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Year : 2019  |  Volume : 15  |  Issue : 3  |  Page : 582-588

Impact of smoking on pathological features in oral cavity squamous cell carcinoma

1 Department of Radiation Oncology, Henry Ford Hospital, Detroit, MI, USA
2 Department of Public Health Sciences, Henry Ford Hospital, Detroit, MI, USA
3 Department of Otolaryngology - Head and Neck Surgery, Henry Ford Hospital, Detroit, MI, USA
4 Department of Pathology, Henry Ford Hospital, Detroit, MI, USA

Date of Web Publication29-May-2019

Correspondence Address:
Dr. Farzan Siddiqui
Department of Radiation Oncology, Henry Ford Hospital, 2799 West Grand Boulevard, Detroit, MI 48202
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcrt.JCRT_641_16

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 > Abstract 

Objectives: We sought to determine whether smokers with oral cavity squamous cell carcinoma (OCSCC) have tumors with more adverse pathological features than in nonsmokers and whether or not these are predictive of outcomes.
Materials and Methods: We retrospectively identified 163 patients with American Joint Committee on Cancer stages I–IVa OCSCC diagnosed between 2005 and 2015 and treated with curative intent. A pathological risk score (PRS) was calculated using the National Comprehensive Cancer Network adverse risk factors: positive margin, extracapsular extension of lymph node metastases, pT3 or pT4 primary, N2 or N3 nodal disease, perineural invasion, and lymphovascular space invasion. Multivariable models were constructed to determine the independent predictors of overall survival (OS), recurrence-free survival (RFS), and PRS.
Results: A total of 108 (66.26%) were smokers and 55 nonsmokers. Three-year actuarial OS and RFS were 62% and 68% in smokers and 81% and 69% in nonsmokers, respectively (P = 0.06 and P = 0.63). Smokers were more likely to have advanced disease stage and tumors with aggressive pathological features than nonsmokers. Smokers had significantly worse PRS (mean ± standard deviation; 2.38 ± 2.19, median; 2.00) than nonsmokers (0.89 ± 1.21, 0.00) (P < 0.001). Older age, higher PRS, and smoking status were independent predictors of OS. Smoking or PRS did not predict for worse RFS. On multivariate analysis, independent predictors of PRS were smoking status and grade (P < 0.001).
Conclusion: In patients with OCSCC, smokers have more aggressive disease as evidenced by more adverse pathological features than nonsmokers. Moreover, smoking is an independent predictor of OS but not RFS. The PRS is a significant predictor of OS and needs validation in the future studies.

Keywords: Head and neck cancer, oral cancer, oral cavity, pathology, prognosis, smoking, squamous cell carcinoma, survival, tobacco

How to cite this article:
Al Feghali KA, Ghanem AI, Burmeister C, Chang SS, Ghanem T, Keller C, Siddiqui F. Impact of smoking on pathological features in oral cavity squamous cell carcinoma. J Can Res Ther 2019;15:582-8

How to cite this URL:
Al Feghali KA, Ghanem AI, Burmeister C, Chang SS, Ghanem T, Keller C, Siddiqui F. Impact of smoking on pathological features in oral cavity squamous cell carcinoma. J Can Res Ther [serial online] 2019 [cited 2021 Dec 9];15:582-8. Available from: https://www.cancerjournal.net/text.asp?2019/15/3/582/243490

 > Introduction Top

The annual incidence of oral cavity squamous cell carcinoma (OCSCC) is approximately 32,000 new cases with around 6500 expected deaths.[1]

