What happened, in summary

A 76-year-old man with a 50-pack-year smoking history developed worsening left hip pain over 3 months. MRI showed a 7.5 cm lesion involving the left iliac bone and acetabulum. Biopsy revealed poorly differentiated adenocarcinoma that was TTF-1 and napsin positive, supporting a lung primary. PET-CT in July 2016 showed a 4.3 cm left lung mass, widespread lymph-node involvement and multiple bone metastases; brain MRI found no central nervous system disease. Molecular testing found no actionable mutations. PD-L1 expression was 0%, while tumour mutational burden was high at 23.16 mutations per megabase. He first received palliative radiation to the thoracic spine and left iliac bone, 20 Gy in 5 fractions, followed by carboplatin and pemetrexed. After four cycles, imaging showed progression with new lung and bone lesions. Nivolumab was started in November 2016. He initially achieved a partial response, but scans after 17 and 21 cycles showed steady enlargement of the left upper-lobe mass and persistent lymphadenopathy. With declining performance status and a preference not to pursue further chemotherapy, he switched to atezolizumab in August 2017. A scan 6 months later showed a complete response. After 35 cycles of atezolizumab, he remained alive and well, with a sustained complete response and no documented immune-related adverse events.