Recurrence and Survival in the American Society of Breast Surgeons (ASBS) MammoSite^® RTS Registry Trial

Article Outline

• Purpose/Objective(s)
• Materials/Methods
• Results
• Conclusions
• Copyright

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Purpose/Objective(s) 

Accelerated partial breast irradiation (APBI) using the MammoSite^® RTS has been performed for over 5 years. Single institution trials have reported their local and regional recurrence rates along with survival; however, the number of patients in these trials are small. This study reports the recurrence and survival data from the American Society of Breast Surgeons (ASBS) MammoSite^® RTS Registry Trial.

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Materials/Methods 

The registry captured data from 1440 women with 1449 primary early stage breast cancers (9 bilateral) were treated with the MammoSite^® device from May 2002 until September 2004. Ipsilateral breast tumor recurrences (IBTR), regional recurrences and survival were recorded and potential factors that could be related were evaluated. Statistical significance was analyzed using SAS.

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Results 

With a median follow-up of 36 months, there were 28 IBTR (10 in the tumor bed and 18 elsewhere) for a 3 year actuarial rate of 2.15%. There were 3 axillary recurrences (3 yr actuarial 0.26%), 11 contralateral new primaries (3 yr actuarial 0.74%), and 16 patients failed distantly (3 yr actuarial 1.23%). The first 400 consecutive cases were examined and had a median follow-up of 44 months. In that group, there were 8 IBTR (2 tumor bed and 6 elsewhere) for a 4 yr actuarial survival of 2.65%, 1 axillary recurrences (4 yr actuarial 0.27%), 6 distant failures (4 yr actuarial 2.16%), and 2 contralateral new primaries (4 yr actuarial 0.44%). Overall four year actuarial survival was 93.9% with a disease-free survival of 88.9% and cancer-specific survival of 100.0%.

The following factors were examined for association with IBTR: margin status (positive vs negative), nodal status, tumor location (inner vs outer), histologic grade, EIC, histology (ductal vs other), age (<45 vs 45+), tumor size (<2 vs 2+), bra size (a/b vs c/d), placement method (OR vs office), tamoxifen use, and chemotherapy use. None of the variables achieved statistical significance; however, the presence of EIC (p = 0.0588), non-use of Tamoxifen (p = 0.089), and high histologic grade (p = 0.0951) approached significance for increased IBTR.

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Conclusions 

APBI with the MammoSite^® RTS results in low IBTR, axillary recurrence and acceptable cancer specific survival. The first 400 consecutive cases with almost 4 years of follow-up had essentially the same recurrence rates as the overall group. Factors known to increase IBTR from previous studies appear to be related to increased IBTR after treatment with the MammoSite^® RTS.