Study shows endometriosis increases risk for multiple surgeries and ovarian cancer

Endometriosis increases risk of multiple surgeries and ovarian cancer

ARTICLE SUMMARY
A recent study published in the British Journal of Obstetrics & Gynaecology found that women with endometriosis have a higher risk of undergoing multiple gynecologic surgeries and developing ovarian cancer than those without the disease.

Drawing from a cohort of over 281,937 women, this is the largest and first study of its kind to evaluate the long-term surgical and cancer risks in women with endometriosis.  Women who’ve had symptomatic endometriosis for a long time usually already know that they’ve likely undergone more surgeries than average. However, until now, researchers had never actually studied this potential effect in a large population and over a long period of time. Unlike other studies, the researchers also evaluated the long-term risks of all cancers, both gynecologic and non-gynecologic forms.

The research team obtained these results by analyzing three decades (1981-2010) of patient records from a Scottish database.  A total of 17,834 women with surgically-confirmed endometriosis were then compared to three different control groups without signs of endometriosis, including 83,303 with a negative finding for endometriosis at laparoscopy, 162,966 with no signs of endometriosis after a laparoscopic sterilization (tubal ligation), and 17,834 age-matched women from the general population, also without signs of endometriosis.

Based on hazard ratio calculations, endometriosis conferred a nearly 6 times increased risk of multiple surgeries compared to healthy controls. Furthermore, women with endometriosis faced a median time to additional surgery of less than 2 years, a significantly shorter period than the other control groups. As well, 16.6% of women with endometriosis had 4 or more surgeries within the study period, and 1 in 5 had either one or both ovaries removed. Women with endometriosis also faced a 1 in 5 risk of hysterectomy, compared to the healthy control group which had only a 1 in 50 rate.

Further surgery was not necessarily for the recurrence of endometriosis, making it difficult to draw inferences about the true incidence of endometriosis recurrence rates after surgery. Rather, the researchers looked at the risk for undergoing several different types of gynecologic surgeries, which included not only repeat diagnostic laparoscopies and endometriosis surgeries, but also pelvic organ prolapse repairs, urinary incontinence surgeries, cystoscopies, and various hysteroscopic procedures.

CANCER RISK
The research also corroborated what has been reported previously by Nezhat et al and other research teams, which is that endometriosis confers an increased risk of developing ovarian cancer, specifically in this study a 77% elevated risk compared to the general population control group. The American Cancer Society estimates that the lifetime probability of developing ovarian cancer in the general American population is approximately 1 in 75 (1/75). In women with endometriosis, this latest study would suggest the rate is increased to 1.77 in 75 (1.77/75).

While the researchers noted that the association they found was “less pronounced” than other reports, nevertheless the fact that this link was observed in such a large population over a long period of time, and despite the higher incidence of oophorectomy in the endometriosis group, strengthens the validity of previous studies demonstrating a correlation between endometriosis and ovarian cancer.

This study also showed that women with endometriosis were at somewhat higher risk of developing all cancers (21% increased risk) and breast cancer (28% increased risk) compared to the general population control group, but had a lower risk of developing cervical cancer. However, even with these findings, the researchers noted that their results were inconsistent across their cohort groups and that “with the exception of ovarian cancer, the association with other cancers remains disputable.”

STUDY STRENGTHS
The study was well-designed in a number of ways, including its selection of only those women with surgically-confirmed endometriosis to be part of the exposure group. Other studies sometimes have included self-reported cases, which are generally less reliable. The researchers also did a good job of ensuring that the general population control group didn’t include those with symptoms of endometriosis, although cases of asymptomatic endometriosis could not be excluded. The follow-up time was also much longer than other studies, averaging 13.1 years for the endometriosis group and general population, 17.4 years for those with negative laparoscopy, and 19.1 years for those with laparoscopic sterilization. And finally, multiple control groups were used, which can be an effective strategy to better detect the true differences between groups, while also controlling for potential hidden biases that may be distorting the observed results.

STUDY LIMITATIONS
As the researchers acknowledged, the study did have some limitations, including the fact that only a relatively homogenous population of patients from a Scottish database was evaluated. Further studies involving different populations would need to be done for the results to have better generalizability from a global health perspective. Due to missing data sets or inability to properly match groups, the researchers were also unable to measure the impact of certain variables, such as parity, smoking history, use of hormonal pharmaceuticals, other prescription history, body mass index (BMI), family history, ethnicity, or other variables which exert influence on health outcomes.

The outcomes of endometriosis surgery are also highly dependent on the skill and experience of the surgeon. However, this study was not able to control for this variable as well. Another drawback was that the endometriosis group included both mild and severe cases of the disease. This makes it difficult to measure the true disease burden of severe endometriosis since the statistical results were averaged in with mild cases.  Future studies will hopefully be able to better stratify these data so that we can understand the full health impact that various stages of the disease may have.

FINAL THOUGHTS
Even with some of these limitations, this study is important as it further substantiates the results of previous research which has shown that women with endometriosis tend to face higher risks of other serious, long-term health issues. With greater awareness of these potential risks, both patients and practitioners can be better equipped to make more timely and informed decisions. Knowledge of the increased risk of ovarian cancer in particular should also help drive changes in the way women with endometriosis are counseled about their health risks and treatment options. From a public health policy perspective, we believe that more preventive measures must be implemented, including routine screening and increased efforts to raise awareness so that women and girls can have a chance for better health outcomes and avoid the unacceptably lengthy delays in diagnosis and treatment that are still currently the norm.

KEYWORDS: ovarian cancer risks, women’s health, endometriosis health risks

SOURCE:
L Saraswat et al. Impact of endometriosis on risk of further gynaecological surgery and cancer: a national cohort study. Sept. 2017: British Journal of Obstetrics and Gynaecology.

FOR FURTHER READING:
1)  Are We Closer to Preventing Ovarian Cancer?
2) Prophylactic removal of Fallopian tubes (salpingectomy) as precaution against ovarian cancer.
3) New insights in the pathophysiology of ovarian cancer and implications for screening and prevention.  Sept. 2015, American Journal of Obstetrics and Gynecology.
4) The relationship of endometriosis and ovarian malignancy.