Oxaliplatin plus leucovorin and 5-fluorouracil (FOLFOX-4) as a salvage chemotherapy in heavily-pretreated platinum-resistant ovarian cancer

Background The purpose of this study was to evaluate the clinical impact of oxaliplatin, leucovorin, and 5-fluorouracil (FOLFOX-4) chemotherapy in terms of the response rate, progression-free/overall survival (PFS/OS) and safety profile in patients with heavily pretreated recurrent epithelial ovarian cancer. Methods Clinical data were reviewed in 29 patients who received FOLFOX-4 as more than third-line chemotherapy, consisting of 85 mg/m2 of oxaliplatin, 200 mg/m2 of leucovorin, and bolus 400 mg/m2 on day 1 of 5-fluorouracil, followed by a 22-h infusion of 600 mg/m2 of 5-fluorouracil for 2 consecutive days every 3 weeks. We also compared the efficacy and toxicity of FOLFOX-4 with that of topotecan, a standard treatment, given at a dosage of 1.5 mg/m2 every three weeks in 26 patients. Results The median age of enrolled patients was 60 years (range 33 to 85). A median of 4 cycles (range 1–17) of FOLFOX-4 were administered. Complete response and partial response were observed in one (3.5%) and 5 (17.2.2%) patients, respectively, while stable disease was reported in 8 (27.6%) patients. Among all patients, grade 3–4 anemia, neutropenia, and thrombocytopenia were observed in 0 (0%), 5 (17.2%), and 3 (10.3%) cases, respectively. Grade 3–4 fatigue was recorded in one (3.4%) patient and diarrhea in 2 (6.9%). Median PFS and OS were 2.8 months [95% confidence interval (CI) 1.7–4.9] and 6.2 months (95% CI 2.4–14.6), respectively. No significant differences in terms of efficacy and toxicity were observed between patients receiving FOLFOX-4 and those treated with topotecan. Conclusions The FOLFOX-4 regimen would seem to obtain similar survival rates to those of standard therapy with topotecan in platinum-resistant ovarian cancer. Further randomized trials are warranted to confirm our findings.


Background
Ovarian cancer remains a highly lethal malignancy, representing the sixth leading cause of cancer death in women and the most lethal gynecologic malignancy [1,2]. The prognosis for advanced ovarian cancer has improved over the last 10 years, especially thanks mainly to the introduction of more personalized therapeutic strategies. However, despite the high response rate to the standard carboplatin-paclitaxel first-line combination, most patients develop recurrent disease, with a median survival ranging from 12 to 24 months. Patients who progress on cisplatin or carboplatin or who relapse within 6 months of the end of treatment show the poorest outcome [2]. Single-agent therapies for platinum-refractory/resistant patients include oral etoposide, taxanes, topotecan, gemcitabine, vinorelbine, liposomal doxorubicin, and oxaliplatin, with response rates of around 15-20% and an overall survival (OS) of less than 12 months [3]. Research is now aiming to improve chemotherapy, identify novel, effective and well-tolerated agents, and overcome platinum resistance.
Cisplatin and carboplatin are the most common platinum compounds used to treat ovarian cancer. Oxaliplatin, a diaminocyclohexane platinum compound, has a different spectrum of activity and toxicity to that of other platinum agents and does not usually show cross-resistance with cisplatin and carboplatin in ovarian cancer [4,5]. In previous phase II studies, oxaliplatin at a dose of 130 mg/m 2 every 3 weeks was administered to patients with cisplatin-or carboplatin-refractory/resistant and taxane-pretreated ovarian cancer, obtaining response rates of 4.3-29.0% and a median OS of 9.5-15 months [6][7][8][9]. The combination of 5-fluorouracil with leucovorin given as intravenous bolus or continuous infusion has also been used to treat platinum-resistant/recurrent ovarian cancer but has shown limited clinical activity [10][11][12][13][14].
Some in vitro studies indicate a potential synergy between oxaliplatin and 5-fluorouracil/leucovorin [15]. The combination of these drugs (called FOLFOX) represents a standard chemotherapeutic regimen in the management of some advanced tumours [16][17][18]. Preliminary data on the use of this treatment in recurrent ovarian cancer have not been entirely satisfactory/have not been encouraging [19][20][21][22]. In the present study we evaluated the efficacy, in terms of clinical outcome, and toxicity of FOLFOX-4 in platinum-resistant ovarian cancer. In addition, through an exploratory analysis, we compared our results with data from patients treated with topotecan, a drug usually administered alone as salvage chemotherapy in platinum-resistant disease.

