Cindy:  There have been a couple of articles about women who breastfed
after lumpectomy and radiation.  I don't have the references handy, but
a significant proportion had very little milk on the affected side
(although some did actually produce enough milk), but there was no problem
breastfeeding on the opposite side.

The physician's concern that breastfeeding will promote cancer in the
remaining breast is not based on good physiologic reasoning.  High
estrogen states (such as pregnancy, HRT) may promote the growth of cancer,
but breastfeeding is a *low* estrogen state.  Therefore, one would not
expect breastfeeding to increase the risk.  One would hope that
breastfeeding may even decrease her risk, although from my reading of the
literature on breast cancer risk reduction from breastfeeding, it's most
likely effective when practiced during earlier years.  I would imagine
(though I don't really know), that once a woman has a cancer,
breastfeeding will have little impact on further breast cancer reduction.
Still, at the very least it is neutral in its effect and may be
protective.

The main concern has to do with surveillance for a new cancer in the
remaining breast.  Regardless of how this mother feeds her baby, she is
already at increased risk of breast cancer in that breast.  It is common
practice to do regular mammograms and exams for early detection.  Although
mammograms can certainly be done in a woman who is lactating, they are
harder to interpret and possibly more likely to yield a false negative
result.  This is a situation in which normal nursing for 3 to 4 years may
not be advisable, and abbreviated nursing of only 6 to maybe 12 months may
be more prudent, although this should be the mother's choice, presented
with the above information.

Hope this helps, Regards, Alicia Dermer, MD, IBCLC.