Progesterone receptor (PR) status was found to be significantly linked to response to progestin-based therapy and could shape hormonal-based treatments after endometriosis-related surgery, according to a retrospective cohort study published in The Journal of Clinical Endocrinology & Metabolism.
A team of researchers from the Yale School of Medicine hypothesized that predictive biomarkers — specifically, PR levels — in endometriotic lesions can provide insight into progestin-based therapy response, which may facilitate customization of endometriosis treatments.
A total of 52 women with confirmed endometriosis, at least 1 available lesion for immunohistochemistry, and a history of medical treatment for endometriosis were included in the study; 21 had multiple lesions collected during surgery and 17 had eutopic endometrium collected during laparoscopy.
Using a rabbit polyclonal immunoglobulin G to detect PR-A and PR-B, the researchers performed immunohistochemistry on loci of the endometriotic lesions. To quantify PR status, the investigators used a Histoscore (H-score) and categorized participants as high (H-score, >80), medium (H-score, 6-80), or low (H-score, ≤5) PR status.
Participants who responded to progestin-based therapy had significantly higher H-scores than those who did not respond. High, medium, and low PR status was reported in 7, 28, and 17 women, respectively.
The investigators noted that the threshold H-score of less than 5 was chosen due to its high sensitivity and its 94% negative predictive value. In addition, the threshold of H-score >80 was chosen due to the associated high specificity and 100% positive predictive value.
“In this study, we have shown that PR status is strongly associated with response of endometriosis to progestin-based therapies,” the authors mentioned. “Subjects who did not respond to progestin-based therapies had significantly lower PR levels than subjects who did respond. These data support the notion that PR levels are an important modulator of progesterone resistance in endometriosis.”
“In summary, although our scoring system/clinical algorithm requires validation in prospective clinical trials, we anticipate that utilization of patients’ PR status will allow for a novel, targeted approach to treating endometriosis,” concluded the investigators.
Flores VA, Vanhie A, Dang T, Taylor HS. Progesterone receptor status predicts response to progestin therapy in endometriosis. J Clin Endocrinol Metab. 2018;103(12):4561-4568.