True local recurrence rate in the conserved breast after magnetic resonance imaging-targeted radiotherapy.
OBJECTIVE
Better accuracy of local radiotherapy may substantially improve local control and thus long-term breast cancer survival. Magnetic resonance imaging (MRI) has high resolution and sensitivity in breast tissue and may depict the tumor bed more accurately than conventional planning techniques. A postoperative complex (POCx) comprises all visible changes thought to be related to surgery within the breast and acts as a surrogate for the tumor bed. This study reports on local recurrence rates after MRI-assisted radiotherapy planning to ensure adequate coverage of the POCx.


METHODS
Simple opposed tangential fields were defined by surface anatomy in the conventional manner in 221 consecutive patients. After MRI, fields were modified by a single radiation oncologist to ensure encompassment of the POCx with a 10-mm margin. Genetic analysis was performed on all local relapses (LRs) to distinguish true recurrences (TRs) from new primaries (NPs).


RESULTS
This was a high risk cohort at 5 years: only 9.5% were classified as low risk (St Gallen): 43.4% were Grade 3 and 19.9% had surgical margins <1 mm; 62.4% of patients received boosts. Adjustments of standard field margins were required in 69%. After a median follow-up of 5 years, there were 3 LRs (1.3%) as the site of first relapse in 221 patients, comprising two TRs (0.9%) and one NP (0.4%).


CONCLUSIONS
Accurate targeting of the true tumor bed is critical. MRI may better define the tumor bed.
Whipp
Elisabeth
E
University Bristol Hospitals Trust, Marlborough Street, Bristol BS1 3NU, United Kingdom. liz@lizwhipp.com
Beresford
Mark
M
Sawyer
Elinor
E
Halliwell
Michael
M
D000328:Adult; D000368:Aged; D001365:Axilla; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D017024:Chemotherapy, Adjuvant; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D019656:Loss of Heterozygosity; D008197:Lymph Node Excision / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D011879:Radiotherapy Dosage; D049291:Seroma / Q000175:diagnosis; D047368:Tumor Burden