Community Oncologist

I have a 54-year-old woman diagnosed with stage IIIA colon cancer in 2019, s/p sigmoidectomy and adjuvant FOLFOX x6 months. She has been on surveillance with no evidence of disease recurrence until recently when she was found to have a <1 cm nodule in the lung that grew to 1 cm on subsequent scan. It was surgically resected and showed metastatic CRC. She is young but has many other medical issues, including severe anxiety/depression and history of papillary thyroid cancer (treated and not active currently). There is no other evidence of metastatic disease. What should be done next? NCCN guidelines recommend observation for metachronous mets that is completely resected in someone who previously received chemotherapy, but others have suggested that adjuvant chemotherapy should be given. Might there be a role for ctDNA in this case, despite it not being FDA approved or part of any current guidelines?

GI Cancer Specialist

What was the official disease free interval? When was the lung met resection and when were the last restaging scans? Do you have a CEA pre & post op? Generally, if dealing with a single pulm met, the size and disease-free interval can be helpful to risk-stratify. Given the size of the single pulm met (1cm), the disease free interval (>1 yr since end adjuvant), I wouldn't be offering further chemo for now unless there is concern about disease left behind (+margin, or other suspicious areas on scan). I think it would be reasonable to do more short interval restaging scans initially (q2 mo) during this early period of surveillance. Would ensure she gets NGS sent off on the tumor (if sufficient yield to do so). If there isn't sufficient tissue for this testing, then would do ctDNA for mutation assessment to inform systemic therapy if/when needed down the road, but would caution using this alone to determine whether or not to do post-op systemic therapy. A negative ctDNA will be reassuring, yes, but a positive ctDNA at this point (if otherwise wouldn't be treating with systemic therapy) will be more anxiety-inducing than anything else. Found this reference to be helpful:

[Community Oncologist Follow up - Thank you for the article reference, that is helpful. To answer your questions, her disease-free interval was almost 3.5 years. Lung met resection was in 2023. She had a PET in 2022 (lung nodule not avid) and just had restaging a few weeks ago. CEA prior to sigmoidectomy in 2019 was 3.2 and has remained in the 2-3 range during her interval surveillance, including most recently. NGS from the lung met is pending.

Specialist Response - Hope she continues to do well. Please reach back out if there are new developments. I would be comfortable just watching her closely for now.]