Emerging Role of Topotecan in First-Line Therapy of Small-Cell Lung Cancer

A phase I trial defining the maximum tolerated systemic exposure of topotecan in combination with Carboplatin and Etoposide in extensive stage small cell lung cancer

PURPOSE

Topotecan is active in relapsed small cell lung cancer; thus, its addition to the standard carboplatin-etoposide regimen may improve outcomes in extensive-stage small cell lung cancer (ES-SCLC) patients. Significant interpatient variability in the topotecan systemic exposure results when it is dosed based on body surface area (mg/m2). The purpose of this Phase I trial was to determine the maximally tolerated systemic exposure (MTSE) of topotecan in combination with carboplatin and etoposide.

METHODS

Thirty-four chemotherapy-naïve ES-SCLC patients received topotecan in combination with carboplatin AUC 5 mg/mL*min and oral etoposide 100 mg/m2/day. Topotecan was administered as a 30-minute infusion either on Days 1-5 or Days 1-3 and the dosage was individualized to attain a topotecan lactone AUC range (ng/mL*hr) in successive patient cohorts from 7 to 23; 24 to 36; 37 to 53; 54 to 66.

RESULTS

The majority (67 percent) of the measured topotecan AUCs were within target range. Overall, 8 of 34 patients experienced Cycle 1 dose-limiting toxicity (DLT), either neutropenia or thrombocytopenia. Carboplatin administration prior to topotecan resulted in 2 of 6 patients having Cycle 1 DLT. When the administration sequence was changed (topotecan, carboplatin, etoposide), Cycle 1 hematologic toxicity decreased; however, the maximum topotecan lactone AUC of 24-36 ng/mL*hr (median dose 0.82 mg/m2) had significant cumulative hematologic toxicity. The number of topotecan doses were reduced from 5 to 3, which resulted in a maximum topotecan lactone AUC of 37 to 53 ng/mL*hr with only 1 of 6 patients having Cycle 1 DLT. Overall response rate was 71 percent with median survival of 10.8 months.

CONCLUSION

It is feasible to target topotecan lactone AUC in adult ES-SCLC patients. However, this triplet regimen resulted in considerable hematologic toxicity and has a median survival comparable to carboplatin-etoposide. Alternative, less toxic regimens should be investigated for improving survival in ES-SCLC.

Paclitaxel/Carboplatin/Etoposide Versus Paclitaxel/Topotecan for Extensive‐Stage Small Cell Lung Cancer: A Minnie Pearl Cancer Research Network Randomized, Prospective Phase II Trial

PURPOSE

To compare the combination of paclitaxel (Taxol; Bristol-Myers Squibb, Princeton, NJ, http://www.bms.com) and topotecan (Hycamtin; Glaxo SmithKline, Philadelphia, http://www.gsk.com) with paclitaxel, carboplatin (Paraplatin; Bristol-Myers Squibb), and etoposide (Etopophos, VePesid; Bristol-Myers Squibb) in patients with previously untreated extensive-stage small cell lung cancer.

PATIENTS AND METHODS

In this phase II trial, 120 patients were randomly allocated to receive either topotecan (1.5 mg/m(2) i.v. days 1, 2, and 3) and paclitaxel (175 mg/m(2) i.v. day 1) every 21 days orpaclitaxe l (200 mg/m(2) i.v. day 1), carboplatin (area under the concentration-time curve 6 i.v. day 1), and etoposide (50 mg/100 mg alternating daily by mouth days 1-10) every 21 days, each regimen for a maximum of eight cycles. The primary end points were objective response rate and time to progression.

RESULTS

The paclitaxel-carboplatin-etoposide combination produced a significantly higher overall response rate (78% versus 48%), longer median time to progression (7.6 months versus 5.5 months), and greater number of patients free from progression at 1 year (14% versus 8%) compared with paclitaxel plus topotecan. There was no difference in overall survival. Toxicities were similar in the two treatment arms.

CONCLUSIONS

The paclitaxel-carboplatin-etoposide combination produced a superior overall response rate and time to progression in patients with extensive-stage small cell lung cancer compared with paclitaxel plus topotecan. The platinum compounds continue to be a necessary component of the initial therapy for these patients.