Workers at Pratt & Whitney in Connecticut did not get brain cancer at higher rates than the population generally, according to the latest results of a multiyear study led by University of Pittsburgh researchers.
An analysis of 212,513 people who worked at Pratt between 1952 and 2001, and who were still alive as of 1976, showed 489 cases of malignant central nervous system tumors. Of those, 275 cases were glioblastomas, a lethal type of tumor that starts in the brain.
The $12 million, multiphase study began in 2002 in response to a suspected brain cancer cluster among workers at Pratt's North Haven plant, which closed in 2001. Of the 275 glioblastomas, 61 occurred in North Haven workers, Marsh said.
Detection of central nervous system tumors became reliable only in the early 1970s, he said.
Although the latest results show that the incidence of brain cancer among Pratt workers was the same or lower than for the population at large, the three-part study has not yet ruled out a connection between Pratt's factories and cancer among the workers diagnosed with it.
"That's a reason for doing Phase 3," Marsh told reporters, calling it "really the definitive step."
Phase 3 will scrutinize the exposure of workers to specific industrial processes and agents, such as chemicals. The work is underway and should be finished by the end of the year, researchers said. They expect to publicize results early in 2011.
In a statement Thursday, Pratt said that it was "reassured that the study does not show an increased rate of brain cancer among our Connecticut employees" and that it was paying for the study "because we care about the safety of our employees."
Suspicion of a brain cancer cluster arose in 1999, when two longtime Pratt workers in North Haven were diagnosed with the same form of highly lethal brain cancer, glioblastoma multiforme. Both men, John Shea and John Greco, eventually died of it.
The results released Thursday showed a slightly higher incidence of glioblastoma formation among North Haven workers, but researchers called the excess "not statistically significant" and said that it was not necessarily work-related.
"Currently, the findings suggest that these excesses may be due to non-work factors, to work outside the P&W plants or to chance," the researchers wrote in a briefing paper.
A higher and statistically significant incidence of glioblastoma was discovered in one subgroup of North Haven workers - those on salary (as opposed to those paid hourly). But researchers said they found "no consistent patterns or trends typically suggestive of a workplace relationship."
It is unknown how the results released Thursday will affect pending workers' compensation claims by families of brain cancer patients who allege that chemicals at Pratt caused the illnesses.
Matthew Shafner, the New London lawyer now handling the cases - about 90 in all - attended the Thursday afternoon briefing, held at Pratt & Whitney's world headquarters, and he sought to cast doubt on the study's reliability.
"I'm just very suspicious of this whole study - bought and paid for by Pratt & Whitney," he said in a brief interview. "Why would they do that without knowing what the results would be?"
The studies are being published in peer-reviewed scientific journals. Phase 2 will be published online on Monday in the journal Neuroepidemiology, Marsh said. It will be published in the journal's print edition in August.
Results for Phase 1, released in September 2008, were published in the Journal of Occupational and Environmental Medicine. Phase I, which focused on the causes of employees' deaths, showed a higher, but statistically insignificant rate of brain cancer deaths among workers at the former North Haven plant than for the Connecticut population as a whole.
As with the latest results, researchers said that the higher rate could have been caused by factors unrelated to the plant.