of breast cancer: The management of ductal carcinoma in situ
[10/03/2001; Canadian Medical Association Journal]
This article provides a summary of changes made by Health Canada’s
Steering Committee on Clinical Practice Guidelines for the Care
and Treatment of Breast Cancer to the article “Clinical practice
guidelines for the care and treatment of breast cancer: 5.
management of ductal carcinoma in situ (DCIS),” originally published
in 19981 (the 2001 update can be found online). Although there
are not many changes to the guideline, new studies have provided
more evidence to support the original recommendations.
DCIS of the breast is a proliferation of malignant-appearing cells
of the ducts and terminal lobular units of the breast that have
not breached the ductal basement membrane. Since more women are
having screening mammography, DCIS is being diagnosed more frequently.
In 1996, over 200000 Canadian women aged 50-69 participated
in 7 provincial screening programs. Of the 991 cancers detected,
171 were DCIS (17%, or 0.8 cases per 1000 women screened).
can be considered a precursor of invasive breast cancer and,
if left untreated, can develop into invasive disease in up to
35% of cases within 10 years.
Again the steering committee emphasizes the importance of careful
surgical removal of the area of DCIS and attention to meticulous
pathological processing and reporting. The most clinically useful
factors in terms of predicting local recurrence of the DCIS and
progression to invasive cancer are nuclear grade, presence of
necrosis, involvement of surgical margins and lesion size.
The original guideline recommended mastectomy, breast-conserving
surgery (BCS) plus radiotherapy or BCS alone as treatment options
for DCIS, and this recommendation has not changed substantially.
The use of breast irradiation after BCS was supported by the
results of 1 randomized trial in the 1998 guideline. A report
has since been published of a second randomized trial, in which
the European Organisation for Research and Treatment of Cancer
randomly assigned 1010 women with DCIS to either BCS or BCS plus
At a median follow-up of 4 years, the rate
of local recurrence was significantly lower in the group treated
by BCS plus radiotherapy than in the group treated by BCS alone
(9% v. 16%, p = 0.005). The survival rate was 99% in both groups.
A large retrospective study has emphasized the importance of
ensuring that there is a wide rim of normal tissue around the
excised tumour if there is consideration that a woman treated
with BCS might not have radiotherapy. The steering committee
feels that it is difficult to identify patients at such a low
risk of breast cancer recurrence that radiotherapy could be omitted
after BCS even though in such women the risk reduction in absolute
terms associated with radiotherapy may be small.
The 1998 guideline
stated that “omission of radiotherapy may be considered when
lesions are small and low grade, and when pathological assessment
shows clear margins.” The updated recommendation states
that “BCS should usually be followed by radiotherapy. Patients
with a sufficiently low risk of local recurrence with BCS alone
are difficult to identify.
However, BCS alone may be considered
after a careful discussion with the patient, if detailed pathological
assessment confirms that the lesion is small and does not have
high-grade nuclei or comedo-type necrosis and the surgical margins
are clear of disease. In addition, in such circumstances the
surgical excision should be cosmetically acceptable.”
In 1998 the steering committee concluded that evidence was not
available to support the use of tamoxifen in the treatment of
women with DCIS. Since then, the results were published of the
National Surgical Adjuvant Breast Project B-24 trial, in which
1804 women with DCIS who received BCS plus radiotherapy were
randomly assigned to receive tamoxifen or placebo.
At 5 years
the incidence of invasive breast cancer was significantly lower
in the tamoxifen group than in the placebo group (4.1% v. 7.2%,
p = 0.004); the corresponding incidence rates of recurrent DCIS
were 4.2% and 6.2% (p = 0.08). Tamoxifen can be associated with
The updated recommendation for DCIS states that “the
role of tamoxifen in the management of patients with DCIS continues
The potential benefits and risks should be discussed