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aLung & Thoracic Malignancies Program, University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA; bPennsylvania State Cancer Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
Key Words. Systemic therapy • Maintenance • NSCLC • Advanced disease
Correspondence: Chandra P. Belani, M.D., Penn State Cancer Institute, Penn State Milton S. Hershey Medical Center, 500 University Drive, H072, Hershey, Pennsylvania 17033, USA. Telephone: 717-531-1078; Fax: 717-531-0002; e-mail: cbelani{at}psu.edu
Received September 17, 2007; accepted for publication October 24, 2007.
Disclosure: No potential conflicts of interest were reported by the authors, planners, reviewers, or staff managers of this article.
| ABSTRACT |
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| INTRODUCTION |
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The treatment of NSCLC is determined by disease stage. Surgery continues to be the mainstay of treatment for early-stage and localized disease. Multimodal therapy has become the norm for regionally advanced disease, and patients with advanced and metastatic disease are candidates for palliative chemotherapy, for which there is documented evidence of improvements in survival and quality of life measures. Systemic chemotherapy also benefits patients with earlier stages of the disease and has now become part of the multimodal therapeutic strategy for stages II and III NSCLC [2–5]. As a result, the development of novel systemic therapy regimens has become an important focus of research efforts in NSCLC. With the notion that a "chemotherapy efficacy plateau" has been achieved with the present regimens, molecular-targeted drugs have entered the therapeutic arena in recent years [6, 7]. Agents that target the epidermal growth factor receptor (EGFR) and the angiogenesis pathway have proven to be efficacious in the management of NSCLC [6, 7]. Several other molecular targets are under evaluation as monotherapy or in combination with systemic chemotherapy.
| TREATMENT OF ADVANCED-STAGE NSCLC |
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Patients with a PS score of 2 have a poor prognosis, with a median survival time of approximately 4 months [15]. The optimal treatment strategy for patients with a PS score of 2 is yet to be defined, although there is greater use of single agents in this patient subset, especially in those with significant comorbid conditions. A reduction in PS as a result of an aggressive tumor warrants standard combination chemotherapy to achieve the best results.
Platinum-Based Regimens
The benefits of platinum-based combination chemotherapy over best supportive care (BSC) as first-line treatment for patients with advanced NSCLC were first reported in a randomized clinical trial published in 1988 [16]. Further evidence for the efficacy of platinum-based chemotherapy was provided by a meta-analysis of all available randomized clinical trials [17]. The analysis demonstrated that cisplatin-based chemotherapy was associated with a 10% greater 1-year survival rate (hazard ratio, 0.73). This led to the evaluation of several platinum-based combinations for the first-line treatment of advanced NSCLC.
Based on promising single-agent activity, newer agents such as the taxanes, gemcitabine, and vinorelbine have been combined with platinum compounds. Several randomized clinical trials have been conducted to evaluate cisplatin as monotherapy or in combination with a taxane, gemcitabine, or vinorelbine [18–20]. The two-drug combinations were proven to have superior efficacy, but at the expense of added toxicity. These studies provided further evidence in support of the use of cisplatin-based combinations for the first-line treatment of advanced NSCLC.
Comparison of Platinum-Based Combinations
The availability of several efficacious regimens led to the direct comparison of these combinations. A four-arm randomized phase III study, the Eastern Cooperative Oncology Group (ECOG) 1594 trial, was conducted to compare the efficacy and toxicity profile of cisplatin plus gemcitabine, cisplatin plus docetaxel, and carboplatin plus paclitaxel, with a reference regimen of cisplatin plus paclitaxel [10]. There was no difference in response rate, median survival time, or 1-year survival rate among the four regimens. However, cisplatin plus gemcitabine did confer a longer time to progression. Similar observations were made in the Southwest Oncology Group 9509 study and other randomized studies that compared various two-drug combinations (Table 1).
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Docetaxel, a semisynthetic taxane, has also been proven to be efficacious in combination with a platinum compound. The regimen of cisplatin plus docetaxel was compared with cisplatin plus vinorelbine and carboplatin plus docetaxel in a randomized phase III study (n = 1,218) [22]. The median and 2-year survival rates were superior for cisplatin plus docetaxel, while the carboplatin plus docetaxel regimen had efficacy similar to that of cisplatin plus vinorelbine. Both docetaxel-based regimens were associated with improvements in several symptomatic and quality-of-life indices when compared with cisplatin plus vinorelbine. These results formed the basis for the U.S. Food and Drug Administration (FDA) approval of the cisplatin plus docetaxel regimen.
