How long would you continue chemotherapy for resectable pancreatic cancer not amenable to surgery due to functional status or comorbidity?

I think it depends upon the severity of functional limitations and comorbidites. If the patient can tolerate systemic therapy, I would favor the use of radiotherapy after an initial trial of systemic therapy (duration purposefully vague as it would be dictated by tolerance). I’ve generally favored SBRT for this specific circumstance as it’s generally well tolerated, the treatment schedule is more convenient, and local control is favorable. In those who cannot tolerate systemic therapy due to comorbidities, I typically reserve radiotherapy for palliation of local symptoms.