Patient selection for partial breast irradiation by intraoperative radiation therapy: can magnetic resonance imaging be useful?—perspective from radiation oncology point of view

Abstract

The guidelines of the European and American Societies of Radiation Oncology (GEC-ESTRO and ASTRO) defined the selection criteria to offer partial breast irradiation (PBI) after lumpectomy in patients with low risk breast cancer regardless pre-operative staging. A recent publication by Tallet et al.explored the impact of preoperative magnetic resonance imaging (MRI) on patient eligibility for PBI. From their study, an ipsilateral BC was detected in 4% of patients, excluding these patients from intraoperative radiotherapy (IORT). The authors suggested that preoperative MRI should be used routinely for patient's candidate to IORT, because of the rate of ipsilateral breast cancer detected. In view of Tallet's article, we analyzed some aspects of this issue in order to envisage some possible perspective on how to better identify those patients who could benefit from PBI, especially using IORT. From historical studies, the risk of breast cancer recurrence outside index quadrant without irradiation is in the range of 1.5-3.5%. MRI sensitivity for detection of invasive cancer is reported up to 100%, and it is particularly useful in dense breast. Other imaging technique did not achieve the same sensibility and specificity as conventional MRI. Of note, none of randomized trials published and ongoing on PBI included preoperative MRI as part of staging. To perform a preoperative MRI in PBI setting is an interesting issue, but the available data suggest that this issue should be preferably studied in the setting of prospective clinical trials to clarify the role of MRI and the clinical meaning of the discovered additional foci.

Single institute experience of intraoperative radiation therapy in early-stage breast cancer

“…MRI precisely defines tumor size, unifocality, and presence of lymph nodes with a sensitivity of around 100%, especially in dense breasts. [35][36][37] Tallet et al [38] demonstrated that a preoperative MRI can aid in detecting 31% more breast abnormalities which were not visible on mammography or ultrasound. Although not mandatory, a preoperative MRI should be encouraged for patients who chose to receive IORT.…”

“…It is reasonable to incorporate high resolution images, such as Magnetic resonance imaging (MRI), to screen, and filter out unsuitable candidates at the beginning. MRI precisely defines tumor size, unifocality, and presence of lymph nodes with a sensitivity of around 100%, especially in dense breasts [35–37] . Tallet et al [38] demonstrated that a preoperative MRI can aid in detecting 31% more breast abnormalities which were not visible on mammography or ultrasound.…”

Multi‐parametric MRI (mpMRI) for treatment response assessment of radiation therapy

“…One approach is that patients can undergo intra‐operative RT (IORT) at the time of breast‐conserving surgery. Preoperative bilateral breast MRI can detect occult lesions in the ipsilateral and contralateral breasts, and provide a valuable tool in the proper selection of patients best suited for IORT 135–137 . Even in highly selected, favorable risk patients, MRI‐detected additional lesions may change surgical and RT recommendations in a substantial percentage of patients 135 .…”

“…Preoperative bilateral breast MRI can detect occult lesions in the ipsilateral and contralateral breasts, and provide a valuable tool in the proper selection of patients best suited for IORT. [135][136][137] Even in highly selected, favorable risk patients, MRI-detected additional lesions may change surgical and RT recommendations in a substantial percentage of patients. 135 Another approach of APBI is pre-operative delivery of external beam irradiation in a single or fractionation delivery.…”