Incidence of oral cancers has decreased overall in the United States in the past 50 years [2],[3] although this trend varies by oral cavity subsite: Incidence was shown to be stable from 1973 to 2004 for oral tongue cancers but significantly decreased during that period for cancers of gingiva, floor of mouth, palate, and other subsites of the oral cavity.[3] This decreasing trend is thought to be due to decreased tobacco use in the United States.[4] Cigarette smoking is indeed the most commonly cited risk factor for OCSCC, and tobacco users have consistently been shown to be at a 5-fold to 25-fold higher risk than nonsmokers, with a clear dose–response relationship.[5],[6] Alcohol consumption works synergistically with tobacco smoking and increases the risk of OCSCC by several folds; a greater multiplicative effect between these two risk factors has been demonstrated.[7] Because around 75% of OCSCCs are attributable to these exposures,[4] the World Health Organization has established the Global Oral Health Program in an attempt to combat modifiable risk factors, the most important of which is smoking.[8]

Based on the National Cancer Institute Surveillance, Epidemiology and End Results Program 2005–2011, the five-year overall survival (OS) for OCSCC is 63%, ranging from 83% for early stages to 38% for advanced stages.[9]

The management of OCSCC relies heavily on a multidisciplinary approach and a close collaboration between surgeons, medical oncologists, and radiation oncologists. For early-stage lesions, surgery is the mainstay of treatment.[10] The presence of certain pathological features, such as lymphovascular space invasion (LVSI), perineural invasion (PNI), extracapsular extension (ECE) of lymph node (LN) metastasis, inadequate resection margins, multiple involved neck LNs, and advanced pathologic T-stage (pT3 or pT4), has been consistently shown to adversely affect outcomes in patients with head and neck squamous cell carcinoma (HNSCC), including OCSCC.[11],[12],[13],[14],[15],[16],[17]

In patients with these adverse features, the National Comprehensive Cancer Network (NCCN) recommends adjuvant radiation therapy (RT) or chemoradiation.[10] Concurrent chemotherapy is recommended in the presence of positive margins or extracapsular extension of LN metastasis. This recommendation is based on the RT Oncology Group (RTOG) 9501/European Organization for Research and Treatment of Cancer (EORTC) 22931 combined analysis.[18],[19],[20]

To the best of our knowledge, the relationship between smoking and all of these adverse clinicopathological features in OCSCC has never been thoroughly investigated. The aim of our study is to determine whether smoking predicts for more aggressive pathological features and worse survival outcomes in patients with OCSCC.

 > Materials and Methods Top


We identified 163 patients with American Joint Committee on Cancer (AJCC) Stages I–IVa OCSCC diagnosed between 2005 and 2015 and treated with curative intent at our institution. Patients with squamous cell carcinoma involving the following subsites were included: buccal mucosa, upper and lower alveolar ridge, retromolar trigone, floor of mouth, hard palate, and anterior two-thirds of the tongue. All patients underwent surgical resection of the primary tumor with or without unilateral/bilateral neck dissection, with or without adjuvant therapy (RT or RT with concurrent chemotherapy [RT/CT]), depending on the presence of risk factors and after multidisciplinary tumor board discussion. A retrospective medical chart review was conducted identifying various clinicopathologic variables, including information on smoking status assessed preoperatively.

A pathological risk score (PRS) was calculated using the NCCN-defined adverse risk factors:[10] 1 point was assigned to each of the following: PT3 or pT4 primary, N2 or N3 nodal disease, PNI, and LVSI, and 2 points were assigned to positive margin as well as to ECE of LN metastases because the presence of these last two parameters would be an indication for trimodality therapy. The sum of these points resulted in a total possible score of 0–8 with a higher score indicating worse pathological features.

Statistical analysis

Differences in participant characteristics were compared by smoking status using Chi-square or Fisher's exact tests for categorical variables and Wilcoxon rank sum for continuous variables. Univariate survival analysis was performed using Cox regression for continuous variables and Kaplan–Meier and log-rank test for categorical variables. OS was calculated from the date of diagnosis to date of death or last contact, and recurrence-free survival (RFS) was calculated from the date of diagnosis to date of disease recurrence, death, or last contact.

