1 . Combinations of taxol, Taxotere and their derivatives with at least one substance which is therapeutically useful in the treatment of neoplastic diseases.
2 . Combinations of Taxotere with alkylating agents, antimetabolites, spindle poisons, epidophyllotoxins, antibiotics, enzymes, topoisomerase inhibitors, various compounds chosen from procarbazizne, mitoxantrone or platinum coordination complexes, biological response modifiers or growth factor inhibitors.
3 . Combinations according to claim 2 , characterized in that the alkylating agents are chosen from cycldphosphamide, ifosfamide, melphalan, hexamethylmelamine, thiotepa or dacarbazine.
4 . Combinations according to claim 2 , characterized in that the antimetabolites are chosen from 5-fluorouracil, cytarabine and folic acid analogues chosen from methotrexate, idatrexate and trimetrexate.
5 . Combinations according to claim 2 , characterized in that the spindle poisons are chosen from vinca alkaloids, their synthetic or semi-synthetic analogues, or estramustine or taxoids.
6 . Combinations according to claim 2 , characterized in that the epidophyllotoxins are chosen from etoposide and teniposide.
7 . Combinations according to claim 2 , characterized in that the antibiotics are chosen from daunorubicin, doxorubicin, bleomycin and mitomycin.
8 . Combinations according to claim 2 , characterized in that the enzyme is L-asparaginase.
9 . Combinations according to claim 2 , characterized in that the topoisomerase inhibitors are chosen from camptothecin and its derivatives chosen from CPT-11 and topotecan and pyridobenzoindole derivatives.
10 . Combinations according to claim 2 , characterized in that the various compounds are chosen from procarbazine, mitoxantrone and platinum coordination complexes chosen from cisplatin and carboplatin.
11 . Combinations according to claim 2 , characterized in that the biological response modifiers and growth factor inhibitors are chosen from interferons and interleukins.
12 . Combinations according to one of claims 1 to 11 , characterized in that they contain, in addition, growth factors of the haematopoietic type.
13 . Combinations according to one of claims 1 to 12 , characterized in that they contain from 10 to 90% by weight of taxol, Taxotere or their analogues.
14 . Products containing Taxotere or their analogues and at least one substance which is therapeutically useful, as defined in one of claims 1 to 12 , in the treatment of neoplastic diseases, as a combined preparation for use simultaneously, separately or spaced out over a period of time in anticancer therapy.
 The present invention relates to combinations of taxol, Taxotere and their analogues and substances which are therapeutically useful in the treatment of neoplastic diseases.
 Taxol, Taxotere and their analogues, which possess noteworthy antitumour and antileukaemic properties, are especially useful in the treatment of cancers of the ovary, breast or lung.
 The preparation of taxol, Taxotere and their derivatives form the subject, for example, of European Patents EP 0,253,738 and EP 0,253,739 and International Application PCT WO 92/09,589.
 Generally, the doses used, which depend on factors distinctive to the subject to be treated, are between 1 and 10 mg/kg administered intraperitoneally or between 1 and 3 mg/kg administered intravenously.
 It has now been found, and this forms the subject of the present invention, that the efficacy of taxol, Taxotere and their analogues nay be considerably improved when they are administered in combination with at least one substance which is therapeutically useful in anticancer treatments and has a mechanism identical to or different from this of taxane derivatives.
 Among substances which may be used in association or in combination with taxol, Taxotere or their analogues, there may be mentioned alkylating agents such as cyclophosphamide; isosfamide, melphalan, hexamethylmelamine, thiotepa or dacarbazine, antimetabolites such as pyrimidine analogues, for instance 5-fluorouracil and cytarabine or its analogues such as 2-fluorodeoxycytidine, or folic acid analogues such as methotrexate, idatrexate or trimetrexate, spindle poisons including vinca alkaloids such as vinblastine or vincristine or their synthetic analogues such as navelbine, or estramustine or taxoids, epidophylloptoxins such as etoposide or teniposide, antibiotics such as daunorubicine, doxorubicin, bleomycin or mitomycin, enzymes such as L-asparaginase, topoisomerase inhibitors such as camptothecin derivatives chosen from CPT-11 and topotecan or pyridobenzoindole derivatives, and various agents such as procarbazine, mitoxantrone, platinum coordination complexes such as cisplatin or carboplatin, and biological response modifiers or growth factor inhibitors such as interferons or interleukins.
