In this article :
http://news.independent.co.uk/uk/hea...cle1090208.ece
the effect of artificial light during sleeping time on cancer risk is studied.
For those women who are NED, a good nightly sleep in complete darkness might help in preventing or in delaying recurrence.
The melatonin & human growth hormones which have an influence on cancer risk are secreted during uninterrupted nightime sleep.
Some commentators have speculated that the relatively low incidence of cancer in people born blind is the result of higher secretion of melatonin resulting from the brain being unable to perceive light.
Also the stress reduction afforded by a good night of sleep keeps the cortisol hormone from rising which is also favorable.