Table 1.

Studies and their patients included in the meta-analysis.

Author, Year	Countrya	Oropharyngeal	HPV+	HPV-	HPV	HPV	p-value*	p-value*
		sub-site	tumours	tumours	prevalence	detection	(TSCC and BOTSCC vs.”other” OPSCC)	(TSCC only vs.”other” OPSCC)
Bahl et al., 2014 [10]	India	Base of tongue	14	61	19% (18–20%)	PCR	NS	NS
		Tonsil	10	15	40% (36–44%)
		Soft palate	0	5	0% (0–0%)
Bhosale et al., 2016 [11]	India	Base of tongue	0	23	0% (0–0%)	p16 IHC	NS	NS
		Tonsil	3	18	14% (11–18%)
		Soft palate	0	5	0% (0–0%)
		Posterior wall	1	4	20% (4–36%)
Broglie et al., 2013 [13]	Switzerland	Base of tongue	22	28	44% (42–46%)	p16 IHC	NS	NS
		Tonsil	31	37	46% (44–48%)
		Post wall/ soft palate	1	5	17% (4–29%)
Broglie et al., 2015 [12]	Switzerland	Base of tongue	3	3	50% (34–66%)	p16 IHC	NS	NS
		Tonsil	36	13	73% (72–75%)
		Post wall	0	2	0% (0–0%)
Busso et al., 2014 [14]	Italy	Base of tongue	1	10	9% (4–14%)	PCR	NS	NS
		Tonsil	13	21	38% (35–41%)
		Soft palate	2	1	67% (36–97%)
		Posterior wall	0	2	0% (0–0%)
Cerezo et al., 2014 [16]	Spain	Base of tongue	10	30	25% (23–27%)	p16 IHC	NS	NS
		Tonsil	11	27	29% (27–31%)
Cerezo et al., 2014 [15]		Soft plate	5	8	38% (31–46%)
		Pharyngeal wall	1	1	50% (1–99%)
Dahlstrom et al., 2015 [17]	United States of America	Base of tongue	139	16	90% (89–90%)	p16 IHC and ISH with/without PCR	0.04	0.04
		Tonsil	172	22	89% (88–90%)
		Other	4	3	57% (43–71%)
Davis et al., 2014 [18]	United States of America	Base of tongue	5	4	56% (45–66%)	p16 IHC	0.003	0.002
		Tonsil	12	3	80% (75–85%)
		Soft palate	0	6	0% (0–0%)
Doná et al., 2015 [19]	Italy	Base of tongue	26	34	43% (42–45%)	PCR	0.002	0.003
		Tonsil	30	34	47% (45–48%)
		Other oropharynx	1	15	6% (3–9%)
Evans et al., 2013 [20]	United Kingdom	Base of tongue and vallecula	15	20	43% (40–46%)	p16 IHC and PCR and/or ISH	0.001	0.0003
		Tonsil	54	39	58% (57–59%)
		Other oropharynx	0	10	0% (0–0%)
Fahkry et al., 2014 [21]	United States of America	Base of tongue	52	36	59% (58–60%)	p16 IHC	0.02	0.002
		Tonsil	39	19	67% (66–69%)
		Soft palate	0	3	0% (0–0%)
		Oropharynx NOS	14	9	61% (57–65%)
		Faucial arch	0	1	0% (0–0%)
		Pharyngeal oropharynx	0	8	0% (0–0%)
Faust et al., 2016 [22]	Sweden	Base of tongue	15	12	56% (52–59%)	PCR	0.001	<0.001
		Tonsil	75	28	73% (72–74%)
		Oropharynx NOS	2	9	18% (11–25%)
Fonmarty et al., 2015 [23]	Not specified	Anterior/lateral oropharynx (tonsil, base of tongue and glossotonsillar sulcus)	20	31	39% (37–41%)	p16 IHC and PCR	<0.001	–
		Other oropharyngeal sites	0	20	0% (0–0%)
Fujimaki et al., 2013 [24]	Japan	Lateral	27	23	54% (52–56%)	p16 IHC and ISH	NS	0.05
		Anterior	4	7	36% (28–45%)
		Posterior	0	3	0% (0–0%)
		Superior	0	2	0% (0–0%)
Grisar et al., 2016 [26]	Belgium	Tongue base	6	36	14% (13–16%)	p16 IHC	NS	0.05