Study population
We retrospectively evaluated 29 patients treated with the FOLFOX-4 regimen from February 2008 to April 2016 as the primary cohort, and 26 patients treated with topotecan between August 2010 and December 2014 as the secondary cohort. Eligibility criteria of both cohorts were histological confirmation of epithelial ovarian cancer, previous treatment with cisplatin or carboplatin plus paclitaxel regimens, and disease recurrence during treatment with or within 6 months of the end of the cisplatin or carboplatin-based chemotherapy. Additional eligibility criteria included Eastern Cooperative Oncology Group (ECOG) performance status 0-2, and adequate cardiac, renal, hepatic and bone marrow function. Metastatic disease was documented by bone scan, computed tomography or magnetic resonance imaging. The retrospective study was approved by the Institutional Review Board of Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS and was conducted in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. The need for written informed consent from participants was waived because of the retrospective nature of the research.
Patients were evaluated for safety and dosing compliance every 2 weeks for the first 3 months of chemotherapy, and then monthly thereafter until treatment discontinuation. Renal, liver and bone marrow function were assessed at every cycle, while cancer antigen 125 (CA-125) and radiographic evaluation were left to the discretion of the treating physician, but were usually performed after at least three months' treatment.

Treatment and evaluation
Treatment with FOLFOX-4 consisted of 85 mg/m 2 of oxaliplatin as a 2-h infusion on day 1, 200 mg/m 2 of leucovorin as a 2-h infusion on day 1, and bolus 400 mg/m 2 of 5-fluorouracil on day 1, followed by a 22-h infusion of 600 mg/m 2 of 5-fluorouracil for two consecutive days every three weeks. Topotecan was administered at a dosage of 1.5 mg/m 2 by intravenous infusion daily for 5 consecutive days, starting on day 1 of a 21-day course. Both therapeutic regimens were administered continuously until there was evidence of either progressive disease (PD) or unacceptable toxicity. Prophylactic granulocyte-colony stimulating factor was only permitted for patients who developed grade 3-4 neutropenia or febrile neutropenia.
Tumor response was evaluated every three cycles by repeating baseline assessments using imaging studies (computed tomography and/or magnetic resonance imaging) according to the Response Evaluation Criteria in Solid Tumors (RECIST) for patients with measurable disease [23]. CA-125 was evaluated in recurrent disease using CA-125 response criteria developed by the Gynecologic Cancer InterGroup [24]. Toxicity was graded using the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), version 4 [25].

Statistical analysis
All data were analyzed by descriptive statistics. Relationships between patient characteristics were testing using the Chi-square test for categorical variables and the median test for continuous variables. The Kaplan-Meier method was used to estimate PFS and OS, with two-sided 95% confidence intervals (95%CI). PFS was defined as the time from the start of FOLFOX-4 or topotecan until disease progression or last tumor evaluation or death from any cause. OS was defined as the time from the start of FOLFOX-4 or topotecan until death from any cause or last follow-up. Survival curves were compared using the log-rank test. Due to exploratory intent, no multiple testing correction was performed. All statistical analyses were carried out with SAS statistical software, version 9.4 (SAS Institute, Cary, NC, USA). A two-sided P-value < 0.05 was deemed statistically significant for all the analyses.
Univariate analysis did not identify any significant factors (including site of metastasis, previous treatment lines, baseline NLR and platelet-to-lymphocyte ratio [PLR]) that predicted PFS (Table 3) and OS (Table 4) within each treatment group and between patients treated with FOLFOX-4 and topotecan, with the exception of NLR, a significant predictor of OS in FOLFOX-4 (P = 0.013).

