Metastatic skin squamous cell carcinoma represents one of the most serious forms of skin cancer, occurring when cancer cells spread beyond their original location to other parts of the body. While most squamous cell carcinomas are caught and treated early, those that become metastatic require complex treatment approaches combining surgery, radiation, and newer therapies designed to help the immune system fight cancer.

Understanding Treatment Goals for Advanced Skin Squamous Cell Carcinoma

When squamous cell carcinoma spreads beyond the skin to lymph nodes or distant organs, the treatment approach becomes more complex than with early-stage disease. The main goals of treating metastatic squamous cell carcinoma include controlling the cancer’s growth, reducing symptoms, preventing further spread, and improving quality of life. Treatment decisions depend on several factors, including where the cancer has spread, how large the tumors are, the patient’s overall health, and whether the cancer has been treated before.^[1]

Medical professionals now recognize that about five percent of skin squamous cell carcinomas advance to a stage where they become far more dangerous and challenging to treat. These advanced cases include locally advanced tumors—which are large or have grown deep into tissues, muscles, or nerves—and metastatic tumors, which have spread beyond the original site to other parts of the body such as lymph nodes or distant organs. These tumors can be life-threatening and require immediate, comprehensive medical attention.^[4]

Today, doctors follow treatment guidelines approved by medical societies and rely on a combination of proven therapies and emerging research. Clinical trials are exploring new medications and treatment strategies that may offer hope to patients whose cancer has not responded to standard approaches or has returned after initial treatment. The field is advancing rapidly, particularly with the development of therapies that harness the body’s immune system to fight cancer cells more effectively.^[5]

Standard Treatment Approaches for Metastatic Disease

The treatment of metastatic skin squamous cell carcinoma traditionally begins with an evaluation by a multidisciplinary team. This team typically includes dermatologists, surgical specialists, radiation oncologists, and medical oncologists who work together to create a personalized treatment plan. The first step involves determining whether surgery or radiation therapy can be used to remove or destroy the cancer.^[6]

When tumors can be surgically removed, excisional surgery is often the preferred approach. This procedure involves cutting out the cancer along with a margin of healthy tissue around it to ensure all cancer cells are removed. For larger or more complex tumors, a specialized technique called Mohs surgery may be used. During Mohs surgery, the surgeon removes thin layers of tissue one at a time, examining each layer under a microscope until no cancer cells remain. This method helps preserve as much healthy tissue as possible while ensuring complete removal of the cancer.^[8]

Radiation therapy uses high-energy beams to destroy cancer cells and shrink tumors. It can be used as a primary treatment when surgery is not possible due to the tumor’s location or size, or after surgery to eliminate any remaining cancer cells. Radiation is delivered in carefully planned doses over several weeks, targeting the tumor while trying to minimize damage to surrounding healthy tissue. Side effects of radiation therapy may include skin irritation, fatigue, and changes to the treated area that can persist after treatment ends.^[8]

Historically, various chemotherapy regimens have been tried for metastatic squamous cell carcinoma, though without rigorous clinical trials to establish their effectiveness. Drugs such as cisplatin (a platinum-based agent that damages cancer cell DNA), fluoropyrimidines (which interfere with cancer cell growth), bleomycin, and doxorubicin have shown some activity in small studies. These medications work by targeting rapidly dividing cells, but they also affect healthy cells that divide quickly, leading to side effects like nausea, hair loss, fatigue, and increased infection risk.^[7]

Combination therapies have also been explored. One randomized trial tested the use of interferon-alpha-2a (a protein that stimulates the immune system) combined with 13-cis-retinoic acid (a vitamin A derivative) after surgery in patients at high risk of recurrence. This study enrolled sixty-six patients but found that the treatment did not improve time to recurrence or prevent new skin cancers from developing. While this study was not conducted in patients with active metastatic disease, its results raised questions about the ability of this combination to control advanced cancer.^[7]

Immunotherapy: A Major Advance in Clinical Trials

The field of immunotherapy has brought new hope to patients with advanced and metastatic squamous cell carcinoma. Unlike traditional chemotherapy that directly attacks cancer cells, immunotherapy works by helping the patient’s own immune system recognize and destroy cancer cells. The immune system normally protects the body from infections and abnormal cells, but cancer cells can develop ways to hide from immune surveillance. Immunotherapy removes these hiding mechanisms, allowing immune cells to attack the tumor.^[4]