		Tonsil	8	7	53% (47–60%)
		Soft palate	1	4	20% (4–36%)
		Oropharynx NOS	8	26	24% (21–26%)
Habbous et al., 2013 [27]	Canada	Base of tongue	159	50	76% (76–76%)	p16 IHC	<0.0001	<0.0001
		Tonsil	308	83	79% (79–79%)
		Other oropharynx	27	56	33% (31–34%)
Hama et al., 2014 [28]	Japan	Anterior	6	20	23% (20–26%)	PCR	<0.0001	<0.0001
		Lateral	73	44	62% (62–63%)
		Upper	0	10	0% (0–0%)
		Posterior	0	4	0% (0–0%)
Henneman et al., 2015 [29]	Netherlands	Base of tongue	13	36	27% (25–28%)	PCR	0.003	0.001
		Tonsil	37	41	47% (46–49%)
		Other oropharynx	1	18	5% (3–8%)
Hong et al., 2013 [32]	Australia	Base of tongue	11	18	38% (35–41%)	PCR and p16 IHC	0.001	<0.001
		Tonsil	99	84	54% (54–55%)
		Other oropharynx	3	18	14% (11–18%)
Hong et al., 2014 [31]	Australia	Base of tongue	29	30	49% (47–51%)	PCR and p16 IHC	<0.001	<0.001
		Tonsil	181	222	45% (45–45%)
		Other oropharynx	10	43	19% (17–20%)
Hong et al., 2013 [30]	Australia	Base of tongue	15	31	33% (31–35%)	PCR and p16 IHC	<0.001	0.0001
		Tonsil	253	298	46% (46–46%)
		Other oropharynx	9	41	18% (16–20%)
Isayeva et al., 2013 [33]	United States of America	Base of tongue	20	16	56% (53–58%)	RT-PCR	NS	0.03
		Tonsil	31	9	78% (75–80%)
		Soft palate/uvula	3	3	50% (34–66%)
		Oropharynx	10	10	50% (45–55%)
Iyer et al., 2015 [34]	United States of America	Base of tongue	50	39	56% (55–57%)	p16 IHC	<0.0001	<0.0001
		Tonsil	48	18	73% (71–74%)
		Soft palate	8	38	17% (16–19%)
Jiang et al., 2015 [35]	United States of America	Base of tongue	12	3	80% (75–85%)	ISH	<0.0001	0.0001
		Tonsil	10	6	63% (57–68%)
		Soft palate	0	10	0% (0–0%)
Kim et al., 2014 [38]	Not specified	Base of tongue	5	12	29% (24–35%)	PCR	NS	NS
		Tonsil	15	32	32% (30–34%)
		Soft palate	1	9	10% (4–16%)
Kim et al., 2015 [37]	South Korea	Base of tongue	1	3	25% (4–46%)	p16 IHC	<0.001	<0.001
		Tonsil	79	25	76% (75–77%)
		Soft palate	1	8	11% (4–18%)
		Oroharynx NOS	8	8	50% (44–56%)
Kwakami et al., 2013 [36]	Japan	Base of tongue	4	9	31% (24–38%)	PCR	<0.001	0.001
		Tonsil	31	29	52% (50–53%)
		Other oropharynx	5	26	16% (14–18%)
Kwon et al., 2016 [39]	New Zealand	Tonsil and tonguebase	86	31	74% (73–74%)	p16 IHC	<0.0001	–
		Other oropharynx	0	14	0% (0–0%)
Lam et al., 2015 [40]	China	Base of tongue	4	35	10% (9–12%)	PCR and E6*I mRNA	0.01	0.003
		Tonsil	36	88	29% (28–30%)
		Soft palate	3	29	9% (8–11%)
		Other oropharyngeal walls	0	12	0% (0–0%)
Lee et al., 2016 [41]	South Korea	Base of tongue	15	4	79% (75–83%)	p16 IHC	<0.0001	<0.0001
		Tonsil	89	12	88% (87–89%)
		Soft palate	0	4	0% (0–0%)
		Posterior wall	0	2	0% (0–0%)
Van Limbergen et al., 2014 [70]	Belgium	Base of tongue	16	67	19% (18–20%)	PCR and p16IHC	0.002	<0.001
		Tonsil	33	72	31% (31–32%)
