Vol. 3, 1527-1533, September 1997 Clinical Cancer Research 1527
Mitoxantrone Combined with Paclitaxel as Salvage Therapy for
Platinum-refractory Ovarian Cancer: Laboratory Study and
Clinical Pilot Trial1
Christian M. Kurbacher,2 Howard W. Bruckner,
Ian A. Cree, Jutta A. Kurbacher,3
Lucas Wilhelm, Gerald P#{246}ch,Dorit Indefrei,
Peter Mallmann, and Peter E. Andreotti
Department of Gynecology and Obstetrics, University of CologneMedical Center, D-5093l Cologne, Germany [C. M. K., L. W., P. M.];Division of Neoplastic Diseases, Derald H. Ruttenberg Cancer Center,Mount Sinai School of Medicine, New York, New York 10029[H. W. B.]; Department of Pathology, Institute of Ophthalmology,University College London, London EC1V 9EL, United Kingdom
[I. A. C.]; Department of Gynecology and Obstetrics, University ofBonn Medical Center, D-53105 Bonn, Germany [J. A. K., D. I.];Institute of Pharmacology and Toxicology, University of Graz,
A-8020 Gras, Austria [G. P.]; and Atlantic Scientific DevelopmentInc., Boca Raton, florida 33428 [P. E. A.]
ABSTRACT
This report describes preclimcal and early clinical in-
vestigations of the mitoxantrone/paclitaxel combination
(NT) for patients with platinum-refractory ovarian cancer.
The preclinical activity of NT was studied ex vivo, evaluating
native tumor specimens with the ATP tumor chemosensitiv-ity assay. Of 24 tumors tested, 20 (83%) were sensitive to
NT, whereas 7 (29%) responded to mitoxantrone and 8
(33%) responded to paclitaxel. In the majority of tumorsassayed (19 of 24), potentiating or major independent effects
between both agents were found. Subsequently, a clinical
pilot trial of NT was initiated for patients with platinum-
refractory ovarian cancer. Patients had failed one to four
(median, two) prior chemotherapy regimens. In 11 cases, NTwas administered every three weeks with 8 mg/rn2 mito-
xantrone and 180 mg/rn2 paclitaxel (NT-I). Seven patientswere treated biweekly with 6 mg/rn2 mitoxantrone andweekly with 100 mg/rn2 paclitaxel (NT-Il). During 92 NTcourses, myelosuppression with leucopenia, anemia, and
thrombocytopenia was the limiting toxicity, occurring morefrequently with NT-Il. No patient required hospitalization
Received 12/30/96; revised 5/15/97; accepted 5/17/97.The costs of publication of this article were defrayed in part by the
payment of page charges. This article must therefore be hereby markedadvertisement in accordance with 18 U.S.C. Section 1734 solely to
indicate this fact.
‘ Supported in part by DCS Innovative Diagnostik Systeme, Hamburg,Germany.2 To whom requests for reprints should be addressed, at Department ofGynecology and Obstetrics, University of Cologne Medical Center,Kerpener Strasse 34, D-50931 Cologne, Germany. Phone: 49-221-478-4910; Fax: 49-221-478-4929.3 Present address: Department of Obstetrics and Gynecology,Johanniter-Krankenhaus, Johanniterstrasse 3-5, 53 1 1 3 Bonn, Germany.
due to any life-threatening complication. Five complete and
nine partial remissions were observed with both NT-I and
NT-Il, accounting for an overall 78% response rate, with a
median progression-free survival of 40 weeks. One patientshowed early progression during therapy. Currently, three
patients (NT-I, two; NT-H, one) have died due to progressive
relapsed ovarian cancer, so that the median overall survival
is not reached after a median follow-up of 40.5+ weeks.
Both schedules were found to be equal in terms of responserate and overall survival. NT is highly active and practical
for salvage treatment of ovarian cancer. NT-Il may be pre-ferred due to both clinical activity and patients’ acceptance.However, NT-I seems to be a less myelotoxic alternative.Both schedules warrant further clinical investigation.
