Relationship between mammographic screening intervals and size and histology of ductal carcinoma in situ

OBJECTIVE. The objective of this study was to determine how the length of t ime between;mammographic screenings is related to the size, grade, and hist ology of mammographically detected ductal carcinoma in situ (DCIS). MATERIALS AND METHODS. We retrospectively reviewed 166 consecutive mammogra ms of women evaluated for DCIS with (n = 24) and without (n = 142) microinv asion. The size of the DCIS was determined by the maximum diameter as measu red on the mammogram. After pathologic analysis, DCIS was classified by his tologic architecture, nuclear grade, presence of microinvasion, and presenc e of multifocality. Four screening intervals were defined: annual (6-17 mon ths), biennial (18-29 months), triennial (greater than or equal to 30 month s), and first time. Patients were grouped according to screening intervals. The average age of all groups was 55 years. RESULTS. The annual group (mean size of DCIS, 1.69 cm) had significantly sm aller DCIS than did the biennial (mean size, 2.27 cm), triennial (mean size , 3.49 cm), or first time groups (mean size, 3.29 cm) (p=.003). Comedo hist ology was more frequently observed in patients screened biennially (73.7%) than in those screened annually (46.8%) (p=.05). High-grade nuclear histolo gy was more commonly seen in the biennial (76.3%) than in the annual (48.1% ) screening group (p =.008). We found no significant correlation between sc reening interval and the incidence of microinvasion and multifocality. CONCLUSION. Small, low-grade noncomedo DCIS was more common in the annual m ammographic screening group than in the biennial screening group. A direct relationship was found between DCIS size and length of screening interval: DCIS detected at annual screening was smaller than that found at biennial s creening, which in turn was smaller than DCIS revealed at triennial screeni ng. This study provides inferential support for annual screening mammograph y for DCIS detection and management.