In Japan, irinotecan has been extensively evaluated in combination with cisplatin for the treatment of advanced NSCLC [23, 24]. The combination was compared with carboplatin plus paclitaxel, cisplatin plus vinorelbine, and cisplatin plus gemcitabine in a four-arm, randomized clinical trial [25]. Similar to the results found in ECOG 1594, the study demonstrated comparable efficacies among the four regimens, and they were all well tolerated. As a result, the regimen of cisplatin plus irinotecan is used commonly in Japan for patients with advanced NSCLC.
Because several chemotherapy regimens have similar degrees of efficacy in advanced NSCLC, the choice of which to use is often made after considering factors such as schedule, toxicity profile, and cost. Efforts to individualize therapy based on molecular markers in the tumor that predict resistance to specific chemotherapeutic agents are under way. Excision repair cross complementing 1 (ERCC1) gene overexpression has been linked to resistance to platinum [26]. Therefore, a randomized study assigned patients to treatments based on ERCC1 mRNA levels in the tumor tissue at baseline [27]. Patients with low ERCC1 mRNA levels were treated with cisplatin plus docetaxel, whereas those with high levels were treated with gemcitabine plus docetaxel. Response rates with cisplatin plus docetaxel were higher in patients with low ERCC1 expression. Similarly, overexpression of the ribonucleotide reductase M1 (RRM1) gene has been linked to resistance to gemcitabine therapy [28]. A randomized phase II clinical trial demonstrated the feasibility of selecting therapy based on RRM1 expression, and reported high response rates with such a pharmacogenomic treatment selection (Simon G et al., personal communication). Based on these results, a confirmatory phase III study is in progress. Such novel and individualized strategies will lead to further optimization therapy in the foreseeable future.
Carboplatin Versus Cisplatin
Carboplatin-based regimens are easy to administer in the outpatient setting and have favorable nonhematologic toxicity profiles compared with cisplatin-based regimens. Several studies have been conducted to compare carboplatin-based regimens with cisplatin-based combinations in the first-line treatment of advanced NSCLC [10, 22, 29]. While some studies have suggested a slight advantage to cisplatin-based regimens, it is unclear whether this counter-balances the higher degree of toxicity found. A meta-analysis of studies comparing cisplatin- and carboplatin-based regimens demonstrated a slightly longer survival time for regimens that included cisplatin with a newer agent [30]. This observation was confirmed in another meta-analysis that used individual patient data to compare the efficacy of cisplatin-based regimens with that of carboplatin-based regimens for advanced NSCLC [31]. Overall, there was a slightly higher response rate with cisplatin-based regimens. Though there was no significant survival difference, studies that used a third-generation agent (gemcitabine or a taxane) in combination with cisplatin yielded a slight advantage over carboplatin-based regimens. Because systemic chemotherapy is administered with the primary goal of palliation, the debate continues as to whether the marginal superiority of the cisplatin-based regimens justifies their use in routine patient care, given that the associated adverse events may have a negative effect on patient quality of life. In a curative setting, as is the case in the earlier stages of NSCLC (adjuvant therapy), cisplatin-based regimens may be preferred over carboplatin-based regimens. Carboplatin-based regimens are commonly used in the U.S., whereas cisplatin-based regimens are preferred in Europe for advanced NSCLC.
Platinum Versus Nonplatinum Regimens
The use of nonplatinum regimens has been widely investigated with a view to improving the therapeutic index of chemotherapy for patients with advanced NSCLC. The advantage of excluding platinum compounds is that they are associated with considerable toxicity. Randomized trials that have directly compared platinum-based regimens with nonplatinum combinations have demonstrated comparable results [13, 14]. A recent randomized study compared carboplatin plus paclitaxel with carboplatin plus gemcitabine and the nonplatinum regimen of gemcitabine plus paclitaxel for advanced NSCLC [14]. All three regimens demonstrated comparable response rates and median survival times. Although the toxicity profiles were different in each arm, there was no clear advantage to the nonplatinum regimen. The observations were confirmed by a recent meta-analysis of all studies comparing platinum-based regimens with nonplatinum combinations, which demonstrated comparable 1-year survival rates [32]. Though the response rate was slightly higher with platinum-based regimens, so was the toxicity. Based on this, nonplatinum regimens are a reasonable choice for first-line therapy of advanced NSCLC and also represent an alternative option for patients who cannot tolerate platinum-based regimens.
