Preoperative breast MRI positively impacts surgical outcomes of needle biopsy–diagnosed pure DCIS: a patient-matched analysis from the MIPA study
Authors: Cozzi Andrea , Di Leo Giovanni , Houssami Nehmat , Gilbert Fiona J. , Helbich Thomas H. , Álvarez Benito Marina , Balleyguier Corinne , Bazzocchi Massimo , Bult Peter , Calabrese Massimo , Camps Herrero Julia , Cartia Francesco , Cassano Enrico , Clauser Paola , de Lima Docema Marcos F. , Depretto Catherine , Dominelli Valeria , Forrai Gábor , Girometti Rossano , Harms Steven E. , Hilborne Sarah , Ienzi Raffaele , Lobbes Marc B. I. , Losio Claudio , Mann Ritse M. , Montemezzi Stefania , Obdeijn Inge-Marie , Aksoy Ozcan Umit , Pediconi Federica , Pinker Katja , Preibsch Heike , Raya Povedano José L. , Rossi Saccarelli Carolina , Sacchetto Daniela , Scaperrotta Gianfranco P. , Schlooz Margrethe , Szabó Botond K. , Taylor Donna B. , Ulus Sila Ö. , Van Goethem Mireille , Veltman Jeroen , Weigel Stefanie , Wenkel Evelyn , Zuiani Chiara , Sardanelli Francesco 
Published: November 2023

Abstract
Objectives
To investigate the influence of preoperative breast MRI on mastectomy and reoperation rates in patients with pure ductal carcinoma in situ (DCIS).

Methods
The MIPA observational study database (7245 patients) was searched for patients aged 18–80 years with pure unilateral DCIS diagnosed at core needle or vacuum-assisted biopsy (CNB/VAB) and planned for primary surgery. Patients who underwent preoperative MRI (MRI group) were matched (1:1) to those who did not receive MRI (noMRI group) according to 8 confounding covariates that drive referral to MRI (age; hormonal status; familial risk; posterior-to-nipple diameter; BI-RADS category; lesion diameter; lesion presentation; surgical planning at conventional imaging). Surgical outcomes were compared between the matched groups with nonparametric statistics after calculating odds ratios (ORs).

Results
Of 1005 women with pure unilateral DCIS at CNB/VAB (507 MRI group, 498 noMRI group), 309 remained in each group after matching. First-line mastectomy rate in the MRI group was 20.1% (62/309 patients, OR 2.03) compared to 11.0% in the noMRI group (34/309 patients, p = 0.003). The reoperation rate was 10.0% in the MRI group (31/309, OR for reoperation 0.40) and 22.0% in the noMRI group (68/309, p < 0.001), with a 2.53 OR of avoiding reoperation in the MRI group. The overall mastectomy rate was 23.3% in the MRI group (72/309, OR 1.40) and 17.8% in the noMRI group (55/309, p = 0.111).

Conclusions
Compared to those going directly to surgery, patients with pure DCIS at CNB/VAB who underwent preoperative MRI had a higher OR for first-line mastectomy but a substantially lower OR for reoperation.

Clinical relevance statement
When confounding factors behind MRI referral are accounted for in the comparison of patients with CNB/VAB-diagnosed pure unilateral DCIS, preoperative MRI yields a reduction of reoperations that is more than twice as high as the increase in overall mastectomies.

Key Points
• Confounding factors cause imbalance when investigating the influence of preoperative MRI on surgical outcomes of pure DCIS.
• When patient matching is applied to women with pure unilateral DCIS, reoperation rates are significantly reduced in women who underwent preoperative MRI.
• The reduction of reoperations brought about by preoperative MRI is more than double the increase in overall mastectomies.