(41,42) The presence of LCIS at margins in association with IC is not associated with an increased risk for IBTR. (43,44) For practical purposes, classical LCIS should be considered a benign neoplasm, and in fact LCIS has been removed from the Tis classification in the 8th edition of the AJCC (American Joint Committee on Cancer) Cancer Staging Manual.
(1) The extent of DCIS in excision specimens is clinically relevant because it correlates with the presence of residual disease following re-excision, (3-6) and perhaps more importantly because it correlates with the risk of IBTR. (7-10) In addition, larger DCIS lesions are associated with a higher probability of finding areas of invasion.
In BCT, omission of radiation can result in IBTR rates of 30-40%, which then necessitates salvage mastectomy and possible compromise on long-term survival.
Additionally, larger tumor size and lymphatic vessel invasion have been reported as risk factors for ipsilateral breast tumor recurrence (IBTR).
Of the 8 IBTR, 3(37.5%) occurred in patients with ER negative invasive tumors (2 triple negative, 1 ER negative/HER2/neu positive).
Table 4 shows the tumor characteristics and surgical management of the patients experiencing an IBTR. Five (62.5%) of the 8 IBTR were treated with repeat breast conservation with 2 patients agreeing to additional radiation therapy (1 WBI, 1 APBI).
In addition, we evaluated individual clinicopathologic features to identify factors predictive of IBTR in patients treated with balloon-based brachytherapy.
We observed a 4-year actuarial IBTR rate of 5.1% for the entire cohort.
Due to the observed excess of IBTR in the IORT group of the ELIOT trial, authors reasoned that IORT could be incorporated into clinical practice using two approaches.
For example, in the ELIOT trial, multivariate analysis of characteristics associated with local relapse revealed that tumor size greater than 2 cm, the presence of four or more positive lymph nodes, poorly differentiated tumors, and triple-negative subtype were independent risk factors for IBTR. Furthermore, when trial participants were grouped based on the presence of one or more of these risk factors, the risk of IBTR was 11.3% at five years compared to 1.5% in women with none of these features.
At five years, the rate of IBTR for suitable, cautionary, and unsuitable groups was 1.5%, 4.4%, and 8.8%, respectively (P = 0.0003), indicating that the ASTRO guidelines translate well to patients treated with the ELIOT technique as a monotherapy [13, 29].
Other series have investigated the use of breast IORT as a technique in the setting of reirradiation for IBTR [33, 34].