		Soft palate	0	11	0% (0–0%)
		Pharyngeal wall	1	30	3% (2–4%)
		Unclear	3	16	16% (12–20%)
Liu et al., 2015 [42]	Australia	Base of tongue	7	13	35% (30–40%)	PCR and ISH	0.002	<0.001
		Tonsil	39	29	57% (56–59%)
		Other oropharynx	2	15	12% (8–15%)
Ljokel et al., 2016 [43], [44]	Norway	Base of tongue	28	13	68% (66–71%)	PCR	<0.0001**	<0.0001
		Tonsil	86	39	69% (68–70%)
Lybak et al., 2016 [45]		Tonsil pillar	1	12	8% (4–12%)
		Overlapping tonsil	1	0	100% (100–100%)
		Oropharynx (ICD-10 C10)	3	22	12% (9–15%)
		Soft palate and overlapping lesion	4	10	29% (22–35%)
		Uvula	1	6	14% (4–24%)
McIlwain et al., 2014 [47]	United States of America	Base of tongue	26	8	76% (74–79%)	p16 IHC	0.04	0.02
		Tonsil	41	5	89% (88–90%)
		Soft palate	4	2	67% (51–82%)
		Posterior wall	0	2	0% (0–0%)
Mazul et al., 2016 [46]	United States of America	Base of tongue	50	23	68% (67–70%)	PCR	NS	NS
		Tonsil	115	33	78% (77–78%)
		Other oropharynx	17	10	63% (59–66%)
Melkane et al., 2014 [48]	France	Lymphoid location (tonsillar and base of tongue)	65	57	53% (52–54%)	p16 IHC	0.03	–
		Nonlymphoid location (posterior oropharyngeal wall and soft palate)	2	9	18% (11–25%)
Melkane et al., 2014 [49]	France	Lymphoid location	28	13	68% (66–71%)	p16 IHC	<0.01	–
		Non-lymphoid location	0	5	0% (0–0%)
Mizumachi et al., 2013 [50]	Japan	Lateral wall	18	23	44% (42–46%)	PCR	NS	0.04
		Anterior wall	4	14	22% (18–27%)
		Superior wall	1	8	11% (4–18%)
		Posterior wall	0	3	0% (0–0%)
Morbini et al., 2014 [51]	Italy	Base of tongue	6	4	60% (50–70%)	mRNA ISH	<0.01	<0.01
		Tonsil	13	8	62% (57–66%)
		Soft palate	1	9	10% (4–16%)
Naik et al., 2015 [52]	United States of America	Base of tongue	70	6	92% (91–93%)	p16 IHC and/or ISH	NS	NS
		Tonsil	56	10	85% (84–86%)
		Other	4	1	80% (64–96%)
Nasman et al., 2013 [53]	Sweden	Base of tongue	75	28	73% (72–74%)	PCR	<0.0001	<0.0001
		Tonsil	217	66	77% (76–77%)
		Other oropharynx	4	27	13% (11–15%)
		Soft palate	7	15	32% (28–36%)
Nichols et al., 2013 [54]	United Kingdom	Base of tongue	15	10	60% (56–64%)	PCR	<0.01	0.01
		Tonsil	31	21	60% (58–61%)
		Other	4	14	22% (18–27%)
Nomura et al., 2014 [55]	Japan	Lateral wall	29	25	54% (52–56%)	PCR and/or p16 IHC	0.02	0.05
		Base of tongue	8	4	67% (59–74%)
		Superior wall	0	7	0% (0–0%)
		Posterior wall	2	2	50% (26–74%)
Oguejiofor et al., 2013 [56]	United Kingdom	Base of tonge	32	27	54% (53–56%)	p16 IHC	NS	NS
		Tonsil	84	51	62% (62–63%)
		Other oropharynx	9	8	53% (47–595)
Ou et al., 2016 [57]	New Zealand	Base of tongue	15	5	75% (71–79%)	p16 IHC and PCR	0.02	0.02
		Tonsil	23	4	85% (83–88%)
		Soft palate	2	1	67% (36–97%)
		Oropharyngeal wall	0	1	0% (0–0%)
		Oropharynx (unspecified)	1	3	25% (4–46%)
Quabius et al., 2015 [58], [59]	Germany	Tonsillar	59	76	44% (43–44%)	PCR	0.03	0.03
