Influence of the radiotherapy target volume and prognostic factors on the results of treatment of patients with cervical lymph nodes metastases of squamous cell carcinoma of unknown primary

Introduction: The issues of the radiotherapy target volumes in cases of cervical lymph nodes metastases of squamous cell carcinoma of unknown primary (SCCUP) remain unresolved due to the lack of clinical studies. Escalation or de-escalation of treatment may be directly related to prognostic factors. Purpose of this study was to evaluate the results of treatment using ipsilateral (only involved side of the neck) or total (bilaterally neck and pharyngeal mucosa) radiation therapy (RT) and to analyze the influence of clinical factors on overall survival (OS) and progression-free survival (PFS).Methods: A retrospective non-randomized clinical trial was conducted. Two-year OS and PFS were assessed in 26 SCCUP patients, who underwent combined treatment, including radiation therapy. Inoperable patients received either definitive RT (3.85 %) or sequential chemoradiation therapy (CRT, 11.5 %), or concurrent CRT (3.85 %). Operable patients underwent neoadjuvant RT with lymph node dissection (34.6 %) or lymph node dissection with adjuvant RT (11.5 %) or adjuvant sequential CRT (7.7 %) or adjuvant concurrent CRT (27 %); 50 % of patients received RT in a dose of more than 60 Gy, in 50 % it was less than 60 Gy. In 54 % of patients, only the ipsilateral cervical lymph nodes were included in the irradiation volume while 46 % of patients received RT to the pharyngeal mucosa and lymph nodes of the neck bilaterally (total radiation therapy group).Results: The median follow-up was 17 months. The 2-year OS was 71.5 % (95 % CI 49.3-85.3 %), the 2-year PFS was 72.1 % (95 % CI 44.5-87.6 %). There were no significant differences in 2-year OS between the ipsilateral and total radiotherapy groups (HR = 1.08 [0.29-4.06], p = 0.904). Only a factor of extranodal extension (ENE) had a statistically significant impact on OS (HR = 6.05 [1.45-25.19], p = 0.0134).Conclusion: There was no statistically significant difference in 2-year OS and PFS between the ipsilateral and total radiation therapy groups. A negative prognostic factor is the extranodal extension (ENE) of a metastatic tumor. Prospective randomized trials are needed.