 Moreover, since the activity of the products depends on the doses used, it is possible to use higher doses and to increase the activity while decreasing the toxicity phenomena or delaying their onset by combining growth factors of the haematopoietic type such as G-CSF or GM-CSF or certain interleukins with taxol, Taxotere, their analogues or their combinations with other therapeutically active substances.
 The combinations or associations according to the invention enable the phenomena of pleiotropic resistance or “multi-drug resistance” to be avoided to delayed.
 More especially, the invention relates to combinations of taxol, Taxotere and their analogues with vinca alkaloids, cyclophosphamide, 5-fluorouracil, doxorubicin, cisplatin and etoposide.
 The improved efficacy of a combination according to the invention may be demonstrated by determination of the therapeutic synergy.
 The efficacy of a combination according to the invention may also be characterized by adding the actions of each constituent.
 A combination manifests therapeutic synergy if it is therapeutically superior to one or other of the constituents used at its optimum dose [T. H. CORBETT et al., Cancer Treatment Reports, 66, 1187 (1982)].
 To demonstrate the efficacy of a combination, it may be necessary to compare the maximum tolerated dose of the combination with the maximum tolerated dose of each of the separate constituents in the study in question. This efficacy may be quantified, for example by the log 10 cells killed, which is determined according to the following formula:
log 10 cells killed= T−C (days)/3.32 ×Td
 in which T−C represents the time taken for the cells to grow, which is the mean time in days for the tumours of the treated group (T) and the tumours of the treated group (C) to have reached a predetermined value (1 g for example), and T d represents the time in days needed for the volume of the tumour to double in the control animals [T. H. CORBETT et al., Cancer, 40, 2660.2680 (1977); F. M. SCHABEL et al., Cancer Drug Development, Part B, Methods in Cancer Research, 17, 3-51,. New York, Academic Press Inc. (1979)]. A product is considered to be active if log 10 cells killed is greater than or equal to 0.7. A product is considered to be very active if log 10 cells killed is greater than 2.8.
 The combination, used at its own maximum tolerated dose, in which each of the constituents will be present at a dose generally not exceeding its maximum tolerated dose, will manifest therapeutic synergy when the log 10 cells killed is greater than the value of the log 10 cells killed of the best constituent when it is administered alone.
 The efficacy of the combinations on solid tumours may be determined experimentally in the following manner:
 The animals subjected to the experiment, generally mice, are subcutaneously grafted bilaterally with 30 to 60 mg of a tumour fragment on day 0. The animals bearing tumours are mixed before being subjected to the various treatments and controls. In the case of treatment of advanced tumours, tumours are allowed to develop to the desired size, animals having insufficiently developed tumours being eliminated. The selected animals are distributed at random to undergo the treatments and controls. Animals not bearing tumours may also be subjected to the same treatments as the tumour-bearing animals in order to be able to dissociate the toxic effect from the specific effect on the tumour. Chemotherapy generally begins from 3 to 22 days after grafting, depending on the type of tumour, and the animals are observed every day. The different animal groups are weighed 3 or 4 times a week until the maximum weight loss is attained, and the groups are then weighed at least once a week until the end of the trial.
 The tumours are measured 2 or 3 times a week until the tumour reaches approximately 2 g, or until the animal dies if this occurs before the tumour reaches 2 g. The animals are autopsied when sacrificed.
 The antitumour activity is determined in accordance with the different parameters recorded.
 For a study of the combinations on leukaemias, the animals are grafted with a particular number of cells, and the antitumour activity is determined by the increase in the survival time of the treated mice relative to the controls. The product is considered to be active if the increase in survival time is greater than 27%, and is considered to be very active if it is greater than 75% in the case of P388 leukaemia.
 The results obtained with combinations of Taxotere and various chemotherapeutic agents, such as cyclophosphamide (alkylating agent), 5-fluorouracil (antimetabolite), etoposide (semisynthetic podophyllotoxin agent) and vincristine (vinca alkaloid), the combinations being used at their optimum dose, are given as examples in the following tables.
