Ovarian Cancer molecular biology and genetics

Mutations in BRCA1, BRCA2 and hereditary nonpolyposis colorectal cancer (HNPCC) genes are associated with an increased risk of ovarian cancer, although only about 10% of ovarian carcinomas occur in those known to carry the recognised mutations 1.

In women with a known BRCA1 mutation, the cumulative lifetime risk of developing ovarian cancer has been estimated to be approximately 50% (95%CI 44.9 to 55.0%) compared with an approximate 1.7% lifetime risk in the general US population 2.

In HNPCC families (also known as Lynch II families) the lifetime risk of ovarian cancer in female mutation carriers is about 12%, which is much less than that for endometrial cancer (approximately 60% in these mutation carriers) 3.

Women who have inherited a gene mutation that puts them at high risk of ovarian cancer may consider having prophylactic surgery or regular screening for the early signs of ovarian cancer although screening on the NHS is only available as part of a research study (see below).

Ovarian cancer molecular biology and genetics

 
 

The future - possibilities of screening

Ovarian cancer fulfils some of the criteria 4 necessary for the introduction of population screening: it is an important health problem, and early detection is associated with improved outcomes. Potential screening tests for ovarian cancer have not yet been shown to reduce mortality, although both ultrasound and tumour markers can detect a significant proportion of ovarian cancers preclinically. 5-,8 Currently there is no national screening programme for ovarian cancer and evidence is awaited from on-going randomized controlled trials.

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Population screening

A very large randomised controlled trial is currently being conducted in the UK which aims to recruit 200,000 post-menopausal women. This trial is named the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS). The primary screening modalities being tested are annual CA125 testing and transvaginal ultrasound 9. The key issues with this trial are that transvaginal ultrasound is a costly process, requiring expertise to interpret the image at the time of screening, and the fact that it is not yet known whether this screening method is acceptable to women. In addition, this trial is not due to be completed until 2010.

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Screening for women with a family history of ovarian cancer

Five thousand women aged over 35 with a significant family history of ovarian cancer are currently being invited to participate in a study assessing the utility of annual screening with CA125 measurement and ultrasound. This study is called the UK Familial Ovarian Cancer Screening Study (UKFOCSS). In addition, blood samples are being collected every four months for retrospective analysis of existing and novel tumour markers 10.

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References for ovarian cancer molecular biology and genetics

  1.  Rubin, S.C., et al., BRCA1, BRCA2, and hereditary nonpolyposis colorectal cancer gene mutations in an unselected ovarian cancer population: relationship to family history and implications for genetic testing. Am J Obstet Gynecol, 1998. 178(4): p. 670-7.
  2.  Brose, M.S., et al., Cancer risk estimates for BRCA1 mutation carriers identified in a risk evaluation program. J Natl Cancer Inst, 2002. 94(18): p. 1365-72.
  3.  Aarnio, M., et al., Cancer risk in mutation carriers of DNA-mismatch-repair genes. Int J Cancer, 1999. 81(2): p. 214-8.
  4.  National Screening Committee, The NSC criteria: the criteria for appraising the viability, effectiveness and appropriateness of a screening programme. 2003.
  5.  Jacobs, I., et al., Multimodal approach to screening for ovarian cancer. Lancet, 1988. 1(8580): p. 268-71.
  6.  Jacobs, I., et al., Prevalence screening for ovarian cancer in postmenopausal women by CA 125 measurement and ultrasonography. Bmj, 1993. 306(6884): p. 1030-4.
  7.  Jacobs, I.J., et al., Screening for ovarian cancer: a pilot randomised controlled trial. Lancet, 1999. 353(9160): p. 1207-10.
  8.  van Nagell, J.R., Jr., et al., The efficacy of transvaginal sonographic screening in asymptomatic women at risk for ovarian cancer. Gynecol Oncol, 2000. 77(3): p. 350-6.
  9.  UK Collaborative Trial of Ovarian Cancer Screening. 2001.
  10.  Jacobs, I., et al., The UK Familial Ovarian Cancer Screening Study. 2001.