How would you approach a patient with simultaneously diagnosed stage IVA SCC of the head and neck and limited stage small cell lung cancer (neither is symptomatic)?
The treatment option with ES-SCLC may be slightly more clear since the patient has incurable disease and will succumb to their lung disease. I would start chemotherapy and keep an eye on the H&N cancer and offer palliation as needed including a QUAD shot (depending on the size of the primary and symptoms). You can consider more definitive radiation depending on response to chemotherapy.
With LS-SCLC you are dealing with 2 cancers that are potentially curable though the survival is going to be driven by the SCLC. I would therefore still start with chemoRT for the lung cancer and start RT with the first cycle and get it done in 3 weeks (bid regimen or if not possible even consider 40 or 45 Gy in 15 as has been recommended elsewhere on the forum). I would start the head and neck part after completion of thoracic RT. Presumably he will still be getting chemo for his lung cancer (and possibly use 80 mg/m2 cisplatin and 100 mg/m2 etoposide regimen instead of 60 mg/m2 cisplatin and 120 mg/m2 etoposide) thus providing him the best chance of cure.