Pharmacokinetic approach to the selection of dose schedules for medroxyprogesterone acetate in clinical oncology

Pharmacokinetics, metabolism and serum concentrations of progestins used in contraception

Many different forms of hormonal contraception are used by millions of women worldwide. These contraceptives differ in the dose and type of synthetic progestogenic compound (progestin) used, as well as the route of administration and whether or not they contain estrogenic compounds. There is an increasing awareness that different forms of contraception and different progestins have different side-effect profiles, in particular their cardiovascular effects, effects on reproductive cancers and susceptibility to infectious diseases. There is a need to develop new methods to suit different needs and with minimal risks, especially in under-resourced areas. This requires a better understanding of the pharmacokinetics, metabolism, serum and tissue concentrations of progestins used in contraception as well as the biological activities of progestins and their metabolites via steroid receptors. Here we review the current knowledge on these topics and identify the research gaps. We show that there is a paucity of research on most of these topics for most progestins. We find that major impediments to clear conclusions on these topics include a lack of standardized methodologies, comparisons between non-parallel clinical studies and variability of data on serum concentrations between and within studies. The latter is most likely due, at least in part, to differences in intrinsic characteristics of participants. The review highlights the importance of insight on these topics in order to provide the best contraceptive options to women with minimal risks.

5-Fluorouracil, Adriamycin and Cyclophosphamide Combined with High-Dose Medroxyprogesterone Acetate in Advanced Breast Cancer

Seventy-six patients with metastatic breast cancer were treated with fluorouracil, adriamycin (doxorubicin) and cyclophosphamide (FAC) plus high-dose medroxyprogesterone acetate (HD-MPA). MPA was given for 21 days at the dose of 500 mg/day i.m., then on a randomized basis, either 500 mg/week i.m. (FAC+HD-MPA i.m.) or 300 mg/day p.o. (FAC+HD-MPA p.o.). Objective response rates were 79% in 39 patients on FAC+HD-MPA i.m. and 73% in the 37 patients on FAC+HD-MPA p.o. There was no significant difference in the median duration of response and median survival for the 2 regimens (respectively, 17 months and 22 months, and 15 months and 21 months for FAC+HD-MPA i.m. and FAC+HD-MPA p.o.). Toxicity was mild and similar in both groups. Although FAC+HD-MPA was highly effective, at present it is difficult to select which regimen provides the best initial treatment for metastatic breast cancer.

Oral Progestin Treatment for Early-Stage Endometrial Cancer: A Systematic Review and Meta-analysis

OBJECTIVE

This study aimed to evaluate the efficacy and safety of oral progestin treatment for early-stage endometrial cancer.

METHODS

We conducted a systematic review and meta-analysis of the proportions from observational studies. Original studies were selected if patients with early-stage endometrial cancer, especially those of reproductive age, were treated with oral progestin. We conducted searches on studies listed in MEDLINE, EMBASE, and Cochrane that were published through June 2014, and relevant articles were also searched. The methodological quality of the included studies was assessed using the Newcastle-Ottawa quality assessment scale. Funnel plots and metaregression analyses were used to assess bias.

RESULTS

The final sample included 25 articles involving 445 patients. Based on a random-effects model, patients achieved a disease regression rate of 82.4% (95% confidence interval [CI], 75.3%-88.7%), a relapse rate of 25.0% (95% CI, 15.8%-35.2%), a pregnancy rate of 28.8% (95% CI, 22.5%-35.5%), and a live birth rate of 19.6% (95% CI, 12.8%-27.4%). Body weight gain, liver dysfunction, and abnormal blood coagulation test results were the most common treatment-related adverse effects. Only 2 disease-related deaths were reported during the follow-up duration.

CONCLUSIONS

Based on the present systematic review and meta-analysis, oral progestin treatment is feasible and safe for patients of reproductive age.