INTRODUCTION
Primary ovarian carcinomas frequently respond to chemo-
therapy. Remission rates of 60-70% have been observed after
platinum-based first-line therapy, reducing the relative risk of
progression and death to 0.7 (1, 2). Nevertheless, the majority of
patients with advanced disease will relapse, resulting in an
overall 5-year survival of only 20% ( 1 , 2). The likelihood of
relapsing patients to respond to either second-line platinum or
nonplatinum regimens strongly depends on the disease-free in-
terval after completion of initial chemotherapy (2-6). The prob-
ability that platinum-refractory patients (i.e., those presenting
with primary progression or recurrence after �6 months) will
benefit from salvage chemotherapy is limited (2, 3, 6, 7). Pa-
clitaxel (Taxol#{174}), ifosfamide, and altretamine are considered to
be the most active single agents in this setting, but at conven-
tional dosages, they produce RRs4 of no more than 30% (2, 6,
7). Unfortunately, higher RRs achieved with dose-escalated
paclitaxel do not translate into improved PFS and OAS, respec-
tively (6, 8, 9). Introduction of paclitaxel into first-line therapy
of ovarian cancer (10) may even create more problems with
recurrent disease. Recently, altretamine and topotecan have
been considered the most effective agents in this setting (1 1,
12), whereas modest activity was demonstrated for gemcitabine
and reinduction with either carboplatin or paclitaxel (13-15).
Therefore, the search for new salvage regimens remains an
important goal to improve treatment for patients with platinum-
refractory ovarian cancer.
Paclitaxel exhibits synergistic cytotoxicity with a number
4 The abbreviations used are: RR, response rate; ATP-TCA, AlP tumorchemosensitivity assay; CR, complete response; G-CSF, granulocyte
colony-stimulating factor; MI, maximum inhibition; NC, no change;NT, mitoxantrone/paclitaxel; OAS, overall survival; PD, progressivedisease; PFS, progression-free survival; PR, partial response; SI, sensi-tivity index; TDC, test drug concentration.
Research. on August 11, 2020. © 1997 American Association for Cancerclincancerres.aacrjournals.org Downloaded from
1528 NT in Refractory Ovarian Cancer
of cytostatics, including platinum and doxorubicin, for a variety
of animal and human tumors (16). Previous preclinical studies
performed in our laboratories used the ATP-TCA (17) to inves-
tigate the activity of the doxorubicin/paclitaxel combination in
native ovarian carcinomas ( 1 8). This method is a valuable
approach for cx vivo testing of clinical tumors and provides
major advantages over classical chemosensitivity assays in
terms of efficacy, reproducibility, robustness, and evaluability
( 17, 19). Clinical correlations are promising for both ovarian
( 17, 20) and breast tumors ( 19). Based on these investigations,
we observed well-tolerated activity of doxorubicin/paclitaxel in
patients with platinum-refractory ovarian cancer who had failed
both single agents (2 1 ). The clinical utility of this combination,
however, may be compromised by the considerable nonhema-
tological side effects of doxorubicin. In particular, cardiotoxic-
ity and mucotoxicity of doxorubicin can be potentiated when
used in combination with paclitaxel (22-24).
The synthetic anthracenedione mitoxantrone (Novantrone)
can often be regarded as a clinical substitute for anthracyclines
(23, 25). It compares favorably to doxorubicin in terms of its
markedly reduced organ toxicity (25, 26). In tests of periopera-
tive breast and ovarian carcinomas, our laboratories have pre-
viously demonstrated that both agents usually have similar
activity, but there seem to be instances of non-cross-resistance
in which mitoxantrone may be superior to doxorubicin (27, 28).
In a variety of human cancer cell lines and some perioperative
tumors, we and others have found NT to be highly synergistic
and, therefore, possibly the best combination (28, 29).