Discussion
Despite relatively high response rates to first-line platinum-based therapies for epithelial ovarian cancer, the majority of patients relapse and a number of treatment-related deaths have also been reported. New-generation chemotherapeutic drugs and biological agents, especially those targeting angiogenesis [26] and the nuclear enzyme poly-(ADP-ribose) polymerase (PARP) [27,28], have recently been introduced into clinical practice, increasing the number of therapies available for relapsed or refractory disease. Consequently, patients with advanced ovarian cancer often undergo multiple chemotherapy courses in an effort to achieve long-term remission and maintain an acceptable quality of life. The main risk from using an increasing number of therapeutic agents is cumulative toxicity, especially myelotoxicity, which may influence subsequent treatments. Hence the need for new, effective and less toxic therapies in patients with recurrent and persistent disease after failure of chemotherapy.
In the present retrospective monoinstitutional study, we analyzed the results obtained in a population of ovarian cancer patients treated with FOLFOX-4 or standard topotecan monotherapy in terms of clinical impact on outcome and toxicity. The choice of therapy and dosing schedule was at the discretion of the treating physician, as was the possibility of initial dose reduction due to older age and poor performance status. Efficacy and safety were comparable in both regimens, with hematological toxicity the most frequent reason for dose reduction. Treatment In terms of response, our findings were comparable to those of other studies [19][20][21][22] on patients with measurable disease. Major limitations of this study were a small number of patients, the retrospective design, and the presence of mismatch of the cohorts related to a lack of randomization. We observed that NLR was the only prognostic factor in our patient cohort, as reported in a recent meta-analysis [29]. However, due to exploratory intent, no multiple testing correction was performed. Although adjustments for multiple comparisons can help control the study-wide falsepositive rate, for exploratory analyses it is more important to judge P values cautiously than to try to formally determine their true significance level. Precise adjustment of P values and confidence intervals is often impractical in the context of exploratory research but can be useful for hypothesis-driven research.
Despite all these several limitations of this study, we showed similar treatment outcomes (PFS, OS, and CA-125   FOLFOX-4 could thus represent a potential alternative to standard chemotherapy, with a similar toxicity profile, in this patient setting. However, more recent studies [30] suggested different dose regimes of topotecan characterized by reduced number of side effects and thus this could alter the comparison of toxicities between FOLFOX-4 and topotecan profiles in our study. The present study did not bring to light any clinical prognostic factors for PFS and OS in either treatment group, probably because of the small sample size and the lack of adequate patient selection. In addition, currently, there are no biomarkers able to improve the selection of patients candidates to FOLFOX-4 combination. Potential predictive biomarkers could derive from the analysis of homologous recombination deficiencies such as BRCA1/2 alterations, especially because they are of particular interest for platinum-based regimens. Therefore, future clinical trials in this disease setting could be supported by genomic and proteomic studies to identify prognostic factors associated with response to fluorouracil. The advances made in genetic and molecular biology could provide a valuable insight into the alterations underlying these types of ovarian cancer, and the relationship between the mechanism of action of fluorouracil and the subsequent downstream molecular pathways activated during tumorigenesis and disease progression.

Conclusion
The retrospective nature of our study and the small sample size do not allow for definitive conclusions to be drawn. However, our results provide further evidence that the FOLFOX-4 regimen may be as effective as standard monotherapies and could be proposed as an appropriate salvage treatment in refractory or resistant ovarian cancer. However, it should be appropriate to consider these heavily-pretreated patients as an ideal group for clinical trials; particularly given the success or emerging data of some newer classes of targeted therapies such as PARP inhibitors, antivascular drugs, dual antibody like molecules, antibody drug conjugates and so randomized multicenter trials comparing the FOLFOX-4 regimen, alone or, particularly, in combination with targeted therapy, are warranted to improve the standard of care in patients with heavily-pretreated disease.