Abstract P6-05-02: Breast cancer increased risk on women using combined oral contraceptive
Authors: Fenile R , Nazario ACP , Simoes CM 
Published: March 2017

The most controversial aspect in relation to oral hormonal contraception is the risk of developing breast cancer. Knowledge of the factors that influence the proliferation of normal breast epithelium is essential to understanding carcinogenesis and proliferative activity can be assessed by various techniques, including the immunohistochemical analysis of Ki 67.

In this work, we aim to compare the overall proliferative activity of breast after 3 cycles of combined oral contraceptive with a natural cycle and with that presented after only one cycle. Were selected 65 women attended in the period July 2006 to February 2007. These underwent excision of breast lump and breast tissue macroscopically regular adjacent to the node, lying this at least 1 cm. The patients were divided into two groups: group A, consisting of 20 women using three cycles of combined oral contraceptive consisting of 150 ug levonorgestrel and 30 ug of ethinyl estradiol, and the group B consisting of 35 women with natural cycles eumenorrheic , ie not used any hormonal medication. In the fourth month after initiation of use of the ACO, the group A patients were divided into four groups according to the use of the contraceptive. The A1 group (5 patients) in the first week; A2 (5 patients) in the second week; A3 (5 patients) in the third week and the A4 (5 patients), the break of the week .

Results: The highest levels of Ki67 count occurred in the third (16.65%) and fourth week (16.56 %) similar to one another. Additionally, it is noted that the average pause week count was greater than the first week (10.25%) and of the second week (8.52%), which in turn were not distinct. When comparing the use of 3 cycles with 1 cycle, we found that there was no difference in Ki67 count levels by the time the first two weeks. However, note that the Ki67 levels were higher in women who used contraceptives for longer both in the third week as the week's break.

Measures summary score * Ki-67 (%) by contraceptive use time over the weeksContraception useMediaMinimumMaximusNumberpWeek 1    0,1801 month use7,022,4418,3811 3 monthas use10,425,6118,345 Week 2    0,1801 month use5,461,1313,1711 3 months use8,525,6610,205 Week 3    0,0051 month use4,772,0411,8411 3 months use16,665,5229,305 Week 4    0,0011 month use4,440,209,789 3 months use16,6911,2922,915                   

In conclusion, the proliferative activity of artificial cycle was significantly higher than the natural cycle, and after three cycles, showed higher rates of proliferation in the third and fourth weeks of the menstrual cycle, representing increased carcinogenesis and possible increased breast cancer risk. More studies including compensatory apoptosis must be considerer to confirm this hipothesis.

Measures summary score * Ki-67 (%) by use of OHC for three months over the weeks and the natural cycle MediaMinimumMaximunNumberpWeek 1    0,0033 months use10,425,6118,345 natural1,100,092,449 Week 2    0,0103 months use8,525,6610,205 Natural3,890,709,5010 Week 3    0,0033 months use16,665,5229,305 Natural2,720,308,5610 Week 4    0,0043 months use16,6911,2922,915 Natural5,391,2015,5511                   

Citation Format: Fenile R, Nazario ACP, Simoes CM. Breast cancer increased risk on women using combined oral contraceptive [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-05-02.