Houston Area Lung Cancer Rates Higher Than Average
|February 5, 2006|
Courtesy: Houston Chronicle
When 68-year-old Lucie Wood tells someone that she is battling lung cancer, she is irritated that most automatically assume she is a smoker.
Terri Diaz, who contracted lung cancer three years ago at 41, also has grown tired of her illness being stigmatized as a "smoker's disease."
Both Houston-area women say they never puffed a single cigarette, and neither has any family history of the disease.
Yet each woman fits into a complex puzzle of cancer data that the Texas Department of State Health Services' Texas Cancer Registry has been studying for the past 10 years. Each year the database has grown until now epidemiological studies can include 10 years of cancer deaths and eight years of cancer cases.
From September 2001 to the present, the registry has conducted 51 studies in the Houston area, and 18 of those, or 35 percent, identified ZIP codes with cancer rates higher than should be expected when compared with statewide rates.
Of all the types of cancer, lung cancer was by far the most frequently found to be elevated. The registry detected higher rates of lung cancer in 24 ZIP codes — or 77 percent of all the ZIP codes with elevated levels.
Neil Carman, clean-air director for the environmental group Sierra Club, said he is surprised the test results had not been publicized before the Houston Chronicle analyzed cancer patterns turning up in these reports.
And for the first time, a pilot study is being initiated to try to link the registry's epidemiological data with possible environmental exposures.
"I've talked to citizens in Houston, and they have been wanting more research in light of all the air pollution in the Houston area," Carman said. "In the past, there seems to have been a history of ignoring these issues."
But the Texas Cancer Registry is not designed to conduct in-depth research of those issues, officials said. The registry simply responds to requests about mortality and incidence of cancer in a specific ZIP code.
"Our studies are meant as a starting point, a very first step that might stimulate more study," said Melanie Williams, a senior epidemiologist with the Texas Cancer Registry. "I've noticed higher patterns of lung cancer in these studies. But we don't know what that's all about. That's why I'm in support of looking deeper into what might be behind it."
In the new pilot study, Williams is turning her data over to the University of Texas School of Public Health, which has been contracted to do the research by the city of Houston's Department of Health and Human Services. The study will look at the Houston Ship Channel and six surrounding counties to see whether it is feasible to link elevated cancer rates, such as lung cancer, with hazardous pollutants.
"The objective will be to correlate specific air-toxic data from the state with relevant cancers in the Houston area and compare it to Dallas (another large metropolitan area)," said Ann Coker, the principal investigator, an associate professor of epidemiology at the UT School of Public Health.
No data on smoking
Unfortunately, the registry has not collected any data on smoking — a key risk factor — that the American Cancer Society estimates could account for as much as 87 percent of all lung cancer.
"Physicians can list smoking as an underlying cause in their death reports," Coker said, but the required reporting fields include nothing to "check off" whether an individual was a smoker.
To compensate, Coker said, she might conduct a survey to try to estimate the percentage of people in the area who smoke.
Meanwhile, Wood and Diaz can't help but wonder whether the environment played a factor in their illnesses.
Wood has lived most of her life in the Houston area, including four years in La Porte, an area that the cancer registry reported had an elevated lung cancer rate in the 77571 ZIP code. The registry's 2001 report found the incidence and mortality rates of lung cancer for women were 70 percent higher than the state average.
No studies have been done on the ZIP codes in Cypress or Dairy Ashford areas where Diaz has made her home since age 5. She was unaware that the cancer registry collects such data, but she wonders what a study would find in her neighborhood. A ZIP code is studied only if an individual or government agency requests it, and none has been made for her area.
"I can't help but think the environment must have had a lot to do with it," said Diaz, who is almost at the end of her treatment options.
Pollution can be a risk factor for lung cancer, but so can radon, asbestos, auto exhaust and family history — making it difficult to prove a connection to industrial releases, experts say.
"Still, it makes sense that something in the air might increase the risk of lung cancer because our lungs are just big filters," Coker said.
To identify a strong cancer cluster, the registry would usually like to see more than 10 times the expected rate of cancer in an area, Williams said.
However, contaminants in a neighborhood will not usually be as concentrated as at a workplace, so cancer elevations in neighborhoods may be much lower, Coker said.
Galveston ZIP codes 77550 and 77551 registered the lowest level of increase in lung cancer of all the elevated areas studied by the registry. The Oct. 31, 2005, study found 21 percent, or .21 times, more males with lung cancer than would usually be expected. Data identified 223 cases of lung cancer, whereas 184 would be expected.
The highest lung cancer elevation was detected Sept. 30, 2005, in the Liverpool area of Brazoria County (ZIP code 77577). Both incidence and mortality rates were more than four times what would be expected in females. For instance, fewer than two lung cancer cases should have been found in this low-populated rural area, but nine were counted.
The registry adjusts its data in an attempt to eliminate the possibility that a higher rate might occur by chance alone, such as when small numbers are involved, authorities said. Adjustments also are made for age, race and ethnicity because older or minority populations can have higher cancer rates.
The data, however, do not track mobility such as whether someone contracted the cancer prior to living in that ZIP code.
Because of numerous requests, the 77530 ZIP code in Channelview has been studied more than any other ZIP code. Three separate studies there documented elevated levels of lung cancer.
Higher than normal
The latest study done there, on April 8, 2004, found the frequency of males both contracting and dying from this disease was 50 percent higher than would be expected.
But two earlier studies, both in 2001, detected even higher elevations of lung cancer incidence (70 percent to 90 percent more) and deaths (70 percent to 200 percent more) in males.
No elevations above the state average were detected for females with lung cancer in the latest 2004 study, but both studies in 2001 found 200 percent more lung cancer deaths and 80 percent to 90 percent more lung cancer cases in women than would be expected.
All three studies used 10 years of cancer deaths, but the 2004 study used six years of cancer cases while the 2001 studies used three.
Lung cancer elevations also were detected in multiple ZIP codes in Pasadena (77502, 77503, 77506) and Houston (77049, 77015, 77017, 77044).
In the new pilot study, Coker is refining the data to look at the entire Houston region by individual addresses rather than using the broad brush of a ZIP code.
She will put this data on a map that also defines areas of high and medium exposures to pollutants. She also will factor in prevailing wind patterns and latency periods, the lag time from when someone may be exposed and then develop cancer.
This 10-month study, being funded by a $27,000 grant, will determine whether more resources should be devoted to researching possible connections to environmental exposures, she said.
But proving any link will be difficult, authorities agree.
"Nobody is sure of the impact of the cumulative effects in the environment of a chemical soup in low concentrations," said Michael Honeycutt, a toxicologist with Texas Commission on Environmental Quality. "Cigarette smoking and asbestos can lead to higher cancer rates, but what about cigarette smoking and chemicals? The bottom line is that we don't know."
At the same time, Dr. Roy Herbst, who handles lung cancer patients at M.D. Anderson Cancer Center, said most people don't realize that lung cancer is the leading cause of cancer death in men and women. He said the illness is often seen as a death sentence.
"Of those who contract the disease, only 15 percent have a five-year survival rate. Unfortunately, there's no shortage of patients," Herbst said. "The best thing to do is to prevent it from happening."
Wood and Diaz say they don't want people telling them to just stop smoking because they never smoked.
They are hoping new research will come up with some better answers.
By CINDY HORSWELL Copyright 2006 Houston Chronicle