Head & Neck, 2024; 0:1–7 https://doi.org/10.1002/hed.27945 1 of 7 Head & Neck ORIGINAL ARTICLE OPEN ACCESS Tumor Microenvironment- Based Risk Stratification of Oropharyngeal Squamous Cell Carcinoma Alhadi Almangush1,2,3,4 | Lauri Jouhi5 | Caj Haglund6,7 | Jaana Hagström1,6,8 | Antti A. Mäkitie2,5,9 | Ilmo Leivo10,11 1Department of Pathology, University of Helsinki, Helsinki, Finland | 2Research Program in Systems Oncology, Faculty of Medicine, University of Helsinki, Helsinki, Finland | 3Department of Pathology, University of Turku, Turku, Finland | 4Faculty of Dentistry, Misurata University, Misurata, Libya | 5Department of Otorhinolaryngology – Head and Neck Surgery, University of Helsinki and Helsinki University Hospital, Helsinki, Finland | 6Research Programs Unit, Translational Cancer Medicine, University of Helsinki, Helsinki, Finland | 7Department of Surgery, University of Helsinki and Helsinki University Hospital, Helsinki, Finland | 8Department of Oral Pathology and Radiology, University of Turku, Turku University Hospital, Turku, Finland | 9Division of Ear, Nose and Throat Diseases, Department of Clinical Sciences, Intervention and Technology, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden | 10Institute of Biomedicine, Pathology, University of Turku, Turku, Finland | 11Turku University Central Hospital, Turku, Finland Correspondence: Alhadi Almangush (alhadi.almangush@helsinki.fi) Received: 13 May 2024 | Revised: 1 September 2024 | Accepted: 17 September 2024 Section Editor: Nicole Schmitt Funding: This work was supported by Finnish Cancer Society, Turku University Hospital Fund, Finska Läkaresällskapet, Maritza and Reino Salonen Foundation, K. Albin Johansson Foundation, the Finnish Dental Society Apollonia, Helsinki University Hospital Research Fund, and Sigrid Jusélius Foundation. Keywords: oropharyngeal squamous cell carcinoma | prognosis | tumor microenvironment | tumor- infiltrating lymphocytes | tumor- stroma ratio ABSTRACT Background: Evaluation of the prognostic impact of tumor microenvironment (TME) has received attention in recent years. We introduce a TME- based risk stratification for oropharyngeal squamous cell carcinoma (OPSCC). Material and Methods: A total of 182 patients treated for OPSCC at the Helsinki University Hospital were included. TME- based risk stratification was designed combining tumor- stroma ratio and stromal tumor- infiltrating lymphocytes assessed in hematoxylin and eosin- stained sections. Results: In multivariable analysis, TME- based risk stratification associated with poor disease- free survival with a hazard ratio (HR) of 2.68 (95% CI 1.11– 6.48, p = 0.029). In addition, the proposed risk stratification was associated with poor disease- specific survival (HR 2.687, 95% CI 1.28– 5.66, p = 0.009) and poor overall survival (HR 2.21, 95% CI 1.23– 3.99, p = 0.008). Conclusion: Our TME- based risk stratification provides a powerful prognostic tool that can be used in daily treatment planning of OPSCC together with tumor- related prognostic markers. 1 | Introduction Oropharyngeal squamous cell carcinoma (OPSCC) is one of the most commonly occurring malignancies in the head and neck region. There is an increasing incidence of human papillomavirus- associated (HPV+) OPSCC tumors [1, 2]. In general, HPV+ OPSCC is associated with a better prognosis than HPV− OPSCC, however many HPV+ cases present also with a poor survival [3]. HPV+ OPSCC patients who are at high risk of recurrence (about 15% of the cases), would require more intensive therapy, but their identification is challenging [2]. Therefore, there is a need for additional prognostic mark- ers beyond the HPV status to predict the clinical behavior of OPSCC. