Appendix 1 - Cohort definitions

The cohort of ovary, fallopian tube and primary peritoneal carcinomas used for this Ovarian Cancer Audit Feasibility Pilot is all tumours coded in ICD-10 and ICD-O-2 to:

C56 (Malignant neoplasm of ovary)

C57 (Malignant neoplasm of other and unspecified female genital organs)

C48 (Malignant neoplasm of retroperitoneum and peritoneum), excluding sarcomas: 8693, 8800, 8801, 8802, 8803, 8804, 8805, 8806, 8963, 8990, 8991, 9040, 9041, 9042, 9043, 9044, 8810, 8811 – 8921, 9120 – 9373, 9490, 9500, 9530 – 9582

D39.1 (Neoplasm of uncertain or unknown behaviour of ovary)

Only female patients are included in the cohort.

This definition aligns with international ovarian cancer analyses and is designed to capture all ovarian cancers; although there may be variation in the coding of the originating site within this group, in practice their prognosis and treatment are similar. The inclusion of D39.1 means that the cohort includes all ‘borderline malignant’ ovarian cancer.

Borderline malignant (“borderline”) ovarian tumours make up approximately 16% of the overall cohort of ovary, fallopian tube and primary peritoneal carcinomas. These tumours have historically been recorded as ovarian cancers, though their malignant potential is now understood to be lower than the rest of the group.

Tumours with ICD-10 site code C56, C57 or C48 are defined as ‘borderline’ if their morphology code in ICD-O-2 is 8442, 8444, 8451, 8463, 8473, 8472 or 8462.
Tumours with ICD-10 site code D39.1 are defined as ‘borderline’ if their morphology code in ICD-O-2 is 8144, 8260, 8313, 8380, 8381, 8440, 8441, 8460, 8470, 8480, 8481, 9000, 9013, 9014 or 9015. However, all tumours at ICD-10 site code D39.1 are excluded from survival analysis in line with National Statistics methodology.

In this report, survival analysis is presented for cohorts including and excluding borderline tumours. Their exclusion is in line with international ovarian cancer analyses and avoids inflation of the survival estimates due to the better survival of the borderline group. Hence, it gives a clearer picture of the survival of women with non-borderline ovarian cancer. We have provided data for the cohort both including and excluding borderline tumours to provide comparability to outputs that do not exclude borderlines.

The definition of ‘ovarian cancer’ used for mortality statistics in this report is C56-C57 in ICD-10. Data on mortality from ovarian cancer are derived from the ONS Mortality Extract which is in turn derived from causes of death recorded on death certificates, which do not include morphology information. Hence the more nuanced cohort descriptions (as used for incidence, stage and survival) which rely on tumour morphology information are not available for this statistic.