High-dose oral medroxyprogesterone acetate or tamoxifen as adjuvant hormone therapy for node-negative early-stage breast cancer: randomized trial with 7-year update

A randomized adjuvant trial compared tamoxifen 20 mg daily for 5 years with high-dose oral medroxyprogesterone acetate (MPA) 1 g orally for 9 months. One hundred ninety-four patients with histologically proven primary node-negative breast carcinoma were enrolled between December 1990 and October 1996, with 98 patients randomized into the tamoxifen arm and 96 into the MPA arm. At a median follow-up of 86 months, 25 relapses and 13 deaths were recorded. The relapse-free survival rate at 7 years in the tamoxifen arm was 93%, versus 81% in the MPA arm (P = 0.02). The difference was observed in patients with stage T2 disease (100% in the tamoxifen group vs. 64% in the MPA group; P = 0.01), in younger and/or premenopausal patients (in patients < 50 years of age, 100% in the tamoxifen arm vs. 81% in the MPA arm [P = 0.02], and in patients > or = 50 years of age, 90% in the tamoxifen arm vs. 82% in the MPA arm [P = 0.16]). Also, the overall survival rate at 7 years was lower in women < 50 years of age (P = 0.04).

Adjuvant high-dose medroxyprogesterone acetate for early breast cancer: 13 years update in a multicentre randomized trial

The authors updated their report on a randomized trial initiated in 1982 comparing, in early breast cancer, high-dose IM Medroxyprogesterone acetate (HD-MPA) adjuvant hormonotherapy during 6 months with no hormonotherapy; node-positive patients also received 6 courses of IV CMF (day 1, day 8; q.4 weeks). 246 node-negative (NN) and 270 node-positive (NP) patients had been followed for a median duration of 13 years. Previous results were confirmed in this analysis on mature data. In NN patients, relapse-free survival (RFS) was improved in the adjuvant hormonotherapy arm, regardless of age while overall survival (OAS) was also increased in younger (less then 50 years) patients. In the whole group of NP patients, no difference was seen regarding RFS or OAS. However, an age-dependant opposite effect was observed: younger patients (< 50) experienced a worse and significant outcome of relapse-free and overall survivals when receiving adjuvant HD-MPA while older patients (> or = 50) enjoyed a significant improvement of their relapse-free survival. For both NN and NP patients, differences in overall survivals observed in older women with a shorter follow-up, were no longer detected.

Benefits of Medroxyprogesterone Acetate (MPA) in Advanced or Recurrent Breast Cancer with Higher Serum Concertration

The efficacy of medroxyprogesterone acetate (MPA) therapy in controlling progressive measurable metastatic breast cancer was assessed in 61 patients. In addition serum MPA concentrations were measured by high performance liquid chromatography (HPLC) and subjective effects of treatment were monitored. Overall 24 patients (39.3%) achieved an objective response(2 complete responses [ CR ] and 22 partial responses [ PR ]). There was no significant relationships between response to therapy and menopausal status, metastatic sites, previous therapy, histological type, or disease-free interval. Patients with estrogen (ER) and progesterone (PgR) receptor-positive tumors responded more frequently. Significant differences in serum MPA concentrations were seen between responders and non-responders, objective tumor shrinkage being seen in patients with serum levels in excess of 55 ng/ml. There were few cases responding to the therapy with serum MPA concentrations lower than 25 ng/ml. The serum MPA levels significantly correlated with an improvement in the performance status and survival. Patients with serum MPA concentrations lower than 25 ng/ml had significantly poorer survival. There was a significant relationship between MPA level and dose per area of boby surface (mg/ m(2)) in cases with CR or PR or no change (NC). However, the serum levels of patients with progressive disease despite therapy were lower than the expected levels based on the body surface area. This study demonstrated that serum MPA concentration is a determining factor for therapeutic benefit in advanced or recurrent breast cancer.

High-dose progestin therapy for metastatic breast cancer

Progestin therapy has become an established endocrine modality for the treatment of metastatic breast cancer, with medroxyprogesterone acetate and megestrol acetate being the most widely used agents. Both drugs display similar effectiveness as initial and secondary therapy for patients with advanced disease, with combined complete and partial response rates of approximately 30% to 40%. Uncontrolled trials have suggested that high doses of medroxyprogesterone may be more effective than lower doses, but randomized trials have yielded conflicting results. Clinical trials of megestrol acetate have demonstrated it to be an affective, well-tolerated oral progestin, and a recent randomized trial has suggested that higher megestrol acetate doses may be associated with not only improved response but also improved time to disease progression and survival. Further trials of high-dose megestrol acetate for both initial and secondary therapy are under way, and their results will provide valuable information concerning the role of such treatment.

