Pharmacological Treatment of Patients with Metastatic, Recurrent or Persistent Cervical Cancer Not Amenable by Surgery or Radiotherapy: State of Art and Perspectives of Clinical Research

Simple Summary The aim of this review is to assess the available literature of the pharmacological treatment of patients with metastatic, recurrent or persistent cervical cancer not amenable by surgery or radiotherapy. The results and toxicities of cisplatin-based doublets are exhaustively described. The combinations of cisplatin plus paclitaxel with or without bevacizumab is the most active regimen in these clinical setting. Immune-check-point inhibitors and molecularly-targeted agents are promising fields of research. Abstract Cervical cancer patients with distant or loco-regional recurrences not amenable by surgery or radiotherapy have limited treatment options, and their 5-year overall survival (OS) rates range from 5% to 16%. The purpose of this paper is to assess the results obtained with chemotherapy and biological agents in this clinical setting. Several phase II trials of different cisplatin (CDDP)-based doublets and a phase III randomized trial showing a trend in response rate, progression-free survival, and OS in favor of CDDP + paclitaxel (PTX) compared with other CDDP-based doublets have been reviewed. The factors predictive of response to chemotherapy as well as the benefits and risks of the addition of bevacizumab to CDDP + PTX have been analyzed. The FDA has recently approved pembrolizumab for patients with recurrent or metastatic cervical cancer in progression on or after chemotherapy whose tumors were PD-L1 positive. Interesting perspectives of clinical research are represented by the use of immune checkpoint inhibitors alone or in addition to chemotherapy, whereas PARP inhibitors and PI3K inhibitors are still at the basic research phase, but promising.


Introduction
GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries have detected 569,874 new cases of cervical cancer and 311,365 deaths due to this tumor in 2018 [1]. The primary treatment of early stage disease is either surgery or definitive radiotherapy consisting of pelvic external beam radiotherapy plus brachytherapy [2][3][4]. According to the new 2018 FIGO staging system, tailored abdominal radical hysterectomy with bilateral pelvic lymphadenectomy is the preferred treatment for stage IA1 disease with lymph vascular space involvement (LVSI) and for stage IA2, IB1, IB2 and IIA1 disease, and definitive radiotherapy is an alternative option for patients not fit for surgery or who refuse surgery [2][3][4][5][6]. Concurrent cisplatin (CDDP)-based chemotherapy and radiotherapy (CCRT) plus brachytherapy is the standard of care for patients with locally advanced disease, i.e., CDDP 50 mg/m 2 , with higher bone marrow and renal toxicity and without any benefit in terms of PFS and OS.
In the experience of Lele and Piver [51], single-agent CDDP obtained an objective response in 4% of central relapses, 33% of liver metastases, 40% of supraclavicular nodal recurrences, and 48% of lung failures.
Several phase II studies have been conducted to identify other active drugs in this clinical setting   (Table 1). Higher response rates were obtained for lesions in previously non irradiated areas compared with those in irradiated fields. Median duration of response ranged from 2.5 to 6.5 months, and median OS ranged from 4.2 to 15.2 months. Nab-paclitaxel is a nanoparticle formulation of albumin-bound PTX, which can be delivered without premedication since the risk of hypersensitivity is very low [80]. It is noteworthy that the 29% response rate is the highest ever recorded in the GOG for a single-agent against platinum resistant disease [79]. This drug was equally active in patients who had primarily lymph node metastases or visceral metastases.