Doxorubicin/paclitaxel is at the forefront of clinical inves-
tigation for breast cancer (30) and exhibits preclinical and
clinical activity against recurrent ovarian cancer as well (21,
3 1 ). NT represents a logical next step that may be less toxic.
This article describes new evidence that NT has high preclinical
activity against tumor cells taken directly from patients with
platinum-refractory ovarian carcinoma. Based on these ex vivo
results, we have initiated a pilot study of NT at two different
schedules in heavily pretreated ovarian cancer patients. All had
previously failed platinum-based chemotherapy. This report
summarizes the first results of this clinical trial.
MATERIALS AND METHODS
Preclinical Studies
Tumor Samples. The preclinical evaluation of NT used
tumor samples taken directly from 24 patients with platinum-
refractory recurrent ovarian cancer, 17 solid tumors and 7 ma-
lignant ascitic fluids. Tumor material was sampled under sterile
conditions and immediately transferred to the laboratory. Sur-
gical specimens were transported in HBSS (Life Technologies,
Inc., Paisley, United Kingdom) supplemented with 300 units/ml
penicillin and 300 p.g/ml streptomycin. Malignant effusions
were stored natively after adding preservative-free sodium
heparin (Vetren 200; Promonta, Hamburg, Germany) at 25-50
units/ml.
Chemosensitivity Testing. Chemosensitivity was as-
sessed using the ATP-TCA. This assay uses commercially avail-
able test kits (TCA-IO0; DCS Innovative Diagnostik Systeme,
Hamburg, Germany) that include all required material not oth-
erwise identified. ATP-TCA methodology has been described in
detail (17, 19, 27).
Briefly, tumor cells were isolated by mechanical and en-
zymatic dissociation and subsequent Ficoll gradient centrifuga-
tion (Lymphoprep; ICN Flow, Meckenheim, Germany). Viabil-
ity and quality of cell suspensions were determined by trypan
blue dye exclusion (0.2%; Merck, Darmstadt, Germany) and
cytological examination, respectively. Approximately 10,000-
20,000 cells were then seeded into each well of a 96-well
polypropylene microplate. Commercial formulations of mito-
xantrone (Novantron; Cyanamid-Lederle, Wolfratshausen, Ger-
many) and paclitaxel (Taxol#{174}, Bristol-Myers Squibb, Munich,
Germany) were used for this investigation. Single agents and the
combination were tested at six different TDCs (i.e., 6.25-200%
TDC) with 0.6 p.g/ml mitoxantrone and 13.6 p�g/ml paclitaxel as
100% TDC (14, 24). Each TDC was tested in triplicate. Addi-
tionally, both no inhibition (MO) and MI controls were set up for
each microplate.
Assay Evaluation. After 5-7 days of culture at 37#{176}Cin
a humidified 5% CO,. 95% air atmosphere, ATP was extracted
from the cells and subsequently measured luminometncally
using the luciferin-luciferase firefly reaction. Comparing treated
cells with both controls, individual tumor growth inhibition
(TGI) was calculated as:
TGI(%) = [1 - (TDC - MI)/(MO - MI)] x 100 (1)
Individual dose-response curves were constructed for both drugs
and the combination, respectively. IC50 and IC90 were deter-
mined by linear interpolation. Four categories of ex vivo sensi-
tivity were defined as (27): (a) strong sensitivity, IC90 � 100%
TDC and IC50 �25% TDC; (b) partial sensitivity, IC90 >100%
TDC and IC50 �25% TDC; (c) weak sensitivity, IC90 � 100%
TDC and IC50 >25% TDC; and (6) resistance, IC90 >100%
TDC and IC50 >25% TDC.
