Carcinoma of the Lung and Cigarette Smoking Effect of Serum Ribonuclease Activity

Our plain-English summary of Carcinoma of the Lung and Cigarette Smoking Effect of Serum Ribonuclease Activity, by D. Maor, M.E. Klein, D.A. Kenady, et al (1978).

The study

• Authors: D. Maor, M.E. Klein, D.A. Kenady, P.B. Chretien, M.R. Mardiney JR
• Published: JAMA, June 30, 1978, Volume 239 No.26
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This study did not concern asbestos. The authors measured the activity of ribonuclease, an enzyme in blood serum, in 53 untreated patients with lung carcinoma, 74 long-term cigarette smokers and 179 healthy people who had never smoked. Activity was tested against three laboratory substrates. A level more than 2 standard deviations above the nonsmokers' mean counted as elevated. Mean activity was higher in both the lung cancer patients and the smokers than in the nonsmokers (P less than .001). Elevated activity against at least one substrate was found in 40 of 53 lung cancer patients, 49 (66%) of 74 smokers and 13 (7%) of 179 nonsmokers. By tumor type, 20 (95%) of 21 patients with epidermoid carcinoma had elevated activity. Among smokers, the authors found no difference by pack-years (6 to 60) or by age. The authors suggested that ribonucleases may have a role in the pathway to cancer. They said it remains unknown whether smokers with elevated activity are more likely to have lung cancer, and whether former smokers still show elevated levels.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Comparative laboratory study of serum enzyme levels in lung cancer patients, smokers and nonsmokers, measured at one point in time
• Who was studied: 53 patients with lung carcinoma, mostly followed in the Surgery Branch of the National Cancer Institute, untreated and diagnosed by biopsy: 21 epidermoid carcinoma, 19 adenocarcinoma, 8 large cell carcinoma, 5 oat cell carcinoma. Also 74 long-term smokers who volunteered from stop-smoking clubs, and 179 never-smokers recruited by the Baltimore Cancer Research Center. People with raised BUN (a kidney test) were excluded. Study dates were not given.
• Exposure: Cigarette smoking. The smokers had histories of six to 60 pack-years. All but one lung cancer patient had a history of smoking. No asbestos or other fiber exposure was studied.
• Main results:
  • Method used for classifying results: activity against a substrate was considered elevated or depressed if it lay beyond 2 standard deviations from the nonsmoker group's mean. Elevated meant above that range and depressed meant below it.
  • For each of the three substrates, mean serum ribonuclease activity was higher in lung cancer patients and in long-term smokers than in healthy nonsmokers (P less than .001).
  • Elevated activity against one or more substrates was found in 40 of 53 lung cancer patients (given as 75% in the summary paragraph and 74% in the discussion), 49 (66%) of 74 smokers, and 13 (7%) of 179 nonsmokers (P less than .001).
  • Among lung cancer patients with epidermoid carcinoma, 95% (20 of 21) had elevated activity, the highest of the four tumor types.
  • Elevated activity was found in 13 of 19 patients with adenocarcinoma (68% in Table 2), 4 (50%) of 8 with large cell carcinoma, and 3 (60%) of 5 with oat cell carcinoma.
  • In the lung cancer group, elevated activity was not correlated with tumor grade, sex or race.
  • Among smokers, neither the percentage with elevated activity nor the mean activity differed with increasing pack-years (six to 60 studied). The supporting data were not presented.
  • Among smokers, elevation was as common in those aged 18 to 35 as in older smokers.
  • Among healthy nonsmokers, mean activity was essentially identical in men and women.
• The authors' conclusion: The authors concluded that these data, together with past data, suggest that ribonucleases play a multifunctional role in the body and may occupy an important position in the pathway to cancer development.
• Limitations the authors state:
  • Pack-year smoking history was not fully defined for the lung cancer group.
  • The authors did not know at what level below six pack-years elevation begins, or whether former long-term smokers still show elevation.
  • The study did not show whether smokers with elevated activity have a greater chance of having lung cancer than smokers without it. The authors left this as an open question.

Topics

Medical terms in this study, explained in our Lexicon: Carcinoma, Lung Cancer.

Browse return to medical research.