HNSCC – Head and neck squamous cell carcinoma

Introduction

Squamous cell carcinomas of the head and neck (HNSCCs) form another entity that could benefit from immune checkpoint inhibitor therapy.

As shown in the table, the following scores with the corresponding cut-offs have been required to date: 

Tumor Proportion Score (TPS) ≥50%

Combined Positive Score (CPS) ≥1

While the CPS is decisive for first-line therapy with pembrolizumab, either as a monotherapy or in combination with platinum and 5-fluorouracil (5-FU) chemotherapy, TPS relates instead to monotherapy with pembrolizumab as a second-line therapy for unresectable recurrent or metastatic squamous cell carcinomas of the head and neck. Nivolumab can be administered without immunohistological testing of the PD-L1 status following platinum-based chemotherapy.

Scores

Definition and calculation of the relevant scores:

TPS/TC

CPS

The cut-off with TPS ≥50% is also applied for NSCLC. Since squamous cell carcinomas of the lung also fall into this category, expression patterns and the evaluation mode can be used in the same way. Guidance on general interpretation with the TPS can be found here.

In addition to carcinoma cells, the expression of PD-L1 by immune cells is also calculated for the CPS. It should be noted that the total of PD-L1-expressing carcinoma cells and immune cells is relative to all carcinoma cells.

Interpretation guidance

Use a high magnification: Even for personnel who are in principle highly skilled in the PD-L1 evaluation of squamous cell carcinomas, interpretation of staining is non-trivial, since keratin pearls, cornoid lamellae, and desmosis makes the evaluation more difficult. High magnification helps here, especially for excluding cases of desmosis. Necrotic or apoptotic cells and cases of dyskeratosis are excluded from the evaluation.

Perform other immunohistological investigations where necessary: Macrophages must be excluded from evaluation when specifying the TPS. Differentiating these from tumor cells is not always easy, especially at the stromal transition. Further immunohistological investigation can be helpful here, so as to present the macrophages either as serial sections or by using double markers.

PD-L1 prevalence in HNSCC

In accordance with the completed studies ^2,3, prevalence for the two therapy-relevant scores and cut-offs is as follows:

CPS ≥1: 78–85%

TPS ≥50%: 22–26%

Test system validation/antibody selection in HNSCC

While the publication of a harmonization study performed in Germany is not yet final, we once again see here – as has also been the case for the entities presented on the Portal to date – that SP142 stains the tumor cells less often and less strongly, while SP263 provides us with a stronger expression pattern overall.

Guidance for practice

Specific interpretation guidance for HNSCC

Support for interpretation is available from Agilent DAKO⁴ at the following link: Agilent DAKO Interpretation Handbook

Please note that at least 100 carcinoma cells should be available for interpretation.

Necrotic cells, plasma cells, and granulocytes are excluded from CPS and TPS scoring.

When evaluating HNSCC, a carcinoma in situ component is excluded from CPS scoring.

The following tables provide you with full details and guidance for interpreting the CPS score. (Agilent DAKO ⁴, page 26)

Interpretation guidance for CPS definition numerator

	Tumor cells	Immune cells	Other cells
Included in numerator	Convincing partial or complete linear membrane staining (at any intensity) of viable invasive tumor cells	Membrane and/or cytoplasmic* staining (at any intensity) of mononuclear inflammatory cells (MICs) within tumor nests and adjacent supporting stroma Lymphocytes (including lymphocyte aggregates) Macrophages ‡ Only MICs directly associated with the response to the tumor are scored.	Excluded
Excluded from numerator	Non-staining tumor cells Tumor cels with only cytoplasmic staining	Non-staining MICs MICs (including lymphoid aggregates) associated with ulcers, chronic cystitis, or other, non-tumor-associated processes MICs associated with carcinoma in situ MICs associated with benign structures neutrophil/eosinophil granulocytes and plasma cells	Carcinoma in situ normal/benign cells Stromal cells (including fibroblasts) Necrotic cells and/or cellular debris

* In MICs, membrane and cytoplasmic stainings often cannot be distinguished due to the high nucleus-plasma relation. For this reason, both membrane and cytoplasmic stained MICs are contained in the score.
† “Neighboring MICs” is the definition of cells that are inside the same 20x field as the tumor. However, MICs that are not directly associated with the reaction to the tumor should be ruled out.
‡ Macrophages and histiocytes are assigned to the same kind of cell.

The following tables provide you with full details and guidance for interpreting the CPS score. (Agilent DAKO ⁵, page 24)

	Tumor cells	Immune cells	Other cells
Included in denuminator	All viable invasive tumor cells	Excluded	Excluded
Excluded from denuminator	Any necrotic or non-viable tumor cells Dysplastic cells	All immune cells of any type	Carcinoma in situ normale/benign cells Stromal cells (including fibroblasts) necrotic cells and/or cellular debris

Guidance for reporting findings

When reporting the PD-L1 CPS value, we recommend specifying the CPS value determined directly and not merely the positivity range (≥1). This makes it easier for the consultant to decide on which of various therapy options to use (monotherapy or combination therapy). The cut-off of CPS ≥1 represents the authorization-relevant cut-off. Notwithstanding this, the cut-off ≥20 has significant clinical relevance, since from this value upwards, tolerability with comparable efficacy is better for pembrolizumab as a monotherapy than for the combination of pembrolizumab with chemotherapy. Accordingly, specifying the exact CPS value helps clinicians make a therapy decision between a pembrolizumab monotherapy and a pembrolizumab combination therapy.

QuIP Proficiency Test PD-L1 HNSCC

Literature

1. Ferris RL et al. Nivolumab vs Investigator’s Choice in Recurrent or Metastatic Squamous Cell Carcinoma of the Head and Neck: 2-year Long-Term Survival Update of CheckMate 141 With Analyses by Tumor PD-L1 Expression. Oral Oncology 2018; 81:45–51.

2.    Cohen, E. E. W. et al. Pembrolizumab versus methotrexate, docetaxel, or cetuximab for recurrent or metastatic head-and-neck squamous cell carcinoma (KEYNOTE-040): a randomised, open-label, phase 3 study. Lancet (London, England) 393, 156–167; 10.1016/S0140-6736(18)31999-8 (2019).

3.    Burtness, B. et al. Pembrolizumab alone or with chemotherapy versus cetuximab with chemotherapy for recurrent or metastatic squamous cell carcinoma of the head and neck (KEYNOTE-048): a randomised, open-label, phase 3 study. Lancet (London, England) 394, 1915–1928; 10.1016/S0140-6736(19)32591-7 (2019).

4.  Scheer, S. PD-L1 IHC 22C3 pharmDx Interpretation Manual, HNSCC (2019). Available at: https://www.agilent.com/cs/library/usermanuals/public/29314_22c3_pharmDx_hnscc_interpretation_manual_us.pdf