Radiation Therapy is Strongly Indicated for This High-Risk Squamous Cell Carcinoma
Adjuvant radiation therapy is definitively indicated for this patient given the presence of perineural invasion, large tumor size (8.5 × 5 cm), significant depth (2.2 cm extending to subcutaneous tissue), and high-risk anatomic location (gluteal region). 1
Primary Indication: Perineural Invasion
- Perineural invasion alone is an absolute indication for adjuvant radiation therapy according to the National Comprehensive Cancer Network guidelines, as this represents substantial perineural involvement requiring postoperative radiotherapy. 1
- Local control approaches 100% in select patients with postoperative radiation therapy for perineural invasion, making this a critical intervention. 1
- Perineural invasion is a significant concern that requires careful evaluation and monitoring, particularly given the potential for neurologic symptoms and disease progression. 2
Additional High-Risk Features Supporting Radiation
Tumor Size and Depth
- This tumor exceeds the 2 cm diameter threshold that defines high-risk disease, with tumors >2 cm having significantly higher recurrence and metastasis rates. 2, 3
- The 2.2 cm depth far exceeds the 2 mm threshold for high-risk classification and approaches the 8 mm depth where elective lymph node dissection has been considered. 4, 3
- Tumors with depth >4 mm have substantially higher recurrence and metastasis rates, and this lesion is 22 mm deep. 2
Subcutaneous Extension
- Extension into subcutaneous tissue represents deep invasion requiring wider surgical margins (6 mm or more) and consideration for adjuvant therapy. 4
- Tumors extending into subcutaneous tissue are classified as high-risk and warrant more aggressive management. 4
Anatomic Location
- The gluteal region, while not traditionally classified with facial high-risk sites, presents unique challenges for achieving adequate margins and has been associated with aggressive disease behavior in case reports. 5, 6
Recommended Radiation Dosing
The standard postoperative adjuvant radiation dosing is 50 Gy in 20 fractions over 4 weeks or 60 Gy in 30 fractions over 6 weeks. 1
- For this patient with multiple high-risk features including perineural invasion and deep subcutaneous extension, the higher dose regimen of 60 Gy in 30 fractions over 6 weeks would be appropriate. 1
- Each treatment session involves only 1-5 minutes of actual radiation exposure, though appointments typically take 15-30 minutes. 7
Consideration for Concurrent Chemotherapy
- Concurrent chemotherapy should be reserved for patients with extracapsular extension in lymph nodes, which is not described in this case. 1
- Without nodal involvement or extracapsular extension documented, radiation therapy alone is the appropriate adjuvant treatment. 1
Critical Prognostic Context
- Despite optimal treatment with resection followed by radiation therapy, high-risk patients still experience locoregional recurrence, distant metastasis, and reduced 5-year survival of approximately 40%. 1
- The combination of large size, deep invasion, perineural involvement, and subcutaneous extension places this patient in the highest risk category. 3, 8
Lymph Node Evaluation
- A lymph node ultrasound is highly recommended for tumors with high-risk characteristics such as this one, particularly given the depth and perineural invasion. 8
- If clinical suspicion or positive imaging findings emerge, histologic confirmation should be obtained by fine needle aspiration or open lymph node biopsy. 8
- Postoperative radiation is recommended for all patients with nodal involvement, and should be considered for regional disease of the trunk and extremities who have undergone lymph node dissection. 1