Table 4.

Estimates of lung cancer risk associated with metformin use, by histologic type

AdenocarcinomaSquamous cell carcinomaSmall cell carcinoma
Metformin useNumber of eventsAdjusteda HR (95% CI)Number of eventsAdjusteda HR (95% CI)Number of eventsAdjusteda HR (95% CI)
Never1211.00 (reference)881.00 (reference)621.00 (reference)
Ever800.88 (0.62–1.25)521.09 (0.71–1.68)361.23 (0.74–2.04)
 Total duration, y
  <2.0260.92 (0.59–1.45)160.94 (0.54–1.66)141.23 (0.66–2.29)
  2.0–4.9300.99 (0.63–1.54)161.10 (0.60–2.01)80.88 (0.39–1.98)
  ≥5.0240.69 (0.40–1.17)201.46 (0.76–2.79)141.82 (0.85–3.91)
 Recency of use
  Former230.99 (0.59–1.67)121.10 (0.54–2.23)81.45 (0.61–3.40)
  Recent110.94 (0.49–1.79)30.52 (0.16–1.69)82.29 (1.03–5.07)
  Current
   <5.0 years310.93 (0.60–1.43)231.17 (0.71–1.95)110.84 (0.42–1.67)
   ≥5.0 years150.61 (0.33–1.13)141.30 (0.65–2.62)91.58 (0.68–3.69)
 Cumulative dose (mg), quartiles
  ≤750,000210.79 (0.49–1.28)181.14 (0.66–1.95)111.08 (0.55–2.14)
  750,001–2,300,000311.12 (0.72–1.74)110.80 (0.41–1.58)80.94 (0.42–2.09)
  2,300,001–4,930,000190.80 (0.46–1.39)121.17 (0.58–2.37)91.59 (0.70–3.61)
  >4,930,00090.61 (0.28–1.30)112.03 (0.90–4.55)83.11 (1.22–7.95)
  • aStratified on age and adjusted for gender, race/ethnicity, birth year, diabetes duration, BMI, alcohol use, Charlson comorbidity index, smoking history (status and pack-years), education, income level, creatinine level, HbA1c level, and use of other diabetes medications.