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Edited comments by Dr Wolmark
NSABP trial B-35: Anastrozole versus tamoxifen in DCIS
NSABP-B-35 is the next protocol in a generation of NSABP
DCIS trials: B-17 compared radiotherapy to no treatment, B-24 added tamoxifen
to lumpectomy and radiotherapy, and B-35, which opened in January 2003, compares
anastrozole to tamoxifen for five years. We're hoping that anastrozole will
be superior to tamoxifen, as it was in the ATAC trial; however, that trial
was powered to detect small differences in efficacy.
We debated considerably whether ER positivity should be required
for eligibility in B-35. Dr Craig Allred reanalyzed data from NSABP-B-24
and demonstrated benefit from tamoxifen only in those patients with ER-positive
DCIS. Ultimately, we decided to limit eligibility for B-35 to patients with
ER-positive DCIS. Only a small subset of women with DCIS - approximately
20 percent - is ER-negative. At the current time, I believe it is overly
restrictive and authoritarian to dictate that the community standard require
estrogen receptor assay prior to treating DCIS.
NSABP-B-32: The value of axillary dissection in patients
with negative sentinel lymph node biopsy
If we accepted the postulate that SLNB is accurate, then
conducting NSABP-B-32 would be unconscionable, because women with negative
axillary lymph nodes would be subjected to an unnecessary procedure with
its associated morbidity. However, we did not accept that postulate.
I am astounded that we are succeeding in enrolling 5,400
women in a trial that randomizes patients to SLNB alone or SLNB followed
by axillary dissection. This has been one of the NSABPs best-accruing protocols.
I'm grateful to the individuals who participated in the study and for the
commitment and persistence of Dr David Krag, who cajoled and convinced us that the trial should be initiated. The response to NSABP-B-32
from the surgical community has been remarkable, and we will meet our target
accrual this year.
Proposed NSABP trial evaluating partial breast irradiation
We have proposed a Phase III randomized, prospective trial
comparing traditional external beam to partial breast radiotherapy. The initial
sample size estimate for this trial was 6,300 women to show a 1.4 risk of
inferiority for interstitial radiotherapy.
We did not believe it was worth the investment, so we are
re-evaluating the sample size necessary to demonstrate the risk of 1.5, which
would likely be 3,000 patients. While the difference between a risk of 1.4
and 1.5 doesn't sound large, when the event rate is relatively small - six
percent to eight percent over a 10-year period - and you alter the power,
there's a significant difference in the overall number of patients required.
Proposed NSABP trial evaluating systemic therapy for locoregional
relapse
Ipsilateral breast tumor recurrence is a biologic event that
increases the risk of disseminated extramammary disease. The NSABP has always
been interested in launching a trial to evaluate systemic treatment for locoregional
relapse, but we were uncertain whether we could complete such a trial. We've
worked out a solution whereby we will conduct this trial in collaboration
with the International Breast Cancer Study Group (IBCSG). The NSABP would
be the North American principal for that trial, with CTSU participation.
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