# Cigarette Smoking as a Major Cause of Lung Carcinoma: research update

Dated 5 October 2026. Local prepublication addendum; archived grade unchanged.

Epidemiology, cessation, experimental carcinogenesis and tumour signatures converge on smoking as a major causal route. Remaining research questions concern individual susceptibility, persistent injury and attribution among overlapping exposures, rather than whether the overall causal relationship exists.

## Research timeline

Electronic year is used where recorded; issue year is retained in each source card. The chronology is selected, not exhaustive, and does not establish priority or causation.

| Year | Primary study | Design and finding | Inference limit |
|---|---|---|---|
| 1950 | [Smoking and carcinoma of the lung; preliminary report.](https://pubmed.ncbi.nlm.nih.gov/14772469/) | Historical hospital case-control report. A foundational report examined smoking and lung carcinoma. | Metadata-only anchor in this update; its original numerical results were not re-examined. |
| 1950 | [Tobacco smoking as a possible etiologic factor in bronchiogenic carcinoma; a study of 684 proved cases.](https://pubmed.ncbi.nlm.nih.gov/15415260/) | Independent historical case-control report. A separate report examined smoking in confirmed lung-carcinoma cases. | Metadata-only anchor; hospital selection and recall remain design limits. |
| 1996 | [Preferential formation of benzo[a]pyrene adducts at lung cancer mutational hotspots in P53.](https://pubmed.ncbi.nlm.nih.gov/8832894/) | Carcinogen-adduct mapping. Benzo[a]pyrene-related adducts targeted major lung-cancer TP53 mutation hotspots. | An adduct mechanism does not identify the initiating cause of each individual tumour. |
| 2000 | [Smoking, smoking cessation, and lung cancer in the UK since 1950: combination of national statistics with two case-control studies.](https://pubmed.ncbi.nlm.nih.gov/10926586/) | National trends plus case-control synthesis. Stopping smoking greatly reduced subsequent lung-cancer risk. | Nonrandomized cessation and historical exposure reconstruction require consideration. |
| 2004 | [Mortality in relation to smoking: 50 years' observations on male British doctors.](https://pubmed.ncbi.nlm.nih.gov/15213107/) | British Doctors long-term cohort. Long follow-up associated persistent smoking with higher mortality and cessation with benefit. | Repeated reports from this cohort are not independent replications; generalization beyond its population requires other cohorts. |
| 2004 | [EGF receptor gene mutations are common in lung cancers from "never smokers" and are associated with sensitivity of tumors to gefitinib and erlotinib.](https://pubmed.ncbi.nlm.nih.gov/15329413/) | Never-smoker tumour sequencing. EGFR-mutant adenocarcinoma was enriched among never smokers. | Alternative causes are compatible with smoking causing a major share, not all tumours. |
| 2005 | [Life-span inhalation exposure to mainstream cigarette smoke induces lung cancer in B6C3F1 mice through genetic and epigenetic pathways.](https://pubmed.ncbi.nlm.nih.gov/15944214/) | Lifetime mouse inhalation study. Long-term smoke exposure induced lung cancer with molecular changes. | Species, dose and exposure conditions limit direct human quantitative extrapolation. |
| 2013 | [21st-century hazards of smoking and benefits of cessation in the United States.](https://pubmed.ncbi.nlm.nih.gov/23343063/) | United States smoking/cessation cohort. Continued smoking reduced life expectancy; earlier cessation provided larger benefit. | All-cause mortality estimates must not be relabelled as lung-cancer-specific effects. |
| 2016 | [Mutational signatures associated with tobacco smoking in human cancer.](https://pubmed.ncbi.nlm.nih.gov/27811275/) | Human tumour mutational-signature analysis. Smoking correlated with several mutational signatures across cancer types. | Different signatures and exposures can overlap; a tumour signature alone does not prove universal exposure specificity. |

## Research gaps

### G1: Which molecular changes initiate cancer rather than accumulate later?

Evidence anchors: [P8832894](https://pubmed.ncbi.nlm.nih.gov/8832894/), [P27811275](https://pubmed.ncbi.nlm.nih.gov/27811275/), [P15944214](https://pubmed.ncbi.nlm.nih.gov/15944214/).

Competing explanation: Passenger mutation burden or promotion may accompany rather than define initiation.

Discriminating test and controls: Exposure-resolved longitudinal airway sampling and lineage/driver analyses with matched controls; compare adduct, mutation and clonal expansion timing.

### G2: What determines persistent risk after cessation?

Evidence anchors: [P10926586](https://pubmed.ncbi.nlm.nih.gov/10926586/), [P15213107](https://pubmed.ncbi.nlm.nih.gov/15213107/), [P23343063](https://pubmed.ncbi.nlm.nih.gov/23343063/).

Competing explanation: Pre-existing clones, epigenetic injury and age-related processes may outlast exposure.

Discriminating test and controls: Prospective cessation cohorts with repeated airway/genomic measurements, verified exposure and lung-cancer incidence; account for competing mortality.

### G3: How specific are tobacco-related signatures across co-exposures?

Evidence anchors: [P27811275](https://pubmed.ncbi.nlm.nih.gov/27811275/), [P8832894](https://pubmed.ncbi.nlm.nih.gov/8832894/), [P15329413](https://pubmed.ncbi.nlm.nih.gov/15329413/).

Competing explanation: Ambient carcinogens, second-hand smoke or shared repair processes may create overlapping patterns.

Discriminating test and controls: Component-resolved exposure measures and independent tumour cohorts; quantify attribution uncertainty rather than assigning cause from a single signature.

### G4: Why do similarly exposed people develop different outcomes?

Evidence anchors: [P15329413](https://pubmed.ncbi.nlm.nih.gov/15329413/), [P15944214](https://pubmed.ncbi.nlm.nih.gov/15944214/), [P27811275](https://pubmed.ncbi.nlm.nih.gov/27811275/).

Competing explanation: Genotype, histology, airway biology and competing exposures may modify risk.

Discriminating test and controls: Large prospective dose-resolved cohorts with predefined effect modifiers and mechanistic validation; separate susceptibility from necessity or sufficiency.

## Methods and access

Case-specific Consensus records assisted gap discovery, chronology and targeted paper questions. Shared template wording about an amyloid-specific Deep follow-up is not evidence of a Deep run for this topic; the dated source records establish the actual use and access limits. Primary identifiers, selected abstract passages, correction notices and available primary-body passages were cross-checked. Generated absence cells, duplicate milestones and unsupported access claims were rejected.

This focused addendum does not establish 50–70 complete primary Methods/Results examinations per review. Baseline reading receipts and scores retain their original scope.

Checked timeline sources: 9; selected full-text checks: 0; abstract-excerpt checks: 7; metadata-only historical anchors: 2. Complete papers examined in this update: 0.

Historical scorecards declare schema 5.4. This enrichment uses HSEF v5.3 causal distinctions without retrospectively relabelling or rescoring those files.

Targeted paper-check scope: Primary abstract/metadata checked. Additional Consensus full-text details remain provider-reported because a separately readable body was unavailable in this update.