Treatment of carcinoma of the breast with high dose oral medroxyprogesterone acetate: does increased bioavailability improve the therapeutic ratio?

Medroxyprogesterone acetate (MPA) is regarded as a valuable hormonal therapy for metastatic breast cancer. The drug is manufactured by more than one pharmaceutical company, and one particular brand of oral MPA (Provera Tablets, Upjohn) has been reformulated to incorporate micronized particles, providing significantly enhanced bioavailability. The response rate and side-effect data from a pilot study, which used the old formulation Provera Tablets 100 mg at a dosage of 800 mg/day in 28 patients with recurrent breast cancer after treatment with tamoxifen, are compared with those from another study in which 59 similar patients received 800 mg/day of new formulation Provera Tablets 200 mg. Neither of these studies, conducted in the United Kingdom, has previously been published. The response rates were similar in both studies, but there were higher incidences of significant weight gain and increased blood pressure in those patients treated with the new formulation. These side effects have been noticed by other workers employing new formulation MPA at a dosage of 800 mg per day, while it has been reported that reducing the dosage to 400 mg perday is accompanied by a lower incidence of side effects, without affecting the response rate. It is concluded that the increased serum levels of MPA, made possible by the micronized product, do not favourably influence the response of metastatic breast cancer to therapy, but may be associated with a higher incidence of side effects. Reducing the dosage of the new formulation MPA to 400 mg/day may allow a more acceptable side-effect profile, without loss of therapeutic efficacy. Such a dose reduction would make this brand of MPA more cost effective.

The multidrug resistant phenotype in clinical practice; evaluation of cross resistance to ifosfamide and mesna after VP16-213, doxorubicin and vincristine (VPAV) for small cell lung cancer.

Eight-eight previously untreated patients with small cell lung cancer were treated with a combination of VP16, adriamycin and vincristine (VPAV) for three courses. Resistance to these drugs is associated with the multidrug resistance (MDR) membrane glycoprotein in cell lines in vitro. The clinical relevance of this mechanism of resistance was assessed by using a second line treatment with intravenous infusions of ifosfamide/mesna 5 g/m2 every 3 weeks in patients with only partial responses or non-responders. Cross-resistance to alkylating agents is rare in the MDR. Ifosfamide produced partial responses in six (43%) of 14 patients unresponsive to prior therapy. Intravenously infused ifosfamide/mesna was also used in consolidation therapy with only minor bone marrow or urinary tract toxicity. This did not prevent CNS relapse. The overall response rate to VPAV was 69% and for all treatment modalities, 75%. Median survival for all patients ws 39.5 weeks and 59 weeks for all patients attaining complete response. The addition of large fraction chest irradiation given with the final course of induction chemotherapy to those with good chemotherapy responses produced a further response in 44% of assessable patients. Combined modality treatment resulted in moderate and reversible toxicity. The lack of improved survival with ifosfamide and the resistance of the majority of patients to salvage with ifosfamide/mesna suggested that the MDR is not the major mechanism of resistance in the clinic, since cross-resistance to alkylating agents of this type is not a feature of MDR cells.

Experience with 24-h infusions of ifosfamide/mesna in small cell lung cancer.

Two studies were carried out (A and B) in order to assess the effectiveness of ifosfamide administered with mesna (IFO/M) in the treatment of small cell lung cancer. The first study (A) was a cross-over study; the second (B) was a randomized trial, and in B IFO/M was evaluated earlier in the course of the disease. IFO/M given be infusion is effective as second-line therapy and can be administered with other cytotoxics at the doses reported here earlier in the course of the disease. The complete remission rates were high.