Ex vivo RR was defined as:
- (all tumors tested - resistant tumors)RRen,,v(, (all tumors tested) (2)
Additionally, a SI represented by the area under the inhibition
curve was calculated by trapezoidal transformation, with high
values indicating high sensitivity, and low values evidencing
resistance ex vivo (1 7, 27). Drug interactions were analyzed by
the sigmoid model described by P#{246}ch(32). Assuming that both
single agents act independently on tumor cells, a theoretical
dose-response curve for the combination was constructed for
each tumor. Drug interactions were defined as independent if the
experimental dose-response curve was equal to the theoretical
one. Potentiation was assumed if NT produced a significantly
higher cell kill, as could be expected theoretically. In tumors
showing an experimental dose-response curve inferior to the
theoretical one, drug interactions were regarded as relative an-
tagonism (if NT was superior to the best single agent) or
absolute antagonism (if the best single agent was superior to
NT).
Clinical Trial
Patients. Since November 1994, 15 patients with histo-
logically confirmed platinum-refractory ovarian carcinoma
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DODD
o�g8 �9
o�g -D�DD- 2DD�
0 0
O�O
0
00 0�0
Clinical Cancer Research 1529
)( 15000a,�0C
.�.
I5000
U Mitoxantrone Paclitaxel Combination
Fig. I. Distribution of SIs for mitoxantrone (0), paclitaxel (G), and
the combination NT (�) in 24 platinum-refractory ovarian cancers testedex vivo with the ATP-TCA. Horizontal lines, mean values.
(characterized by either progression during initial platinum-
based chemotherapy or relapse after a disease-free interval of
�6 months after a minimum of four courses of platinum drugs)
were enrolled. All patients recruited were distinct from those
who had sent tumors for the preceding ex vivo study. Written
informed consent was obtained from all patients. Two patients
underwent reinduction, resulting in a total of 1 8 NT treatments.
Patients had one to four prior chemotherapies (median, two).
Prior second-line regimens included alkylators, topoisomerase II
inhibitors, paclitaxel, doxorubicin/paclitaxel, and high-dose
chemotherapy with autologous stem cell support. Cytoreductive
surgery was unsuccessfully attempted for eight patients before
NT; none of these operations reduced the tumor to less than 2
cm in diameter.
Eligibility criteria included: (a) bidimensionally measur-
able tumor before starting NT therapy; (b) leukocytes �3,000/
pA, neutrophils �1,500/pA, serum hemoglobin �8 g/dl, and
platelets � 100,000/pA; (c) absence of other severe serum chem-
istry abnormalities; (d) Karnofsky performance status �60%;
(e) an anticipated life span of � 12 weeks; and (f) complete
recovery from surgery.
Before starting NT, patients underwent complete tumor
staging including serum marker measurements (CA 125, CEA,
or CA 19-9), transvaginal and abdominal ultrasound, thoracic
X-ray scans, and computed or magnetic resonance tomography
of both chest and abdomen, if indicated.
Chemotherapy. In 1 1 cases, NT was administered every
three weeks with iv. bolus injections of 4 mg/m2 mitoxantrone
on days 1 and 2 followed by a 24-h infusion of 180 mg/m2
paclitaxel (NT-I). Routine supportive treatment included both
antiemesis and delivery of corticosteroids, clemastine, and ra-
nitidine for prevention of hypersensitivity-like reactions. En-
couraging preliminary experiences with weekly fractionated pa-
clitaxel evidenced both considerable clinical activity and well-
tolerated toxicity that might be particularly important for
combination chemotherapy (33-35). The regimen was thus mod-
ified in the remainder to provide an optimized protocol for
future Phase Il/Ill trials. This schedule used a 6 mg/m2 bolus
injection of mitoxantrone on day 1 followed by a I -h infusion of
100 mg/m2 paclitaxel on days I and 8 (NT-Il). The whole course
was repeated on day 15. Between courses 3 and 4, treatment was
Table I Patterns of chemosensitivity cx viva exhibited by 24perioperative ovarian cancer specimens”
Pattern of
Drug(s)
chemosensitivity
Partial Weaktested Sensitivity sensitivity sensitivity Resistance
Mitoxantrone 3 - 4 17Paclitaxel 2 3 3 16
NT 13 - 7 4a Response rate ex vivo: mitoxantrone. 7 of 24 (29%): paclitaxel. 8
of 24 (33%); NT, 20 of 24 (83%).
