Among the causes of pain in this situation, where a diagnosis of recurrence has not yet being made with histopathological certainty, the following may warrant consideration – recurrent disease, neuropathic pain syndrome, pancreatitis in the remnant (trastuzumab related immune mediated – known but rare), visceral hypersensitivity and psychological distress. Interestingly, this situation characterized by the presence of previous surgery, chronic inflammation and repetitive nociceptive signaling is also ripe with the possibility of central and peripheral sensitization, which might be unrelated to tumor recurrence.

Clinical features that support involvement of coeliac plexus include epigastric location, radiation to the back and worsening after meals. Only partial response to opioids might point towards an underlying neuropathic component or sympathetically maintained pain. Anxiety related to the fear of recurrence activates vigilance mechanisms which perceive visceral sensations and might lead to lowering of pain thresholds.

A small node in the region of the coeliac plexus may lead to pain disproportionate to its size, though there is no documented size cut-off beyond which it assumes significance. To formulate a diagnoses of recurrent disease, other features such as FDG avidity, tumor marker elevation and CT scan findings need to be taken into consideration.

While, a 1-2 cm lymph node has the potential to cause symptoms by directly infiltration into neural tissue, compression of surrounding nerves, local inflammatory changes, and perineural spread, a sub-centimetric node, does not lend itself naturally to the designation of a pain generator and may shift the weight towards alternative etiological diagnoses.

The threshold beyond which an interventional pain procedure (coeliac plexus neurolysis) is indicated in the absence of documented disease recurrence and proportionate strong opioid dose escalation also remains a matter of some debate. A potentially difficult approach (post operative status) along with the possibility of impairment of neurolytic spread in the presence of anatomical distortion might also mar the success of the procedure. It is also to be borne in mind that data on the efficacy of coeliac plexus neurolysis has been derived from the pancreatic cancer population, distinct from the post-whipple setting, as in this case.

The answer to the question might not be straightforward and may lie in effective clinico-radiological correlation.

References

Ceyhan, G. O., Bergmann, F., Kadihasanoglu, M., Altintas, B., Demir, I. E., Hinz, U., Müller, M. W., Giese, T., Büchler, M. W., Giese, N. A., & Friess, H. (2009). Pancreatic neuropathy and neuropathic pain—A comprehensive pathomorphological study of 546 cases. Gastroenterology, 136(1), 177–186.e1. https://doi.org/10.1053/j.gastro.2008.09.029

Kwon, J. H. (2014). Overcoming barriers in cancer pain management. Journal of Clinical Oncology, 32(16), 1727–1733. https://doi.org/10.1200/JCO.2013.52.4827

Caraceni, A., Shkodra, M., & Kaasa, S. (2019). Cancer pain assessment and classification. Cancers, 11(4), 510. https://doi.org/10.3390/cancers11040510