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2024 The Author(s). Head & Neck published by Wiley Periodicals LLC. 2 of 7 Head & Neck, 2024 The tumor stroma as part of the tumor microenvironment (TME) has a prominent role in the progression of many cancer types including those of various subsites of head and neck re- gion, as widely reported recently [4]. Tumor stroma consists of fibroblasts, myofibroblasts, endothelial cells, and immune cells. The stromal tissue serves as a supporting framework where the tumor cells are embedded [5]. Assessment of the quantity of stromal compartment has been re- cently introduced in the form of tumor- stroma ratio (TSR) using hematoxylin and eosin (HE)- stained sections and it has shown to have a powerful prognostic value [6– 9]. Moreover, immune cells may infiltrate tumor tissue, and their organization within the TME is tightly connected with the clinical behavior of many solid cancers [10]. Of note, the combination of TSR and immune status in TME has also been studied in some tumor types includ- ing head and neck cancer [11, 12]. Up to date, there are no TME- related classifiers included in the prognostication of OPSCC. TME- based stratification could improve accuracy in the assessment of the clinical behav- ior of OPSCC. Therefore, the aim of this study was to intro- duce a TME- based risk stratification for the prognostication of OPSCC. 2 | Material and Methods All cases treated for OPSCC at the Helsinki University Hospital (Helsinki, Finland) in the period between January 2000 and December 2009 were included in this study. This research project was approved by the Research Ethics Committee of the Helsinki University Hospital. The following patients were excluded: those with palliative treatment intent (n = 44), with treatment for previous head and neck cancer (n = 11), with concurrent head and neck cancer (n = 5), other histology than squamous cell carcinoma (n = 18), and those in whom a suffi- cient tumor- host interface was not available (n = 71). A total of 182 cases of OPSCC were eligible for this study. We used both tumor resection specimens and representative incisional diag- nostic specimens. All unrepresentative samples were excluded. Both p16 immunohistochemistry and Ventana Inform DNA in situ hybridization assay were performed on tissue samples and used to determine HPV status based on the algorithm described by Smeets et al. [13]. All representative HE- stained cancer specimens were as- sessed. TME- based risk stratification was designed based on the abundance of tumor stroma and the stromal TILs (Figure 1). TSR and stromal TILs were combined as follows: category I in which the stromal component was less than 50% and TILs more than or equal to 30%, and category III in which the stromal component was more than or equal to 50% and TILs less than 30%. All other tumors were assigned to cate- gory II. The evaluation of TSR and TILs was performed by two observ- ers (AA and IL) as described in the recent guidelines [14– 17]. In brief, the assessment of TSR started with scanning of the whole slide with ×5 objective to select the area with the highest amount of tumor- associated stroma, and then with ×10 objective to assess the amount of tumor- associated stroma in a chosen mi- croscopic field with cancer cells present in all four sides [14, 15]. In any heterogenous tumor with areas of both high and low amounts of tumor- associated stroma, the stroma- high area was considered decisive for scoring the case, as recommended in the guidelines [14, 15]. For the assessment of TILs, the whole tumor section was evaluated at low magnification using ×5 or ×10 ob- jective, and then at higher magnification using ×20 objective. The percentage of stromal area occupied by TILs was assessed for scoring. To obtain an average score of TILs this assessment was carried out in multiple stromal areas. Stromal areas not ad- jacent to the tumor, tonsillar lymphatic tissue and areas of ne- crosis were excluded. 