A Prospective Phase II Clinical Trial of Stereotactic Ablative Radiotherapy for Metastatic Lymphadenopathy

Lymph node metastasis is one of the most common sites to develop disease recurrence or progression after initial local treatment for primary solid malignancies or systemic treatment for advanced metastases. No specific treatment modality has been established as the standard therapy. Systemic therapy is usually considered since lymphadenopathy is considered as a sign of disease dissemination though aggressive local treatment, including surgical lymphoadenectomy or radical radiotherapy might result in long-term survival in selected patients. The concept of stereotactic ablative radiotherapy (SABR), a high dose of radiation targeted to a pathological entity and delivered in a few fractions, has proven so successful at treating both benign and malignant lesions that it changed the paradigm for radiation therapy. The radiobiology of SABR has been shown to be very favorable for tumor control. Clinical experiences suggested that SABR might offer excellent in-field tumor control with low toxicity profile in selected patients, although the majority of reports are retrospective and include small patients series with heterogeneous tumor sites and dose-fractionation schedules.

At present, there is lack of validated prognostic factors to identify the patients who might benefit most from ablative local therapy for metastatic lymph node(s). The mechanism of effect of SABR on the cancer lesions is not yet clear. Apart from its direct effect on clonogenic cancer cells, an immune-mediated process was also hypothesized. Therefore, the present study is aimed to provide a better understanding about utilization of SABR for metastatic lymph node(s). The associated translational researches will also advance our knowledge in the immune system reactions to SABR.