Table 3.
Study details and effect estimates.
| Study | First author, year of publication | Method of exposure assessment | Cancer site | Adjustment factorsa | Exposure (period) | Sex | Cases/Controlsb | OR/RRc(95% CI) |
| 1 | Broders 1920 [74] |
NS | Lip | Smoking | Chewing (NS) | M+F | 537/500 | 2.05 (1.48–2.83)de |
| None | Snuff (NS) | M+F | 537/500 | 1.76 (0.12–26.2)ef | ||||
| None | Smokeless (NS) | M+F | 537/500 | 2.05 (1.48–2.83)efg | ||||
| 2 | Moore 1953 [57] |
Interview | Buccal mucosa, gum, floor of mouth | None | Smokeless (20+ years) | M | 112/38 | 3.00 (1.37–6.54)f |
| 3 | Wynder 1957 [58] |
Interview | Lip, floor of mouth, gum, buccal mucosa, tongue, palate, tonsil, pharynx | Smokingh | Chewing (ever) | M | 525/186 | 2.00 (1.16–3.47)ef |
| 4 | Peacock 1960 [93] |
Interview | Buccal mucosa, alveolar ridge, floor of mouth | Age, ins. | Smokeless (20+ years) | M | 25/191 | 3.06 (1.08–8.63)di |
| F | 20/172 | 2.00 (0.66–6.01)di | ||||||
| 5 | Vogler 1962 [62] |
Interview or questionnaire | Lip, buccal mucosa, tongue, palate, gingiva, floor of mouth, minor salivary glandsk | None | Chewing (ever) | M | 14/402 | 7.38 (4.31–12.62)dij |
| Snuff (ever) | F | 75/826 | 38.28 (21.49–68.15)dei | |||||
| 6 | Vincent 1963 [94] |
Interview | Oral cavity, pharynx | None | Snuff (NS) | M | 66/100 | 4.22 (1.41–12.63)fi |
| 7 | Martinez 1969 [95] |
Interview | Mouth and pharynx | Smokingl | Chewing (last 20 years) | M | 18/81 | 2.29 (0.62–8.48)fim |
| F | 16/79 | 0.34 (0.04–2.79)fim | ||||||
| 8 | Keller 1970 [75] |
Hospital records | Lip | Smoking | Smokeless (NS) | M | 258/207 | 3.63 (1.02–12.95)d |
| 9 | Browne 1977 [96] |
Interview, proxy interview | Buccal mucosa, upper alveolus and hard palate, lower alveolus, floor of mouth, pillar of fauces, soft palate, unspecified or multiple | None | Chewing (NS) | M+F | 75/150 | 0.67 (0.27–1.66)f |
| 10 | Williams 1977 [97] |
Interview | Lip, tongue, salivary glands, gum, mouth, pharynx | None | Smokeless (ever) | M | 190/1788 | 0.91 (0.53–1.56)fgi |
| F | 79/3188 | 1.54 (0.37–6.42)fgi | ||||||
| 11 | Wynder 1977 [98] |
Interview | Oral cavity | None | Chewing (ever) | M | 591/2560 | 1.15 (0.85–1.55)f |
| Snuff (ever) | M | 591/2560 | 0.62 (0.32–1.22)f | |||||
| Smokeless (ever) | M | 591/2560 | 1.02 (0.78–1.34)fgn | |||||
| 12 | Westbrook 1980 [63] |
Hospital records | Buccal mucosa, gum | None | Snuff (ever) | F | 55/55 | 540.0 (60.97–4782.82)f |
| 13 | Winn 1981 [13] |
Interview, proxy interview | Mouth and pharynx | Smoking, race | Snuff (ever) | F | 232/410 | 2.67 (1.83–3.90)d |
| 14 | Wynder 1983 [99] |
Interview | Oral and pharyngeal | None | Chewing (ever) | M | 414/414 | 1.00 (0.62–1.61)ef |
| Snuff (ever) | M | 414/414 | 0.42 (0.11–1.65)f | |||||
| Smokeless (ever) | M | 414/414 | 0.90 (0.57–1.41)efgn | |||||
| 15 | Stockwell 1986 [65] |
Medical records | Lip, tongue, salivary glands, gum, floor of mouth, other parts of mouth, pharynx | None | Smokeless (ever) | M+F | 1462/8285 | 2.02 (1.01–4.02)fi |
| 16 | Blot 1988 [100] |
Interview, proxy interview | Oral and pharyngeal | None | Smokeless (ever) | M | 762/837 | 0.85 (0.57–1.26)ef |
| F | 352/431 | 3.44 (1.09–10.91)ef | ||||||
| 17 | Spitz 1988 [101] |
Questionnaire | Larynx, tongue, orohypopharynx, oral cavityo | None | Chewing (ever) | M+F | 185/185 | 1.00 (0.54–1.85)f |
| NS | Snuff (ever) | M+F | 185/185 | 3.40 (1.00–10.90)p | ||||
| None | Smokeless (ever) | M+F | 185/185 | 1.05 (0.57–1.91)fg | ||||
| 18 | Franco 1989 [102] |
Interview | Oral cavity, tongue, gum, floor of mouth | None | Smokeless (ever) | M+F | 232/464 | 1.40 (0.59–3.33)f |
| 19 | Blomqvist 1991 [103] |
Questionnaire | Lower lip | Smokingl | Snuff (ever) | M+F | 14/10 | 0.67 (0.08–5.75)f |
| 20 | Maden 1992 [104] |
Interview | Lip, tongue, gum, floor of mouth, oropharynx, other parts of mouth | Age | Smokeless (ever) | M | 131/136 | 4.50 (1.50–14.30)p |
| 21 | Sterling 1992 [67] |
