by the present study. T h e data relating to the rectosigmoid junction are difficult to explain because both the distal colonic data and the rectal data tend to favor the male so that errors in
1972-75
ASC~IDING
*' DESdNDING A
TRANSVERSE
RECTO-
A
SIGMOIO SIGMOIO RECTUM
FIG. 3. C h a n g e in subsite incidence of colorectal c a n c e r - - N e w Zealand 1968 to 71 a n d 1972 to 75.
TABLE 1. Age-standardized Incidence per 100,000 per Year
Males Females Difference
Ascending
Transverse
6.35 7.78
4.30 5.20
-1.43
-0.90
Descending
Sigmoid
Rectosigmoid
Rectum
1.59 1.84
8.94 7.62
1.30 1.30
13.68 9.34
-0.75
1.32
0.00
4.34
660
S'I'EWAR'I------------, ET AL.
a n a t o m i c classification s h o u l d n o t have resulted i n the present finding. T h e f i n d i n g s i n this study s t r o n g l y s u p p o r t the theory that there are differences between the sexes i n the etiology of the disease. T h i s m a y partly e x p l a i n the f i n d i n g s i n r e l a t i o n to the d e v e l o p m e n t of colorectal cancer followi n g cholecystectomy where a very clear sex difference has been observed. Since d e v e l o p m e n t of the disease is affected i n some way by the sex of the patient, it is possible that therapies w o u l d have different results i n males a n d females. F u t u r e studies s h o u l d e x a m i n e response rates to therapy i n males a n d females separately, a n d furthermore, sex differences a n d site differences s h o u l d be taken i n t o c o n s i d e r a t i o n w h e n o u t c o m e s are evaluated. If all patients are g r o u p e d together, it is clear that the r e s u l t i n g p o p u l a t i o n will n o t be h o m o g e n o u s .
Conclusion T h e r e are differences i n the subsite d i s t r i b u t i o n of colorectal cancer between males a n d females. T h e s e differences s h o u l d be taken into a c c o u n t i n assessing all modalities
Dis.October Col.g:Rect. 1983
of t r e a t m e n t a n d the o u t c o m e of treatment i n future studies r e l a t i n g to colorectal cancer.
Acknowledgment T h e a u t h o r s w o u l d like to t h a n k Mr. F. H. Foster, Director, N a t i o n a l C a n c e r Registry, D e p a r t m e n t of Health, W e l l i n g t o n , New Zealand.
References 1. World Health Statistics Annual 1979-80. Geneva: World Health Organization, 1980. 2. Turnbull PR, Isbister WH. Colorectal cancer in New Zealand: a Wellington study. Aust NZ J Surg 1979;49:45-8. 3. Stewart RJ, Robson RA, Stewart AW, Stewart JM, Macbeth WA. Cancer of the large bowel in a defined population: Canterbury, New Zealand, 1970-4. Br J SuN 1979;66:309-14. 4. Turnbull PR, Smith A, Isbister WH. Cholecystectomyand cancerof the large bowel. Br J Surg 1981;68:551-3. 5. Foster FH. The New Zealand Cancer Registry. NZ Med J 1977;86: 341-3. 6. Doll R. Comparison between registries age standardized rates. In: Waterhouse, Muir, Correa, Powel, eds. Cancer incidence in five continents. Lyon: InternationalAgency for Research on Cancer, 1976;3:453-9.
Announcement T H E S O U T H E R N MEDICAL ASSOCIATION The Southern Medical Association will hold its 77th Annual Scientific Assembly November 6-9, 1983 at the Baltimore Convention Center, Baltimore, Maryland. There is no fee for registration; fees for postgraduate courses are $15 for members of SMA and $22.50 for nonmembers. For further information, contact Ms. Jeanette Stone, Southern Medical Association, P.O. Box 2246, Birmingham, AL 35201. Telephone (205) 323-4400.
