To our knowledge, this is the first study to evaluate, separately by index diagnosis of CH or AH, the association between index biomarker expression and persistence/progression of EH among women treated with oral progestin (search: PubMed; terms: endom* hyperplasia, progest*, immunohistochemistry, adult, female; language: English; dates: June 1979 – January 2012). We found that among women with an index diagnosis of AH, high PRB expression, and possibly high expression of both PRA and PRB, were associated with a decreased risk of AH persistence/progression with progestin therapy.
The presence of progesterone receptor expression at baseline, leading to a decreased risk of EH persistence/progression following progestin therapy, makes clinical and biological sense. EH is stimulated by estrogen. Clinical research has demonstrated that unopposed estrogen therapy in postmenopausal women increases EH risk and that most revert with administration of progestin.27
In our prior study, we found over a six month period that women treated with oral progestin had a 61% decreased risk of persistence/progression of AH as compared to women not treated (RR 0.39, 95% CI: 0.21–0.70).16
(The majority of women who took progestin in that study contributed to the analyses reported here). While the complex mechanism of progestin action at the molecular level is not known, progestin may potentiate EH regression by antagonizing estrogen-induced proliferation through decreased synthesis of estrogen receptors and/or promoting the enzymatic conversion of estradiol to estrone.28–30
Progestin may also act via estrogen-independent pathways.31, 32
These possible biological effects of progestin require the presence of progesterone receptors. Thus, low progesterone receptor expression, particularly PRB, may identify a neoplastic subpopulation prone to progestin resistance.
Our finding is consistent with two studies of women with a baseline diagnosis of AH or endometrial endometrioid carcinoma treated with oral progestin. Utsunomiya et al33
studied 16 women with endometrial endometrioid adenocarcinoma treated with MPA (600mg/day) for at least 6 months. Defining progestin responsiveness as regression to normal endometrium or hyperplasia without atypia, the investigators found that women who responded to MPA had greater expression of both PRA and PRB or an increased ratio of PRB/(PRB+PRA) at index.33
An unpublished study conducted among women with AH or grade 1endometrioid adenocarcinoma (G1EAC) who were treated with progestin for at least 8 weeks found that strong expression of PRB at baseline was associated with resolution of AH or G1EAC (definition of resolution not provided).34
One additional study may have relevance to our findings among women with CH. Women with EH were treated for 3 months with oral MPA (6 women with CH, 8 with AH and 15 with SH) or the levonorgestrel intrauterine system IUS (21 with EH).21
Among those treated with MPA (not stratified by EH type), there was no difference in glandular or stromal expression of PRA or PRB at baseline, between women who regressed to normal proliferative or atrophic endometrium and women with persisting hyperplasia. Complete resolution of EH was noted in all women treated with the levonorgestrel IUS, regardless of PR status.21
Others have confirmed the association of PR and progestin therapy response with levonorgestrel IUS treatment of EH.18, 20
Akesson et al18
showed that among levonorgestrel IUS users, a greater proportion of the 29 women with CH and 5 women with AH who had PRA or PRB expression at baseline were more likely to resolve any form of EH, as compared to women without PRA or PRB expression; the median time interval for response was 9.9 months.
We did not find an association between baseline PTEN expression and EH persistence/progression. The PTEN
tumor suppressor gene regulates epithelial growth by inhibiting cell proliferation and inducing apoptosis.35
Progesterone has been demonstrated to increase PTEN protein levels by decreasing PTEN phosphorylation.36
A small study of 31 women diagnosed with CAH or G1EAC treated with oral MPA, found that the presence of PTEN null glands at baseline may be suggestive of an increased risk of hysterectomy (performed if no change in diagnosis or carcinoma relapse after MPA treatment).37
A second study, among women with predominantly CH treated with the levonorgestrel IUS, found no association of PTEN with EH progression.18
These inconsistent study findings may be due to small numbers, differences in subject selection, and/or determination of PTEN loss.
We also did not find an association between Pax-2 or Bcl-2 expression and progestin therapy resistance. While Pax-2 has not previously been investigated with regard to progestin therapy resistance, others have reported loss of Pax-2 protein expression with EH and endometrial carcinogenesis.25, 38
is an antiapoptoic gene that suppresses programmed cell death and is expressed in a variety of human neoplasms.39
Previous studies suggested that Bcl-2 is expressed in the early stage of the neoplastic continuum39–42
and is down-regulated with administration of progesterone.19, 22
There are strengths and limitations of our study. Baseline and follow-up EH diagnoses were strictly adjudicated by blinded research pathologists,15
minimizing potential diagnostic misclassification.15
This allowed analyses to be stratified by EH type (CH, AH) to elucidate associations that may be missed by grouping together women with potentially different disease pathways and likelihood for cancer progression. Some limitations are similar to those of previous publications. First, it is possible that women with an index diagnosis of AH had concomitant endometrial carcinoma that was not detected by endometrial sampling.43
Treatment decisions in clinical practice are therefore made, at times, without knowledge of concurrent existence of endometrial carcinoma. Guidelines indicate that atypical hyperplasia and grade 1 adenocarcinoma may be treated with progestin therapy if conservation of the uterus and fertility is desired.44
Biomarkers predictive of progestin therapy resistance in the setting of atypical hyperplasia or endometrial carcinoma would be even more clinically valuable than biomarkers predictive of progestin therapy resistance in atypical hyperplasia alone. Thus, this is potentially a benefit of our study design, not a limitation. Second, this was not a randomized controlled trial of women with EH and, despite collecting 20 years of data, the study inclusion criteria requiring progestin therapy and the availability of two biopsies within a 6 month time frame resulted in a limited sample. The sample size affected our study power and the precision of the estimates of the associations, as seen by wide confidence intervals. However, unlike the majority of prior studies which reported P
-values, we additionally reported odds ratios and 95% confidence intervals for transparency about statistical instability, and to provide the magnitude of the association. Third, IHC interpretations are prone to subjective bias, specifically in assigning a value for the percent of cells staining. To overcome this limitation and minimize exposure misclassification, we used a binary categorization of biomarker expression with a conservative threshold for high expression and no loss. Fourth, cases with AH had a shorter mean duration of progestin use and were more likely to receive lower progestin dose than controls. While progestin duration and dose would not confound our results since progestin treatment occurred after index biopsy, the specimen used for biomarker measurement, it is possible that the associations between individual biomarkers and progestin therapy resistance may vary by progestin duration and dose. The similar results observed among women treated with progestin for at least 8 weeks compared to those of the main analysis, minimize this concern. Fifth, endometrial hyperplasia is increasingly being treated with intrauterine levonorgestrel. However, the larger number of women with atypical hyperplasia in our study compared to studies of intrauterine levonorgestrel use,18, 20, 21
and the continued use of oral progestins in practice,45
highlight the relevance of our study. Lastly, we did not evaluate, in the long-term, whether expression of biomarkers like PRB persist after progestin therapy is stopped.
The need persists for biomarkers that can serve the clinically important role of identifying which women with EH will respond to progestin treatment and warrants further research. While PRB expression shows promise as an easily evaluable biomarker of progestin response in women with AH, these results should be confirmed in adequately powered studies to better understand how PRB expression may guide treatment decisions.