To our knowledge, this phase II neoadjuvant trial is the first to investigate changes in aromatase expression and other protein markers with the addition of the selective COX-2 inhibitor celecoxib to exemestane. In this study, no significant differences in aromatase expression were detected with treatment. There were statistically significant decreases in ER, PR, Ki-67, and COX-2 expression. The decrease in ER and COX-2 expression was evident only after the addition of celecoxib to exemestane, but not with exemestane alone.
The hypothesis that this trial was designed to test, namely that aromatase expression would decrease with the addition of celecoxib to exemestane, was not observed. There are several possible explanations. Protein expression as measured by IHC did not change. However, the trial was initially intended to measure gene expression and fresh frozen tissue cores were collected with each biopsy expressly for this purpose. When the RNA was isolated and real time polymerase chain reaction for the genes of interest was performed the results suggested that the RNA was significantly degraded causing highly variable results in expression of both genes of interest as well as β-actin and other housekeeping genes used for standardization. These experiments were repeated in different laboratories using different machines with the same result. Thus, we have no information on gene expression of aromatase.
The combination of celecoxib with aromatase inhibitor therapy has been previously investigated in several trials in postmenopausal patients who had hormone receptor–positive metastatic breast cancer. One of the earliest feasibility studies of the combination reported clinical benefit rates of 74% in metastatic patients who were treated with a combination of exemestane and celecoxib.16
A randomized phase II study of exemestane versus exemestane plus celecoxib showed similar time to progression in both groups, but duration of clinical benefit was significantly longer in the combination group. A double-blind placebo-controlled phase III study (GINECO) of exemestane plus celecoxib versus placebo was terminated early because of CV complications and was underpowered to detect a difference between the two arms.17
The Celecoxib Anti-Aromatase Neoadjuvant (CAAN) trial evaluated exemestane alone, letrozole alone, and exemestane combined with celecoxib showing similar response rates between arms with greater tumor marker CA15.3 reductions in the celecoxib containing arm.6
Biomarker studies were not reported with these studies. Most recently, a neoadjuvant study of single-agent celecoxib for 14 days before surgery did not show significant changes in ER, PR, Ki-67, or COX-2.18
The only placebo-controlled randomized trial comparing exemestane and placebo to exemestane and celecoxib was conducted in patients who had ductal carcinoma in situ. In that trial, there were significant reductions in Ki-67 and PR expression after 14 days of exemestane and there was no additional expression level decreases with the addition of celecoxib.19
Several other trials have reported biomarker changes with single-agent neoadjuvant tamoxifen and an aromatase inhibitor as summarized in . Consistent with other trials in , Ki-67 and PR levels deceased in the current trial. In addition, there was a significant decrease in ER expression when celecoxib was added to exemestane. Possibly, a non-steroidal may affect the ER pathway differently that than the non-steroidal aromatase inhibitors such as letrozole or anastrazole that were tested in other neoadjuvant studies. Because the decrease in ER expression was observed only after the addition of celecoxib, possibly the inhibition of the COX-2 pathway signaling may have been responsible. Estrogen biosynthesis is stimulated by PGE2 production that is modulated by COX-2 inhibition.20
Additional studies are required to validate the decrease in ER expression and to elucidate the possible mechanisms.
Biomarker Changes in Neoadjuvant Endocrine Trials
The addition of celecoxib did not change the toxicity profile of exemestane in most women. However, in this small study, higher rates of hypertension were observed than in previously reported combination studies with aromatase inhibitors and celecoxib.6
Grade 3 hypertension was only observed in two women older than 60 years who had pre-existing hypertension. In addition, two women had CV toxicity at 1 and 4 months after exposure to celecoxib, and it is uncertain in this small non-randomized trial if celecoxib exposure was a potential contributor to this toxicity. In a recent pooled analysis of six placebo-controlled trials there was a dose-response relationship between celecoxib and CV toxicity with highest risk at 400 mg twice a day and with underlying CV risk factors.21
The small sample size limited the evaluation of the biomarker changes that could be detected in this trial. Originally, 34 patients were to be enrolled, but reports of increased CV complications with celecoxib in the Adenoma Prevention Trial in December 2004 led to suspension of the trial.22
Even after re-opening this trial in March of 2005 after an amendment that detailed the CV risks of celecoxib, physicians were reluctant to enroll women. In addition, for those women who were enrolled in the trial, physicians had a lower threshold for removing them from trial for toxicities attributed to celecoxib. This explains, in part, why grade 2 rash, grade 1 edema, and grade 1 creatinine elevations led to 3 women being removed from this trial. Eventually the trial closed with only 22 women enrolled because of low accrual. Also contributing to small numbers was the difficulty in procuring mid-treatment biopsy specimens that some women refused, and the fact that some core biopsy specimens did not have adequate tumor tissue for analysis. The latter highlights the difficulty of conducting small trials with multiple sequential biopsy specimens.