Findings support adjuvant radiotherapy in cSCC with perineural invasion

Patients with cutaneous squamous cell carcinoma with perineural invasion who underwent adjuvant radiotherapy in addition to Mohs micrographic surgery experienced improved outcomes compared with patients who underwent surgery alone.

Mary L. Stevenson, MD, of The Ronald O. Perelman Department of Dermatology at New York University School of Medicine, and colleagues suggested that perineural invasion in cutaneous squamous cell carcinoma (cSCC) carries elevated risks for local recurrence, nodal metastases and disease-specific death. “Adjuvant radiotherapy has been suggested to mitigate aggressive behavior of cSCC with perineural invasion,” they wrote in a research letter in JAMA Dermatology.

The current study included 31 patients with histologically confirmed cSCC at New York University between Jan. 1, 2005, and Dec. 31, 2014.

Patients were treated surgically with or without adjuvant radiotherapy and assessed for outcome measures of local recurrence, nodal metastases, distant metastases and disease-free survival.

The cohort was 77.4% men with a mean age of 70.8 years. Mohs micrographic surgery yielded negative surgical margins in all patients in the cohort.

Despite the entire cohort being recommended for adjuvant radiotherapy, only 48.4% of patients completed the treatment regimen, which ranged from 1,500 cGy to 6,000 cGy over 10 to 30 treatment sessions.

Results showed that no cases of local recurrence occurred by 5 years of follow-up.

No patients who underwent adjuvant radiotherapy experienced nodal metastases compared with five patients in the surgery-alone group who experienced this outcome (P = .02).

The researchers observed estimated 5-year disease-free survival rates of 100% (95% CI, 100%-100%) for patients in the adjuvant radiotherapy group and 68.8% (95% CI, 60.9%-76.7%) for no adjuvant radiotherapy (P = .01).

Among the five patients with nodal metastases, large-diameter perineural invasion was reported in 80%. Moreover, all of those patients had at least one additional high-risk feature.

The overall rate of large-caliber perineural invasion in this cohort was 71%.

Results also showed that one patient had small-diameter perineural invasion. This individual “had additional high-risk features of tumor size greater than 2 cm, invasion beyond the subcutaneous fat and location on the temple,” according to the researchers.

Other findings showed that 80% of patients with nodal metastases had T2b tumors as defined by Brigham & Women’s Hospital staging, while one patient had a T3 tumor.

Safety data showed that six patients developed mild dermatitis associated with adjuvant radiotherapy.

“Our data support the use of adjuvant radiotherapy for cSCC with perineural invasion and highlight the need to stratify patients at highest risk in an effort to identify those who might benefit from adjuvant radiotherapy to mitigate the risk of metastasis,” the researchers wrote. They noted that current recommendations call for adjuvant radiotherapy in cSCC with substantial perineural invasion. “Adjuvant radiotherapy may improve prognosis for patients with small-caliber perineural invasion in the setting of additional high-risk features and should be considered.”