The fine line between regional and metastatic pelvic lymph nodes in rectal cancer: Patterns of care among U.S. radiation oncologists.

758 Background: Management of rectal cancer with involved lateral pelvic lymph nodes (LPLNs) at the time of diagnosis – the stage we refer institutionally to as Stage 3.5 – is controversial. Asian investigators consider internal, external and common iliac lymph nodes (LNs) as regional disease and treat these patients (pts) with curative intent, which often includes LPLN dissection. Conversely, AJCC 7thedition classifies internal iliac LNs as regional, whereas both external and common iliac LNs as metastatic. NCCN guidelines recommend definitive trimodality therapy for Stage III rectal cancer, and palliative chemotherapy for Stage IV disease. Radiation oncologists (ROs) in the U.S. irradiate iliac LNs in the setting of other pelvic malignancies, but it is unknown how they approach newly diagnosed rectal cancer pts with LPLN involvement. Methods: We conducted an anonymous IRB-approved online survey of practicing U.S. ROs, probing their approach to management of rectal cancer pts with clinically involved LPLNs. Results: We received 220 responses. Among the responders, 85 are academically affiliated and the majority self-declared a specialization in treating GI malignancies, with 98 seeing more than 10 rectal cancer pts annually. Among respondents, 10.5% and 34.2% recommend biopsy of clinically involved internal and common iliac LNs, respectively. The vast majority of responders – 98.6% and 94.5% – treat involved internal and common iliac LNs with curative intent, respectively. Respondents recommend treatment intensification to involved internal iliac LNs by dissection of the nodal basin (88.2%) and radiation therapy (RT) boost (59.1%), and treatment intensification to involved common iliac LNs by LN dissection (76.4%) and RT boost (63.6%). Conclusions: Our analysis reveals that the vast majority of surveyed U.S. ROs approach pts with involved LPLNs, both regional (internal iliac) and metastatic (i.e. common iliac) with curative intent. They recommend treatment intensification with surgical resection and/or RT boost to involved nodes. Prospective clinical trials need to determine the appropriate management of pts with Stage 3.5 rectal cancer.