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Immunotherapy in Carcinoma of the Vulva: A Comprehensive Overview

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1. Background and Disease Context

• HPV-associated pathway (~30-40%): Driven by HPV 16/18 oncoproteins E5, E6, E7 - typically in younger women, arising from usual-type VIN
• HPV-independent pathway (~60-70%): Associated with lichen sclerosus and differentiated VIN - older women, worse prognosis

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2. Immunological Rationale for ICIs in VSCC

2.1 Tumor Microenvironment (TME)

┌─────────────────────────────────────────────────────────────────┐
│              VSCC TUMOR MICROENVIRONMENT                        │
├───────────────────────┬─────────────────────────────────────────┤
│   PRO-IMMUNE SIGNALS  │     IMMUNE EVASION MECHANISMS           │
├───────────────────────┼─────────────────────────────────────────┤
│ • CD8+ TIL infiltrate │ • PD-L1 overexpression (in ~40% VSCC)   │
│ • HPV-specific T cells│ • IDO (indoleamine 2,3-dioxygenase)      │
│ • NK cell activity    │   production → tryptophan depletion      │
│ • MHC-I expression    │ • TGF-β signaling → T-cell suppression   │
│   (HPV+ tumors)       │ • CTLA-4 upregulation on Tregs           │
│                       │ • LAG-3 / Galectin-3 axis                │
│                       │ • MHC-I downregulation (HPV-neg tumors)  │
└───────────────────────┴─────────────────────────────────────────┘

2.2 Key Biomarker Landscape

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3. Approved Immunotherapeutic Agents

3.1 Regulatory Approvals Summary

Note: The European Medicines Agency (EMA) has NOT yet approved ICIs specifically for VSCC as of 2025, highlighting ongoing unmet need.

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4. Key Clinical Trials

4.1 Trial Results Summary Table

4.2 Meta-Analysis Pooled Outcomes (Maiorano et al., Cancers 2025)

┌────────────────────────────────────────────────────────────┐
│         META-ANALYSIS RESULTS (2025, N=181 patients)       │
├─────────────────────┬──────────────────────────────────────┤
│ Pooled ORR          │ 21% (all regimens)                   │
│ Monotherapy ORR     │ 11% (95% CI: 6-18%)                  │
│ Combination ORR     │ 46% (p not significant vs mono)      │
│ Median PFS          │ 2.2 months                           │
│ Median OS           │ 6.4 months                           │
│ Any-grade AE        │ 73%                                  │
│ Grade ≥3 AE         │ 23%                                  │
│ Treatment-related   │ 3%                                   │
│   death             │                                      │
├─────────────────────┴──────────────────────────────────────┤
│ PD-L1+ vs PD-L1- ORR: SIMILAR (not predictive)            │
│ HPV+ vs HPV- response: HPV+ shows more favorable profile  │
└────────────────────────────────────────────────────────────┘

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5. Treatment Flowcharts

5.1 Overall ICI Decision Algorithm for Advanced/Recurrent VSCC

                    ADVANCED / RECURRENT / METASTATIC VSCC
                                      │
                    ┌─────────────────▼──────────────────┐
                    │   Biomarker Testing (MANDATORY)     │
                    │  • PD-L1 (CPS, IHC 22C3 assay)     │
                    │  • MSI / MMR status (IHC/PCR)       │
                    │  • TMB (NGS panel)                  │
                    │  • HPV status                       │
                    │  • NTRK fusion (NGS)                │
                    └─────────────────┬──────────────────┘
                                      │
              ┌───────────────────────┼───────────────────────┐
              │                       │                       │
    ┌─────────▼──────────┐  ┌────────▼────────┐   ┌─────────▼──────────┐
    │ 1st LINE THERAPY   │  │ NTRK FUSION +   │   │ MSI-H / dMMR       │
    │                    │  │                 │   │ TMB-High ≥10 mut/Mb │
    │ Pembrolizumab +    │  │ Larotrectinib   │   │                     │
    │ Paclitaxel +       │  │   OR            │   │ Pembrolizumab       │
    │ Cisplatin/Carbo    │  │ Entrectinib     │   │ (any line)          │
    │ ± Bevacizumab*     │  │                 │   │                     │
    │ (PD-L1+ preferred) │  └─────────────────┘   └─────────────────────┘
    └─────────┬──────────┘
              │
    ┌─────────▼──────────┐
    │   PROGRESSION /    │
    │   2nd LINE+        │
    │                    │
    │ PD-L1+ (CPS≥1):    │
    │ Pembrolizumab mono │
    │                    │
    │ HPV+:              │
    │ Nivolumab          │
    │                    │
    │ PD-L1+ or -:       │
    │ Nivo + Ipi         │
    │ (DART regimen)     │
    │                    │
    │ Any SCC:           │
    │ Pembro + Vorinostat│
    │ (PEVOsq data)      │
    └─────────┬──────────┘
              │
    ┌─────────▼──────────┐
    │ MONITORING &       │
    │ RESPONSE ASSESS    │
    │                    │
    │ RECIST v1.1 q8-12w │
    │ irAE surveillance  │
    │ PD-L1 re-biopsy if │
    │ initial -ve        │
    └────────────────────┘

