ASO Author Reflections: Lymph Node Station 16 Status—Becoming a Student of Your Patients’ Cancer

PAST

The prognosis in gastrointestinal (GI) (gastrointestinal, colorectal, pancreatic, and hepatobiliary) cancers has been improving at various rates (GI and colorectal more than pancreatic).¹ While there is differential improvement when comparing different cancers with each other, when comparing outcomes of the same cancer type, in general, all patients who undergo complete cancer resection fare better compared with patients who undergo palliative treatment. Hence, facilitating the appropriate patient to undergo complete resection is at the center of improved prognosis. The appropriate patient is selected by having a deep understanding of tumor biology and spread. Therefore, becoming a student of your patients’ cancer is the essence of accurately selecting a patient for radical surgery. This avoids harming the patient with cancer surgery in the spirit of the socalled Hippocratic injunction primum non nocere (unlikely attributable to either Hippocrates or Galen but possibly the English physician Sydenham in 1860). While it is intuitive that the trauma of unnecessary surgery is not only unhelpful, but also harmful, how do we avoid unhelpful surgery that may harm and not help patients? In this context, we have developed the ABCD acronym that helps us to remember and discuss among cancer care providers the components of accurate risk stratification for cancer surgery: A—Anatomy (technical feasibility),² B—Biology (genetics and lymph node status),³ C—Chemotherapy (response to systemic treatment),⁴ D—Disparity (social determinants of health interfering with cancer treatment).⁵

PRESENT

At the heart of B (tumor biology) of the ABCD acronym, surgeons play a vital role in providing critical information through assessment of lymphatic spread as one important determinant for prognostication. More specifically, aortocaval lymph node station 16 involvement is often overlooked during lymphadenectomy but should influence the decision of whether to proceed with oncologic surgery. For instance, a positive station 16 lymph node is associated with a poor 2-year survival of 3% in patients with pancreas adenocarcinoma (PDAC), akin to stage IV disease.¹ It is our practice to dissect station 16 during pancreaticoduodenectomy for PDAC early and proceed only in a few select cases if station 16 is positive on frozen section analysis. Similarly, we have shown for gallbladder cancer that involvement of station 16 cannot be predicted from hepatoduodenal ligament lymph nodes and hence station 16 should be harvested.³ Thus, station 16 involvement plays a critical factor for risk/benefit stratification of whether to move forward with radical surgery. While the posterior retroperitoneal location, flanked by aorta and inferior vena cava (IVC) of station 16, can make its harvest challenging, its dissection can be accomplished safely if the strategic and stepwise approach we have shown is followed.² In this context, the caudal view of minimally invasive surgery, where the viewing axis aligns with the IVC, may facilitate a safe station 16 dissection.

FUTURE

The more precisely we can risk/benefit stratify cancers, the more favorable the oncologic surgical outcomes. One piece of information (e.g., genomics) or a snapshot in time (e.g., original extend of the tumor at diagnosis) is not as precise as following the tumor over time and collecting multiple data points (e.g., response to neoadjuvant therapy, mapping the lymphatic spread at oncologic surgery), hence the importance of becoming a student of the patients’ cancer. While intraoperative mapping of lymphatic spread, including station 16, has served us well in gathering an additional data point to deeply understand our patients’ cancers, the future will move beyond harvesting a lymph node station to determine, binarily, whether it is positive or negative. The future will involve real-time in vivo assessment using, for example, fast infrared spectroscopic laser scanning confocal microscopy⁶ that examines the chemical basis of disease without reagents or human supervision or using real-time chemical imaging with machine learning to provide fast, gold-standard pathology information.⁷ Once these technologies are miniaturized for minimally invasive application, harvesting lymph node stations with its associated risk will be obviated.