Progestins in breast cancer treatment. A review

The two most widely used synthetic progestins in breast cancer treatment, medroxyprogesterone acetate (MPA) and megestrol acetate (MA), are reviewed with regard to pharmacological, endocrinological and clinical aspects. In high oral doses as second- or first-line endocrine therapy in advanced breast cancer, they give a similar response rate as tamoxifen (TAM) and aminoglutethimide (AG). The mechanism of action is probably complex. Considerable changes in serum levels of different hormones are induced by progestin treatment. The decrease of serum estrone sulfate (E1S) may be part of the therapeutic mechanism. Some studies suggest that the two drugs, MPA and MA, have a different mode of action, and possibly a low cross resistance. Randomized studies using the two progestins with a cross-over design may answer these questions. Further studies on the influence of progestin on different receptors and growth factors are warranted. To determine the most effective clinical dose of the two progestins, studies with increasing therapeutic doses are needed.

Improved bioavailability of a new oral preparation of medroxyprogesterone acetate

Medroxyprogesterone acetate (MPA) is widely used in the hormonal therapy of breast cancer. So far, oral formulations of MPA commercially available present a very low bioavailability, with a less than 10% extent of oral absorption. A new oral preparation of MPA has been recently developed. Based on a pilot study, an open, randomized, crossover trial has been performed on 22 breast and endometrial cancer patients to evaluate the relative bioavailability of this new oral formulation (200-mg sachet, twice daily) as compared with a standard formulation (Farlutal, 500-mg tablet, twice daily). The bioavailability evaluation was mainly based on the area under the curve measured between two administrations at steady state, after 15 days of continuous therapy. Wide interpatient variability of MPA plasma levels after oral MPA administration was confirmed. The MPA plasma levels were higher in patients treated with the new formulation than in patients treated with Farlutal. The relative bioavailability of the new preparation was 3.5 times higher than that of the standard. This new formulation represents a great improvement in the extent of oral absorption of MPA and could lead to better management of hormone-responsive tumors by hormonal therapy.

Sequential alternating medroxyprogesterone acetate and epirubicin in the treatment of advanced breast cancer

A phase II trial of sequential oral medroxyprogesterone acetate (MPA) and epirubicin was performed in 12 postmenopausal women with advanced breast cancer. Patients received MPA at a dose of 500 mg twice daily by mouth for 25 days. Following a 3-day washout, epirubicin was administered in a dose of 75 mg/m2. After a 3-week hiatus, the cycle was recommenced with MPA. Responses were evaluated at the end of the first 25-day period of MPA and following the end of the first cycle. Partial responses were obtained in two patients (17%)--one after the first 25 days of MPA and the other at the end of the first cycle. One of the patients had chest wall disease and the other had hepatic involvement with ascites. Minimal toxicity was experienced from this regimen and the response durations were 2 and 7 months. The response rate reported here does not warrant the further development of sequential therapy. The dose intensity of both MPA and epirubicin are compromised and may be the cause of this low response rate.

Medroxyprogesterone acetate: steady-state pharmacokinetics bioequivalence of two oral formulations

Two micronized oral formulations of medroxyprogesterone acetate (MPA) (Farlutal and Clinovir) were compared in order to evaluate their relative bioavailability. Sixteen female patients with metastatic breast cancer were entered in a randomized cross-over study on 500-mg MPA tablets repeatedly administered (twice daily for 20 days). At the steady state, similar mean +/- SD serum levels of MPA were obtained (131 +/- 44 ng/ml for Farlutal and 136 +/- 45 ng/ml for Clinovir) and the two formulations proved to be bioequivalent (confidence interval at a significance level of 0.95 = 93%-107%).