*Bevacizumab + pembrolizumab may be continued as maintenance after response

5.2 Locally Advanced (Unresectable) VSCC - Perioperative Immunotherapy

         LOCALLY ADVANCED UNRESECTABLE VSCC (Stage III-IVA)
                              │
              ┌───────────────▼───────────────┐
              │    MULTIDISCIPLINARY TEAM      │
              │     (Gyn-Onc + Rad-Onc)        │
              └───────────────┬───────────────┘
                              │
         ┌────────────────────┼────────────────────┐
         │                    │                    │
┌────────▼───────┐  ┌────────▼────────┐  ┌────────▼───────┐
│ NEOADJUVANT   │  │ CONCURRENT CRT  │  │ MITO VULVA-01  │
│ CHEMOTHERAPY  │  │ IMMUNOTHERAPY   │  │ (Ongoing Trial) │
│               │  │                 │  │                 │
│ Carboplatin + │  │ Pembrolizumab + │  │ Lenvatinib +    │
│ Paclitaxel    │  │ Cisplatin +     │  │ Pembrolizumab   │
│ ± Bevacizumab │  │ IMRT (68.4 Gy) │  │ x4 cycles then  │
│               │  │ (Yeku trial:   │  │ Pembro maint.   │
│               │  │  ORR 75%)      │  │ x35 cycles      │
└────────┬───────┘  └────────┬────────┘  └────────┬───────┘
         │                   │                    │
         └───────────────────┼────────────────────┘
                             │
              ┌──────────────▼──────────────┐
              │  RESPONSE ASSESSMENT        │
              │  (MRI ± biopsy at 8-12 wks) │
              └──────────────┬──────────────┘
                             │
              ┌──────────────┴──────────────┐
              │                             │
    ┌─────────▼──────┐           ┌──────────▼─────┐
    │ COMPLETE /     │           │ STABLE / PD    │
    │ PARTIAL        │           │                │
    │ RESPONSE       │           │ Consider       │
    │                │           │ exenteration   │
    │ Surgical       │           │ or palliative  │
    │ resection OR   │           │ care           │
    │ continued ICI  │           │                │
    │ maintenance    │           │                │
    └────────────────┘           └────────────────┘

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6. Mechanisms of Action: ICI Classes Used in VSCC

┌─────────────────────────────────────────────────────────────────────┐
│                    ICI MECHANISMS IN VSCC                           │
├─────────────────┬───────────────────────────────────────────────────┤
│ DRUG CLASS      │ MECHANISM                                         │
├─────────────────┼───────────────────────────────────────────────────┤
│ Anti-PD-1       │ Blocks PD-1 receptor on T cells → prevents        │
│ (Pembrolizumab, │ PD-L1/PD-L2 binding → restores T-cell activation  │
│  Nivolumab,     │ and cytotoxic killing of tumor cells              │
│  Cemiplimab)    │                                                   │
├─────────────────┼───────────────────────────────────────────────────┤
│ Anti-CTLA-4     │ Blocks CTLA-4 on T cells/Tregs → disinhibits      │
│ (Ipilimumab)    │ T-cell priming phase in lymph nodes → enhances    │
│                 │ systemic anti-tumor immune activation             │
├─────────────────┼───────────────────────────────────────────────────┤
│ Anti-PD-L1      │ Blocks PD-L1 on tumor/APCs → prevents engagement  │
│ (Atezolizumab,  │ with PD-1 on T cells; also preserves PD-L2 signal │
│  Avelumab,      │ for peripheral tolerance                         │
│  Durvalumab)    │                                                   │
├─────────────────┼───────────────────────────────────────────────────┤
│ Dual PD-1 +     │ Synergistic: CTLA-4 block expands T-cell pool;    │
│ CTLA-4 block    │ PD-1 block re-activates exhausted TILs in TME     │
│ (Nivo + Ipi)    │ → higher ORR (18.8% DART; CBR 25%)               │
└─────────────────┴───────────────────────────────────────────────────┘

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7. Predictive Biomarkers: What We Know (and Don't Know)

