To prospectively assess the incidence of peritoneal carcinomatosis for women with isolated STIC (serous tubal intraepithelial carcinoma). Moreover, to identify histopathological characteristics of STIC which are reproducible and associated to the risk of peritoneal carcinomatosis and to report the findings of additional diagnostics.

Women with a BRCA pathogenic variant (PV) undergo a risk-reducing salpingo-oophorectomy (RRSO) to reduce their ovarian cancer risk of 17-44%. A residual risk for peritoneal cancer (PC) persists, with most patients having extensive tumour spread throughout the abdomen. Despite surgery and chemotherapy, the five-year survival rate of PC is only 14-30%. Recently it became apparent that PC is frequently preceded by a preinvasive serous tubal intraepithelial cancer (STIC) at RRSO. The entity STIC is often found conjointly with ovarian cancer, but can also be present as an isolated condition, mostly in high risk women. If this STIC is found at RRSO, the risk for PC was found to be 27.5% (95% CI, 15.6-43.9) after ten years whilst this risk was <1% without STIC. The pathophysiological mechanism of this association is not yet known and it is unknown which women with STIC are most at risk. Moreover, the additional value of diagnostics and management is unknown as data is lacking.

Objective: To prospectively assess the PC incidence for women with isolated STIC, to identify histopathological characteristics of STIC which are reproducible and associated to the risk of PC, and to report the findings of additional diagnostics.

Inclusion Criteria:

• Women
• Bilateral salpingectomy (with or without oophorectomy)
• A serous tubal intraepithelial carcinoma at histopathological review

Exclusion Criteria:

• Invasive cancer at initial surgery or pathological examination (either macroscopic and/or microscopic)

For the retrospective cohort: All women with STIC diagnosed between 2015 and start of the prospective study are identified. Data up until that time-point will be collected. At the end of the data collection follow-up will be updated on the women in the retrospective cohort.

For the prospective cohort: All consecutive women with isolated STIC from participating centres are informed on the study and requested to participate.

In collaboration with participating centers upon reasonable request.