Adjuvant treatment with high dose medroxyprogesterone acetate in node-negative early breast cancer. A 3-year interim report on a randomized trial (I)

After initial surgery, 240 pre-, peri- or postmenopausal patients with early node-negative breast carcinoma were randomized to receive either no hormone therapy or adjuvant therapy with medroxyprogesterone acetate at high dosage (HD-MPA; 500 mg IM per day times 28 or 500 mg intramuscularly (i.m.) 5 days a week for 5 weeks then 500 mg i.m. twice weekly for the 5 following months. After a median follow-up time of 3 years, relapse-free survival and overall survival appeared significantly improved in the HD-MPA arm. Side effects were tolerable.

Plasma concentrations of medroxyprogesterone acetate and megesterol acetate during long-term follow-up in patients treated for metastatic breast cancer

A total of 32 patients with metastatic breast cancer responding with at least disease stabilization to treatment with two commercially available preparations of medroxyprogesterone acetate (MPA) or one preparation of megestrol acetate (MA) were followed for their plasma concentrations. The MPA and MA were measured by HPLC. MPA from Upjohn and Farmitalia was given to 12 patients (median age, 61 years; median follow-up, 20 weeks) and 8 patients (54 years, 16 weeks), respectively, on a schedule of 1000 mg daily i.m. for 10 days followed by 200 mg t.i.d.p.o. for the remainder of the treatment course. The peak concentrations (means, 163 vs 97 ng/ml), the time to peak levels (medians, 3 vs 10 weeks), and the areas under the concentration curves from time 0 to 24 weeks (means, 2400 vs 1868 ng/ml X weeks) were significantly different in the respective treatment groups (t-test; significance level, 0.05). MA from Bristol-Myers was administered orally in one daily dose of 160 mg throughout the treatment course in 12 patients (median age, 51 years; median follow-up, 20 weeks). A mean MA peak concentration of 218 ng/ml was reached after a median of 7 days. Plateau plasma levels were higher for MA than MPA.

Aminoglutethimide and medroxyprogesterone acetate in the treatment of patients with advanced breast cancer. A phase II study of the Association of Medical Oncology of the German Cancer Society (AIO)

One hundred twenty-eight women with advanced metastatic breast cancer were treated with a combination of aminoglutethimide (AG) (1000 mg orally, daily) and medroxyprogesterone acetate (MPA) (1500 mg orally, daily for six weeks and thereafter 500 mg orally, daily; omitting cortisone substitution). AG/MPA did not lead to side effects other than those described under AG or MPA monotherapy. Mental and personality changes seem to be more severe and frequent under combined therapy than under monotherapy. Impairment of mental functions, depressive syndromes, fatigue, ataxia, skin rash, and transient increase of gammaglutamyl transferase appeared and disappeared within the first 4 to 6 weeks of treatment. Objective remissions of at least 3 months duration from initiation of therapy were seen in 21 of 128 patients (21.9%) (3.9% complete remission [CR], 18% partial remission [PR]). A no change (NC) status occurred in an additional 25.8%. The remission duration (mean and range) was 19 (10.5-54) for CR, 16.5 (4.5-52+) for PR and 6 (3-27) months for NC patients. The highest response rate was registered for patients with only bone involvement (PR, 11; and NC, 11 of 26 patients). There was a distinct correlation of response to prior systemic treatment, receptor status of the primary tumor, disease-free interval, menopausal status, age and condition of the patient. PR was obtained in 4 of 20 patients with receptor-negative primary tumors. These results justify a prospective trial comparing AG/MPA with other forms of endocrine therapy in selected patient subgroups.

