I've been battling stage 4 ESCC for 7yrs. I have undergone several rounds of intensive radiotherapy, chemotherapies (FOLFOX and FOLFIRI) immunotherapies
(Pembrolizumab and panitumamab). While I've been fortunate enough to achieve several excellent responses to these various treatments, including a period of > 2 yrs of PET and CT-MIPs scans that showed NED. Theses series of treatments while modestly effective at providing disease control take a debilitating toll upon your body. They oxyplatin component of FOLFOX causes peripheral neuropathy, neutropenia, and vasculopathies.

The irinotecan component of FOLFIRI may increase risks of bone marrow dysfunction and risk of myelofibrosis and cerebellar/neurologic dysfunction.

All of the monoclonal immunotherapies also have significant adverse events associated with them including the development of infusion site reactions, anaphylaxis, cardioxicities and the development of various autoimmune diseases.

That said, I've endured all of these long term treatment regimens, albeit with a somewhat diminished QOL. I think it's been worth it as everyday above ground beats the alternative.

Maintain a positive mental attitude, exercise as much as possible ( walking, seated ellipticals, light weights and pay attention to your diet/nutrition/ hydration
You should work with your oncology team to adjust the dosages and infusion rates of your various therapies. These steps help improve tolerability via a slower onset of the pharmacodynamic effects of the various chemo-immunotherapy agents. If you achive stable oligomeric disease control you may placed on low dose 2nd line maintenance chemotherapies (FOLFIRI or Leukovorin) or lower doses of immunotherapies to maintain disease control and treatment toxicities.