7.1 Current Biomarker Summary Table

7.2 Biomarker Testing Flowchart

          NEW DIAGNOSIS OF ADVANCED/RECURRENT VSCC
                           │
            ┌──────────────▼──────────────┐
            │   TISSUE BIOPSY (REQUIRED)  │
            │   Fresh or archival FFPE    │
            └──────────────┬──────────────┘
                           │
         ┌─────────────────┼─────────────────┐
         │                 │                 │
┌────────▼───────┐ ┌───────▼────────┐ ┌─────▼──────────┐
│ STANDARD IHC   │ │  MMR STATUS    │ │   NGS PANEL    │
│                │ │                │ │                │
│ PD-L1 (22C3)  │ │ MLH1, MSH2     │ │ TMB (≥10       │
│ → CPS score   │ │ MSH6, PMS2     │ │ mut/Mb)        │
│               │ │ → IHC loss     │ │                │
│ p16/HPV status│ │ → MSI-PCR      │ │ NTRK1/2/3      │
│               │ │   if IHC +ve   │ │ fusions        │
└────────┬───────┘ └───────┬────────┘ └─────┬──────────┘
         │                 │                 │
         └─────────────────▼─────────────────┘
                           │
            ┌──────────────▼──────────────┐
            │  TREATMENT DECISION MATRIX  │
            │  (See Section 5 flowchart)  │
            └─────────────────────────────┘

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8. Combination Strategies: Emerging Evidence

8.1 ICI + Chemotherapy

• Pembrolizumab + Cisplatin/Carboplatin + Paclitaxel ± Bevacizumab: NCCN Category 1 preferred first-line for recurrent/metastatic VSCC (extrapolated from KEYNOTE-826 cervical cancer data)
• Rationale: chemotherapy induces immunogenic cell death (ICD), increases tumor antigen presentation, potentially synergizing with ICI

8.2 ICI + HDAC Inhibitors (PEVOsq Trial - Nat Cancer 2025)

• Vulvar/vaginal cohort ORR: 19%
• Median OS: 17.5 months (best OS data in the field)
• 91% had any-grade treatment-related AE; 39% grade 3+
• Vorinostat dose reduction required in 66% due to toxicity
• Biomarker analysis: HDAC activation signatures, HLA expression predict response (ESMO 2025 presentation)
• Mechanism: HDAC inhibition reverses epigenetic silencing of immune genes, re-sensitizes "cold" tumors to PD-1 blockade

8.3 ICI + Radiation (CRT + Immunotherapy)

• Yeku et al. (Phase II): Pembrolizumab (200 mg IV q3w x12 cycles) + weekly cisplatin (40 mg/m²) + IMRT (68.4 Gy primary; 45 Gy pelvic/inguinal)
• ORR 75% in locally advanced setting - highest reported ORR in VSCC
• Rationale: radiation induces abscopal effect, enhances tumor antigenicity and PD-L1 upregulation, creating an "in situ vaccine" effect

8.4 ICI + Anti-Angiogenics

• Lenvatinib + Pembrolizumab (MITO VULVA-01, NCT07290894 - recruiting):
  • 3 cohorts: locally advanced treatment-naive, recurrent/metastatic chemo-naive, 2nd-line+
  • Lenvatinib 20 mg/day + pembrolizumab 200 mg q3w
  • Rationale: VEGFR/FGFR inhibition normalizes vasculature, reduces immunosuppressive M2 macrophages in TME

8.5 Dual Checkpoint Blockade (SWOG S1609 DART)

• Ipilimumab (1 mg/kg q6w) + Nivolumab (240 mg q2w) [PMID: 39561273]
• N=16, ORR 18.8%, CBR 25%, 3 durable responses >1 year
• Median OS 7.6 months; Grade 3-4 AE in 25%; one grade 5 death
• All responders had squamous histology; correlative biomarker studies ongoing

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9. Immune-Related Adverse Events (irAEs) in VSCC Immunotherapy

9.1 irAE Profile Table

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10. Special Considerations

10.1 HPV+ vs HPV- VSCC: Differential ICI Response

┌───────────────────────────────────────────────────────────────┐
│              HPV STATUS AND ICI RESPONSE                      │
├──────────────────────────┬────────────────────────────────────┤
│ HPV-POSITIVE VSCC        │ HPV-NEGATIVE VSCC                  │
├──────────────────────────┼────────────────────────────────────┤
│ • Inflamed TME           │ • "Desert" or "excluded" TME       │
│ • Higher TIL density     │ • Lower TIL density                │
│ • MHC-I expression       │ • MHC-I downregulation common      │
│   preserved              │ • Lichen sclerosus associated      │
│ • HPV oncoproteins E6/E7 │ • PD-L1 positivity paradoxically   │
│   as neoantigens         │   more frequent but less ICI       │
│ • More favorable ICI     │   responsive                       │
│   response (emerging)    │ • Lower overall ICI response       │
│ • UCPVax vaccine target  │ • May need combination strategies  │
│   (telomerase CD4 TH1    │   to overcome "cold" TME           │
│   inducer; VolATIL trial)│                                    │
└──────────────────────────┴────────────────────────────────────┘

