Complex sentence: Patients who received breast-conserving surgery plus radiation therapy had a lower DCIS recurrence rate than patients who received breast conserving surgery alone, and the use of radiation therapy did not have an effect on mortality.
Split into simpler sentences: Patients who received breast-conserving surgery plus radiation therapy had a lower DCIS recurrence rate than patients who received breast conserving surgery alone. The use of radiation therapy did not have an effect on mortality.