interrupted for 1 week. G-CSF was used if leukocytes were
<2,000/pA or the neutrophils were < 1,000/pA. Delayed hema-
tological recovery in spite of G-CSF or any severe organ tox-
icity required both dose reduction or interval prolongation until
recovery of bone marrow or any other involved organ. In re-
sponding patients, a maximum of six NT courses was adminis-
tered. Therapy was discontinued in patients with evidence of
either progression or unresolved life-threatening toxicities.
Evaluation of Toxicity. Patients enrolled in this trial
were regarded as eligible for toxicity if they received at least one
course of NT. All adverse effects were monitored and recorded
using the WHO score. Toxicity was assessable for all 18 NT
therapies.
Evaluation of Response. Therapy was monitored by
measurements of the appropriate serum marker preceding each
NT course. Tumor evaluation was performed every 6 weeks by
transvaginal ultrasound, X-ray scan or computed tomography of
the chest, and computed or magnetic resonance tomography of
the abdomen, respectively. Additional tumor imaging was per-
formed at any time when progression was suspected. A mini-
mum of two NT cycles was required to classify a patient as
evaluable for response. Responses were assessed using standard
criteria: (a) CR, complete disappearance of all measurable tu-
mor and normalization of elevated serum markers for a mini-
mum of 4 weeks; (b) PR, a �50% decrease in the sum of the
products of two diameters of all measurable lesions (or clinical
CR with elevated tumor markers) for at least 4 weeks; (c) NC,
any condition distinct from CR, PR, or PD; and (d) PD, a �25%
increase in the sum of two diameters of all measurable lesions or
the appearance of new metastases.
Follow-Up. All patients entered a follow-up program
including gynecological checks, transvaginal ultrasound, and
measurements of tumor markers every 3 months. Tumor imag-
ing was performed as appropriate. OAS and PFS were measured
from the start of the first NT course. All causes of death were
used to calculate OAS. PFS was defined as the minimal interval
between commencing NT therapy and evidence of progression,
death, or loss to follow-up.
Statistics. Statistical calculations were performed using
GraphPAD software (San Diego, CA). SI values for mitox-
antrone, paclitaxel, and NT were analyzed by repeated measure
ANOVA. Differences in ex vivo RRs were analyzed by extended
x2 tests. Survival analyses were performed using Kaplan-Meierprocedures. For all statistical calculations, P �O.05 indicated
significance.
Research. on August 11, 2020. © 1997 American Association for Cancerclincancerres.aacrjournals.org Downloaded from
Patient(initials)
Age(yrs)
Priorchemotherapy” Metastatic site”
NTschedulec
No. ofNT courses
Quality ofresponse
TPP”(wks)
C. B. 43 aCP, EPI, aCC Pelvis, abdomen I 6 CR 88+M. C. 48 CC, CP Pelvis, abdomen I 6 CR 76+M. E. 55 CP, VP-l6 Pelvic, paraaortic LNS I 3 NC 65+B. F. 67 CP Pelvis, abdomen, lung I 2 PD - (alive)P. F. 63 CC Abdomen, abdominal wall, subhepatic LNS I 6 NC 55 (dead)K. 0. (a) 45 CP Pelvis, subhepatic LNS I 6 PR 50 (alive)
K. 0. (b) 46 CP, NT-I, Pelvis, liver, spleen capsule II 6 PR 28K. G. (c) 46 CP, NT-I, NT-Il Pelvis, spleen II 6 PR 16E. K. 63 CC Pelvis, abdomen II 4 NC 10+
M. J. (a) 67 CC, PTX Subhepatic and paraaortic LNS II 4 PR 28
M. J. (b) 68 CC, PTX, NT Subhepatic, retroperitoneal, sigma II 6 PR 20+
