Outcome of Screening MRI in Premenopausal Women as a Function of the Week of the Menstrual Cycle.

The objective of our study was to determine whether there are differences in outcome of screening MRI examinations in premenopausal women as a function of the week of the menstrual cycle in which the study was performed. The reports of consecutive screening MRI examinations performed from January 1, 2011, through December 31, 2012, of premenopausal women were reviewed. Only cases for which the 1st day of the last menstrual cycle was documented were included. Associations between the week of the menstrual cycle, degree of background parenchymal enhancement (BPE), final BI-RADS assessment, positive predictive values (PPVs), cancer detection rate (CDR), sensitivity, and specificity were noted. A total of 1536 MRI examinations of 1239 women were performed. Distribution of MRI examinations by menstrual cycle week was as follows: 21.8% ( = 335) in week 1, 35.4% ( = 544) in week 2, 23.4% ( = 360) in week 3, and 19.3% ( = 297) in week 4. In the overall comparison, there was no significant difference in BPE, BI-RADS assessment, PPV1, PPV2, PPV3, CDR, sensitivity, or specificity by the week of the menstrual cycle. When outcomes for cases with MRI performed in week 2 were compared with those of cases with MRI performed in weeks 1, 3, and 4 combined, there was no significant difference in the same outcome measures. There was no evidence of a difference in outcomes of screening MRI examinations as a function of the week of menstrual cycle in which the study is performed. The results of our study do not support the need for screening MRI to be performed in week 2 of the menstrual cycle.