Strategies to Improve the Efficacy of Systemic Chemotherapy
From the randomized trials that compared various platinum-based regimens, it became evident that a plateau in efficacy had been reached with the available agents for advanced NSCLC. Consequently, several novel approaches have been evaluated in an attempt to improve patient outcomes. One approach involved the evaluation of three-drug chemotherapy combinations in comparison with standard two-drug regimens [33]. There was no difference in efficacy with the addition of a third cytotoxic agent, and the toxicity profile was worse. This approach has subsequently been discarded. A comparison of platinum-based two-drug combinations with novel single-agent therapy demonstrated higher survival and response rates with the combination [34, 35]. Thus, two-drug combinations form the foundation of systemic therapy for NSCLC.
Recent efforts have focused on the addition of a molecular-targeted agent to standard platinum-based combination regimens. The EGFR inhibitors have been the most extensively studied in combination with chemotherapy. Despite promising preclinical data in support of the combination regimens, phase III studies failed to demonstrate a survival advantage associated with the addition of an EGFR tyrosine kinase inhibitor (TKI) to systemic chemotherapy [36–38]. Monoclonal antibodies against EGFR, which have demonstrated intriguing activity in combination with chemotherapy in phase II studies [39, 40], are now undergoing phase III evaluation. Other targeted agents that have been tested in combination with chemotherapy, such as the matrix metalloproteinase inhibitors, farnesyl transferase inhibitors, and protein kinase C alpha inhibitors, have all shown efficacy greater than that seen with chemotherapy. These large negative trials have underscored the need for extensive preclinical evaluation of combination regimens before large phase III studies are launched, and also the importance of studying patient selection methods to identify molecular/clinical parameters that predict benefit from the targeted agent being evaluated.
More recently, bevacizumab, a monoclonal antibody against vascular endothelial growth factor, was demonstrated to lead to longer survival when administered in combination with chemotherapy [7]. The pivotal phase III study (ECOG 4599) randomized patients with advanced nonsquamous NSCLC to treatment with carboplatin plus paclitaxel alone or in combination with bevacizumab. Patients with squamous-cell histology, major hemoptysis, brain metastasis, or uncontrolled hypertension and those on therapeutic doses of anticoagulation were excluded because of concerns regarding the heightened risk of bleeding with bevacizumab. Following six cycles of therapy, patients in the experimental arm with a response or stable disease were given maintenance monotherapy with bevacizumab until disease progression or unacceptable toxicity. There were higher incidences of neutropenia, hypertension, hemorrhage, proteinuria, and treatmentrelated deaths with the three-drug regimen. Despite this, there was a longer overall survival time (12.3 months versus 10.3 months) and a higher response rate (35% versus 15%) with the addition of bevacizumab to carboplatin plus paclitaxel. Based on this study, bevacizumab has now been approved by the FDA for the first-line therapy of advanced nonsquamous NSCLC in combination with carboplatin plus paclitaxel. The results of ECOG 4599 were confirmed in a preliminary report of another phase III study (Avastin in Lung Cancer [AVAiL], BO17704) that evaluated the regimen of cisplatin plus gemcitabine alone or in combination with one of two doses of bevacizumab (7.5 mg/kg or 15 mg/kg every 3 weeks) (Fig. 1) [42]. The formal presentation of the study results is awaited. It remains to be seen whether the lower dose of bevacizumab is regimen specific (cisplatin plus gemcitabine) or will possess a degree of efficacy similar to the higher dose when combined with any regimen.
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| MAINTENANCE THERAPY |
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Smith et al. [43] conducted a randomized trial to compare the administration of mitomycin, vinblastine, and cisplatin for three cycles with administration for six cycles in patients with advanced NSCLC. Seventy-two percent of patients randomized to three cycles completed treatment, compared with 31% of patients randomized to six cycles. The median survival times and 1-year survival rates were similar for the two treatment arms. Furthermore, quality-of-life parameters were slightly better in patients randomized to three cycles. This study concluded that continuation of chemotherapy beyond three cycles was not associated with any additional advantage. In a similar study, Socinski et al. [44] randomized patients with advanced NSCLC to treatment with carboplatin and paclitaxel for four cycles or continuation of chemotherapy until disease progression or unacceptable toxicity. Interestingly, the median number of cycles received by patients in both arms of the study was four. There was no significant difference in response rate or overall survival time between the two arms of the study. The results of these two randomized, phase III studies led to the notion that maintenance therapy was not beneficial to patients with advanced NSCLC. One important limitation of both studies is the fact that the majority of patients randomized to longer courses of chemotherapy did not receive the planned number of cycles. Treatment was discontinued either because of toxicity or because of disease progression. Therefore, one can only conclude that continuation of combination chemotherapy (two or three drugs) beyond three to four cycles is not feasible, and that the benefit from well-tolerated active monotherapy cannot be excluded, provided there is no added toxicity.
