Nodal involvement and p16-staining in upper alveolar ridge and hard palate cancer

Introduction

Squamous cell carcinomas (SCC) of the hard palate and upper alveolus ridge are relatively rare^[1]. Prognostic factors and neck management in head and neck SCC (HNSCC) have been extensively studied in series of tongue or floor of mouth SCC, or on series with a mixture of SCC tumor sites^[2]. Only small retrospective series have evaluated the behavior of hard palate and upper alveolus, and suggest that they have a low rate of regional node metastases^[3-8]. However, recent studies find higher rates of both neck lymph node involvement and neck recurrence in these malignancies, and, there is a need to identify those aggressive cases that would benefit from more aggressive treatment^[9,10].

Several clinicopathological features have been implicated in recurrence risk and prognosis in HNSCC. These include tumor size, nodal involvement, tobacco and alcohol consumption, and presence of human papillomavirus (HPV) infection^[11,12].

The prevalence of HPV infection is higher in oropharyngeal squamous cell carcinoma (OPSCC) (35.6%) and has been associated with both better prognosis and higher response rate to chemoradiation^[12,13]. P16 staining is highly correlated with HPV infection in OPSCC and has also been associated with good prognosis^[14-17]. There is no information about the rate of p16 expression in rare locations like hard palate and upper alveolar ridge.

The aim of the present study was to evaluate predictive factors associated with node involvement, prognostic factors, and prevalence of p16 staining in hard palate and upper alveolar ridge SCC.

Methods

Results

Tumor primary location for this cohort was distributed in 5 patients for hard palate and 73 for upper alveolar ridge. Mean age was 64.47 years old and 55.1% were female. There were tabaquismo and alcoholism history in 10.3% and 6.4% cases, respectively. Two (40%) hard palate and 52 (71.2%) upper alveolar ridge tumors were clinically classified cT4, and 3 (60%) hard palate and 21 (28.8%) upper alveolar ridge tumors were clinically node-positive at presentation. Clinical stages I-IV of upper alveolar ridge SCC were found in 1 (1.4%), 13 (17.8%), 5 (6.8%) and 54 (74%) of cases, respectively. Clinical stages II-IV of hard palate SCC were found in 1, 1 and 3 cases, respectively [Table 1].

The primary tumor was resected in all cases (n = 78). Neck dissections were initially performed in 24 cases (21 in clinically node-positive and 3 in node-negative). Nineteen (79.16%) of cases who went to neck dissections had confirmed nodal metastases on pathological examination (including the 3 clinically node-negative cases). Cervical metastases in these 19 node-positive cases were distributed between levels I (94.7%), II (73.7%), and III (26.3%). Extracapsular extension at presentation was noted in 7 specimens of upper alveolar ridge tumors.

In no instances were age (P = 0.329), location (P = 0.590), cT (P = 0.629), histological grade (P = 0.361), PNI (P = 0.825), or LVI (P = 0.080) associated with cervical metastases [Table 2].

Expression of p16

A total of 41 (52.5%) lesions were tested for p16 expression. Overall, 7.3% (3 of 41) were p16 positive: 1 of 2 in hard palate (50%) and 2 of 39 in alveolar ridge (5.1%) [Figure 1]. The p16 positive tumors were not associated with age (P = 0.067), tumor location (P = 0.143), cT (P = 1.000), or histological grade (P = 0.560) [Table 4].

Table 4

Relationship between p16 staining and clinicopathological features (n = 41)

	p16 staining (%)		P
	Negative (n = 38)	Positive (n = 3)
Age (years), mean (range)	63.71 (21-89)	48.67 (44-55)	0.067
cT
T1-3	10 (26.3)	1 (33.3)
T4	28 (73.7)	2 (66.7)	1.000
cN
N (−)	30 (78.9)	3 (100.0)
N (+)	8 (21.1)	0 (0.0)	-
Location
Upper alveolus	37 (97.4)	2 (66.7)
Hard palate	1 (2.6)	1 (33.3)	0.143
Grade
Poor/moderate differentiation	15 (39.5)	2 (66.7)
Well differentiated	23 (60.5)	1 (33.3)	0.560
PNI
No	12 (40.0)	1 (50.0)
Yes	18 (60.0)	1 (50.0)	1.000
LVI
No	22 (73.3)	2 (100.0)
Yes	8 (26.7)	0 (0.0)	-
Tobacco
No	35 (92.1)	2 (66.7)
Yes	3 (7.9)	1 (33.3)	0.271
Alcohol
No	35 (92.1)	3 (100.0)
Yes	3 (7.9)	0 (0.0)	-