Interview (controls), proxy interview (cases) | Oral and pharyngeal | Smoking, sex, race, age, alc, occ. | Smokeless (100+ times) | M+F | 6976/NS | 1.04 (0.41–2.68)q |
| Sex, race, age | Snuff (ever) | M+F | 6976/NS | 2.42 (1.28–4.59)p | ||||
| 22 | Zahm 1992 [72] |
Questionnaire | Buccal cavity, pharynx | Age, time | Smokeless (ever) | M | 129/248046 | 4.11 (2.90–5.84)r |
| 23 | Mashberg 1993 [68] |
Interview | Oral cavity, oropharynx | Smoking, age, race, alc. | Snuff (ever) | M | 359/2280 | 0.80 (0.40–1.90)p |
| Chewing (ever) | M | 359/2280 | 1.00 (0.70–1.40)p | |||||
| Smokeless (ever) | M | 359/2280 | 0.96 (0.70–1.33)nq | |||||
| 24 | Perry 1993s |
NS | Oral | Smoking, age, sex, race, alc, occ. | Smokeless (100+ times) | M+F | 133/678 | 1.43 (0.64–3.21)q |
| 25 | Kabat 1994 [59] |
Interview | Tongue, floor of mouth, gums, gingiva, buccal mucosa, palate, retromolar area, tonsil and other pharynx | Smokingl | Snuff (ever) | M+F | 195/918 | 4.79 (1.19–19.30)f |
| Smoking | Chewing (ever) | M | 1097/2075 | 1.11 (0.81–1.53)de | ||||
| 26 | Bundgaard 1995 [105] |
Questionnaire | Retromolar area, buccal mucosa, floor of mouth, hard palate, upper alveolus, lower alveolus, tongue | None | Chewing (ever) | M+F | 161/400 | 1.44 (0.59–3.51)d |
| 27 | Lewin 1998 [64] |
Interview | Oral and pharyngeal | Smoking, age, area, alc. | Snuff (ever) | M | 266/641 | 0.98 (0.63–1.50)r |
| 28 | Muscat 1998 [106] |
Interview | Major salivary gland | None | Chewing (ever) | M+F | 128/114 | 0.89 (0.18–4.49)d |
| Smokeless (ever) | M+F | 128/114 | 1.19 (0.26–5.45)dgn | |||||
| 29 | Schildt 1998 [73] |
Questionnaire from next-of-kin for deceased cases/controls | Lip, tongue, gum, mouth | Smoking, alc. | Snuff (ever) | M+F | 354/354 | 0.80 (0.50–1.30)p |
| None | Chewing (ever) | M+F | 354/354 | 0.60 (0.20–2.00)p | ||||
| Smokeless (ever) | M+F | 354/354 | 0.87 (0.61–1.25)fgn | |||||
| 30 | Schwartz 1998 [69] |
Interview | Tongue, gum, floor of mouth, tonsils, oropharynx, other parts of mouth | Smoking, age, alc, sex | Smokeless (ever) | M | 165/302 | 1.00 (0.40–2.30)p |
| 31 | Boffetta 2005 [82] |
Questionnaire | Oral and pharyngeal | Smoking, age | Snuff (ever) | M | 34/10136 | 1.10 (0.50–2.41)p |
| 32 | Henley 2005 [66] |
Questionnaire | Oral and pharyngeal | Smokingl, age, race, educ., alc, exer, asp, bmi, diet, occt. | Smokeless (current) | M (CPS-I) | 13/77407 | 2.02 (0.53–7.74)p |
| Smokeless (ever) | M (CPS-II) | 46/114809 | 0.90 (0.12–6.71)p |
a alc = alcohol consumption, asp = aspirin, bmi = body mass index, educ = education, exer = exercise, ins = insurance status, occ = occupation
b At risk population for cohort studies
c OR = odds ratio (case-control studies), RR = relative risk (cohort studies)
d Estimated from multiple independent 2 × 2 tables using fixed-effect meta-analysis
e Numbers of exposed and unexposed cases and controls estimated from proportions exposed given numerically
f Estimated from 2 × 2 table
g Numbers of exposed cases and controls combined over levels of exposure
h Analysis based on smokers only (only one SLT user was a non-smoker)
i Numbers of cases combined over cancer types specified
j Numbers of exposed and unexposed cases and controls estimated from proportions exposed given graphically
k Due to the joint reporting of pharynx and larynx cases, both sites excluded from analysis
l Analysis based on non-smokers only
m Note that in Table 13 of source chewing only data for mouth cancer wrongly given under pipe only
n Calculated assuming no-one chewed tobacco and used snuff
o Larynx cases cannot be sorted out due to incomplete reporting
p As reported by the authors
q Estimated from non-independent relative risks by level of exposure using method of Fry and Lee
r Estimated from non-independent relative risks for cancer types using method of Fry and Lee
s Attributable oral cancer risk due to smokeless tobacco use based on a case-control study at Sinai Hospital in Detroit; unpublished
t Occupation only adjusted for in CPS-II