Lymph Node Yield After Neoadjuvant Chemoradiotherapy in Rectal Cancer Specimens: A Randomized Trial Comparing Two...

Area of Science:

• Oncology
• Surgical Pathology
• Cancer Research

Background:

• Neoadjuvant chemoradiation is known to reduce lymph node yield in rectal cancer specimens.
• The adequacy of ≥12 lymph nodes for accurate staging is debated, with fewer nodes potentially leading to understaging and worse survival.
• Diligent specimen analysis has been shown to increase lymph node counts.

Purpose of the Study:

• To compare the effectiveness of Carnoy's solution versus formalin in enhancing lymph node yield from rectal cancer specimens post-neoadjuvant chemoradiation.
• To evaluate the impact of different fixation methods on achieving adequate lymph node counts for staging.

Main Methods:

• A prospective randomized trial involving 130 rectal cancer patients undergoing low anterior resection with total mesorectal excision post-neoadjuvant chemoradiation.
• Rectosigmoid specimens were randomized for fixation with either Carnoy's solution or formalin.
• A revision step involved immersing formalin-fixed specimens in Carnoy's solution to identify missed lymph nodes.

Main Results:

• Carnoy's solution yielded a significantly higher lymph node count (24.0) compared to formalin (16.3) (p < 0.01).
• Fewer specimens in the Carnoy's group had <12 lymph nodes (6 vs 22, p = 0.001).
• The revision step identified an average of 11.1 additional lymph nodes, reducing cases with <12 nodes from 33.8% to 4.6% and upstaging 2 patients.

Conclusions:

• Carnoy's solution is superior to formalin for increasing lymph node count in rectal cancer specimens after neoadjuvant chemoradiation.
• Routine analysis misses clinically relevant lymph nodes, highlighting the importance of improved retrieval methods.
• A low lymph node count (<12) does not indicate a good response to neoadjuvant chemoradiation.