Re: sex, smoking, and cancer: a reappraisal

An examination of male and female odds ratios by BMI, cigarette smoking, and alcohol consumption for cancers of the oral cavity, pharynx, and larynx in pooled data from 15 case-control studies

BACKGROUND

Greater tobacco smoking and alcohol consumption and lower body mass index (BMI) increase odds ratios (OR) for oral cavity, oropharyngeal, hypopharyngeal, and laryngeal cancers; however, there are no comprehensive sex-specific comparisons of ORs for these factors.

METHODS

We analyzed 2,441 oral cavity (925 women and 1,516 men), 2,297 oropharynx (564 women and 1,733 men), 508 hypopharynx (96 women and 412 men), and 1,740 larynx (237 women and 1,503 men) cases from the INHANCE consortium of 15 head and neck cancer case-control studies. Controls numbered from 7,604 to 13,829 subjects, depending on analysis. Analyses fitted linear-exponential excess ORs models.

RESULTS

ORs were increased in underweight (< 18.5 BMI) relative to normal weight (18.5-24.9) and reduced in overweight and obese categories (≥ 25 BMI) for all sites and were homogeneous by sex. ORs by smoking and drinking in women compared with men were significantly greater for oropharyngeal cancer (p < 0.01 for both factors), suggestive for hypopharyngeal cancer (p = 0.05 and p = 0.06, respectively), but homogeneous for oral cavity (p = 0.56 and p = 0.64) and laryngeal (p = 0.18 and p = 0.72) cancers.

CONCLUSIONS

The extent that OR modifications of smoking and drinking by sex for oropharyngeal and, possibly, hypopharyngeal cancers represent true associations, or derive from unmeasured confounders or unobserved sex-related disease subtypes (e.g., human papillomavirus-positive oropharyngeal cancer) remains to be clarified.

Cigarette smoking and lung cancer: modeling effect modification of total exposure and intensity

BACKGROUND

A recent analysis indicates that the excess odds ratio for lung cancer by smoking is described by a function that is linear in pack-years and exponential in the logarithm of smoking intensity and its square (Cancer Epidemiol Biomarkers Prev. 2006;15:517-523). The model suggests that below 15-20 cigarettes per day there is a "direct exposure rate" effect, ie, the excess odds ratio per pack-year for higher intensity (and shorter duration) smokers is greater than for lower-intensity (and longer duration) smokers. Above 20 cigarettes per day, there is an "inverse-exposure-rate" effect, ie, the excess odds ratio per pack-year for higher intensity smokers is smaller than for lower-intensity smokers.

METHODS

Using pooled data from 2 large case-control studies of lung cancer (the European Smoking and Health Study and the German Radon Study), we evaluated effect modification of the association between smoking and lung cancer.

RESULTS

Interaction effects are very specific. Variations in risk of lung cancer with years since cessation of smoking, age, method of inhalation, and type of cigarette result from interactions with smoking intensity, and not total pack-years. In contrast, risk variations by sex result from the interaction with total pack-years, while intensity effects are homogeneous. Risk variations by age at which smoking started result from interactions with both total pack-years and intensity. All intensity interactions are homogeneous across studies.

CONCLUSIONS

The specificity of the interactions may provide clues for the molecular basis of the smoking and lung cancer relationship.

Gender differences in non–small-cell lung cancer survival: an analysis of 4,618 patients diagnosed between 1997 and 2002

BACKGROUND

Gender has been reported as a predictor for nonsmall cell lung cancer (NSCLC) survival. Most of the reports are limited to selected groups of patients. The magnitude of gender effect on NSCLC survival across disease stage, tumor histology, and therapies needs to be further characterized.

METHODS

A cohort of 4,618 patients diagnosed with NSCLC was prospectively enrolled and actively followed. Vital status of each patient was verified through multiple complementary sources. Cox proportional hazards models were developed to compare postdiagnosis survival between genders adjusting for age at diagnosis, tumor histology and grade, stage, pack-years smoked, and treatment received (resection, radiation, or chemotherapy).

RESULTS

There were 2,724 men (59%) and 1,894 women (41%), with a median age at diagnosis of 68 years in men and 66 in women (p < 0.01). More men smoked and were heavier smokers than women. Adenocarcinoma was the most frequent histology in both genders. No difference was found in stage and treatment between genders. The estimated survival in men was 51% (95% CI: 49%, 53%) and 15% (95% CI: 12%, 17%) at one and five years, respectively, and in women was 60% (95% CI: 58%, 62%) and 19% (95% CI: 16%, 22%). Men were at a significantly increased risk of mortality compared to women following a diagnosis of NSCLC (adjusted relative risk: 1.20, 95% CI: 1.11, 1.30), particularly for patients with stage III/IV disease or adenocarcinoma.

CONCLUSIONS

Male gender is confirmed to be an independent unfavorable prognostic indicator for NSCLC survival.