New information strongly suggests that most ovarian cancers originate, not in the ovary, but in the fallopian tube. If this is so, then removal of the fallopian tubes may actually prevent ovarian cancer.
The evidence is powerful enough that the American Congress of Obstetricians & Gynecologists is now recommending that fallopian tube removal be considered in women planning to undergo surgical sterilization or hysterectomy.
The Fallopian Tube Origin of Ovarian Cancer
We used to think that ovarian cancer originated in the peritoneal lining that covers the ovaries and abdominal organs. But the fallopian tube origin of ovarian cancer makes so much more sense when you consider what we know about ovarian cancer.
Think about it. The fallopian tube is an open tube that almost caresses the ovary at its distal end, where it is open to the abdominal cavity. Its blood supply is intimately shared with the ovary, and its inner surface is bathed in fluid that it shares with the fluid of the abdominal cavity. According to the theory, cancerous cells arise in the fallopian tube from small precancerous precursor lesions, where they grow undetected until they metastasize to the nearby ovary, or to the abdominal wall and surface of the pelvic and abdominal organs.
This goes a long way to explain why ovarian cancer is more often spread beyond the ovary to the pelvis and abdomen (Stage 3) and not just confined to the ovary (Stages 1 and 2) at diagnosis.
It also helps to explain how ovarian cancer has stubbornly eluded our attempts at screening. Because by the time the ovary appears abnormal on ultrasound, the cancer has already spread beyond its primary site. (Fallopian tubes are not easily visualized on pelvic sonogram.)
Note that the type of ovarian cancer thought to originate in the fallopian tubes is the so-called “serous” ovarian cancer. Serous cancers account for about two-thirds of ovarian cancers. The other third of ovarian cancers are endometriod and small cell cancers (which are thought to originate in the uterus or within the ovary), mucinous cancers (which may originate in the ovary or in the GI tract), and germ cell tumors (which originate from germ cells in the ovary).
What evidence is there?
Data a rapidly accumulating to support the fallopian tube origin of ovarian cancer. Here’s what we know so far –
- In BRCA positive women at high risk for ovarian cancer, prophylactic removal of the tubes and ovaries finds hidden cancers in 7-15 % of women, but over half of these cancers are in the distal end of the tube, not the ovary.
- The gene mutations found in serous ovarian cancers are the same ones found in the fallopian tube cancers, and the gene expression of serous ovarian cancer cells is more like that of a fallopian tube cell than an ovarian cell.
- Scientists have found precursor lesions at the ends of the fallopian tube, that while not cancerous, look an awful lot like ovarian cancer cells.
- Women who have had their tubes tied have 30% lower rates of ovarian cancer than those with intact tubes. The cancer prevented are the types (clear cell and endometriod) that would seem to originate in the uterus, based on the type of cells in the cancer.
- Women who have their fallopian tubes removed have a 60% lower risk of ovarian cancer, and the type of cancer prevented are both the types that originate in the uterus and the type that we now think originates at the end of the fallopian tube nearest to the ovary (serous type).
So sign me up, already.
Not so fast.
As safe as it has become, surgery is not without risks. Operating on every woman to prevent a cancer that few (1% or less) will get may not make sense.
But for women who are already planning to undergo surgery for hysterectomy or tubal sterilization, it is not unreasonable at this juncture to consider removing the tubes while you’re there. This will add little to the risks of the procedure already planned, and may have the potential benefit of preventing ovarian cancer.
What if I am at high risk for ovarian cancer?
At this point in time, the standard of care for prevention of ovarian cancer in BRCA carriers and others at high risk is prophylactic removal of both the tubes and ovaries, a procedure called bilateral salpingo-oophorectomy, or BSO.
But there are downsides to salpingo-oophorectomy for ovarian cancer prevention. Even though the procedure is usually performed after completion of childbirth, it can cause early menopause, with its own risks of osteoporosis, heart disease and earlier death. If removal of the tubes proves to prevent ovarian cancer, this would be massively important for high risk women, who would have an option for ovarian cancer prevention that will NOT put them into menopause.
Large clinical trials are in progress to determine whether tubal removal will provide the same protection as BSO, but the results of these trials are years away. If the 60% reduction found in the general population holds up, this may not be a good enough for high risk women, who currently get a 95% risk reduction from salpingo-oophorectomy.
There are reasons other than cancer protection to recommend tubal removal at the time of sterilization
Tubal sterilization is not perfect.
We now know from large longitudinal studies that failures occur more than you’d expect after sterilization, and range from a low of 3.8/1,000 for post partum tubals to as high as 54/1,000 for cautery (burning) of the tube. Failure rates from the Essure procedure are even higher – 96 per 1,000 – that’s almost 10%. Pregnancies that occur after these failed tubals are very likely to be life threatening ectopic pregnancies.
Renowned family planning researcher Mitchell Crenin, MD and colleagues argued persuasively in a recent editorial that the time for sterilization by tubal removal is long overdue. Moreover, if we gynecologists had included women in the discussion from the get go as we began to bandy about sterilization options, including Essure, most women would tell us they want the most effective procedure there is – which happens to be tubal removal.
The recent discoveries of a link between the Fallopian tube and ovarian cancer have brought this issue to the forefront; however, women have not been included in the discussion about their desires, specifically around pregnancy prevention. If failure (pregnancy) is considered a major morbidity, how much more complicated is a bilateral salpingectomy as compared with laparoscopic tubal interruption… the question should not be focused only on ovarian cancer prevention; rather, the more important question should be why we are not offering women a chance for near 100% efficacy by removing the Fallopian tube completely for sterilization.
I’d have to agree.
- Britt Erikson et al. The Role of the Fallopian Tube in the Origin of Ovarian Cancer – A well done state of the art review.
- M Crenin et all – Female Tubal Sterilization – the Time has come to routinely consider removal. Excellent editorial
- ACOG . Salpingectomy for Ovarian Cancer Prevention
- Society of Gynecologic Oncologists (SGO) Statement on prophylactic salpingectomy.
Image by CDC, Mysid [Public domain], via Wikimedia Commons