The PARAMOUNT phase III trial demonstrated that pemetrexed continuation maintenance significantly reduced the risk of disease progression (hazard ratio = 0.62) and death (hazard ratio = 0.78) versus placebo in patients with advanced nonsquamous non–small-cell lung cancer. To further understand the survival data, descriptive subgroup analyses were undertaken.
Nine hundred thirty-nine patients received induction therapy (four 21-day cycles pemetrexed 500 mg/m2 and cisplatin 75 mg/m2), after which 539 nonprogressing patients with an Eastern Cooperative Oncology Group performance status (PS) of 0/1 were randomized (2:1) to maintenance pemetrexed (500 mg/m2) cycles or placebo until disease progression.
Baseline characteristics of patients surviving for longer periods were comparable to patients surviving shorter periods, suggesting overall survival (OS) benefit for all subgroups of patients on maintenance therapy. An examination of type and severity of induction adverse events also found no association with survival duration. Response to induction (tumor response versus stable disease) was not determinate of pemetrexed maintenance OS outcome as assessed by waterfall plot and scattergrams and by the distribution of patients among various OS intervals. The length of the interval before beginning maintenance therapy (<7 days versus ≥7/≤30 days) also did not impact the survival results. PS, a known prognostic factor, was the only baseline characteristic associated with improved OS; however, both PS 0 and PS 1 patients exhibited a survival benefit from pemetrexed maintenance.
In PARAMOUNT, the OS benefit was seen across all subgroups. Other than PS, no baseline or clinical parameter clearly identified a subgroup more likely to benefit. Maintenance treatment decisions should be made on an individual basis.