		Soft palate and posterior wall of oropharynx	3	17	15% (12–18%)
Rietbergen et al., 2013 [60]	Netherlands	Base of tongue	51	161	24% (24–24%)	p16 IHC and PCR	<0.0001	<0.0001
		Tonsil	96	248	28% (28–28%)
		Soft palate	9	115	7% (7–8%)
		Oropharynx NOS	7	122	5% (5–6%)
Rietbergen et al., 2013 [61]	Netherlands	Base of tongue	13	54	19% (18–21%)	P16 IHC and PCR	<0.001	<0.0001
		Tonsil	23	60	28% (27–29%)
		Soft palate	0	31	0% (0–0%)
		Oropharynx NOS	5	54	8% (8–9%)
Saito et al., 2015 [62]	Japan	Lateral wall	45	48	48% (47–49%)	p16 IHC	0.005	0.002
		Base of tongue	12	29	29% (27–31%)
		Superior wall	1	10	9% (4–14%)
		Posterior wall	0	5	0% (0–0%)
Schache et al., 2013 [64]	United Kingdom	Base of tongue	5	8	38% (31–46%)	qRT-PCR	NS	NS
		Tonsil	22	21	51% (49–53%)
		Soft palate	4	9	31% (24–38%)
		Oropharynx NOS	2	7	22% (13–31%)
Schache et al., 2016 [65]	United Kingdom	Base of tongue	179	183	49% (49–50%)	p16 IHC and PCR or ISH	<0.0001	<0.0001
		Tonsil	528	326	62% (62–62%)
		Soft palate/uvula	8	80	9% (8–10%)
		Oropharynx NOS	49	121	29% (28–29%)
Schouten et al., 2016 [66]	Not stated	Base of tongue	12	7	63% (58–68%)	p16 IHC and PCR	NS	NS
		Tonsil	12	6	67% (62–72%)
		Oropharynx NOS	3	4	43% (29–57%)
Steinau et al., 2014b[67]	United States of America	Base of tongue	149	64	70% (70–70%)	PCR	<0.0001	<0.0001
Saraiya et al., 2015b[63]		Tonsil	201	49	80% (80–81%)
Goodman et al., 2015b[25]		Other oropharynx	46	48	49% (48–50%)
Strojan et al., 2015 [68]	Slovenia	Base of tongue	4	16	20% (16–24%)	E6/E7 mRNA ISH	NS	0.05
		Tonsil	12	28	30% (28–32%)
		Other oropharynx	4	35	10% (9–12%)
Tural et al., 2013 [69]	Turkey	Base of tongue	12	15	44% (41–48%)	PCR	NS	NS
		Tonsil	26	19	58% (56–60%)
		Other	4	5	44% (34–55%)
Wang et al., 2016 [72]	China	Base of tongue	6	68	8% (7–9%)	PCR	NS	<0.0001
		Tonsil	7	3	70% (61–79%)
		Soft palate	3	47	6% (5–7%)
		Oropharynx NOS	6	48	11% (10–12%)
Ward et al., 2014 [73]	United Kingdom	Base of tongue	40	28	59% (57–60%)	p16 IHC and ISH	<0.0001	<0.0001
		Tonsil	99	57	63% (63–64%)
		Other oropharynx	10	36	22% (20–23%)
Wagner et al., 2015 [71]	Germany	Tonsil	20	12	63% (60–65%)	P16 IHC and PCR and/or ISH	–	<0.0001
		Other than tonsil	12	84	13% (12–13%)

^*p-value calculated by chi-2 test (tonsil and tongue base vs other oropharynx and soft palate; or tonsil vs other oropharynx and soft palate) after patient numbers had been extracted from article.

^**p-value calculated by chi-2 test (tonsil and tongue base, overlapping tonsil vs tonsil pillars other oropharynx and soft palate) after patient numbers been extracted from article.

^aCountries from which the patient material and data were collected.

^bPatients reported in Stainau et al. presented.