Contralateral breast cancers following treatment for initial breast cancers in women.

The risk of a second primary cancer arising in the contralateral breast following treatment of an initial breast cancer was evaluated for 1,630 women whose first breast cancers were diagnosed and treated at University of California at Los Angeles between 1955 and 1979. Based on follow-up data ranging from 5 to 30 years, the rate of development of nonsimultaneous contralateral breast cancers was slightly in excess of 2.5 per 1,000 person-years at risk. There was no detectably significant difference in the frequency of second primary cancers related to the type of treatment of the first cancers, whether that was surgery, radiation therapy, or surgery plus radiation therapy.