Background: Interval carcinoma is defined as a carcinoma detected between two mammographic screening rounds after a negative screening. By some authors these carcinomas are considered to be more aggressive than screen-detected carcinomas.
Methods: In a group of 937 patients referred for breast cancer in the period 1975-1990, 76 interval carcinoma patients were treated. In a retrospective study the outcome was studied of patients with an interval carcinoma in comparison with patients with screen-detected carcinomas and of patients with clinically detected carcinomas outside the screening program.
Results: No significant difference was found in the 5-year and 10-year disease-free survival of patients with interval carcinoma (80%, 68%) and the screen-detected group (89%, 81%) (P = 0.12). The interval group did significantly better than the patients with carcinomas detected outside the screening program (P = 0.03).
Conclusion: Interval-detected cancers for patients in the screening program had an outcome intermediate between patients with screen-detected cancers and patients with cancers detected outside the screening program. The difference between interval-detected cancers and cancers detected outside the screening program was significant, whereas the difference between screen-detected and interval cancers was not.