Breast carcinoma diagnosis, treatment, and prognosis before and after the introduction of mass mammographic screening

Background: The introduction of breast carcinoma screening leads to early detection and is believed to reduce mortality and increase the proportion of patients for whom breast-conserving surgery is possible.

Methods: In 1992, a population-based mammographic screening program was introduced in the Dutch city of Tilburg and its surroundings; the program achieved total coverage in 1996. The authors examined the effects of this screening program by investigating disease stage, treatment, and survival among women diagnosed with breast carcinoma at a teaching hospital in Tilburg during the periods 1985-1991 and 1992-1999.

Results: Between January 1, 1985, and December 31, 1999, 1400 patients were diagnosed with breast carcinoma. Among patients ages 50-69 years, the proportion of TNM Stage I breast carcinoma increased from 24% in 1985-1991 to 45% in 1992-1999 (P<0.001). The proportion of patients age <50 years with invasive breast carcinoma who underwent breast-conserving surgery decreased from 45% to 33% (P=0.011). Among patients ages 50-69 years, the overall survival rate during the period from 1992 to 1999 was significantly greater than the corresponding rate during the period from 1985 to 1991 (P=0.0009). Even after adjustments were made for tumor stage and patient age, a slight reduction in mortality risk was observed in this age group. No difference in stage distribution or prognosis was found among patients age <50 years or among patients age > or =70 years. Of the 168 invasive malignancies found in patients ages 50-69 years between 1997 and 1999, 68 (40%) were detected by the screening program, 47 (28%) were interval malignancies, and 53 (32%) were detected in nonparticipants or in women who did not participate in 1 or more screening rounds. Patients with screen-detected tumors had a much more favorable prognosis than did patients with interval malignancies (P=0.0018) or patients with clinically detected breast carcinoma (P<0.0001).

Conclusions: Between 1992 and 1999, after the introduction of breast carcinoma screening, improved prognosis and more favorable tumor stage were observed among patients ages 50-69 years. Even after the screening program was fully implemented in 1996, the majority of invasive malignancies still were detected between screening rounds or in patients who did not participate in the program.