10.2 Cemiplimab in VSCC

• Cemiplimab (anti-PD-1) has been reported in case reports for VSCC - including a notable case of induction chemotherapy with cemiplimab in a patient with coexistent vulvar cancer and autoimmune disease [PMID: 39252763]
• Demonstrates feasibility of ICI even in select autoimmune disease patients with careful monitoring
• No large trial data specific to VSCC yet; NCCN lists as "useful in certain circumstances" for some vulvar tumor subtypes

10.3 Therapeutic Vaccines (Emerging)

• UCPVax (telomerase-specific CD4 TH1-inducer cancer vaccine) + atezolizumab - VolATIL study (Phase II): targets HPV+ cancers including vulvar; aims to combine active vaccination with ICI to overcome low neoantigen load
• Therapeutic HPV vaccines targeting E6/E7 in HPV+ VSCC - preclinical and early clinical development

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11. Current Ongoing Trials (Active as of 2025-2026)

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12. Limitations and Future Directions

12.1 Current Limitations

┌─────────────────────────────────────────────────────────────────┐
│                    KEY LIMITATIONS                              │
├─────────────────────────────────────────────────────────────────┤
│ 1. Small sample sizes (most VSCC ICI trials: <20 vulvar pts)    │
│ 2. No randomized controlled trials in VSCC-specific ICI         │
│ 3. PD-L1 NOT reliably predictive in meta-analysis (ORR similar  │
│    in PD-L1+ and PD-L1- subgroups)                             │
│ 4. HPV status association not yet validated for selection        │
│ 5. Short mPFS (2.2 mo) despite durable responses in minority    │
│ 6. EMA has NOT approved ICIs for VSCC                           │
│ 7. Vorinostat combination: high toxicity (66% dose reduction)   │
│ 8. Lack of head-to-head comparisons                             │
│ 9. No validated predictive biomarker panel for VSCC             │
│10. Disease rarity limits accrual to biomarker-stratified RCTs   │
└─────────────────────────────────────────────────────────────────┘

12.2 Future Directions

┌─────────────────────────────────────────────────────────────────┐
│                 FUTURE RESEARCH PRIORITIES                      │
├─────────────────────────────────────────────────────────────────┤
│ BIOMARKER DEVELOPMENT                                           │
│ • Validate HLA expression and HDAC signatures as predictors     │
│ • Multiplex IHC for immune contexture (TIL density, CD8/Treg   │
│   ratio)                                                       │
│ • Integrate spatial transcriptomics of TME                      │
│                                                                 │
│ COMBINATION STRATEGIES                                          │
│ • ICI + LAG-3 inhibitors (relatlimab)                          │
│ • ICI + EGFR inhibitors (cetuximab - EGFR overexpressed 60-80%)│
│ • ICI + PARP inhibitors (DNA damage → immunogenic cell death)  │
│ • ICI + therapeutic HPV vaccines (neoantigen-directed)          │
│                                                                 │
│ CLINICAL TRIAL DESIGN                                           │
│ • Biomarker-stratified RCTs (urgently needed)                   │
│ • Window-of-opportunity trials (neoadjuvant ICI)                │
│ • Basket trials stratified by molecular subtype                 │
│ • International collaboration (due to rarity of VSCC)          │
└─────────────────────────────────────────────────────────────────┘

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13. Summary Evidence Table

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Key References

1. Maiorano MFP et al. Immunotherapy and Advanced Vulvar Cancer: A Systematic Review and Meta-Analysis of Survival and Safety Outcomes. Cancers. 2025 Jul;17(14):2392. PMID: 40723274
2. Chae YK et al. A Phase II Basket Trial of Dual Anti-CTLA-4 and Anti-PD-1 Blockade in Rare Tumors SWOG S1609: Vulvar Cancers. Clin Cancer Res. 2025 Jan 17. PMID: 39561273
3. Borcoman E et al. Efficacy of pembrolizumab and vorinostat combination in patients with recurrent and/or metastatic squamous cell carcinomas: a phase 2 basket trial. Nat Cancer. 2025 Aug. PMID: 40588522
4. Arenhardt MP et al. Efficacy and safety of targeted therapy and immunotherapy in advanced vulvar squamous cell carcinoma: A scoping review. Crit Rev Oncol Hematol. 2025 Jun. PMID: 40068805
5. Zafar M et al. Advances and Challenges in the Treatment of HPV-Associated Lower Genital Tract Cancers by Immune Checkpoint Blockers. Cancers. 2025 Apr. PMID: 40282436
6. Santoro A et al. The emerging and challenging role of PD-L1 in patients with gynecological cancers. Gynecol Oncol. 2024 May. PMID: 38295614
7. MITO VULVA-01 Trial. Pembrolizumab + Lenvatinib in Vulvar Cancer. NCT07290894. 2025.

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What This Overview Covers

Key Takeaways: