This study result showed that >5 years' length of oral contraceptive pills use increased breast cancer risk in Southeast Asian women with risk opportunity was more than doubled. The results were also homogeneous which means the studies will give consistent or insignificantly different if the study performs at the same time and place.
Furthermore, Indonesia has been known that this country has the greatest risk opportunities for breast cancer, followed by Thailand and Malaysia. Our study findings described possibly relate to the high rates of oral contraceptive application in those country mentioned in advance [11,13,24].
The previous studies found breast cancer incidence related to oral contraceptive application in several ethnicities. Non-Hispanic Caucasians have the highest percentage of oral contraceptive application (55%) as well as the highest number of incidence of breast cancer (6%). Interestingly, the lowest proportion of oral contraception application (37.5%) yet being the second-highest in the percentage of breast cancer incidence (5.7%) in non-Hispanic/Pacific Islanders. Non-Hispanic African-Americans and Hispanics have the same percentage of oral contraceptive application (52.2%) with a relatively lower figure of breast cancer incidence with 3.8% and 4.7%, respectively . Our study had found the percentage of oral contraceptive application with breast cancer incidence followed by a range of 3.7-13.9%. The figure was higher in some ethnic than others as we had described, possibly due to oral contraception application percentage is known was also relatively high in the Southeast Asian region with 12.8% .
Based on the risk opportunities found, it was demonstrated that there was a higher breast cancer risk in Southeast Asian regions with ≤ 5 years' duration of oral contraceptive application was OR = 1.21 (95% CI 0.96-1.52), while >5 years' duration of oral contraceptive use was OR = 2.66 (95% CI 1.79-3.94). Previous study also had found risk opportunities of breast cancer related to oral contraceptive included non-Hispanic Caucasians (HR = 1.09 (95% CI 1.01-1.18), non-Hispanic African Americans (HR = 0.95 (95% CI 0.64-1.42), and non-Hispanic Asian / Pacific Islander (HR = 0.93 (95% CI 0.63-1.39) .
Data from 39 case-control studies led from 1980 to 2006 have discovered a association of contraceptive pills with breast cancer among premenopausal . Another study recommended that present utilization of contraceptive pills which substance is estrogen appears to somewhat elevate the breast cancer risk. A few factors adding to the advancement of breast disease incorporate hormones, which is estrogen itself [27-29]. The use of contraceptive pills which contains estrogen the breast tissue to be presented to large amounts of hormones for longer periods. That estrogen stimulates growth factors that exist in breast cancer cells resulting in tumor progression [30,31].
The previous research on the impact of age at beginning of utilization of the pill on the rate of breast cancer growth presumed that ladies that had begun utilizing the pill before 18 years old contracted disease 4 years sooner . In a study, the researcher accepts prolonged use increases the risk. Another study found a relative risk of 2.2 with over 10 years of length of using . The other study found the afinity between breast cancer and contraceptive pills use (OR=2.11). The investigation results show that women that utilization preventative pills have more noteworthy requirements for preventive and screening measures .
Based on data oral contraceptive is the most common means of contraception in the world and Southeast Asian countries, utilized by millions of women [35-37]. According to the duration of oral hormonal contraceptives use more than 5 years will increase breast cancer risk which will be higher compared to those who have never used hormonal contraception. If a person stops taking hormonal contraception for 5 years then she will have no risk of breast cancer. This result is supported by a theory found about the imbalance of the hormones estrogen and progesterone used in hormonal contraception [4,38,39]. This hormonal imbalance has resulted in a feedback mechanism that can physiologically control the number of hormones in the body when it is not functioning properly . It was triggered by the estrogen receptors up regulation so that the number of hormones continues to increase. Exposure to sexual hormones over a period of more than 5 years will increase the proliferation of breast cells and increase breast cancer stem cell mitosis .
A meta-analysis data in this study has several limmitations. First, there were 2 potential articles should be included in this study but the full-text articles are inavailable. Second, there were 2 studies are also potentially included in data analysis yet the data presented were incomplete and different risk factors in the calculations were also performed.
Based on our analysis, as we found of the significant association of oral hormonal contraceptives use with breast cancer risk as well as increase for more than five years' duration of contraceptive pills use, we suggest people to select effective and efficient long-term contraceptive methods to prevent pregnancy, yet safe in accordance with infertility and breast cancer risk. Another suggestion is breast cancer screening programs are necessary for Southeast Asian countries.