After three years, millions of dollars and countless hours of work, frustrated medical researchers conceded Thursday they still are at a loss to explain a cluster of deadly brain cancers at BP Amoco PLC’s Naperville research center.
Researchers from the University of Alabama-Birmingham and Johns Hopkins University concluded that six cases of the cancer, called glioma, are more likely than not to be workplace related based on stark similarities of the victims.
All six were long-term white male employees who worked in Building 503, most on the third floor and on similar projects, during the same years in the late 1970s and early 1980s.
But 13 other tumors, all benign, show no pattern that suggests a link to the job, the researchers added–a conclusion sure to spark anger and protests from those patients and their attorneys.
Although the findings are disappointing and leave many questions unanswered, the study itself is considered unprecedented and, some observers believe, may prompt other companies to investigate their workplaces. On-the-job exposures are believed to account for up to 10 percent of all cancers.
The tumors at the BP Amoco center, particularly the rare and puzzling gliomas, have generated more than a dozen lawsuits but little noticeable fear at the Naperville campus, where a briefing on Thursday’s report drew about 175 of 800 employees.
While researchers couldn’t identify what may have caused the gliomas, they did uncover two tantalizing clues, said Michael S. Wells, manager of health, safety and environment at the Naperville site.
A chemical called n-hexane, which is used to make plastics, and a process involving ionizing radiation, used to track individual compounds in chemical reactions, were used more by the six glioma victims than their counterparts at the center.
While n-hexane and ionizing radiation can be linked to specific health risks under certain circumstances, Wells said the researchers are almost certain neither is the culprit in the glioma cases. N-hexane hasn’t been linked to cancer, and the BP Amoco researchers were exposed to far less ionizing radiation than is considered dangerous, he said.
“There was possibly something underlying the projects,” he said.
The next step will be to look for more clues in those projects. BP Amoco will ask third-party researchers to review and confirm the study’s conclusions and make suggestions about further steps.
But Jim D. Lowry, head of BP Amoco’s task force on the glioma cluster, cautioned that further study likely will yield little valuable information because six patients is too small a sample.
Other than that, BP Amoco plans to monitor its workforce, fund additional research and hope that publishing of results so far will spur other companies and researchers to look for similar patterns. That could generate a larger database of glioma cases that would allow researchers to see patterns more clearly.
“We must rely on the outside world for some help,” Lowry said.
The study has cost BP Amoco “considerably” more than $1 million, Lowry and Wells said.
The study was launched in 1996 after a fourth case of deadly glioma was discovered among current or former employees of Building 503 at the Naperville center of what was then Amoco Corp. Although the incidence of brain cancer has increased to 7.2 cases per 100,000 men in 1996 from 5.9 cases per 100,000 in 1973, it remains a relatively rare–and little understood–disease.
The Chicago-based company was acquired by British Petroleum PLC on Dec. 31, and it has kept Amoco’s commitment to try to find a cause of the cancers.
But even at the beginning of their detective work, Wells and Lowry cautioned that the likelihood of pinpointing a single specific cause was a long shot.
Nevertheless, Thursday’s announcement was disappointing. Yet a frustrated Lowry refused to characterize the results as a failure.
“We’re also a little hopeful,” he said. “What was done here has never been done before.”
Specifically, the Alabama-Johns Hopkins study covered more ground than any similar effort, Lowry said. The study included all of the approximately 7,000 people who have worked at the Naperville campus since it opened in 1970 as well as the more than 6,700 chemicals that have been used there.
However, the final step–the case control study announced Thursday–looked only at the gliomas and benign tumors among employees in the three buildings that make up the 500 complex.
Each was compared with approximately 10 other healthy employees at the same complex matched by sex, race and type of work. A total of 131 people were included in the study, most of them in the healthy control group.
The goal was to see whether there were any striking differences between the two groups; the only differences uncovered were the degrees of exposure to n-hexane and ionizing radiation.
Results of the study are unlikely to end speculation that other illness among current and former employees may be linked to the job. The majority of lawsuits filed against BP Amoco to date are on behalf of people with other illnesses, ranging from lung cancer to benign tumors.
Critics also have questioned the Alabama and Johns Hopkins researchers’ decision to limit the study to tumors in the neck and head. Wells noted early steps of the study did look at broader health questions and other cancers, but didn’t find any unusual patterns.
Until recently, the official number of cases in the study was 20, including seven gliomas and 13 benign tumors. But in the course of confirming diagnoses, researchers determined that one of the cases classified as a glioma really was another form of cancer, and it was dropped from the study.
Before the public announcement of the study’s findings, lead researcher Dr. Elizabeth Delzell of the University of Alabama reviewed them Thursday with employees at the Naperville campus.
Non-employees were not allowed into that briefing, and Delzell declined to talk to reporters. Wells said protocol forbids researchers from publicly discussing their work until it has been published and subject to peer review.
Delzell plans to publish her findings, but no date was given.
Meanwhile, the third floor of Building 503 remains closed.