Medroxyprogesterone acetate pharmacokinetics following oral high-dose administration in humans: a bioavailability evaluation of a new MPA tablet formulation

The pharmacokinetics of medroxyprogesterone acetate (MPA) in healthy female volunteers have been investigated following oral administration of single doses of six different high-dose MPA tablet formulations. Blood samples were obtained over 96 hrs following administration. The plasma was separated and analyzed in duplicate for MPA by radioimmunoassay (RIA) after extraction with petroleum ether. A two compartment open model with first order absorption was computer-fitted to the plasma concentration of MPA. Following oral administration MPA is rapidly transferred from the gastrointestinal tract to the blood circulation with a half-life of the absorption process of 15-30 min. The peak plasma concentration is reached 1-3 hrs after administration, and the biological half-life of MPA is 40-60 hrs. Following administration of 1000 mg MPA the areas under the plasma concentration-time curves (AUC 0-infinity) were calculated to (mean and S.E.): 3357 (438) nmol/l and 2403 (245) nmol/l for Leo formulation A and Farlutal, respectively (P less than 0.02). Following administration of 500 mg the areas were: 2325 (389) nmol/l, 1793 (312) nmol/l, 1778 (239) nmol/l, 1178 (209) nmol/l, and 556 (89) nmol/l for Gestapuran, Leo formulation A (P = n.s.), Leo formulation B (P = n.s.), Provera (P less than 0.001), and Lutopolar (P less than 0.001), respectively. The in vitro dissolution rates of MPA from the tablet formulations were determined and compared with the results of the bioavailability studies, indicating that a rapid dissolution rate as well as the particle size of MPA are two important factors to ensure optimal absorption of MPA from the gastrointestinal tract.

Lack of correlations between plasma concentration of medroxyprogesterone acetate, hypothalamic-pituitary function, and tumour response in patients with advanced breast cancer

Plasma medroxyprogesterone acetate (MPA) concentrations were measured in 61 patients with advanced breast cancer, after 3 weeks' treatment using 200 mg PO 8-hourly, to determine whether the previously reported wide interpatient variations correlated with tumour response or toxicity. Seventeen patients (28%) responded to the drug, and their mean plasma MPA concentration was 97 ng/ml +/- 68 SD, compared with 115 ng/ml +/- 87 SD for the patients whose disease progressed. Side-effects attributed to MPA were seen in 18 patients, who had a mean drug concentration of 113 ng/ml +/- 104 SD. This was not significantly higher than that of the patients who did not experience drug toxicity. Because of a suggestion that some of the antitumour activity of the drug could be mediated via an effect on the hypothalamic-pituitary axis, we also measured plasma FSH, LH, and prolactin concentrations after the 3-week treatment with MPA, but found no correlations with either drug concentration or tumour response. These results indicate that with the present treatment schedule the monitoring of plasma MPA concentrations has no role in routine practice and suggest that the inherent sensitivity of the tumour to progesterone is probably the major determinant of response.

Pharmacokinetic and pharmacodynamic basis for the treatment of metastatic breast cancer with high-dose medroxyprogesterone acetate

Postmenopausal patients with metastatic breast cancer were treated with medroxyprogesterone acetate (MPA) (Clinovir) in dosages between 500 and 1500 mg orally per day. The relation of MPA plasma concentrations and endocrine effects were studied in a longitudinal fashion. MPA exerted suppressive effects on the basal and gonadotropin-releasing hormone (GnRH) stimulated gonadotropin secretion, cortisol, dehydroepiandrosterone (DHEA), and estradiol (E2) in a dose-dependent manner leading to a complete suppression with 1500 mg orally per day. The depression of thyroid hormones (T3 and T4) coincided with a depression of the thyroxine-binding index (TBI). MPA did not affect human growth hormone (hGH), basal and thyrotropin-releasing hormone (TRH) stimulated thyroid-stimulating hormone (TSH) and aldosterone. Basal and TRH-stimulated prolactin (PRL) secretion showed a slight but distinct elevation. From these data it is concluded that in postmenopausal patients MPA exerts its antitumor activity by an interference with the hypothalamo-pituitary adrenal axis in the sense of a selective pharmacologic hypophysectomy leading to complete suppression of adrenal steroid secretion. Additionally, MPA inhibits tumor cell growth through the progesterone receptor. A dual mechanism for the antitumor activity of high dose is postulated MPA: ablative through suppression of the hypothalamo-pituitary-adrenal axis and subsequent estrogen deprivation, and additive via the progesterone receptor directly on the tumor cell. The significance of gonadotropin suppression in the postmenopause for breast cancer growth is unclear. The depression of T3 and T4 is due to a depression of thyroid hormone-binding proteins. The elevation of PRL secretion may be explained by a slight estrogenic activity of MPA metabolites.