The most promising immunotherapies for metastatic skin squamous cell carcinoma are PD-1 inhibitors. These medications target a protein called PD-1 (programmed death-1) found on the surface of immune cells called T-cells. Cancer cells can produce a molecule called PD-L1 that binds to PD-1, essentially turning off the T-cells and preventing them from attacking the tumor. By blocking this interaction, PD-1 inhibitors keep T-cells active and able to fight cancer cells.^[10]

Two PD-1 inhibitors have shown particularly encouraging results in clinical trials: cemiplimab and pembrolizumab. Both medications are administered through intravenous infusion, typically every few weeks. Clinical studies have demonstrated that these drugs can produce responses in patients with advanced disease, including cases where previous treatments had failed. Patients receiving these medications in trials have experienced tumor shrinkage and improved clinical parameters in a significant percentage of cases.^[10]

Cemiplimab has been specifically studied in Phase II and Phase III clinical trials for advanced cutaneous squamous cell carcinoma. Phase II trials focus on determining whether a drug works against a specific type of cancer and what dose should be used, while Phase III trials compare the new treatment against the current standard of care in larger groups of patients. Results from these studies have shown that cemiplimab can be effective in both locally advanced and metastatic disease, with some patients experiencing long-lasting responses.^[17]

Pembrolizumab, another PD-1 inhibitor originally approved for melanoma and other cancers, has also demonstrated activity against metastatic squamous cell carcinoma in clinical trials. Studies evaluating pembrolizumab have included patients whose tumors were not amenable to surgery or radiation therapy, providing evidence that immunotherapy can serve as a first-line treatment option for these advanced cases.^[10]

The mechanism of action of these immunotherapy drugs differs fundamentally from chemotherapy. Rather than directly killing cancer cells, they essentially teach the immune system to do its job more effectively. This approach can lead to durable responses—meaning the cancer stays under control for extended periods—even after treatment is stopped in some cases. However, this immune activation can also cause side effects related to overactive immune responses, such as inflammation of the lungs, intestines, liver, or other organs. These side effects require careful monitoring and may need to be managed with medications that suppress the immune system temporarily.^[17]

Targeting Growth Signals: EGFR Inhibitors

Another promising area of research involves targeting the epidermal growth factor receptor (EGFR), a protein found on the surface of many cells. In normal cells, EGFR helps regulate cell growth and division. However, many squamous cell carcinomas have abnormally high levels of EGFR on their surface, which can drive cancer cell growth and survival. Research has shown that the presence of high EGFR levels appears to be associated with worse outcomes in patients with squamous cell carcinoma.^[7]

Several medications that block EGFR have been tested in clinical trials for advanced squamous cell carcinoma. These include cetuximab, an antibody that attaches to EGFR on the cell surface, and small molecule drugs like erlotinib and gefitinib that block the signaling pathway inside cells. Early Phase II clinical trials and case reports have shown preliminary evidence that these drugs can have antitumor activity in patients with metastatic disease.^[7]

Cetuximab is given through intravenous infusion, while erlotinib and gefitinib are taken as oral pills. These medications work by preventing growth signals from reaching cancer cells, essentially starving them of the signals they need to grow and divide. Side effects of EGFR inhibitors often include skin rashes, diarrhea, and nail changes, which occur because EGFR is also present in normal skin and digestive tract cells. These side effects can be managed with supportive care medications and dose adjustments.^[5]

While EGFR inhibitors have shown promise in early studies, they have not been as extensively studied as immunotherapy drugs for this indication. Many oncologists consider them as potential options when immunotherapy is not suitable or has stopped working, though more rigorous randomized trials are needed to establish their proper role in treatment.^[7]

Clinical Trial Access and Eligibility

Clinical trials for metastatic squamous cell carcinoma are being conducted at major cancer centers throughout the United States, Europe, and other parts of the world. Patients interested in participating in clinical trials typically need to meet specific eligibility criteria, which may include the stage and extent of their cancer, previous treatments received, overall health status, and specific characteristics of their tumor.^[5]