2.1 | Statistical Method All statistical analyses was conducted using IBM SPSS Statistics (version 27). The prognostic impact of the TME- based risk stratification was assessed with univariable and multivariable FIGURE 1 | Tumor microenvironment- based risk stratification of oropharyngeal squamous cell carcinoma. (A) Category I: Tumor with low stroma (< 50%) and high infiltration of TILs (≥ 30%). (B) Example of category II: High stroma (≥ 50%) and high infiltration of TILs (≥ 30%). (C) Category III: High stroma (≥ 50%) and low infiltration of TILs (< 30%). [Color figure can be viewed at wileyonlinelibrary.com] 10970347, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/hed.27945 by D uodecim M edical Publications Ltd, W iley O nline Library on [01/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on W iley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 3 of 7 analyses. Hazard radio (HR) with 95% confidence interval (CI) was reported for each variable. Cross- tabulation was used to an- alyze the relationship between TME- based stratification and the clinicopathologic characteristics. Kaplan– Meier analyses were conducted for disease- free survival, disease- specific survival, and overall survival. 3 | Results A total of 140 (76.9%) males and 42 (23.1%) females were in- cluded in the study. The median follow- up time was 4.48 years (range 3.51– 5.00 years). The clinicopathologic features of the cases and their relationship with the TME- based risk strat- ification are summarized in Table  1. The TME- based strati- fication had a total of 81 (44.5%) tumors categorized in the TME- based category I, 39 (21.4%) in category II, and 62 (34.1%) in category III. There was a good inter- observer agreement in the assessment of TILs (Kappa value = 0.78) and TSR (Kappa value = 0.752), which indicates a good reproducibility of the proposed TME- based stratification. In the cross- tabulation (Table 1), we noted a sig- nificant association was noted between the age of patients and the TME- based stratification (p = 0.006). On the other hand, no significant association (p > 0.05) was found between the TME- based risk stratification and other clinicopathologic factors including gender, HPV status, smoking history, TNM stage, his- topathologic grade, and treatment. In survival analyses using a cutoff point of 30% for TILs (Table 2), category III of the TME- based risk stratification was associated with significantly worse disease- free survival with a HR of 3.52 (95% CI 1.50– 8.22, p = 0.004) in univariable and multivariable analyses (HR 2.68, 95% CI 1.11– 6.48, p = 0.029). Similarly, category III of TME- based stratification was associ- ated with significantly worse disease- specific survival with a HR of 3.43 (95% CI 1.67– 7.05, p < 0.001) in univariable and mul- tivariable analyses (HR 2.687, 95% CI 1.28– 5.66, p = 0.009). In addition, category III of the TME- based risk stratification was associated with poor overall survival in univariable analysis with a HR of 2.83 (95% CI 1.60– 4.99, p < 0.001) as well as in mul- tivariable analysis (HR 2.21, 95% CI 1.23– 3.99, p = 0.008). Our multivariable analyses included the routinely considered param- eters of HPV- status and tumor stage. The results indicate the independence of the proposed TME- based risk stratification in predicting the prognosis of OPC. In addition, Kaplan– Meier sur- vival curves (Figure 2A– C) indicated significantly worse prog- nosis for category III of TME- based stratification in disease- free survival (p = 0.008), disease- specific survival (p = 0.002), and overall survival (p < 0.001). When using a cutoff point of 20% for TILs in the TME- based risk stratification, a significant prognostic power was ob- served for disease- free survival (HR 2.80, 95% CI 1.78– 6.66, p = 0.020). However, no significant prognostic power was reached for disease- specific survival (HR 1.45, 95% CI 0.75– 2.81, p = 0.271) or overall survival (HR 1.47, 95% CI 0.85– 2.52, p = 0.166). This indicates that the above described 30% provides an optimal cutoff point for TILs in TME- based risk stratification. A 50% cutoff point was optimal for TSR in our TME- based risk stratification. 