Generalizability of trial results to elderly Medicare patients with advanced solid tumors (Alliance 70802)

In the United States, patients who enroll in chemotherapy trials seldom reflect the attributes of the general population with cancer, as they are often younger, more functional, and have less comorbidity. We compared survival following three chemotherapy regimens according to the setting in which care was delivered (ie, clinical trial vs usual care) to determine the generalizability of clinical trial results to unselected elderly Medicare patients.

Using SEER-Medicare data, we estimated survival for elderly patients (ie, age 65 years or older, n = 14097) with advanced pancreatic or lung cancer following receipt of one of three guideline-recommended first-line chemotherapy regimens. We compared their survival to that of similarly treated clinical trial enrollees, without age restrictions, with the same diagnosis and stage (n = 937). All statistical tests were two-sided.

Trial patients were 9.5 years younger than elderly Medicare patients. Medicare patients were more often white and tended to live in areas of greater educational attainment than trial enrollees. For each tumor type, Medicare patients who were 75 years or older had median survivals that were six to eight weeks shorter than those of trial patients (4.3 vs 5.8 months following treatment with single agent gemcitabine for advanced pancreatic cancer, P = .03; 7.3 vs 8.9 months following treatment with carboplatin and paclitaxel for stage IV non-small cell lung cancer, P = .91; 8.2 vs 10.2 months following treatment with CDDP/ VP16 for extensive stage small cell lung cancer, P ≤ .01), whereas younger Medicare patients had survival times that were similar to those of trial patients.

Results of clinical trials for advanced pancreatic cancer and lung cancers tended to correctly estimate survival for Medicare patients aged 65 to 74 years, but to overestimate survival for older Medicare patients by six to eight weeks. These estimates of Medicare patients' survival may aid subsequent patients and their oncologists in treatment decision-making.