Despite recent progress, locally advanced non-small-cell lung cancer (NSCLC) represents an ongoing treatment challenge. With more than 140,000 new cases annually, non-small-cell lung cancer remains the leading cause of cancer-related mortality in the United States. Of these new cases, nearly one-third present with locally advanced, unresectable disease (stages IIIA and IIIB).
Despite efforts to reduce smoking, the previously declining percentage of Americans who smoke seems to have reached a plateau at approximately 25%, with some evidence of an increase in the number of young smokers. This trend, along with the aging of the baby-boom generation, will certainly foreshadow a continuation of high lung cancer rates during the coming years.
Despite trials of chemoprevention of lung cancer and efforts to establish better screening strategies to identify earlier-stage cancers, non-small-cell lung cancer continues to be one of the major challenges facing the practicing oncologist. The use of radiation therapy alone has been the traditional treatment for unresectable stage III disease; however, this approach has led to few cures, with a dismal long-term survival rate of £ 10%.
This article will review the evolving role of chemotherapy in the treatment of both advanced and earlier-stage non-small-cell lung cancer, as well as recent work pointing toward the additive benefits of combined treatment with chemotherapy and radiation therapy. These observations provided the rationale for a phase I study, in which we assessed chemotherapy and concurrent chest irradiation as a means of ultimately improving both local and systemic control of non-small-cell lung cancer. Preliminary results of this investigation are reported here.
In view of the fact that a majority of patients with non-small-cell lung cancer will die of distant disease progression, better systemic therapy is needed. A few of the older standard chemotherapy drugs have demonstrated encouraging activity in non-small-cell lung cancer; these include cisplatin(Drug information on cisplatin) (Platinol), ifosfamide(Drug information on ifosfamide) (Ifex), etoposide(Drug information on etoposide) (VePesid), mitomycin(Drug information on mitomycin) (Mutamycin), vinblastine(Drug information on vinblastine), and vindesine(Drug information on vindesine) (Eldisine).
Using these drugs alone or in combination, several randomized studies have compared chemotherapy to best supportive care alone in the palliative setting.[5-11] Although these studies have often been too small to demonstrate statistically significant differences, or have employed older, less-efficacious chemotherapy regimens, a universal trend favoring patients treated with chemotherapy has been evident. In addition, four meta-analyses have now been performed using data from these trials; all have shown significantly longer survival among patients treated with chemotherapy than in those receiving supportive care alone for metastatic non-small-cell lung cancer.[12-15]
In the most recent meta-analysis, the 1-year survival rate improved from 15% to 25% (P < .0001) and the median survival was prolonged by 6 weeks in patients receiving cisplatin-based chemotherapy. Thus, chemotherapy has proved beneficial in the management of advanced non-small-cell lung cancer.
Several new chemotherapeutic drugs have been identified and studied in the treatment of non-small-cell lung cancer during the past several years. Those with encouraging activity have included vinorelbine (Navelbine), paclitaxel(Drug information on paclitaxel) (Taxol), docetaxel(Drug information on docetaxel) (Taxotere), irinotecan(Drug information on irinotecan) (Camptosar), and gemcitabine(Drug information on gemcitabine) (Gemzar); as single agents, each has produced a response rate of at least 15%. Phase II and III trials are currently evaluating these drugs, both as single agents and in combination therapy, to document their activity in non-small-cell lung cancer. These newer chemotherapeutic agents may offer improved efficacy with fewer toxic side effects, or a better therapeutic index, in the management of this disease.
Based on improved outcomes with chemotherapy in non-small-cell lung cancer, as well as the high rate of distant relapse in patients with locally advanced disease, several recent studies have attempted to apply the principle of systemic therapy to patients with earlier-stage disease. The Lung Cancer Study Group conducted a randomized trial of postoperative cyclophosphamide(Drug information on cyclophosphamide) (Cytoxan, Neosar), doxorubicin(Drug information on doxorubicin) (Adriamycin), and cisplatin plus radiation vs radiation alone in patients with completely resected stage IIIA disease.
The results suggested that adjuvant chemotherapy is associated with a survival advantage in patients with resected, locally advanced disease. Although the difference between groups did not reach statistical significance, the median duration of survival was longer in patients who received chemotherapy than in those who did not (20 vs 13 months).