Weekly Paclitaxel as Maintenance Therapy
Belani et al. [47] conducted a randomized phase II clinical trial to evaluate the optimal schedule for weekly administration of paclitaxel in combination with carboplatin for advanced NSCLC. Patients were randomized to one of three different weekly schedules of paclitaxel. Following four cycles of therapy, patients who experienced a response or disease stabilization were then randomized to receive maintenance therapy with weekly paclitaxel or observation alone. Of the 401 patients who entered the study, 130 entered the maintenance phase. The data from this group of patients were pooled with the results of patients who received maintenance therapy with weekly paclitaxel in a phase III study that compared weekly and 3-weekly schedules of paclitaxel in combination with carboplatin [48]. Overall, 206 patients received maintenance therapy with paclitaxel from both studies. The outcome data were compared with those from patients who did not receive maintenance therapy [49]. Overall, the median survival time was 75 weeks in those using maintenance therapy, compared with 58 weeks in patients without maintenance therapy. Furthermore, maintenance therapy with weekly paclitaxel was well tolerated in both studies. Because the objective of these studies was not to establish the efficacy of maintenance therapy, the results of this analysis warrant prospective confirmation, but they are suggestive of the feasibility of prolonged administration of a less-toxic single agent as maintenance therapy for advanced NSCLC.
Docetaxel as Maintenance Therapy
Docetaxel is the only agent that is approved for both the first- and second-line treatment of advanced NSCLC. A recent study by Fidias et al. [50] demonstrated a potential role for docetaxel as maintenance therapy. In that study, patients with advanced NSCLC were treated with four cycles of carboplatin and gemcitabine. Patients who achieved a response or disease stabilization were randomized to treatment with docetaxel as maintenance therapy (early) or as salvage therapy at the time of disease progression (delayed). Of the 526 patients enrolled in the study, 231 were randomized after initial therapy. The overall response rate was higher for patients who received early docetaxel therapy than for those whose docetaxel was delayed (42% versus 6%). The survival data are awaited. The results are preliminary and limited by the small number of patients (n = 109) who were evaluable after randomization. Despite this, if the survival data favor the early docetaxel arm, this will serve as additional evidence in support of maintenance therapy for patients with advanced NSCLC.
Gemcitabine as Maintenance Therapy
The favorable tolerability profile of gemcitabine makes it an ideal choice for evaluation as maintenance therapy. Brodowicz et al. [51] conducted a phase III study to evaluate the role of gemcitabine in the maintenance setting. Patients with advanced NSCLC were treated with a combination of cisplatin plus gemcitabine for four cycles. Those patients showing a response or disease stabilization were subsequently randomized to maintenance therapy with gemcitabine or BSC. Of the 352 patients enrolled in the study, 206 were randomized in a 2:1 ratio to maintenance therapy or BSC. In this maintenance phase, the median time to progression was 3.6 months with gemcitabine, compared with 2 months with BSC (p < .01). Overall survival also favored the maintenance therapy arm (13 months versus 11 months; p = .195). A median of three cycles of gemcitabine was given as maintenance therapy. Approximately 18% of patients experienced objective responses during the maintenance phase of the study. One of the limitations of the study was that 42 patients who had disease stabilization or response in the initial phase did not enter the maintenance phase for various reasons. Furthermore, treatment delays were noted in 22% of patients randomized to gemcitabine maintenance. Despite these limitations, the study documents both feasibility and evidence of benefit in favor of gemcitabine as maintenance therapy. In order to evaluate this further, a randomized clinical trial is under way in the U.S. (Fig. 2). In that study, patients with advanced NSCLC are treated with four cycles of carboplatin plus gemcitabine combination therapy. Following the induction phase, patients with response or disease stabilization will be randomized to gemcitabine as maintenance therapy versus BSC alone. The study has an estimated sample size of 600 patients and enrollment is nearing completion (as of May 2007).
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The favorable tolerability profile of pemetrexed also allows for its evaluation in the maintenance setting. In an ongoing randomized clinical trial, patients with advanced NSCLC who have stable disease or response following four cycles of platinum-based therapy are randomized in a 2:1 ratio to maintenance therapy with pemetrexed or placebo (Fig. 3). Maintenance therapy is continued until disease progression or unacceptable toxicity. All patients receive vitamin B12 and folic acid supplementation. The estimated sample size is 660 patients. Because this is a potentially definitive study with survival as the primary endpoint, it is hoped that it will lead to a new paradigm for the treatment of advanced NSCLC.
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| SUMMARY |
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