R. R. 64 CC, PTX, CP Subhepatic and paraaortic LNS II 6 PR 15+B. R. 35 CC, CI, ICE (high dose) Pelvis, pelvic and paraaortic LNS, bursa omentalis I 6 CR 40 (alive)U. R. 55 CP, TREO Pelvis, abdomen, paraaortic LNS I 2 PR 36+
T. S. 49 CC Pelvis, abdomen I 6 CR 20+M. S. 55 CP Pelvis, paraaortic LNS I 6 CR 23 (dead)R. T. 58 CP, CC, VP-l6, P1 Pelvis, pelvic LNS I 6 PR 20+P. U. 40 CC, aCP, CPA, AT Pelvis, perihepatic and paraaortic LNS, spleen II 4 PR 22 (dead)
a The abbreviations used are: aCC, cytosine arabinoside/carboplatin; aCP, cytosine arabinoside/cisplatin; AT, doxorubicin-paclitaxel; CC,
cyclophosphamide/carboplatin; CI, carboplatin/ifosfamide; CP, cyclophosphamide/cisplatin; CPA, cyclophosphamide; EPI, epirubicin; ICE, ifosf-amide/carboplatin/etoposide; P1, cisplatin/ifosfamide; PTX, paclitaxel; TREO, treosulfan; VP-l6, etoposide.
b LNS, lymph nodes.Cl NT-I; II, NT-Il.d y�’p time to progression. + , patients still on response.
1530 NT in Refractory Ovarian Cancer
Table 2 Patients’ characteristics and therapeutic outcome
RESULTS
Preclinical Studies
All 24 drug assays were evaluable. Mean SI values for all
three regimens are presented in Fig. 1. NT was significantly
more active compared to both mitoxantrone (P < 0.01) and
paclitaxel (P < 0.001). Patterns of preclinical chemosensitivity
are summarized in Table 1. Ex vivo RRs for mitoxantrone (29%)
and paclitaxel (33%) did not differ significantly, whereas NT
produced a significantly higher ex vivo RR of 83% (P <0.0001).
Strong sensitivity was observed in 13 of 20 tumors responding
to NT. Seven tumors resistant to both single agents exhibited
sensitivity to the combination. In 10 tumors, drug interactions
showed potentiation according to the P#{246}chmodel (32). In an
additional nine samples, both agents were found to act inde-
pendently. In only five tumors, relative or absolute antagonism
was obvious.
Clinical TrialToxicity. A total of 92 NT courses were administered
(NT-I, 56 courses; NT-Il, 36 courses); all were evaluable for
toxicity. The predominant adverse effect was myelosuppression
with grade 3-4 leukopenia, grade 3 thrombocytopenia, and grade
3-4 anemia occurring during 59, 7 and 9% of cycles. Myelo-
toxicity was seen more frequently in patients receiving NT-Il,
with 75% of cycles complicated by grade 3-4 leukopenia. In
comparison, grade 3-4 leukopenia was observed during 48% of
NT-I cycles. Severe thrombocytopenia and anemia were seen in
4 and 7% of NT-I cycles and in I 1 and 1 1 % of NT-Il cycles,
respectively. However, bone marrow function recovered spon-
taneously in most cases within 3-5 days or was successfully
supported by G-CSF required during 10 of 18 treatments (56%).
There were no febrile episodes seen with NT at either schedule.
In patient P. U., the last two NT-Il cycles were administered
with 4 mg/m2 mitoxantrone and 70 mg/m2 paclitaxel due to both
persistent grade 3 thrombocytopenia and grade 4 anemia requir-
ing erythrocyte transfusion. In patients P. F. and M. E., NT-I
treatment was delayed for 7-11 days due to leukopenia in spite
of G-CSF support. As expected, all patients experienced grade
2-3 alopecia. With the exception of grade 3 nausea/vomiting
occurring during one cycle of NT-I and grade 3 malaise/fatigue
observed during five courses of NT-Il, nonhematological side
effects such as peripheral neuropathy, myalgia, diarrhea, or
mucositis were generally mild (grade 1-2) and occurred infre-
quently. There were no symptomatic bradycardia or other car-
diac complications, nor did any patient require hospitalization
due to infection or other life-threatening events.
