Cancer

The Correlation Between Cystic Fibrosis and Cancers: A Literature Study | by Amirtha Srinivasan | Dec, 2021

Amirtha Srinivasan

Cystic Fibrosis is a deadly inherited disorder that causes severe damage to the lungs, digestive system, and peripheral organs of the body. Cystic fibrosis is recognized as a disease that stems from the defective CFTR Protein (cystic fibrosis transmembrane conductance regulator). This defective protein regulator affects the viscosity of mucosal secretions. People with CF are known to have mucus with sticky, thick, and cloggy characteristics. Furthermore, people with CF tend to have high amounts of salt in the sweat, resulting from an excess of chloride. The genetic basis of cystic fibrosis is categorized as a recessive disorder found predominantly in the Caucasian male population of European ancestry and the disease itself affects about 1 in 2,500 to 3,500 white newborns and only 1 in 17,000 African-Americans and 1 in 100,000 Asian-Americans.

Much of the genetic and biological implications of CF are largely unknown. However, many studies are taking place to uncover the truths about this fascinating disease. In my research, I came across a particular study that piqued my interest. The 1985 study utilized a cohort study to study the correlation between cancers and cystic fibrosis. I began to wonder a few different questions.

  1. Why would these vastly different diseases have any correlation with each other, other than of course, the inevitable chance?
  2. Would epithelial cancer or Carcinoma, specifically Adenocarcinoma (epithelial cells that produce mucus) be the most prevalent kind of cancer in CF patients?
  3. Is the data produced in this study even scientifically valid?

And of course, as a researcher myself, I knew that I had to validate this study myself.

Introduction

The first sentence of the paper states, “Anecdotal reports suggest an increased frequency of certain cancers in patients with cystic fibrosis, the commonest genetic disorder of whites” (Neglia 1995). To elaborate, readers are informed that there is no previous physical evidence of the increased frequency of cancers in patients with CF; the study is based mainly on hypotheses. The study specifically observed adult CF patients in North America and Europe. A total of 28,511 CF patients were studied in North America, specifically from 1985 to 1992. In Europe, 18,000 patients were studied across 17 different nations.

Methodology

The U.S cohort contained 115 centers and the Canadian cohort consisted of 33 centers. 15,161 were male (53.2 %) and 13,350 were female (46.8 %). 95% of the cohort was described as white and 2.8% as black. The age ranged from birth to 64 years of age. All American and Canadian cohorts were to respond to a questionnaire asking for the number of cancer occurrences from January 1 1985 to December 31, 1992. The expected number of cancers was calculated by applying age, sex, and race-specific demographics from the SEER Program (Surveillance, Epidemiology, and End Results). Furthermore, the number of expected cancers in 3 subcategories (digestive tract, leukemia, and lymphoma) were calculated along with age group subcategories. Using cystic fibrosis databases in Europe that maintain information on cases, the number of estimated patients were an estimated total of 24,500 across 17 countries (UK, Austria, Belgium, Germany, France, Iceland, Ireland, Denmark, Hungary, Sweden, Switzerland, Norway, Romania, Spain, Italy, The Netherlands, Finland).

Results — North American Study

Between 1985 and 1992, 41 cancers were reported to the North American cohort, however, 4 cases were redacted due to the basis of SEER data, resulting in 37 histologically confirmed cases of cancer in CF patients (32 in the U.S, 5 in Canada). Explicitly, this consisted of 13 digestive tract cancers, 8 cases of leukemia and lymphoma, 5 central nervous system cancers, 4 testicular cancers, 2 cervical cancers, 2 breast cancers, 1 cancer in the tongue. All of these cases only occurred in white patients. The expected number of cancers for the North American cohort was 45.6, yielding an observed to expected ratio of 0.8. The reason for the difference in the expected and observed incidences could be closely related to the possible underreporting of the cases during the period.

European Study

From 1982 to 1994, 41 patients were also diagnosed with cancer in the European cohorts. 2 patients were not included in the statistical analysis. 11 cancers were recognized to have originated in the digestive tract area. Similar to the North American study, the number of digestive tract cancers was elevated compared to the expected levels.

Discussion & Conclusions

Data alone reveals an elevated number of digestive tract cancers that could be associated with a risk factor in the frequency of cancers in CF patients. A possible reason for the excessive number of digestive tract cancers could have to do with the effect of the disease on the digestive tract system organs. For instance, hepatobiliary tract cancers are often found in patients with gallstones, and gallstones are found in CF patients quite often. Steatorrhea is not uncommon in CF patients, which may be linked to small bowel cancer. Truthfully, because age-specific and site-specific results were not calculated and analyzed, much of the data is left inconclusive.

Furthermore, there were several limitations and sources of bias in this study. Firstly, the European cohort relied on Physicians to indicate the number of CF patients with cancer could have led to an overreporting or underreporting. However, this seems unlikely as the data nearly matches the American cohorts. Moreover, an underreporting could have taken place in the North American cohorts as well, however, this seems unlikely as well.

I was truly taken by surprise by the results of this study. Despite the evidence of excessive digestive tract cancers in CF patients, I would still consider this study inconclusive. There are a very limited number of studies studying the correlation between cancer and CF, indicating the inconclusiveness of this hypothetical correlation. I think it would be greatly useful to study the genes in CF patients associated with cancer patients and vice versa. Of the 38,000 patients monitored, only 76 were diagnosed with cancer, indicating an overall 0.02% positive rate overall. Because of the very low incidence rate in this study, it is not possible to directly correlate cancer and cystic fibrosis without more indicative physical evidence.

CITATIONS

1. Neglia, J. P., S. C. FitzSimmons, P. Maisonneuve, M. H. Schöni, F. Schöni-Affolter, M. Corey, and A. B. Lowenfels. 1995. “The Risk of Cancer among Patients with Cystic Fibrosis. Cystic Fibrosis and Cancer Study Group.” The New England Journal of Medicine 332 (8): 494–99. https://doi.org/10.1056/NEJM199502233320803.

2. “Cystic Fibrosis Foundation.” 2000. Cff.org. Cystic Fibrosis Foundation. 2000. https://www.cff.org/.

‌3. Mayo Clinic. 2020. “Cystic Fibrosis — Symptoms and Causes.” Mayo Clinic. Mayo Clinic. March 14, 2020. https://www.mayoclinic.org/diseases-conditions/cystic-fibrosis/symptoms-causes/syc-20353700.

4. Lyczak, J. B., C. L. Cannon, and G. B. Pier. 2002. “Lung Infections Associated with Cystic Fibrosis.” Clinical Microbiology Reviews 15 (2): 194–222. https://doi.org/10.1128/cmr.15.2.194-222.2002.


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