Analysis Shows Pancreatic Cancer Survival Rates Lower in Real World Than Clinical Trials

Analysis Shows Pancreatic Cancer Survival Rates Lower in Real World Than Clinical Trials

James D. Murphy, MD, MS

Patients with pancreatic adenocarcinoma enrolled on clinical trials have "profoundly improved survival" compared with patients in the general population, suggesting that oncologists who use trial data to prognosticate may be missing the mark, according to researchers whose work was presented at the 2016 Gastrointestinal Cancers Symposium.

"Physicians often use clinical trial data to estimate expected survival for their patients; however, clinical trial results may not generalize to a broader population," said first author Reith R. Sarkar, BA, a medical student at the University of California, San Diego (UCSD), School of Medicine, who presented the poster.

The paper's senior author was James D. Murphy, MD, MS, of UCSD.

"We believe that lots of clinicians use trial data to predict their own patients' survival, but our findings suggest that physicians should use caution when extrapolating survival estimates from clinical trials to the real world," he said.

"We know that clinical trial patients, in general, are somewhat different from the real-world population," he acknowledged. "We know they have to be fit to enroll, and they tend to live near academic centers (ie, trial sites), be wealthier, and to have better access to health care. If they are on a trial, they are also likely to have closer follow-up. Still, there have not been many studies determining if being on a trial actually translates into a difference in survival."

The authors' aim, therefore, was to produce a more accurate idea of survival of patients with pancreatic adenocarcinoma "in the real world," he said.

Study Design

The researchers conducted a literature search of phase III trials published between 2005 and 2012. They excluded secondary or pooled analyses trials with second-line treatments and nonrandomized studies. They compared clinical trial patients with a cohort of patients from the Surveillance, Epidemiology, and End Results (SEER) program, matching for diagnosis year, age, and stage of disease, looking for differences in median survival, 1-year survival, and 2-year survival between the SEER registry patients and clinical trial cohorts.

The search resulted in 27 trials that fit the search criteria, consisting of 55 clinical trial arms involving 8438 patients.

They analyzed the studies by these categories: (1) patients with mixed metastatic and locally advanced unresectable metastatic pancreatic cancer, (2) those with unresectable locally advanced disease, and (3) patients deemed resectable.

Almost 100% of all the randomized trials had survival outcomes that were better than those outcomes seen in the SEER registry, and this held true for each of the three different populations, Sarkar reported.

The average increases in median overall survival for trial patients were as follows:

• 3.23 months in the mixed metastatic/locally advanced unresectable group, a 92% increase (P<.0001)
• 2.96 months in the unresectable locally advanced group, a 41% increase (P= .0012)
• 6.1 months in the resectable group, a 36% increase (P= .0013)

The average increase in 1-year survival, in these respective groups, was 88.8% (P<.0001), 45.3% (P<.0001), and 23.7% (P<.0001). Absolute differences in 1-year survival were more than 12% in each category.

Average increases in 2-year survival were 72.7% (P<.0001), 49.9% (P= 0.0094), and 34.0% (P <.0001), which were associated with absolute differences of 2.5%, 4.6%, and 11.9%, respectively.

"We saw that for metastatic patients, average survival was almost double for clinical trial patients, versus real-world patients. The differences were greatest for the worst-prognosis cancers," Sarkar said. "We think this is a pretty profound difference."

Sarkar acknowledged that he and his team could not assess the SEER database for patient performance status, underlying comorbidities, and differences in treatment-factors that may help explain some of the survival differences.

References

1. Sarkar RR, Matsuno R, Murphy JD. Pancreatic cancer: Survival in clinical trials versus the real world.J Clin Oncol. 34, 2016 (suppl 4S; abstr 216).