4 | Discussion Tumor microenvironment has a significant role in cancer pro- gression [18]. Recently, stromal- related prognostic biomarkers have been introduced for risk assessment in head and neck cancers [9]. Identification of stromal markers can aid in tar- geting tumor- associated stromal cells for cancer therapy [19]. In daily practice of OPSCC, however, TME is not considered during the management of oropharyngeal cancer. In addi- tion, it is sometimes challenging to select the most suitable treatment for OPSCC patients [20]. In the present study we have introduced for the first time in a large cohort of OPSCC a TME- based grading system that can be evaluated using rou- tine hematoxylin and eosin (HE)- stained slides and, therefore, can be easily included in pathology reports without addi- tional costs. Our proposed system combines features of stro- mal microenvironment and immune microenvironment and has shown a powerful prognostic value in risk stratification of OPSCC. Interactions of cancer cells with cells of tumor stroma are com- plex and implicated as key players in cancer invasion. During cancer progression, cancer cells and other components modify stromal cells to form a phenotype that promotes tumor devel- opment [19]. Tumor stroma can regulate tumor growth and it has the potential of regulating the aggressiveness of the tumor. Thus, research efforts on novel therapeutic strategies aim at tar- geting anti- tumoral and anti- stromal agents [21]. Research efforts which have included immune parameters as prognostic classifiers have shown promising findings [10]. Importantly, the assessment of stromal TILs is the most widely used immune parameter and has been reported as a powerful prognosticator in recent studies on various tumors [22– 25]. It is necessary to point out that the prognostic value of intra- tumoral TILs was limited (p > 0.05), as also previ- ously reported in oral cancer [23]. In the current study, the method used for the assessment of stromal TILs is standard- ized, and it has shown a promising prognostic value and good inter- observer agreement [22– 25]. In addition, the method is cost- effective as the assessment of TILs is made on HE- stained sections which are already available as diagnostic samples. Similarly, the assessment of TSR is cost- effective and has shown a significant prognostic value and good reproducibil- ity [6– 9]. Of note, recent research has proposed stromal- related char- acteristics for risk stratification of different tumors to sup- plement the currently used tumor- related features in risk stratification of cancer. Interestingly, two recent studies have reported the prognostic significance of stroma- based stratifi- cation in oral squamous cell carcinoma [11, 12]. Our current study corroborates the results of these studies. Importantly, when using diagnostic biopsy sections for the assessment of TSR, it is necessary to have a representative sample including sufficient amounts of both tumor and stromal compartments. 10970347, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/hed.27945 by D uodecim M edical Publications Ltd, W iley O nline Library on [01/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on W iley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 4 of 7 Head & Neck, 2024 In such samples, a good agreement on the TSR score in pre- treatment biopsies and surgical specimens has been reported in head and neck cancers [26, 27]. Interestingly, there is evidence indicating that TSR and response to neoadjuvant chemoradiotherapy are correlated so that in esophageal can- cer stroma- low tumors show a better response to neoadjuvant TABLE 1 | Relationship between tumor microenvironment- based risk stratification and clinicopathologic features in cases of oropharyngeal squamous cell carcinoma (n = 182). Variable Total Stromal category I Stromal category II Stromal category III p of Chi- square testTotal, N = 182 Number (%) Number (%) Number (%) 81 (44.5%) 39 (21.4%) 62 (34.1%) Age 0.006 < 60 years 101 55 (54.5%) 15 (14.9%) 31 (30.7%) ≥ 60 years 81 26 (32.1%) 24 (29.6%) 