New information strongly suggests that removing the fallopian tubes (salpingectomy) may actually prevent 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 theory of ovarian cancer makes so much more sense when you consider what we know about ovarian cancer.
The fallopian tube is an open tube that almost caresses the ovary at its distal end, where it opens to the abdominal cavity. Its blood supply is shared with the ovary, and its inner surface is bathed in fluid that it shares with the abdominal cavity. According to the theory, cancerous cells arise in the fallopian tube from small precursor lesions, which turn cancerous and 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 in explaining why ovarian cancer is more often spread beyond the ovary to the pelvis and abdomen (Stage 3) than just confined to the ovary (Stages 1 and 2) at diagnosis.
It also helps to explain how ovarian cancer has stubbornly eluded screening. Fallopian tubes are not easily visualized on pelvic sonogram. So, by the time the ovary appears abnormal on ultrasound, the cancer has already spread beyond its primary site.
So-called “serous” ovarian cancers, accounting for two-thirds of all cases, are thought to originate in the fallopian tubes. The rest are endometrioid and small cell cancers (thought to begin in the uterus or within the ovary), mucinous cancers (which may start in the ovary or in the GI tract), and germ cell tumors (which originate from germ cells in the ovary).
What’s the evidence?
Data are rapidly accumulating to support the fallopian tube origin of ovarian cancer.
- In BRCA-positive women at high risk for ovarian cancer, prophylactic removal of the tubes and ovaries finds hidden cancers in 7-15 percent 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 percent lower rates of ovarian cancer than those with intact tubes. The cancers prevented are the types (clear cell and endometrioid) that would seem to originate in the uterus.
- Women who have their fallopian tubes removed have a sharply 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).
What if I am at high risk for ovarian cancer?
The standard of care for BRCA carriers and others at high risk for ovarian cancer is removal of both tubes and ovaries, a procedure called bilateral salpingo-oophorectomy, or BSO. It virtually eliminates the cancer risk.
But the procedure can cause early menopause, with its own risks of osteoporosis, heart disease and earlier death. If removal of the tubes is all that is needed to protect these women, it would be an option that would not put them into menopause.
Large clinical trials are in progress to see if the two options are comparable, but results are years away. If the 50 percent reduction found in the general population is the same for high-risk women, they may prefer the 95 percent risk reduction from salpingo-oophorectomy.