Clinical Activity. All patients treated with NT received
at least two courses, and all were evaluable for response. The
median follow-up is 40.5 + weeks. Table 2 summarizes patients’
characteristics and their therapeutic outcome. Objective re-
sponses were seen in 14 patients (5 CR and 9 PR), resulting in
an overall 78% RR. Remissions were achieved with both NT
schedules and tended to be long enough to have clinical utility.
Median OAS is not yet reached, and median PFS is 40 weeks
(Fig. 2). Although CRs were achieved with NT-I only. RR for
NT-H was slightly higher, but not significantly so (NT-I, 73%;
NT-Il, 86%). Patient K. G., who experienced a PR of 50-week
duration after treatment with NT-I, was successfully reinduced
twice with NT-Il when presenting with recurrent disease after
6.5 months without therapy. Correspondingly, NT-Il was deliv-
ered two times to patient M. J., producing a PR of 28- and
20+-week duration. In three additional patients, disease was
stabilized (NC) for 65+, 55, and 10+ weeks, respectively. Only
one patient showed PD during NT-I therapy, and treatment thus
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A
lOG
� 800>
� 60(I)
Ca,U 40a,
a-
20
0>
‘I)
a,a,
�1-
U,a.a,a,
Ca,U
a,a.
0 1�0 2’O 30 40 50 60 70 80 90100
V�eks after start of NT chemotherapy
0 10 20 30 40 50 60 70 80 90 100
V�eks after start of NT chemotherapy
Fig. 2. Kaplan-Meier plots for 15 patients with platinum-refractory
ovarian cancer receiving a total of 18 blocks of salvage chemotherapywith NT. A, OAS estimated for 15 patients treated. B, PFS estimated for18 NT treatments administered.
Clinical Cancer Research 1531
was discontinued after two cycles. Three patients (NT-I, two
patients; NT-Il, one patient) have died due to progressive recur-
rent tumor at 32, 37, and 62 weeks from the start of NT. The
remainder are still alive, and nine are even progression-free
(NT-I, six patients; NT-Il, three patients).
DISCUSSION
Taxanes such as paclitaxel are considered the most active
agents in platinum-refractory recurrent ovarian cancer, produc-
ing a 25-30% RR and a median PFS of6 months (2, 6-8, 22, 36).
Increasing the paclitaxel dose may increase the RR, but this,
unfortunately, did not improve survival (8, 9, 37).
In various preclinical studies, paclitaxel was shown to act
synergistically with a number of standard cytostatics. including
topoisomerase II inhibitors (16). In a clinical trial based on prior
ex viva evaluation of fresh tumor specimens ( I 8), we found
doxorubicin/paclitaxel to have well-tolerated activity in ovarian
cancer patients who had failed both platinum and single-agent
paclitaxel (21). Testing a limited number of human tumor cell
lines, GlOck et a!. (29) observed a strong synergism between
paclitaxel and mitoxantrone that compared favorably with other
paclitaxel-based combinations including doxorubicin, etopo-
side, cyclophosphamide, or platinum (29). Mitoxantrone is less
cardiotoxic and mucotoxic than doxorubicin, and lack of cross-
resistance has been demonstrated for various clinical tumors in
a considerable number of patients (25, 26, 38, 39). Both the
promising clinical activity of doxorubicin/paclitaxel and the
confirmed preclinical experiences provide evidence that NT
should be regarded as a logical next step in developing a
well-tolerated regimen for the treatment of platinum-refractory
recurrent ovarian carcinoma.
