Stage 4 lung cancer: immunotherapy plus particle therapy halts progression

What happened, in summary

A 73-year-old man with a 20-pack-year smoking history was diagnosed with oligometastatic non-small cell lung cancer after routine imaging found a left upper-lung lesion. PET/CT showed a 6.6 cm necrotic left upper-lung mass, left hilar, mediastinal, and subcarinal lymphadenopathy, and a single metastasis in the left proximal femur. Brain MRI showed no metastasis. Biopsy confirmed poorly differentiated invasive adenocarcinoma of lung origin. Molecular testing showed high tumor mutational burden, PD-L1 expression of 90%, and mutations in PIK3CA E545K, TP53, and MET L1195V. The disease was staged T3N3M1b, Stage IV. He received 4 cycles of carboplatin, pemetrexed, and pembrolizumab, with CT showing decreased size of the cavitary lung mass and no new metastases. Because the central lung and mediastinal disease made standard SBRT too risky, the team used PULSAR radiotherapy with concurrent pembrolizumab: 36 Gy in 3 monthly fractions, with adaptive planning for the lung/mediastinum and non-adaptive treatment for the left femur lesion. Treatment was completed without interruption. Pembrolizumab continued through the first 2 PULSAR fractions but was held at the 3rd because of grade 1 fatigue and cough. At 1-month follow-up, grade 2 pneumonitis was treated with a 4-week prednisone 40 mg taper and symptoms improved. Six months after treatment completion, he showed no signs of disease progression. During adaptive planning, treatment was adjusted to meet heart, pericardium, and bronchus constraints while maintaining target coverage, which was why adaptive PULSAR was central to this case. This supports Responding Well rather than NED or complete remission in this record.