Opportunities for use of radiation therapy in penile cancer based on patterns of care in the United States from 2007 to 2013

Background: Radiation therapy (RT) is an effective modality for the treatment of squamous cell carcinomas of the penis. The National Comprehensive Cancer Network recommends consideration of primary radiation for penile preservation, in surgically unresectable tumors, and as adjuvant therapy for positive margins, bulky groin nodes or pelvic nodes. We performed a population-based analysis to evaluate the usage of RT in penile cancer from 2007 to 2013. Methods: We used the Surveillance, Epidemiology and End Results (SEER) database to identify men diagnosed with squamous cell carcinoma of the penis from 2007 to 2013. Patients were grouped as early stage (T1-T2N0), locally advanced (T3-T4N0), node-positive (T1xN1-3) and metastatic. We used linear regression model to test for factors associated with adjuvant radiation in node-positive patients. Results: We identified 2200 men diagnosed with penile cancer between 2007 and 2013. Of these, 66.4% had early stage, 10.7% had locally advanced, 15.5% had node-positive, 3.2% had metastatic cancer. Among patient with early stage cancer, RT was used in 14 patients (1.0%) and postoperative radiation in an additional 45 patients (3.1%). Among 340 patients with node-positive cancer, 62.1% received surgery alone, 5.6% radiation alone, 21.8% surgery with adjuvant radiation, and 10.6% neither surgery nor radiation. Of patients who had surgery, 26.0% had adjuvant radiation. On univariate analysis, higher nodal stage (N2-3 versus N1) was associated with adjuvant radiation (p = 0.02), while there was a trend for higher T-stage (T3/T4 versus T1/T2) (p = 0.08) and history of prior malignancy (p = 0.06). On multivariate analysis, only higher nodal stage (N2-3 versus N1) was associated with use of adjuvant radiation [hazard ratio (HR) 1.94, p = 0.03]. Conclusions: A small percentage of patient who are eligible for primary or adjuvant RT in the United States receive this treatment. Further work should be done to assess barriers to use of radiation in patients with penile cancer.