PNI: perineural invasion; LVI: lymphovascular infiltration

Figure 1. P16 by immunohistochemistry in upper maxilla. (A, B, C) Positive status of p16 staining indicated by brown staining of nuclear and cytoplasmic membrane in three cases; (D) negative status for p16 staining. (Magnification 40×)

Survival analysis

Median overall survival (OS) was 40 months. Neither smoking nor alcohol consumption was associated with shorter disease-free survival (DFS) (P = 0.815 and 0.507) nor OS (P = 0.597 and 0.634). LVI (P = 0.026) was associated with shorter DFS in univariate analysis. Larger cT (P = 0.019), presence of PNI (P = 0.039), LVI (P = 0.021), and neck dissection (P = 0.010) were associated with shorter OS in univariate analysis [Figure 2]. Neck involvement had a trend both for shorter DFS (31% vs. 48.7%, P = 0.278) and shorter OS (25.1% vs. 48.5%, P = 0.340). There was also a trend to shorter OS (9.3% vs. 52.3%, P = 0.064) in the presence of neck recurrence [Table 5].

Table 5

Survival analysis

	5-year-OS	P	5-year-DFS	P
All group	43.9%		44.5%
Age
≤ 60 years	56.1%		41.8%
> 60 years	38.9%	0.667	45.8%	0.643
Gender
Female	53.4%		51.0%
Male	31.2%	0.539	37.8%	0.323
Tobacco
Yes	21.9%		52.5
No	46.2%	0.597	43.7	0.815
Alcohol
Yes	0.0%*		40.0%**
No	46.6%	0.634	44.8%	0.507
Location
Hard palate	66.7%		53.3%
Upper alveolus	42.7%	0.707	43.6%	0.851
cT
T2-T3	69.3%		44.2%
T4	36.7%	0.019	44.0%	0.743
Grade
Poor/moderate differentiation	47.0%		51.7%
Well differentiated	42.1%	0.715	39.9%	0.289
PNI
No	61.2%		52.4%
Yes	26.1%	0.039	36.3%	0.334
LVI
No	48.8%		50.9%
Yes	23.5%	0.021	24.7%	0.026
P16
Negative	27.9%		35.0%
Positive	100.0%	-	100.0%	-
Neck dissection
No	53.4%		50.1%
Yes	18.8%	0.010	29.6%	0.129
pN
N−	48.5%		48.7%
N+	25.1%	0.340	31.0%	0.278
Neck recurrence
No	52.3%
Yes	9.3%	0.064
N+ and N− with neck recurrence
No	55.5%
Yes	21.6%	0.192

*Estimated at 41 months; **estimated at 9 months. PNI: perineural invasion; LVI: lymphovascular infiltration

Figure 2. Estimated curves of OS regarding clinical tumor (A), perineural infiltration (B) and lymphovascular infiltration (C). OS: overall survival; PNI: perineural invasion; LVI: lymphovascular infiltration

Discussion

Our rate of survival at 5 years was 44.5% and is similar to those reported by other studies (21% to 76%)^[18,19]. This poor prognosis could reflect higher prevalence of neck node involvement at diagnosis or higher prevalence of poor prognotic factors like p16-negative status^[1].

The incidence of neck metastasis has been extensively described in cancer of the tongue and floor of the mouth (20% to 30%) and has been assigned a significant prognostic role in patients with clinically node-negative disease^[20,21]. Clinicopathologic factors like large tumor size, tumor depth, higher grade, and microvascular invasion have been associated with the development of cervical lymph node metastasis in oral SCC^[21]. Elective treatment of the neck with staging neck dissection is generally carried out in patients with SCC of the oral cavity when the risk of clinically occult metastases exceeds 15% to 20%, and treatment of the clinically N0 neck is now accepted for certain oral cavity subsites, such as the tongue and floor of mouth, where elective neck dissection produces a survival advantage^[22-26].

