# The Rationale for Postoperative MRI Surveillance in Lobular Breast Cancer

## TL;DR

This study shows that MRI is better than mammography at detecting new breast cancers after surgery, especially for patients with invasive lobular carcinoma.

## Contribution

The study demonstrates that MRI can detect new malignancies in invasive lobular carcinoma patients that mammography misses.

## Key findings

- New breast malignancies were more common in patients with invasive lobular carcinoma.
- MRI detected all new malignancies in invasive lobular carcinoma patients, while mammography missed two of three cases.
- Most new malignancies occurred within five years of initial treatment.

## Abstract

Mammography remains the primary method for postoperative follow-up in breast cancer, despite its known limitations in detecting certain tumor subtypes. Invasive lobular carcinoma is a common type of breast cancer that often grows without forming a distinct mass, making recurrences more difficult to detect on standard imaging. This study evaluated whether magnetic resonance imaging can more effectively detect new breast malignancies after surgery, particularly in patients with invasive lobular carcinoma. In this retrospective study, new breast malignancies were more frequent in patients with invasive lobular carcinoma and were more often detected by magnetic resonance imaging than by mammography. These findings suggest that magnetic resonance imaging may provide added value in the follow-up of patients with invasive lobular carcinoma and may help improve detection of new breast malignancies post-surgery.

Background/Objectives: Postoperative breast cancer imaging follow-up primarily relies on annual mammography, while magnetic resonance imaging is reserved for selected cases. Invasive lobular carcinoma has growth characteristics that can limit detection on conventional imaging and may influence recurrence patterns. This study aimed to determine whether histological type can help guide postoperative magnetic resonance imaging follow-up. Secondary objectives were to assess inter-reader agreement and evaluate timing of new breast malignancies in relation to tumor features. Methods: This retrospective, single-center study included patients with invasive breast carcinoma diagnosed during 2015 and 2016 who underwent surgery, had pre-treatment magnetic resonance imaging, at least one postoperative magnetic resonance imaging within five years, and a minimum follow-up of seven years. Clinical, pathological, and imaging data were collected. New breast malignancies included both local recurrences and second primary tumors. Two radiologists independently reviewed postoperative magnetic resonance imaging examinations in patients, and inter-reader agreement was assessed using Cohen’s kappa coefficient. Results: Seventy-seven patients with 80 tumors were included. Six patients (8%) developed a new breast malignancy. New malignancies were more common in patients with invasive lobular carcinoma (p = 0.04). Magnetic resonance imaging detected all new malignancies in patients with primary invasive lobular carcinoma, whereas mammography missed two of three cases. New breast malignancies were classified as early (within 5 years of diagnosis and initial treatment) or late (at or after 5 years); most occurred within five years, with one late occurrence at 5.6 years. Inter-reader agreement for both magnetic resonance imaging and mammographic detection showed complete concordance (κ = 1.00). Conclusions: Patients with primary invasive lobular carcinoma had a higher rate of new breast malignancies, and postoperative magnetic resonance imaging detected new malignancies missed by mammography. These findings suggest that tumor histology may be relevant when considering postoperative imaging and that patients with invasive lobular carcinoma may benefit from magnetic resonance imaging follow-up.