A. M. Dinaux1,2, R. Amri1,2, L. Bordeianou1,2, H. Kunitake1,2, D. L. Berger1,2 1Massachusetts General Hospital,Surgery,Boston, MA, USA 2Harvard School Of Medicine,Surgery,Brookline, MA, USA
Introduction:
Neoadjuvant therapy for patients with advanced stage rectal cancer remains the gold standard. Patients with either T3 or greater disease and/or suspected lymphadenopathy presently receive neoadjuvant chemoradiation. These patients have 3 possible outcomes to treatment. They can have a complete pathologic response. They can have a partial response and be pathologically node negative at surgery or they can have persistent disease with positive nodes. This abstract addresses outcomes in these groups.
Methods:
All patients with clinically AJCC-stage III who received neoadjuvant treatment were selected from an IRB-approved, retrospective, prospectively maintained database, which contains all surgically treated rectal cancer patients who received their surgery between 2004-2014 at a single center.
Results:
A total of 207 patients were clinically stage III based on preoperative imaging and received neoadjuvant treatment. Seventy-six of those still had nodal disease on pathology after treatment, compared to 131 nodal responders, of which 33 had a pathologic complete response. Compared to nodal responders with residual tumor, patients with positive nodes on pathology had higher rates of high-grade tumors (17.1% vs .4.1%; P=0.016), extramural vascular invasion (30.3% vs. 7.1%; P<0.001), perineural invasion (31.6% vs. 11.2%; P=0.001), large vessel invasion (27.6% vs. 7.1%; P<0.001) and small vessel invasion (27.6% vs. 10.2%; P=0.003). Distant metastatic recurrence percentage was also higher in the pN+ group (26.3% vs. 9.9%), with a shorter median disease free survival (18.5 months, IQR [8.7-32.3] vs. 32.3 [16.8-59.3]). Disease specific survival analysis showed a significant difference between clinically stage III patients with pathologic complete response, with residual tumor but no more nodal disease on pathology, and with persistent nodal disease. Previous mentioned groups are listed in order from best to worst survival in a Kaplan Meier-curve.
Conclusion:
Persistent nodal disease after neoadjuvant therapy is a very poor prognostic sign. Patients with residual nodal disease had significantly worse short and long-term oncological outcomes compared to those who had residual tumor but no positive lymph nodes. Considering that pathologically node positive patients showed higher rates of specific pathologic features, these features may be indicators of a poor response to neoadjuvant therapy. These prognostic factors may be detectable on preoperative assessments, biopsy and MRI. It is possible that these patients may benefit from receiving a full course of chemotherapy prior to surgical resection as they clearly have systemic disease.