The understanding of the behavior of hard palate and upper alveolar cancers is poor due to their low incidence and because some of these studies indistinctly included different both other head and neck malignancy locations and special pathological entities like salivary gland tumors^[27,28]. A series of 606 upper and lower alveolar SCCs reported 37% of cervical metastasis and 19% of harbored occult disease in elective neck dissections. Lymph node involvement at level II to V carried shorter survival than negative lymph node involvement^[19]. A series of 347 cancers of the upper and lower gums that had an elective neck dissection rate of 58% found occult disease in 5.6%. Neck recurrence was found in 9% of the whole group. Ipsilateral and contralateral neck node involvement predicted cervical recurrence. Positive neck lymph nodes, tumor stage, and involved soft-tissue margins were significant covariates in survival prediction; clinical stage remained significant in multivariate analysis^[29]. A series of 252 cases of palate SCC including 62 in the specific region of the hard palate found node involvement in more than 29% of the hard palate tumors. Neck recurrence was predicted by the presence of fixed or contralateral node metastases, but not by the presence of nodal metastasis itself. Size of the primary tumor and histological grade was significantly associated with survival, and clinical stage was the most important prognostic indicator^[30]. Recent retrospective series with 26 to 146 upper alveolar ridge and hard palate cases reported a neck lymph node involvement between 11% and 36.6%, and regional recurrence in N0 neck from 14% to 27%^[1,5-8]. These studies had several findings: cases with neck node involvement had higher grade; clinical stage but not margin status was associated with prognosis; and T3 (55%) and T4 (52%) tumors exhibited higher rates of neck lymph node involvement than smaller tumors (T1 = 15%; T2 = 28%). An analysis of the Surveillance, Epidemiology, and End Results (SEER) database evaluated 314 hard palate SCC and 411 upper alveolar ridge cases. They found a 13.65% prevalence of cervical metastasis and its correlation with larger tumor (4.1% for T1 to 24.7% for T4 tumors, P < 0.001). Extension of lymph node involvement was correlated to survival (P < 0.001).

We found a neck lymph node involvement rate of 24.4% and it has a trend associated with shorter survival (P = 0.340). The traditional concept has been that SCC of the hard palate and maxillary alveolus exhibits a low rate of occult metastasis^[7,31,32]. However, our results suggest that regional lymph node involvement is also frequent and relevant, and an elective treatment of the neck should be performed.

Regional recurrence rates in oral cancer have been described as between 30% and 47% in T1-2 carcinoma with untreated N0 neck, and they produce a significant decrease in patient survival. Some studies, including two prospective randomized trials, describe that neck recurrence rates decrease with the use of elective neck dissection^[22,33-35]. Regional recurrences in oral malignancies were associated with poor differentiation, larger tumor size, positive lymph node, and extracapsular involvement^[33,35]. A series of 114 cases with SCC of the maxillary alveolus and hard palate report regional recurrence rates of 26% in the N0 cohort (n = 100), and 35% of the patients had either initially N-positive neck or a later conversion from N0 to N-positive neck. Neck recurrence was associated with diminished overall survival but not with larger tumor size or postoperative radiation to the neck. Patients with initial diagnoses of N-positive and those who later developed neck recurrences had similar OS^[36].

Neck node recurrences occurred in 18 cases (23.1%) of our series and appeared at a mean time of 8.6 months; this likely represents occult metastases at presentation. Therefore, we had 42.3% of neck node involvement if we consider initial patients with positive nodes and N0 patients who developed neck recurrence. We also found that 25.9% of cases without clinical evidence of neck involvement developed recurrences at the neck. Neck recurrence had a trend to poor prognosis but did not achieve significance, probably because these cases received effective treatment including surgery (44.4%) or chemoradiation (11.1%).

Large tumor size, PNI, and LVI have been extensively associated with nodal metastasis and with shorter survival in HNSCC^[37,38]. Evaluation of classical prognostic factors in our series confirmed that larger tumors (P = 0.019), presence of PNI (P = 0.039), and LVI (P = 0.021) were associated with shorter OS, and LVI (P = 0.026) was associated with shorter DFS.

HNSCCs associated with smoking or drinking alcohol has been associated with a poor prognosis and are frequently located in laryngeal and hypopharyngeal cancer, respectively^[39]. Our analysis did not indicate higher prevalence rates of these carcinogen agents and did not find an association with prognosis in the upper maxilla.

Expression of p16 is a confident biomarker of HPV infection in OPSCC and both are associated with better outcome^{[12,13,40-44]}. In contrast to OPSCC, the rates of positive HPV in oral cancer are low, and recent studies suggest a disparity between the detection of HPV DNA and p16 expression when the prevalence of HPV is low^[45]. Evaluation of p16 staining in our series found that only 3 (7.4%) of upper maxilla SCC cases were considered positive for p16 staining. The p16-positive cases had a trend to be younger (48.7 vs. 63.7 years, P = 0.067), and all 3 cases were free of neck recurrence and alive at 5 years. This is the first time to our knowledge that p16 staining has been evaluated in upper maxilla SCC and could identify a group of patients with specific behavior. However, our analysis has the weakness of its small sample size and it needs to be confirmed by larger series (required size of series increases because of the low rates of p16-positive status in non-OPSCC).

The results of this retrospective analysis reveal that tumors of the hard palate and upper alveolus are associated with a high rate of neck node involvement and regional failure, which had a tendency to result in poor survival. Expression of p16 has a low rate in this pathology and could be associated with specific features.