A multivariate analysis (MVA) using Cox regression models was performed to determine independent predictors of OS and RFS endpoints. A multivariable linear regression model was built to study the association between different predictive variables and PRS. Multivariable models were selected by first including any predictor with a univariate P < 0.2 and then employing stepwise selection. We constructed two different multivariable models for each of the OS and RFS outcomes: one model excluding the PRS variable while including all of its individual components and a second model including the PRS variable and with all of its six score components excluded to avoid collinearity. All variables in the final models were significant at P < 0.05.

To determine whether smokers were more likely to receive adjuvant treatment (RT or RT/CT) than nonsmokers given a specific pathological score, we studied the interaction between smoking status and PRS, with postoperative treatment as the outcome of interest in this final logistic regression analysis.

All analyses were performed using SAS® 9.4 software (Cary, NC, USA), and statistical significance was set at P < 0.05.

 > Results Top

Patients' characteristics

Patients' characteristics are shown in [Table 1]. Median age of patients' population was 60 years (range, 25–93). A total of 108 (66.26%) patients in our cohort were smokers and 55 were nonsmokers. On univariate analysis, smokers were more likely to use alcohol (60.2% in smokers vs. 34.6% in nonsmokers, P < 0.01) and more likely to have advanced disease stage and tumors with aggressive pathologic features than nonsmokers: 38.9% pT3–pT4 in smokers versus 18.2% in nonsmokers; 38.0% N2 in smokers versus 7.3% in nonsmokers; 27.8% ECE of LN metastases in smokers versus 7.3% in nonsmokers; 29.6% LVSI in smokers versus 10.9% in nonsmokers; and 47.2% PNI in smokers versus 16.4% in nonsmokers, all with P < 0.01. Consequently, adjuvant concurrent chemoradiation was more commonly used in smokers (38.9%) than nonsmokers (20%) (borderline significance, P = 0.057).
Table 1: Characteristics of the study population of 163 patients with oral cavity squamous cell carcinoma

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Survival analysis

A total of 143 patients (99 smokers and 44 nonsmokers) were included in the survival analysis. The remaining 20 patients were not included in the survival analysis due to insufficient follow-up time. After a median follow-up of 44.5 months, 55 deaths were recorded (43 [43.4%] in smokers and 12 [27.3%] in nonsmokers). Three-year actuarial OS was 62% and 81% in smokers and nonsmokers, respectively (P = 0.06) [Figure 1]. Three-year actuarial RFS was 68% and 69% in smokers and nonsmokers, respectively (P = 0.63) [Figure 2].
Figure 1: Overall survival rates of smokers and nonsmokers with squamous cell carcinoma of the oral cavity

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Figure 2: Recurrence-free survival rates of smokers and nonsmokers with squamous cell carcinoma of the oral cavity

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[Table 2] depicts the first multivariable model, which includes the six NCCN adverse risk factors and excludes the PRS. In the entire sample, older age, presence of LVSI (hazard ratio [HR] = 2.27, 95% confidence interval [CI] 1.28–4.02), presence of PNI (HR = 2.19, 95% CI 1.13–4.24), and nodal status (N2 vs. N0: HR = 3.47, 95% CI 1.70–7.10) were independent predictors of OS. The presence of LVSI, female gender, advanced T-stage, and nodal status significantly predicted for worse RFS. No independent predictors of RFS were found in this MVA model in the entire sample. In particular, smoking did not predict for worse RFS. In smokers, the presence of ECE and nodal status significantly predicted for worse OS in this MVA model. Positive margins and nodal status were independent predictors of RFS in smokers.
Table 2: Multivariate analysis of survival outcomes in the entire sample and in the subset of smokers

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[Table 3] consists of the second multivariable model, which includes PRS as a continuous variable and excludes its individual components. In the entire sample, older age, smoking status, and worse PRS were independent predictors of OS. The HR for death of smokers versus nonsmokers was 2.28 (95% CI 1.12–4.64). Furthermore, for every point increase in the PRS, the risk of death increased by 1.50-fold (95% CI 1.30–1.72). Similarly to the first MVA model, smoking status did not predict for worse RFS.
Table 3: Multivariate analysis of survival outcomes in the entire sample and in the subset of smokers

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Older age and higher PRS predicted for worse OS in smokers. There were no independent predictors of RFS in smokers in this model.