Combination Chemotherapy
In the phase II trials reported in Table 2, the combination of CDDP with other drugs, with additive or synergistic activity and non-overlapping toxicity, obtained response rates of 21-50%, with a median PFS of 4.8-10.5 months and a median OS of 6.4-25+ months [44,[81][82][83][84][85][86][87][88][89][90][91][92][93]. These regimens usually achieved higher response rates and longer PFS compared with single-agent CDDP, but at the cost of greater toxicity and with no improvement in OS. Still again, response rates were sharply higher in non-irradiated (57-70%) than in irradiated areas (15-36%). The GOG179 trial randomized 356 patients with stage IVb or recurrent or persistent squamous andnonsquamous cell cervical carcinoma unsuitable for surgery and/or radiotherapy with curative intent to receive either single-agent CDDP (50 mg/m 2 ) q21 or topotecan (0.75 mg/m 2 d1-3) + CDDP (50 mg/m 2 d1) q21 or methotrexate + vinblastine + doxorubicin + CDDP (MVAC regimen) every 28 days (q28) [94]. The MVAC arm was early discontinued because of four toxic deaths, principally due to neutropenic sepsis, among 63 patients. CDDP + topotecan achieved a higher response rate (p = 0.004), a longer median PFS (adjusted Relative Risk (RR) = 0.738 (95% Confidence Interval (CI) = 0.578-0.942) and a longer OS (adjusted RR = 0.77, 95%CI = 0.600-0.992) compared with single-agent CDDP, associated with anincreased incidence of severe adverse events, and especially of grade 3-4 neutropenia (70% versus 1.4%) and thrombocytopenia (31.3% versus 3.4%) ( Table 3). The addition of topotecan to CDDP improved PFS and OS both in patients who had received prior CDDP asradiation sensitizer and in those who had not. GOG179 is the first randomized trial able to demonstrate an OS benefit for CDDP-combination chemotherapy versus single-agent CDDP in this clinical setting. Monk et al. [95] randomly allocated 513 patients with stage IVB, recurrent, or persistent squamous and nonsquamous cell cervical cancer to undergo either PTX + CDDP or vinorelbine + CDDP or gemcitabine + CDDP or topotecan + CDDP 50 (Table 3). Although the trial was stopped early at a planned interim analysis for futility, there was a trend in response rate, PFS, and OS in favor of CDDP + PTX. The rate of severe neutropenia was approximately 50% with all regimens except gemcitabine + CDDP where it was approximately 15%. There were 11 toxic deaths, but no correlation was found with the chemotherapy regimen.
A randomized phase III trial, including 253 patients with recurrent or metastatic squamous and nonsquamous cell cervical cancer who had undergone one or less one platinum-based-treatment and no prior taxane, demonstrated a noninferiority in terms of OS of the combination of PTX + carboplatin (CBDCA) compared with PTX + CDDP [96] (Table 3). However, among the patients who had not received prior CDDP, median OS was worse for PTX + CBDCA arm (13.0 versus 23.2 months; Hazard Ratio (HR) = 1.571; 95%CI = 1.062-2.324).
CDDP-based three-or four-drug regimens obtained no clear improvement in the clinical outcome compared with CDDP-based doublets [98][99][100][101][102]. In a randomized trial enrolling 287 patients with advanced, recurrent, or persistent squamous cell cervical carcinoma, the addition of bleomycin (30 U over 24 h) to CDDP (50 mg/m 2 ) + IFO (5 g/m 2 over 24 h) q21 did not change response rate, PFS, and OS [98]. Whereas TIP appears to be the most active regimen as NACT followed by radical surgery, this combination chemotherapy achieved response rates of 46-67% and a median OS of 6-19 months in patients with recurrent, persistent, or metastatic disease, similar to those obtained with CDDP-based doublets [99][100][101]. Response rates ranged from 36% to 52% in irradiates sites and from 60% to 75% in areas outside the previous radiotherapy fields. The excision repair cross-complement 1 (ERCC1) status appears to be a predictive and prognostic factor in this clinical setting. This nucleotide excision repair gene is involved in resistance to platinum compounds in different malignancies [103][104][105][106][107]. A study performed on 45 tissue samples from patients with recurrent or metastatic cervical cancer treated with CDDP + IFO with or without PTX, reported that high ERCC1 expression was an independent poor predictor of both PFS (HR = 2.473, 95% CI = 1.146-5.339) and OS (HR = 3.187, 95% CI = 1.346-7.546) [106]. In another study on 32 women with recurrent or metastatic disease undergoing platinum-based chemotherapy, the patients with high ERCC1 expression experienced a lower response rate (15% versus 74%, p = 0.001), a shorter PFS (HR = 2.428; 95%CI =1.145-5.148), and a shorter OS (HR = 2.322; 95% CI = 1.051-5.29) compared to those with low ERCC1 expression [106].

