Previous lung cancer

This is a 61 y/o man who was seen in our office last year. He had significant obesity and OSA and was found to have a RUL mass. He underwent resection of a IIB (T2N1M0) NSCLCa (squamous), followed by xRt and chemoTx. His course since then has been remarkable for a fall and a hip Fx but no respiratory problems.
He came back to his PCP this past month with a new cough and R chest tightness. His CT showed some loss of volume and more soft tissue swelling in the hilar area (see below):

Incidentally he had this huge gallstone (cool pic):

I bronch'ed him and he had narrowing and scarring of the residual RML bronchus with normal RLL and a healthy looking RUL stump. EndoBBx, brushings and lavages were remarkable for radiation changes and atypia but no neoplasm. Would you do a PET, a more invasive sampling (e.g. Mediastinoscopy) or just follow him after some ABTx since he has already had maximal therapy to the area and would have limited options with recurrent Ca?