Improved breast cancer survival following introduction of an organized mammography screening program among both screened and unscreened women: a population-based cohort study.
BACKGROUND
Mammography screening reduces breast cancer mortality through earlier diagnosis but may convey further benefit if screening is associated with optimized treatment through multidisciplinary medical care. In Norway, a national mammography screening program was introduced among women aged 50 to 69 years during 1995/6 to 2004. Also during this time, multidisciplinary breast cancer care units were implemented.


METHODS
We constructed three cohorts of breast cancer patients: 1) the pre-program group comprising women diagnosed and treated before mammography screening began in their county of residence, 2) the post-program group comprising women diagnosed and treated through multidisciplinary breast cancer care units in their county but before they had been invited to mammography screening; and 3) the screening group comprising women diagnosed and treated after invitation to screening. We calculated Kaplan-Meier plots and multivariable Cox proportional hazard models.


RESULTS
We studied 41,833 women with breast cancer. The nine-year breast cancer-specific survival rate was 0.66 (95%CI: 0.65 to 0.67) in the pre-program group; 0.72 (95%CI: 0.70 to 0.74) in the post-program group; and 0.84 (95%CI: 0.80 to 0.88) in the screening group. In multivariable analyses, the risk of death from breast cancer was 14% lower in the post-program group than in the pre-program group (hazard ratio 0.86; (95%CI: 0.78 to 0.95, P = 0.003)).


CONCLUSIONS
After nine years follow-up, at least 33% of the improved survival is attributable to improved breast cancer management through multidisciplinary medical care.
Kalager
Mette
M
The Cancer Registry of Norway, P,O,B 5313 Majorstuen, N-0304 Oslo, Norway. mette.kalager@kreftregisteret.no
Haldorsen
Tor
T
Bretthauer
Michael
M
Hoff
Geir
G
Thoresen
Steinar O
SO
Adami
Hans-Olov
HO
D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality / Q000628:therapy; D002173:Cancer Care Facilities / Q000458:organization & administration / Q000706:statistics & numerical data; D015331:Cohort Studies; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008327:Mammography / Q000706:statistics & numerical data*; D019221:Mandatory Reporting; D008403:Mass Screening / Q000458:organization & administration / Q000706:statistics & numerical data*; D008875:Middle Aged; D009313:National Health Programs; D009664:Norway / Q000453:epidemiology; D015397:Program Evaluation; D016016:Proportional Hazards Models; D012042:Registries; D015996:Survival Rate