The ATP-TCA may be useful for ex vivo chemosensitivity
testing of clinical tumors and seems to be applicable to anthra-
cyclines and taxanes ( I 8, 27, 28). It possibly provides major
advantages over classical chemosensitivity assays in terms of
efficacy, reproducibility, robustness, and evaluability, with
promising clinical correlations reported for both ovarian and
breast cancers (1 7, 19, 20). This assay was thus considered a
suitable model to assess the preclinical activity of NT in native
platinum-refractory ovarian cancers.
Generally, the ex vivo results described herein show activ-
ity for both mitoxantrone and paclitaxel that is consistent with
clinical experience (8, 36, 40). The combination produced an
unexpectedly high rate of antineoplastic activity ex vivo. Seven
tumors with apparent resistance to both single agents were
sensitive to NT. Ex vivo resistance is a highly reliable predictor
of clinical resistance (41); thus, reversal of resistance as we
found here is a noteworthy success. The analysis of the effect of
the NT combination indicates potentiation or at least major
independent activity for both drugs in the majority of tumors.
Although the reasons for these effects are not clear at present,
our findings argue in favor of a real synergism between the
drugs.
Our first clinical results provide evidence that NT given at
either schedule has acceptable toxicity and produces exception-
ally high clinical efficacy in patients with platinum-refractory
ovarian cancer. Compared to clinical results with doxorubicin/
paclitaxel described by us and others (2 1 , 3 1 ), NT seems to be
a further improvement. Both the 78% RR and particularly the
response duration observed in this study compare favorably with
those achieved with other salvage therapies such as paclitaxel,
docetaxel, altretamine, ifosfamide, or topotecan (2, 6-8, 1 1, 12,
22, 36, 42). These findings therefore challenge the traditional
view that drug combinations have no advantage for salvage
therapy of ovarian carcinoma as compared to single agents (42).
Work in progress seeks the optimal dosage for NT-Il, which
may be preferred for future evaluation because this regimen
combines both high clinical activity and convenience for the
patients. However, NT-I seems to be a reasonable alternative to
NT-Il, particularly in patients with impaired bone marrow func-
tion or in those who are otherwise unable to undergo weekly
chemotherapy.
Responses in ovarian cancer patients failing both platinum
and paclitaxel are rare. In this setting, altretamine and topotecan
are the only drugs with proven major clinical activity (1 1, 12).
Therefore, the activity of NT that we have found in patients
pretreated with paclitaxel alone or in combination is of partic-
ular interest. Considering the published single-agent activities of
mitoxantrone (35) and paclitaxel (8, 22, 36), the results of this
pilot trial provide evidence for a clinical synergism between
these drugs that parallels our previous and current laboratory
experience (28). We made similar observations with platinum
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1532 NT in Refractory Ovarian Cancer
and cytosine arabinoside even when both single agents were
completely inactive (43, 44). Moreover, it should be noted that
NT clearly produced a higher clinical activity than doxorubicin/
paclitaxel, although this was not expected from the preclinical
and clinical single-agent activities ( 1 8, 21 , 23, 25, 3 1 ). Modern
ex vivo test systems such as the ATP-TCA thus provide an
effective and time-saving method for the preclinical selection of
innovative chemotherapy regimens for further clinical use. In
conclusion, NT showed unusually promising anticancer activity
in heavily pretreated patients with platinum-refractory ovarian
cancer, without producing nontolerated toxicity. This combina-
tion should thus be considered for large-scale clinical trials.
ACKNOWLEDGMENTS
We thank H. HObner and R. Klasen for skillful technical assistance.
Special thanks are addressed to all colleagues and nurses of the onco-
logic staff of the Departments of Gynecology and Obstetrics, University
of Cologne and University of Bonn Medical Centers, for their engage-ment in care and treatment of the patients. This work was performedwithin the framework of the Preclinical Therapeutic Models Group of
the European Organization for Research and Treatment of Cancer.
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