Para-Aortic Nodal Irradiation: Practical Concerns for the Radiation Oncologist

Abstract

TO THE EDITOR: Gouy et al recently reported a prospective study in locally advanced cervical cancer in which patients with negative positron emission tomography-computed tomography (PET/CT) of the para-aortic (PA) area underwent laparoscopic PA staging. The authors found a 12% false negative rate of PET/CT in the PA region. Prognostic factors of PA nodal involvement included the presence of pelvic uptake on PET/CT. The authors found that the rate of pathologically positive PA nodes was 9% in those with negative pelvic lymph nodes and 24% in those with positive pelvic nodes by PET/CT. These rates are similar to those from other published reports. The implication for the radiation oncologist is multifold. In patients who are found to have positive pelvic nodes on PET/CT and do not undergo surgical PA staging, the risk of PA nodal involvement is sufficiently high to warrant extended field radiation therapy. In addition, there appears to be a subset of those with negative pelvic nodes by PET/CT who harbor PA nodal disease and may be receiving insufficient treatment. To clarify some of the practical ramifications, we have several questions for the authors. First, In the subset of patients with negative pelvic lymph nodes and positive PA nodes, what was ithe distribution of size of the nodal metastases? In the entire cohort, the authors found that those with PA nodal metastases 5 mm had outcomes comparable to those without PA nodal disease. If the PA disease is primarily microscopic in the subset, perhaps it is reasonable to expect chemotherapy to sterilize this disease. Otherwise, perhaps treatment intensification is required in a subset of those with radiographically nodenegative disease. Second, we are interested to learn whether the authors could identify any subset of patients with positive pelvic nodes in whom PA nodal irradiation may be excluded. We hypothesize that in patients with few involved pelvic lymph nodes or with lower location of pelvic nodal disease (as compared with common iliac nodal involvement), the risk of positive PA disease may be lower. Such data is important for optimal treatment decision making in these patients until the results of prospective randomized studies clarifying the role of PA nodal staging are available.