Eligibility for trials often depends on whether the cancer can be surgically removed or treated with radiation. Trials for immunotherapy and other systemic treatments usually enroll patients whose tumors are unresectable (cannot be removed with surgery) or who have metastatic disease that has spread to lymph nodes or distant organs. Some trials specifically recruit patients who have not received any prior systemic therapy, while others accept patients whose cancer has progressed despite previous treatments.^[10]

The process of enrolling in a clinical trial begins with a comprehensive evaluation that may include imaging studies, blood tests, and sometimes genetic testing of the tumor. Some newer trials use genomic testing, which analyzes the DNA of cancer cells to identify specific mutations or characteristics that might predict which treatments will work best. This personalized approach to cancer care is helping doctors make more informed decisions about treatment selection.^[4]

Most common treatment methods

• Surgery
  • Excisional surgery to remove tumors along with surrounding healthy tissue margins
  • Mohs surgery for complex cases, removing thin layers and examining each microscopically
  • Used when tumors can be completely removed and in operable locations
• Radiation Therapy
  • High-energy beams delivered over several weeks to destroy cancer cells
  • Primary treatment when surgery is not possible due to tumor size or location
  • Adjuvant therapy after surgery to eliminate remaining cancer cells
  • May cause skin irritation, fatigue, and tissue changes
• Immunotherapy
  • PD-1 inhibitors including cemiplimab and pembrolizumab
  • Works by removing cancer’s ability to hide from the immune system
  • Given through intravenous infusion every few weeks
  • Can produce durable responses in advanced disease
  • May cause immune-related side effects requiring monitoring
• Chemotherapy
  • Cisplatin—platinum-based drug that damages cancer cell DNA
  • Fluoropyrimidines—interfere with cancer cell growth processes
  • Bleomycin and doxorubicin—cytotoxic agents used in various combinations
  • Causes side effects including nausea, hair loss, and increased infection risk
  • Limited rigorous evidence for effectiveness in metastatic disease
• Targeted Therapy
  • EGFR inhibitors such as cetuximab, erlotinib, and gefitinib
  • Block growth signals that cancer cells need to multiply
  • Cetuximab given by infusion; erlotinib and gefitinib taken orally
  • Common side effects include skin rash, diarrhea, and nail changes
  • Preliminary evidence of antitumor activity in Phase II trials

Determining Treatment Duration and Follow-Up Care

The duration of treatment for metastatic squamous cell carcinoma varies considerably depending on the specific therapies used and how the cancer responds. Immunotherapy treatments are typically continued as long as the patient is experiencing benefit and tolerating the medication without serious side effects. Some patients may receive treatment for many months or even years if the cancer remains under control.^[17]

Radiation therapy is usually given over a defined period, commonly spanning several weeks with treatments five days per week. The total dose is divided into smaller daily doses (called fractions) to allow normal tissues time to recover between treatments while maintaining pressure on cancer cells. After completing the planned radiation course, patients undergo regular monitoring to assess the treatment’s effectiveness.^[8]

Chemotherapy regimens, when used, are typically given in cycles with periods of treatment followed by rest periods to allow the body to recover. The number of cycles depends on how well the cancer responds and how well the patient tolerates the side effects. Treatment may continue for several months or until the cancer progresses or side effects become too severe.^[5]

Throughout treatment and afterward, patients require regular follow-up appointments that include physical examinations, imaging studies such as CT scans or PET scans to check for cancer growth or spread, and blood tests to monitor overall health and detect any treatment-related complications. The frequency of these visits is typically highest in the first few years after treatment, when the risk of recurrence is greatest, and may gradually decrease over time.^[16]

Managing Side Effects and Quality of Life

Side effects from treatment for metastatic squamous cell carcinoma can significantly impact quality of life, and modern cancer care emphasizes managing these effects as an integral part of treatment. Each type of therapy carries its own potential side effects that patients and doctors must watch for and address promptly.^[7]

Surgery side effects depend on the location and extent of the procedure but may include pain, infection risk, scarring, and loss of function if the tumor involved important structures. When surgery is performed on the head and neck—common locations for metastatic spread—it may affect appearance, speech, or swallowing. Reconstructive surgery techniques can help restore function and appearance in many cases.^[8]