31 (38.3%) Gender 0.688 Male 140 61 (43.6%) 29 (20.7%) 50 (35.7%) Female 42 20 (47.6%) 10 (23.8%) 12 (28.6%) HPV status 0.252 Positive 91 46 (50.5%) 18 (19.8%) 27 (29.7%) Negative 91 35 (38.5%) 21 (23.0%) 35 (38.5%) Smoking 0.550 Never 20 9 (45.0%) 3 (15.0%) 8 (40.0%) Former 46 21 (45.7%) 13 (28.3%) 12 (26.1%) Current 85 33 (38.8%) 19 (22.4%) 33 (38.8%) Stage 0.262 Early (I– II) 27 10 (37.0%) 9 (33.3%) 8 (29.6%) Advanced (III– IV) 155 71 (45.8%) 30 (19.4%) 54 (34.8%) T stage 0.174 T1 35 22 (62.9%) 7 (20.0%) 6 (17.1%) T2 68 30 (44.1%) 15 (22.1%) 23 (33.8%) T3 40 15 (37.5%) 10 (25.0%) 15 (37.5%) T4 39 14 (35.9%) 7 (17.9%) 18 (46.2%) N stage 0.601 N0 35 13 (37.1%) 9 (25.7%) 13 (37.1%) N+ 147 68 (46.3%) 30 (20.4%) 49 (33.3%) Grade 0.301 I 15 5 (33.3%) 6 (40.0%) 4 (26.7%) II 70 29 (41.4%) 13 (18.6%) 28 (40.0%) III 97 47 (48.5%) 20 (20.6%) 30 (30.9%) Treatment 0.157 Sx ± (C)RT 120 58 (48.3%) 21 (17.5%) 41 (34.2%) (C)RT ± Sx 62 23 (37.1%) 18 (29.0%) 21 (33.9%) Abbreviations: CRT, chemoradiotherapy; RT, radiotherapy; Sx, surgery. 10970347, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/hed.27945 by D uodecim M edical Publications Ltd, W iley O nline Library on [01/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on W iley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 5 of 7 TABLE 2 | Disease- free survival, disease- specific survival, and overall survival analyses of the prognostic significance of tumor microenvironment (TME)- based risk stratification and clinicopathologic parameters of 182 patients treated for oropharyngeal squamous cell carcinoma. Parameter Univariable analysis Disease- free survival Disease- specific survival Overall survival HR (95% CI), p HR (95% CI), p HR (95% CI), p Gender Male Reference Reference Reference Female 2.08 (0.80– 5.39), p = 0.13 2.19 (0.99– 4.88), p = 0.054 1.50 (0.85– 2.64), p = 0.16 Smoking Never Reference Reference Reference Former 1.69 (0.47– 6.15), p = 0.42 1.66 (0.46– 6.05), p = 0.44 1.24 (0.48– 3.21), p = 0.65 Current 1.89 (0.56– 6.42), p = 0.31 3.29 (1.01– 10.7), p = 0.048 2.36 (1.01– 5.53), p = 0.048 T stage T1 Reference Reference Reference T2 1.58 (0.51– 4.89), p = 0.43 1.97 (0.74– 5.27), p = 0.18 1.92 (0.84– 4.43), p = 0.12 T3 2.34 (0.74– 7.47), p = 0.15 1.79 (0.62– 5.26), p = 0.28 2.44 (1.03– 5.81), p = 0.044 T4 2.35 (0.69– 8.04), p = 0.17 3.62 (1.31– 9.96), p = 0.013 4.18 (1.79– 9.76), p = 0.001 N stage N0– N1 Reference Reference Reference N2– N3 1.55 (0.59– 4.01), p = 0.37 2.09 (1.05– 4.19), p = 0.037 1.49 (0.89– 2.48), p = 0.129 HPV status Positive Reference Reference Reference Negative 2.59 (1.26– 5.35), p = 0.010 2.51 (1.38– 4.56), p = 0.003 2.46 (1.52– 3.98), p < 0.001 Treatment Sx ± (C)RT Reference Reference Reference (C)RT ± Sx 1.24 (0.62– 2.49), p = 0.551 1.01 (0.56– 1.82), p = 0.98 1.13 (0.71– 1.81), p = 0.604 TME- based stratification Category I Reference Reference Reference Category II 1.79 (0.62– 5.14), p = 0.383 2.39 (1.04– 5.52), p = 0.041 1.65 (0.81– 3.34), p = 0.165 Category III 3.52 (1.50– 8.22), p = 0.004 3.43 (1.67– 7.05), p < 0.001 2.83 (1.60– 4.99), p < 0.001 Parameter Multivariable analysis Disease- free survival Disease- specific survival Overall survival HR (95% CI), p HR (95% CI), p HR (95% CI), p T stage T1 Reference Reference Reference T2 1.77 (0.54– 5.82), p = 0.35 2.22 (0.79– 6.22), p = 0.13 2.21 (0.88– 5.58), p = 0.09 T3 1.56 (0.46– 5.29), p = 0.47 1.43 (0.48– 4.25), p = 0.52 1.90 (0.73– 4.95), p = 0.19 T4 1.95 (0.55– 6.86), p = 0.30 2.76 (0.97– 7.89), p = 0.06 3.72 (1.47– 9.41), p = 0.006 HPV status Positive Reference Reference Reference (Continues) 10970347, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/hed.27945 by D uodecim M edical Publications Ltd, W iley O nline Library on [01/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on W iley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 6 of 7 Head & Neck, 2024 chemoradiotherapy [28]. In agreement to that, in esophago- gastric junction adenocarcinoma the assessment of TSR in