***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract Objective . To investigate risk factors for colorectal cancer following breast cancer . Methods . In this nested case-control study , all women ( n=14,900 ) with a first primary breast cancer ( 1978–1992 ) were identified from the western Washington population -based Surveillance , Epidemiology , and End Results Cancer Registry . Cases ( n=160 ) developed a second primary colorectal cancer before 1995 , at least 6 months after the first cancer diagnosis . Controls ( n=310 , matched to the cases on calendar year , age and breast cancer stage ) were r and omly selected from those who did not develop a second primary cancer and who survived to the case 's colorectal cancer diagnosis date . Characteristics of the cases and controls at initial diagnosis were compared using conditional logistic regression . Results . The incidence of colorectal cancer was associated with a family history of breast cancer ( v.s. no family history , matched odds ratio (mOR)=2.1 , 95 % confidence interval ( CI ) : 1.1–4.1 ) , high body mass index ( ≥30 kg/m2 v.s. < 30 kg/m2 , mOR=2.2 , CI : 1.2–3.9 ) , and lobular breast cancer histology ( v.s. ductal , mOR=2.0 , CI : 0.9–4.4 ) . Risk was unrelated to menopausal status , prior hormone replacement therapy and estrogen/progesterone receptor status of the breast tumors . Conclusions . The risk of developing a second primary colorectal cancer may be elevated among certain subsets of breast cancer patients BACKGROUND Women treated with tamoxifen for breast cancer are at increased risk of endometrial cancer . We conducted a retrospective cohort study to evaluate the risk of second primary cancers after  adjuvant tamoxifen therapy for breast cancer in Japan . PATIENTS AND METHODS The subjects of the study were 6148 women who had been diagnosed with stage I , II , or IIIA unilateral primary breast cancer and had received surgical treatment during the period from January 1982 through December 1990 at nine institutions in Japan . The information on each patient was obtained from medical records or a prospect ively compiled computer data base at each institution . RESULTS Of the 6148 women , 3588 ( 58.4 % ) were administered tamoxifen as an adjuvant treatment and 2560 ( 41.6 % ) were not administered .  Median follow-up periods were 7.64 years for tamoxifen-treated patients and 8.10 years for non-tamoxifen-treated patients , respectively . The duration of tamoxifen treatment was mostly two years or less ( 80.7 % ) , and few patients received tamoxifen for more than five years . The cumulative incidence rates of all second cancers at 10 years were 4.61 % and 4.09 % among tamoxifen-treated and non-tamoxifen-treated patients ( P = 0.62 ) , respectively , and the incidence rate ratio ( IRR ) for all second cancers was 1.06 ( 95 % confidence interval ( CI ) : 0.77 - 1.47 ) after adjustment of several covariates . The numbers of endometrial cancers was 9 and 3 among tamoxifen-treated and non-tamoxifen-treated patients , respectively , and the IRR was 2.37 ( 95 % CI : 0.64 - 8.77 , P = 0.20 ) . Of the 12 patients who developed endometrial cancer , 4 died of cancer ( for 3 of them , the cause of death was breast cancer ) , and the other 8 patients were alive as of March 1996 . Stomach cancer was the most frequent second cancer and the IRR was 1.34 ( 95 % CI : 0.76 - 2.38 , P = 0.31 ) . There was no substantial increase in any other type of gastrointestinal cancer such as colorectal and liver cancers among tamoxifen-treated patients . CONCLUSIONS The incidence and risk of second primary cancers associated with tamoxifen therapy is low . The potential benefit of adjuvant tamoxifen therapy in breast cancer patients outweighs the risk of second primary cancers for Japanese breast cancer patients BACKGROUND Both chemotherapy and tamoxifen are widely used either alone or in combination as adjuvant treatment following mastectomy . Despite the fact that both of them exhibit carcinogenic properties in experimental models , detailed reports on the incidence of new primaries following chemotherapy and /or tamoxifen in patients with early breast cancer are limited . PURPOSE To investigate the incidence of new primaries ( including opposite breast tumors and skin cancers ) in untreated patients and in patients treated with either tamoxifen or chemotherapy or with both modalities . PATIENTS AND METHODS A total of 1696 patients with early breast cancer , 1286 of whom were treated with either CMF-based adjuvant chemotherapy ( n = 410 ) , tamoxifen ( n = 656 ) or with a combination of the two ( n = 220 ) were considered for the present analysis . Patients were operated on between November 1983 and December 1991 and were followed up to June 1994 . Detailed information about second malignancies were available for all patients . RESULTS Overall , 53 new primaries , 19 of them opposite breast tumors , occurred in 53 patients . The actuarial cumulative incidence rates at 5 years were : 3.1 % ( 95 % CI : 1.4%-4.8 % ) in untreated patients ; 1.7 % ( 95 % CI : 0.0%-3.5 % ) in tamoxifen-treated patients ; 4.2 % ( 95 % CI : 1.3%-7.1 % ) in chemotherapy-treated patients and 2.6 % ( 95 % CI : 0.0%-5.2 % ) in the chemo-tamoxifen group ( all groups : P = n.s . ; chemotherapy-treated versus tamoxifen-treated : P = 0.01 ) . The corresponding figures , after exclusion of the patients with opposite-breast and skin tumors , were : untreated patients : 2 % ( 95 % CI : 0.6%-3.4 % ) ; tamoxifen-treated patients : 0.95 % ( 95 % CI : 0.0%-2.4 % ) ; chemotherapy-treated patients : 2.6 % ( 95 % CI : 0.4%-4.8 % ) ; chemotherapy plus tamoxifen : 1.65 % ( 95 % CI : 0.4%-3.8 % ) ; ( all groups : P = n.s . ; CT versus TAM P = 0.05 ) . Chemotherapy-treated patients showed a risk that was about two-fold that of the one to be expected in the general population . By contrast , a decrease in the total risk was observed in patients treated with tamoxifen . Patients who received chemotherapy and tamoxifen as well as those in the no-treatment group showed a risk which was comparable to that of the general population . CONCLUSIONS Adjuvant chemotherapy appears to increase the risk of second malignancies . By contrast , tamoxifen seems to exert an overall protective effect in this regard , and it also appears to counteract , at least partially , the carcinogenic effect of chemotherapy . IMPLICATION S While there is plenty of evidence that the benefit achieved by adjuvant chemotherapy considerably exceeds the risk of second malignancies , the indiscriminate use of chemotherapy should be avoided , particularly in patients with a low risk of relapse . Moreover , it seems reasonable to prefer tamoxifen over chemotherapy for patients likely to obtain comparable therapeutic benefit from antiestrogenic treatment 
    Output:
    
Patients with breast cancer should not undergo CRC screening at intervals different from the general population .