Long-term results of targeted intraoperative radiotherapy (Targit) boost during breast-conserving surgery.
OBJECTIVE
We have previously shown that delivering targeted radiotherapy to the tumour bed intraoperatively is feasible and desirable. In this study, we report on the feasibility, safety, and long-term efficacy of TARGeted Intraoperative radioTherapy (Targit), using the Intrabeam system.


METHODS
A total of 300 cancers in 299 unselected patients underwent breast-conserving surgery and Targit as a boost to the tumor bed. After lumpectomy, a single dose of 20 Gy was delivered intraoperatively. Postoperative external beam whole-breast radiotherapy excluded the usual boost. We also performed a novel individualized case control (ICC) analysis that computed the expected recurrences for the cohort by estimating the risk of recurrence for each patient using their characteristics and follow-up period.


RESULTS
The treatment was well tolerated. The median follow up was 60.5 months (range, 10-122 months). Eight patients have had ipsilateral recurrence: 5-year Kaplan Meier estimate for ipsilateral recurrence is 1.73% (SE 0.77), which compares well with that seen in the boosted patients in the European Organization for Research and Treatment of Cancer study (4.3%) and the UK STAndardisation of breast RadioTherapy study (2.8%). In a novel ICC analysis of 242 of the patients, we estimated that there should be 11.4 recurrences; in this group, only 6 recurrences were observed.


CONCLUSIONS
Lumpectomy and Targit boost combined with external beam radiotherapy results in a low local recurrence rate in a standard risk patient population. Accurate localization and the immediacy of the treatment that has a favorable effect on tumour microenvironment may contribute to this effect. These long-term data establish the long-term safety and efficacy of the Targit technique and generate the hypothesis that Targit boost might be superior to an external beam boost in its efficacy and justifies a randomized trial.
Vaidya
Jayant S
JS
Research Department of Surgery, Division of Surgery and Interventional Science, University College London, London, UK. jayant.vaidya@ucl.ac.uk
Baum
Michael
M
Tobias
Jeffrey S
JS
Wenz
Frederik
F
Massarut
Samuele
S
Keshtgar
Mohammed
M
Hilaris
Basil
B
Saunders
Christobel
C
Williams
Norman R
NR
Brew-Graves
Chris
C
Corica
Tammy
T
Roncadin
Mario
M
Kraus-Tiefenbacher
Uta
U
Sütterlin
Marc
M
Bulsara
Max
M
Joseph
David
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D016022:Case-Control Studies; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007432:Intraoperative Period; D015412:Mastectomy, Segmental / Q000379:methods*; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D018570:Risk Assessment; D047368:Tumor Burden