preoperative biopsies has shown a predictive power for neoadjuvant therapy response [29]. Indeed, further studies are needed to compare TSR in tumor specimens before and after radiotherapy/chemo- radiotherapy. In high- income countries, HPV- positive OPSCC is one of the most rapidly increasing cancers [2]. In addition, it is well doc- umented that HPV status is a valuable prognostic parameter in classifying OPSCC into risk groups. Therefore, in the present study we have included HPV status as a prognostic parameter together with our proposed TME- based risk stratification in the multivariable analyses (Table 2), and both parameters showed a significant prognostic value indicating prognostic independence of each. This also indicates that our proposed TME- based risk stratification can provide a risk stratification beyond the HPV status. This is an important observation to support optimal treatment planning based on multiple prognostic indicators. The clinical decision- making in OPSCC is sometimes challeng- ing as cases that are usually considered as low risk (particu- larly the HPV+ tumors), may still present with poor outcome [2]. Thus, additional prognostic factors are needed to optimize risk stratification to personalize the treatment and avoid both under- and over- treatment. The findings of our study indicate that category III tumors of the proposed TME- based risk strat- ification carry a high risk of recurrence and mortality and thus require close follow- up. More importantly, they might require more aggressive treatment even when diagnosed at an early stage. In conclusion, the proposed TME- based risk stratification is cost- effective and has a valuable prognostic power in identify- ing OPSCC cases at high risk of poor outcome. After validation studies, TME- based risk stratification can be incorporated in the routine pathology reports, and it can be considered for treat- ment planning for OPSCC patients. It is a shortcoming of the present study that the patient cohort was limited to the period 2000– 2009. Thus, further validation in a recent, preferably large multicenter cohort is desirable. Acknowledgments The authors acknowledge the funding of the Finnish Cancer Society, Turku University Hospital Fund, Finska Läkaresällskapet, Maritza and Reino Salonen Foundation, K. Albin Johansson Foundation, the Finnish Dental Society Apollonia, Helsinki University Hospital Research Fund, and Sigrid Jusélius Foundation. Parameter Multivariable analysis Disease- free survival Disease- specific survival Overall survival HR (95% CI), p HR (95% CI), p HR (95% CI), p Negative 2.56 (1.18– 5.57), p = 0.02 2.98 (1.55– 5.71), p = 0.001 2.59 (1.52– 4.42), p < 0.001 TME- based stratification Category I Reference Reference Reference Category II 1.94 (0.66– 5.69), p = 0.225 2.696 (1.16– 6.29), p = 0.022 1.74 (0.85– 3.55), p = 0.127 Category III 2.68 (1.11– 6.48), p = 0.029 2.687 (1.28– 5.66), p = 0.009 2.21 (1.23– 3.99), p = 0.008 Note: Values in bold refers to the significant prognostic power of TME- Based stratification. TABLE 2 | (Continued) FIGURE 2 | Kaplan– Meier survival curves for oropharyngeal squamous cell carcinoma cases categorized by tumor microenvironment- based risk stratification. Cases with category III tumor microenvironment- based stratification are associated with poor disease- free survival (A), disease- specific survival (B), and overall survival (C). [Color figure can be viewed at wileyonlinelibrary.com] 10970347, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/hed.27945 by D uodecim M edical Publications Ltd, W iley O nline Library on [01/10/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on W iley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 7 of 7 Conflicts of Interest The authors declare no conflicts of interest. Data Availability Statement The data that support the findings of this study are available from the corresponding author upon reasonable request. 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