Pathological risk score

Smokers had a significantly worse PRS (mean ± standard deviation; 2.38 ± 2.19, median; 2.00) than nonsmokers (0.89 ± 1.21, 0.00) (P < 0.001) on univariate analysis. On MVA, independent predictors of PRS were smoking status and grade (P < 0.01). Smokers were not more likely to receive adjuvant treatment based on adverse pathological score than nonsmokers (P for interaction = 0.224).

 > Discussion Top

To our knowledge, this is the first study on the impact of smoking on a specific set of pathological features that are used to guide adjuvant therapy.

Our study showed that smoking is an independent predictor of worse pathological score, as defined in this study. Smokers seem to have significantly more aggressive disease as evidenced by more adverse pathological features than nonsmokers. Some experts have argued that HNSCC in nonsmokers is a “distinct clinical and molecular entity.” Koch et al. have shown that most nonsmokers with oral cavity tumors had an oral tongue primary, while most of the oral cancers in smokers involved the floor of mouth.[21] In our study, there was a borderline difference in the distribution of oral cavity subsites on univariate analysis between smokers and nonsmokers (69.1% oral tongue in nonsmokers vs. 50% in smokers; 12.7% floor of mouth in nonsmokers vs. 33.3% in smokers, P = 0.052). Furthermore, in the same study by Koch et al., tumors of nonsmokers harbored fewer genetic alterations than tumors in nonsmokers.[21] It has been established that “carcinogens leave fingerprints,” in the form of mutations of tumor suppressor genes and oncogenes, among others.[22] Smoking is no exception to this rule; tobacco has been associated with high frequency of p53 mutations in patients with HNSCC, and these mutations confer resistance to apoptosis.[23] A recently published paper studying the relationship between expression of matrix metalloproteinases (MMP) 2 and 9 and the clinicopathological features of OSCC revealed that patients with a smoking history had higher expression of MMP 2 and 9, two proteins that play a role in extracellular matrix degradation and cell migration.[24] Similarly, a novel protein, migration, and invasion enhancer 1, which facilitates cell migration and invasion, was shown to be correlated with smoking and associated with significantly lower survival.[25] These are all examples of molecular “fingerprints” caused by tobacco smoking. Whether smoking-related alterations in the above-mentioned and other molecular targets translate into more aggressive histopathological features has only been investigated superficially so far. An earlier study showed significant correlation between tobacco smoking and an empirically calculated histological score, incorporating eight different cellular morphological features, such as cytoplasmic and nuclear differentiation, growth pattern, mitosis, and depth of invasion.[26] Another study on oral cancer in women supported the association between cigarette smoking and mitotic activity.[27] Nevertheless, none of these histopathological features has been shown to have a direct impact on survival, and none is directly implicated in decision-making. No studies were found on the association between smoking and the presence of the NCCN adverse clinicopathological risk factors taken as a whole. These risk factors were established following the two major EORTC 22931 and RTOG 9501 trials.[18],[19],[20] Specific mutations leading to cell migration and mitosis could explain the more aggressive pathology found in smokers. Whether smoking status should be incorporated into patient management decisions and whether smokers require intensification of treatment need further evaluation. Future studies should focus on comparing molecular alterations in smokers and nonsmokers to better understand the mechanisms of carcinogenesis in these two populations and help in more effectively managing patients with OCSCC. The field of prognostic molecular signatures is still relatively new, and treatment paradigms for OCSCC still rely heavily on tumor stage. Future directions include whole-genome sequencing to study specific targetable mutations in smokers and nonsmokers for molecular therapies [28],[29],[30] and possibly prognostication.