Radiation therapy side effects typically develop gradually during treatment and may continue for weeks afterward. Skin in the treatment area may become red, dry, and sensitive, similar to a sunburn. Fatigue is common and may persist after treatment ends. When radiation is directed at the head and neck region, patients may experience dry mouth, difficulty swallowing, changes in taste, and dental problems. These effects require supportive care including moisturizers, pain medications, nutritional support, and dental care.^[8]

Immunotherapy side effects result from the activated immune system attacking normal tissues along with cancer cells. Common side effects include fatigue, skin rash, diarrhea, and inflammation of various organs such as the thyroid gland, lungs, liver, or intestines. These immune-related adverse events can range from mild to severe and may require treatment with corticosteroids or other immune-suppressing medications. Patients receiving immunotherapy need education about symptoms to watch for and when to seek immediate medical attention.^[10]

EGFR inhibitor side effects frequently involve the skin, as EGFR is naturally present in skin cells. An acne-like rash on the face and upper body is very common and may actually indicate that the drug is working. Other side effects include diarrhea, nail changes, and dry skin. These effects can often be managed with topical medications, antibiotics for infected rashes, and antidiarrheal medications.^[5]

The Importance of Multidisciplinary Care

Modern treatment of metastatic squamous cell carcinoma relies on a team approach involving specialists from multiple fields. When a patient is diagnosed with advanced disease, the treating physician typically recommends evaluation by a multidisciplinary team. This collaboration ensures that all treatment options are considered and that the chosen approach is best suited to the individual patient’s situation.^[6]

The multidisciplinary team typically includes dermatologists who specialize in skin cancer, Mohs surgeons skilled in complex skin cancer removal, medical oncologists who manage systemic therapies like chemotherapy and immunotherapy, radiation oncologists who plan and deliver radiation treatments, and surgical specialists who can perform complex reconstructive procedures. Other team members may include pathologists who examine tissue samples, radiologists who interpret imaging studies, and support staff such as nurses, nutritionists, social workers, and counselors.^[4]

This team approach is particularly valuable because metastatic squamous cell carcinoma often requires multiple treatment modalities used in sequence or combination. The team meets regularly to discuss individual cases, review test results and imaging studies, and develop comprehensive treatment plans. They consider not only the medical aspects of treatment but also factors such as the patient’s preferences, overall health status, other medical conditions, and personal circumstances.^[16]

Genomic testing has become an increasingly important tool for multidisciplinary teams. By analyzing the genetic characteristics of an individual’s tumor, doctors can sometimes identify specific mutations or biomarkers that predict which treatments are most likely to be effective. This personalized medicine approach helps guide treatment selection and may identify clinical trials that could benefit specific patients.^[4]

Prognosis and Factors Affecting Outcomes

The outlook for patients with metastatic squamous cell carcinoma has improved with the advent of immunotherapy and other advanced treatments, though it remains a serious condition requiring aggressive management. Several factors influence prognosis, including the extent of cancer spread, the patient’s overall health, whether the cancer has been previously treated, and how well it responds to therapy.^[2]

Tumors that have spread to nearby lymph nodes generally have a better prognosis than those that have spread to distant organs such as the lungs, liver, or bones. The number of lymph nodes involved and whether cancer has broken through the lymph node capsule also affect outcomes. These prognostic factors help doctors estimate likely outcomes and guide treatment intensity.^[16]

Patient-related factors also play an important role. Younger patients and those in better overall health typically tolerate aggressive treatments better and may have improved outcomes. Patients with weakened immune systems—such as organ transplant recipients who must take immunosuppressive medications—face additional challenges, as their immune systems are less able to fight cancer even with immunotherapy support.^[3]

The three-year disease-specific survival rate for cutaneous squamous cell carcinoma after definitive treatment is approximately eighty-five percent overall, though this figure includes all stages of disease. Metastatic disease carries a more serious prognosis, making aggressive treatment and close monitoring essential. However, the availability of effective immunotherapy has provided new hope and improved outcomes for many patients with advanced disease.^[2]