Bevacizumab
In a phase II GOG trial, single-agent bevacizumab (BEV) (15 mg/kg q21) was administered to 46 patients with persistent or recurrent squamous cell carcinoma of the cervix [109]. Eleven patients (24%) survived progression free for at least 6 months, and 5 patients (11%); experienced partial responses. The median response duration was 6.21 months, and median PFS and OS for all patients were 3.40 months and 7.29 months, respectively.
An update of the study with a longer follow-up confirmed that chemotherapy + BEV was associated with a longer OS compared with chemotherapy alone (HR = 0.77,95%CI = 0.62-0.95) [47]. There was no negative rebound after progression while receiving BEV, since post-progression survival was not significantly different between the patients treated with chemotherapy + BEV and those treated with chemotherapy alone. These results represent the proof-of-concept of the efficacy of anti-angiogenesis therapy in cervical cancer.
Other studies have confirmed the efficacy of BEV combined with CDDP + PTX in patients with persistent, recurrent, or metastatic carcinoma of the uterine cervix [112,113]. According to a systematic review of 23 studies, CDDP + PTX + BEV and topotecan + PTX + BEV were likely to prolong OS compared with non-BEV-containing therapies, and CDDP + PTX + BEV had the highest probability of being the most efficacious regimen [112]. Response rates and fistula rates with CBDCA + PTX + BEV are similar to those reported with CDDP + PTX + BEV [114,115]. The risks and benefits of the addition of BEV to chemotherapy should be exhaustively discussed with the patient herself, taking into account the increased probability of fistula formation, especially in the case of locally persistent or recurrent disease after radiotherapy or CCRT [116][117][118]. Hypoalbuminemia is an additional risk factor for fistula formation [119].
Tewari et al. [120] retrospectively classified the patients enrolled in the GOG 240 trial in three subgroups based on the predictive factors of poor response to chemotherapy suggested by Moore et al. [108]. The application of the Moore's criteria classified most patients in the mid-risk subset (67%), whereas low-risk and high-risk patients accounted for 19% and 14%, respectively, of the entire population. The HRs of death for treating with BEV in low-risk, mid-risk, and high-risk subgroups were 0.96 (95% CI = 0.51-1.83; p = 0.9087), 0.673 (95%CI = 0.5-0.91; p = 0.0094), and 0.536 (95%CI = 0.32-0.905; p = 0.0196), respectively. Therefore, BEV could be avoided in previously irradiated low-risk patients, since the OS advantage given by the addition of this antiangiogenic agent is not significant.

Immune Checkpoint Inhibitors
Recent data seem to suggest a promising role for immune checkpoint inhibitors in the treatment of patients with advanced carcinoma of the uterine cervix [121][122][123][124].
The anti-programmed death [PD]-1 antibody nivolumab (240 mg every 14 days) obtained an objective response in 26% of 19 patients with recurrent or metastatic cervical cancer and in 20% of 5 patients with recurrent or metastatic vaginal/vulvar cancer [122]. As for the former, the median duration of response was not yet reached after a median follow-up of 19.2 months.
The phase II KEYNOTE-158 study, investigating the anti-PD-1 antibody pembrolizumab (200 mg q21) in several cancer types, included 98 patients with pretreated advanced squamous and nonsquamous cell cervical cancer [123]. Of these 82 had PD-ligand 1 (PD-L1)-positive tumors, according to the PD-L1 IHC 22C3 pharmDx assay, and 77 had undergone more than one chemotherapy line for recurrent or metastatic disease. The measure of PD-L1 expression was the combined positive score (CPS), defined as the ratio of PD-L1-positive cells (tumor cells, lymphocytes, and macrophages) to the total number of tumor cells × 100. A tumor was considered to be PD-L1 positive if CPS was >1. There were 3 complete responses and 9 partial responses, with an overall response rate of 12%, and all 12 responses were detected in patients with PD-L1-positive tumors. Nine of the 12 responses were still ongoing after >9 months of follow-up. The safety profile was the same previously reported for pembrolizumab in patients with advanced cancer, and no novel adverse event occurred. Based on these results, the Food and Drug Administration (FDA) has approved pembrolizumab for patients with recurrent or metastatic cervical cancer in progression on or after chemotherapy whose tumors were PD-L1 positive.
Several trials of immune checkpoint inhibitors are currently ongoing in metastatic, recurrent, or persistent cervical cancer ( Table 4). One of the most interesting is the phase III, randomized BEATcc (NCT03556839) trial which will enroll a total of 404 women with squamous and nonsquamous cell carcinoma of the uterine cervix [125]. Patients will be randomly allocated to receive either CCDP (50 mg/m 2 ) + PTX (175 mg/m 2 ) + BEV (15 mg/kg) q21 or the same regimen plus atezolizumab (1200 mg q21). Complete responders after ≥6 cycles will be allowed to continue only on biologic therapy, i.e., BEV or BEV + atezolizumab. OS is the primary endpoint of the study which is estimated to close in 2022. Table 4. Ongoing trials with immune checkpoint inhibitors in metastatic, recurrent, or persistent carcinoma of the uterine cervix. Avelumab (anti-PD-L1 antibody) with Axitinib 2 in persistent or recurrent cervical cancer after platinum-based chemotherapy a proof-of-concept study (ALARICE Study) Table 4. Cont.
PI3K pathway was strongly activated in PTX-resistant HeLa and ME180 cell lines established from metastatic sites of cervical cancer compared to parental cells, and the combination of PTX and a PI3K inhibitor revealed a synergistic antiproliferative activity by enhancing PTX-induced S and G2/M arrest in PTX-resistant cell lines [130]. Therefore, therapeutic strategies targeting PI3K pathway could revert the chemoresistance of cervical cancer cells to PTX and could provide an promising research perspective for the management of patients with this malignancy.

In Human Studies
A retrospective study conducted on 82 squamous and nonsquamous cell cervical cancer patients treated with CCRT showed that PIK3CA mutational status correlated with a worse OS (HR = 6.0; 95%CI = 2.1-17.5) in FIGO stage Ib /II disease, but not in stage II-IVa disease (HR = 1.0, 95%CI = 0.32-3.1) [127]. Very few and conflicting clinical data are currently available in the literature as for the use of PI3K/AKT/mTOR pathway targeted agents [128,131,132]. A phase II trial of temsirolimus (25 mg iv q28) reported a partial response in one (3%) and a stable disease in 19 (58%) of 33 patients with recurrent, unresectable locally advanced, or metastatic squamous and nonsquamous cell carcinoma of the uterine cervix [131]. The single patient with a partial response experienced no evidence of progression for 13.9 months, whereas the median duration of stable disease was 6.5 months with no correlation with PTEN and PIK3CA status. A phase I clinical study on 55 patients with metastatic or recurrent squamous and nonsquamous cell cervical cancer, of which 22 had PIK3CA mutations and/or PTEN loss, found that those patients treated with PI3K/AKT/mTOR targeted agents (such as temsirolimus) matching the aberrations in this pathway achieved a longer median PFS (6.0 months versus 1.5 months, p = 0.026) than those who did not receive such matched therapy [128]. Conversely, in a phase II trial, the combination of the pan-AKT inhibitor GSK2141795 and the MEK inhibitor trametinibobtained no confirmed response in 14 patients with squamous and nonsquamous cell persistent or recurrent carcinoma of the uterine cervix [133].  [132,134,135]. PARPi are still at the basic research phase, but promising. Bianchi et al. [134] reported that none of 9 primary cervical cancer cell lines had homologous recombination (HR) deficiency, but 3 of these showed strong PARP protein activity, i.e., PAR expression, and were very high sensitive to olaparib in vitro. This PARPi caused cell cycle arrest in the G2/M phase and induced apoptosis. In vivo antitumor activity of olaparib was tested in severe combined immunodeficiency (SCID) mice who were given a subcutaneous injection of human cervical cancer cells. Animals treated with olaparib experienced a slower tumor growth and a prolonged survival compared to controls. PAR expression might be a novel biomarker able to identify a subset of cervical cancer patients who could benefit from PARPi.Additional studies with PARPi alone or combined with other agents are strongly warranted, especially in patients with radiotherapy and/or chemotherapy-resistant disease.
The α-specific PI3K inhibitor alpesilib and the PARPi talazoparib synergized to inhibit cervical cancer cell proliferation, migration, and invasion in vitro and in vivo [135]. Cancer cells with aberrant PI3K activation were more responsive to these combined agents. Besides catalytic activity, talazoparib trapped PARP on damaged DNA and induced cytotoxic effects. Alpesilib could co-operate with talazoparibto increase PARP trapping on chromatin andto induce severe DNA damage.

In Human Studies
Roszik et al. [136] found a significantly higher expression of DNA repair genes, especially those involved in HRand mismatch repair pathways, in tumor tissues compared with adjacent normal tissues from 28 patients with recurrent cervical cancer who underwent pelvic exenteration. High-risk HPV E6 and E7 reduced the ability of the HR pathway to complete double-strand break repair by approximately 50%, thus leading to HR deficiency [137]. The combination of immune checkpoint inhibitors and PARPi should be investigated in patients with recurrent cervical cancer. NCT04068753 is an ongoing phase II trial of niraparib in combination with the anti-PD-1 antibody dostarlimab in this clinical setting.

Conclusions
Cervical cancer patients with distant or loco-regional recurrences not amenable by surgery or radiotherapy have a very poor prognosis, and pharmacological treatment options have only a palliative intent.CDDP-baseddoublets have obtained response rates of 21-50%, with a median PFS of 4.8-10.5 months and a median OS of 6.4-25+ months in this clinical setting. A phase III randomized trial has shown a trend in response rate, PFS and OS in favor of CDDP + PTX compared with CDDP+ vinorelbine, CDDP+ gemcitabine or CDDP + topotecan. The addition of BEV to CDDP + PTX significantly improved PFS and OS, but increased the risk of adverse events and especially of grade >3 gastrointestinal or genitourinary fistulas. BEV could be avoided in previously irradiated low-risk women according to Moore's criteria, where the OS benefit is small. Pembrolizumab has been approved by the FDA for patients with recurrent or metastatic cervical cancer in progression on or after chemotherapy whose tumors were PD-L1 positive, and several interestingtrials with immune checkpoint inhibitors are currently ongoing. PARP inhibitors and PI3K inhibitors are still at the basic research phase, but promising.