TABLE 1 Activity of the combination Taxotere + cyclophosphamide at the optimum dose against advanced MA13/c mammary adenocarcinoma grafted subcutaneously Dose Total log 10 mg/kg/injection Administration dose cells Product i.v. on days: mg/kg killed Taxotere 15 14, 17, 20 45 2.8 Cylcophosphamide 118 14 118 1.3 Taxotere + 7.5 14, 17, 20, 14 22.5 3.4 cyclophosphamide 90.0 90
  TABLE 2 Activity of the combination Taxotere + etoposide at the optimum dose against early B16 melanoma grafted subcutaneously Dose Total log 10 mg/kg/injection Administration dose cells Product i.v. on days: mg/kg killed Taxotere 17.5 4, 7, 10, 13 70 2.8 Etoposide 46.2 4, 7, 10, 13 184.8 2.8 Taxotere + etoposide 15.7 4, 7, 10, 13 62.8 4.1 13.8 (simultaneous) 55.2
  TABLE 3 Activity of the combination Taxotere + 5-fluorouracil at the optimum dose against advanced C38 colon adenocarcinoma grafted subcutaneously Dose Admini- Total log 10 mg/kg/injec- stration dose cells Product tion i.v. on days: mg/kg killed Taxotere 22 21, 25, 29, 33 88.0 1.4 5-fluorouracil 43.4 21, 25, 29, 33 173.6 1.1 Taxotere 17.6 21, 25, 29, 33 70.4 4.8 + 27.0 (simul- 108.0 5-fluorouracil taneous)
  TABLE 4 Activity of the combination Taxotere + vincristine at the optimum dose against P388 leukaemia (10 6 cells i.p.) Dose Total log 10 mg/kg/injection Administration dose cells Product i.v. on days: mg/kg killed Taxotere 17.5 4, 7, 10, 13 70 2.8 vincristine 46.2 4, 7, 10, 13 184.8 2.8 Taxotere + vincristine 21.75 1, 4, 7 65.25 62 1.2 (simultaneous) 3.6 Taxotere + vincristine 21.75 1, 4, 7 65.25 77 1.2 (4 hours 3.6 apart)
 The present invention also relates to pharmaceutical compositions containing the combinations according to the invention.
 The products of which the combination are composed may be administered simultaneously, separately or spaced out over a period of time so as to obtain the maximum efficacy of the combination; it being possible for each administration to vary in its duration from a rapid administration to a continuous perfusion.
 As a result, for the purposes of the present invention, the-combinations are not exclusively lid ted to those which are obtained by physical association of the constituents, but also to those which permit a separate administration, which can be simultaneous or spaced out over a period of time.
 The compositions according to the invention are preferably compositions which can be administered parentally. However, these compositions may be administered orally or intraperitoneally in the case of localized regional therapies.
 The compositions for parental administration are generally pharmaceutically acceptable, sterile solutions or suspensions which may optionally be prepared as required at the time of use. For the preparation of non-aqueous solutions or suspensions, natural vegetable oils such as-olive oil, sesame oil or liquid petroleum or injectable organic esters such as ethyl oleate may be used. The sterile aqueous solutions can consist of a solution of the product in water. The aqueous solutions are suitable for intravenous administration provided the pH is appropriately adjusted and the solution is made isotonic, for example with a sufficient amount of sodium chloride or glucose. The sterilization may be carried out by heating or by any other means which does not adversely affect the composition. The combinations may also take the form of liposomes or the form of an association with carriers as cyclodextrins or polyethylene glycols.
 The compositions for oral or intraperitoneal administration are preferably aqueous suspensions or solutions.
 In the combinations according to the invention, the application of the constituents of which may be simultaneous, separate or spaced out over a period of time, it is especially advantageous for the amount of taxane derivative to represent from 10 to 90% by weight of the combination, it being possible for this content to vary in accordance with the nature of the associated substance, the efficacy sought and the nature of the cancer to be treated.
 The combinations according to the invention are especially useful in the treatment of cancers of the breast, ovary or lung. In particular, they can afford the advantage of being able to employ the constituents at considerably lower doses than those at which they are used alone.
 The example which follows illustrates a combination according to the invention.
 10-cm 3 ampoules containing 100 mg of Taxotere are prepared, for intravenous administration, according to the usual technique.
 5-cm 3 ampoules containing 100 mg of etoposide are prepared, for intravenous administration, according to the usual technique.
 These solutions are administered simultaneously, after appropriate dilution, by perfusion.
 The treatment may be repeated several times daily or weakly until there is a partial or total remission or a cure.