Additive hormonal therapy in women with advanced breast cancer

A great deal of work has been done over the last decade in the assessment of additive hormonal treatment approaches in women with advanced breast cancer. This work has been prompted by a number of factors which include: (1) the introduction of new hormonal agents, (2) increased knowledge of the physiologic actions of several hormonal agents, (3) the development of hormonal receptor assays to better predict the probability of hormonal responsiveness in a given patient, and (4) the apparent plateau in efficacy of cytotoxic chemotherapeutic approaches. The hormonal agents that have been studied most extensively in the recent past include tamoxifen (an antiestrogen), aminoglutethimide (an aromatase inhibitor), and medroxyprogesterone acetate (a progestin). In postmenopausal women, several agents exist that appear about equal in efficacy; but, currently, tamoxifen appears to be preferred as the initial hormonal treatment, primarily because of its low incidence of side effects. Studies involving combination hormonal therapy have produced interesting results, but further work is needed to establish superiority over tamoxifen alone. In premenopausal women, tamoxifen does have antitumor activity in some patients but has not been established as a replacement for oophorectomy. Properly conducted comparative trials will remain essential for the determination of the proper place of newer hormonal therapy approaches in clinical practice.

[High dose medroxyprogesteroneacetate in metastasizing breast cancer: correlations between course of the disease and hormone profiles]

Based upon preliminary observations that tumor response to MPA was correlated to cortisol suppression 42 patients were treated with MPA at different dose levels. 1500 mg MPA p.o. almost completely suppressed endogenous cortisol production in 23 out of 23 patients. Consequently, 51 patients with advanced stage metastatic breast cancer were treated with Medroxyprogesteroneacetate (HD-MAP) at a dosage of 1500 mg p.o. daily or 500 mg i.m. on 5 days per week. There were 5 complete and 7 partical remissions, 23 patients with no change and 10 with progressive disease. 7 patients were not evaluable. Clinical results correlated to plasma cortisol and prolactin blood levels bot not to LH, FSH, TSH, TBI, T3, T4, ACTH and aldosterone measurements. There was no patient with relapse and suppressed cortisol or normal prolactin measurements. The development of pituituary resistance to MPA is suggested. HD-MPA was equally effective in estrogen and/or progesterone receptor positive as in receptor negative patients. It is proposed that cortisol and prolactin determinations are useful to monitor for effective MPA treatment and the early detection of MPA resistance.

Plasma concentrations of megestrol acetate and medroxyprogesterone acetate after single oral administration to healthy subjects

Plasma concentrations of megestrol acetate (MA) were measured by radioimmunoassay (RIA) after a single oral dose of 60 mg either in the form of one tablet, or four 15 mg tablets, to 10 women 21-40 years old using a cross-over design. No statistically significant difference between the two preparations was observed with respect to plasma concentrations, the area under the curve from 0 to 24 h or the maximum concentration (c(max)). For comparison, data are presented on the plasma level of medroxyprogesterone acetate (MPA) following a single oral dose of 100 mg given using a cross-over design in two different tablet forms to 10 healthy men, when no significant difference was observed for these parameters. The mean c(max) for MA after 2.6 h was 43.9 ng/ml (range 21.7-87.7 ng/ml), whereas that for MPA at 3.1 h was 13.1 ng/ml (range 4.4-29.5 ng/ml) despite the higher dose. After 24 h immunoreactive MA and MPA ranged from 9.6 to 29.0 ng/ml and from 0.2 to 4.0 ng/ml respectively. Moreover, it was found that petroleum ether extraction gives the most specific result by RIA, although considerable amounts of metabolites are still co-estimated. By comparison with selected ion monitoring using GC-MS, metabolite interference in RIA increases with time after administration of the steroids and is considerably greater for MPA than for MA. It is concluded that after oral administration the relative bioavailability of MA is significantly better than that of MPA.