Dr. Fowble's well-written review concludes that, in certain subgroups
of patients with breast cancer (ie, patients with primary tumors larger
than 5 cm, four or more positive axillary lymph nodes, or tumor involvement
of the pectoralis fascia), postmastectomy irradiation improves local control
and may result in a modest increase (10% or less) in the breast cancer-specific
survival rate. The paradigm that survival from breast cancer depends on
the eradication of occult micrometastases has led to a debate about the
extent of local therapy (surgery and/or irradiation) that is necessary.
Today, with the increasing use of induction (preoperative) chemotherapy
for tumor downstaging, the role of local therapy is becoming one of controlling
residual disease with an acceptable locoregional relapse rate and minimal
disfigurement or morbidity.
In surgery, this issue is exemplified by the recent questioning of the
necessity of axillary node dissection if systemic therapy is planned on
the basis of the features of the primary tumor rather than on the basis
of axillary nodal status. As with postmastectomy irradiation, a breast
cancer-specific survival benefit, if any, from the axillary node dissection
itself is probably small (less than 10%). The concern then becomes local
control. Can systemic therapy substitute for local therapy (eg, axillary
node dissection) if the axilla is clinically negative? As this review shows,
systemic therapy may decrease the locoregional recurrence rate, at least
in certain patient subsets. However, if the risk of locoregional recurrence
is high (20% to 30% relapse rate), the addition of irradiation to systemic
therapy provides optimal local control (5% to 10% relapse rate).
Clinical Significance of Reduced Locoregional Failure Rate
Is this additional reduction in the locoregional failure rate clinically
significant? The answer depends on whether the locoregional relapse can
be effectively treated if it occurs.
The likelihood of reestablishing local control of the postmastectomy
chest wall with delayed irradiation is only approximately 50%. Although
locoregional recurrence after mastectomy has historically been considered
a harbinger of distant metastases and subsequent death, selected patients
with locoregional recurrence experience a long distant disease-free interval
and occasionally long-term survival. The emotional impact on the patient
of experiencing a locoregional recurrence, especially as the first site
of relapse, should also be considered. Thus, the goal of local control
is best pursued at the initial treatment of the primary tumor.
Does this goal of local control outweigh the potential side effects
of irradiation? With the recent advances in radiation technology, the overall
morbidity of postmastectomy irradiation has substantially decreased. However,
further follow-up is needed to determine whether the risk of cardiovascular
disease associated with irradiation of the left chest wall will also decline.
Our practice guidelines at The University of Texas M. D. Anderson Cancer
Center call for postmastectomy irradiation for patients with tumors larger
than 5 cm, four or more positive axillary nodes, positive surgical margins,
dermal lymphatic involvement, or direct skin invasion. We do not use irradiation
for patients with microscopic extranodal axillary disease or small multicentric
primary tumors. As Fowble states, irradiation of the internal mammary nodes
for assumed occult disease has largely been abandoned as clinically irrelevant.
Finally, the patient's personal goals must be incorporated into the
treatment plan. An honest, open discussion of the disease and the anticipated
results from different treatment modalities often empowers the patient
to become an active participant in the decision-making process.