Evidence that chemotherapy may have better efficacy in early-stage non-small-cell lung cancer also led researchers to pursue induction protocols in resectable, locally advanced disease. In a study by Rosell et al, patients with stage IIIA disease were randomized to receive either mitomycin, ifosfamide, and cisplatin or no chemotherapy before resection. All patients received adjuvant radiation therapy. The patients treated with chemotherapy had a remarkably superior median survival of 26 months, compared with 8 months in the control group (P < .001).
These results were confirmed by Roth et al, who randomized patients to receive either cyclophosphamide, etoposide, and cisplatin or no chemotherapy before surgical resection. Again, the median duration of survival was significantly better in the patients who received chemotherapy than in those who did not (64 vs 11 months; P < .008). These trials strongly support the role of induction chemotherapy as standard treatment for patients with resectable stage IIIA non-small-cell lung cancer.
Chemotherapy is also becoming standard treatment for unresectable stage IIIB non-small-cell lung cancer. Recently, investigators completed several studies that compared chemotherapy plus radiation to the previous standard of radiation alone. In a randomized trial conducted by the Cancer and Leukemia Group B (CALGB), the use of cisplatin and vinblastine followed by radiation was significantly superior to radiation alone with regard to both median survival (14 vs 10 months) and 5-year survival (19% vs 7%; P = .0066).
Sause et al confirmed these findings in another randomized trial that used the same regimen. Patients who received chemotherapy plus radiation had an improvement in median survival similar to those not receiving chemotherapy (14 vs 11 months) and a superior 1-year survival rate (60% vs 46%; P = .03). In a French study, Le Chevalier et al also found an improved 3-year survival rate with chemotherapy plus radiation vs radiation alone (12% vs 4%). Taken together, these studies confirm that chemotherapy prolongs survival when added to radiation in unresectable non-small-cell lung cancer.
With the evolving success of chemotherapy, it was logical to study optimal sequencing when this treatment is used in conjunction with radiation therapy. This line of investigation was also sparked by evidence that the simultaneous use of chemotherapy can sensitize tumor cells to the cytotoxic effects of radiation.
Vinorelbine was shown to potentiate the effects of radiation on a human non-small-cell lung cancer line in vitro, with a fivefold decrease in surviving cells exposed to the drug and radiation compared with radiation alone. This is thought to occur by tumor-cell synchronization into the radiosensitive G2M phase of the cell cycle. In addition, preclinical in vitro and in vivo data support the role of cisplatin as a radiation sensitizer, causing increased damage to tumor cells.
The goal of this bimodality approach is to improve local control within the radiation field, while addressing systemic disease control through the use of effective chemotherapy. The mechanism of benefit may be based on simple physical cooperation of the two modalities, which work on different sites or cell populations.
An alternative mechanism would be biologic synergy, wherein one modality actually helps sensitize cells so that they become more responsive to the other therapy; this can occur by means of chemotherapy-induced synchronization of tumor cells to a radiation-sensitive phase, or by actual inhibition of repair of sublethal damage produced by radiation therapy, thereby augmenting cell death.[25-27]
A randomized study by Schaake-Koning et al demonstrated that the addition of radiosensitizing chemotherapy could improve survival in stage IIIB non-small-cell lung cancer. The 3-year survival rate was 16% in patients who received daily cisplatin and radiation therapy vs 3% in those treated with the latter modality alone. This effect was explained almost entirely by the improved local control (31% vs 19%, at 2 years) provided by the addition of cisplatin. Nonetheless, the study provided evidence that chemotherapy has a critical role in locally advanced non-small-cell lung cancer.
In a feasibility study, the Southwest Oncology Group (SWOG) showed that patients could receive concomitant chemotherapy and radiation therapy before surgical resection for locally advanced non-small-cell lung cancer. Patients received two cycles of concomitant radiation therapy and full, systemically active doses of chemotherapy (50 mg/m2 of cisplatin on days 1 and 8 and 50 mg/m2 of etoposide on days 1 through 5) before planned resection.
Although the incidence of toxicity was high (with grade 4 toxicity in 13% of patients), more than 80% of the study group was able to undergo resection, with an impressive 3-year survival rate of 27% in stage IIIA disease (median survival, 13 months). This study helped establish the feasibility of delivering systemically active doses of chemotherapy concurrently with thoracic radiation.