In our study, smoking was shown to be an independent predictor of OS in patients with OCSCC, corroborating findings in other studies on HNSCC, and on OCSCC specifically. In a study by Fortin et al. of 1871 HNSCC patients, including 343 patients with primaries in the oral cavity, smoking was shown to have a detrimental effect on local control and OS.[31] Similarly, in a cohort of 504 patients with HNSCC, pretreatment smoking status was the strongest predictor of survival, out of an array of selected health behaviors (including alcohol, physical activity, diet and sleep patterns), with both current smokers (HR = 2.4; 95% CI 1.3–4.4) and former smokers (HR = 2.0; 95% CI 1.2–3.5) showing significantly poorer survival than nonsmokers.[32] A Japanese retrospective study of 222 OCSCC patients showed that pretreatment smoking was associated with significantly worse survival among patients treated with definitive chemoradiation or RT.[33]

The PRS that we used in this study, although not a validated tool, was helpful in assessing the predictive capacity of the NCCN clinicopathological features taken as a whole, and not as individual, isolated parameters. We assigned arbitrary weights to each of the six NCCN risk factors, with more weights assigned to ECE of LN metastasis and positive margins, two risk factors that would entail the addition of concurrent chemotherapy to adjuvant radiation. Interestingly, this tool was shown to be an independent predictor of OS, but not of RFS, in the entire sample and in the subgroup of smokers, after adjusting for all other predictive variables. We would not recommend the use of our scoring system before further validation in the future studies. A number of histological scoring systems have been devised in the past, such as invasive cell grading, which is a significant, and reproducible predictor of survival, and was validated in OCSCC.[34],[35] Another scoring system used in OCSCC is the risk model devised by Brandwein-Gensler et al., incorporating three histological features: perineural invasion, lymphocytic host response, and worst pattern of invasion.[36],[37],[38] Interestingly, patients with early-stage tumors, who might otherwise have been managed with surgery alone, may be offered multimodality therapy based on a high Brandwein-Gensler et al.'s risk score indicating a high propensity for recurrence.[36],[37],[38],[39] A modified tumor classification including histopathological features has been proposed as an alternative to the AJCC tumor classification,[40],[41] as the paramount importance of histological prognosticators is being increasingly appreciated.

We recognize that our study has some important limitations. One major limitation lies in the inherent biases of a retrospective study design. A multicenter prospective study would be needed to validate our results in a larger sample of patients. In addition, we only recorded pretreatment smoking status and did not gather information on whether patients continued smoking during treatment. This could have some impact on our results as other studies have shown that smoking during RT was associated with worse prognosis.[42],[43] This effect has been postulated to be related to hypoxia which confers resistance to radiotherapy.[44]

One of our study's strengths is that complete follow-up and information on vital status for all of the patients included in this study were present, as well as details on the different treatments received. Another important study strength relates to our institution's compliance with quality assurance measures in the treatment of head and neck cancers.[45] In particular, we use standardized histopathology reporting by a head and neck pathologist (CK), following the College of American Pathologists protocol for examination of specimens from patients with OCSCC.[46] Furthermore, all head and neck cancer cases are presented in our multidisciplinary tumor boards, and treatment recommendations follow the NCCN and other well-established national guidelines.[45]

 > Conclusion Top

Smoking is an independent predictor of OS, but not RFS in patients with OCSCC. Moreover, smokers have more aggressive disease as evidenced by more adverse pathological features than nonsmokers. In future clinical trials, smoking status should be used to stratify patients with OCSCC. The PRS, as defined in our study, seems to be a valuable and easy tool in the evaluation of important clinicopathological features in OCSCC and is shown in our study to be significantly associated with OS. However, it would require further validation in randomized controlled trials.


The training of the first author was in part supported by the Fogarty International Center and Office of Dietary Supplements of the National Institutes of Health under Award Number D43 TW009118. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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