Hormone receptor expression patterns define clinically meaningful subgroups of endometrioid ovarian carcinoma

Numerous studies have investigated the association between hormone receptor expression and clinical outcome in ovarian carcinoma (OC); however, these have largely focussed on serous OCs, with few studies reporting specifically on endometrioid OCs (EnOC). Where analyses have been stratified by histotype, expression has been assessed using the percentage of positive tumor cells, without accounting for nuclear expression intensity.

Here we assess the expression levels of progesterone receptor (PR), estrogen receptor alpha (ER) and androgen receptor (AR) using histoscore - a nuclear scoring method incorporating both proportion of positive cells and the intensity of nuclear staining - across a cohort of 107 WT1 negative EnOCs.

Hierarchical clustering by PR, ER and AR histoscores identified four EnOC subgroups (PR+/ER+, PR+/ER-, PR-/ER+ and PR-/ER-). EnOC patients in the PR+/ER+ and PR+/ER- groups displayed favorable outcome (multivariable HR for disease-specific survival 0.05 [0.01-0.35] and 0.05 [0.00-0.51]) compared to the PR-/ER+ group. Ten-year survival for stage II PR^high and PR^low cases was 94.1% and 42.4%. ER^high EnOC patients (PR+/ER+, PR-/ER+) had higher body mass index compared to ER^low cases (P = 0.015) and high grade serous OC patients (P < 0.001).

These data demonstrate that endometrioid OC cases with high PR expression display markedly favorable outcome. Stage II EnOCs with high PR expression represent potential candidates for de-escalation of first-line therapy. Future work should seek to characterise the sensitivity of PR and ER positive EnOCs to endocrine therapy.