PMC8733470_01
The comparison of chest CT before and after sintilimab treatment. (A) Chest CT scan before sintilimab treatment (July 2020). Images of A1, A2, and A3 consecutively showing the tumour at the posterior segment of the left lower lobe, and the tumour size was 2.1x1.4 cm, 2.4x1.5 cm, 2.7x1.5 cm, respectively (solid lines indicate the tumour). (B) Chest CT scan after sintilimab treatment (September 2020). Images of B1, B2 and B3 showing the tumour at the same location when compared with A1, A2, and A3, separately, and the tumour size was 0.4x0.4 cm, 0.5x0.4 cm, 1.0x0.7 cm, respectively (dotted lines indicate the tumour).
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After two cycles of second-line treatment, response to treatment was assessed as PR ( Figure 1 ).
Clinical course over methylprednisolone therapy (A) and timeline of treatment course (B). Drug dosage: bevacizumab, 7.5mg/kg; carboplatin, (area under the concentration-time curve) 4-5 mg/mL/min; ibandronic acid, 4mg; levofloxacin, 500mg; methylprednisolone (initial), 1mg/kg/d; paclitaxel-albumin, 260mg/m2; pemetrexed, 500mg/m2; sintilimab, 200mg.
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The laboratory values were also decreased during corticosteroids treatment ( Figure 2A ). The timeline of treatment course was summarized in  Figure 2B .
Cystoscopy of bladder (A) revealed diffuse redness of bladder mucosa and histopathological findings (B) of bladder biopsy showed lymphocyte-dominant bladder inflammation and interstitial tissue hyperplasia (white arrow), which was shown in the increased number of fibrocytes (H&E staining, magnification x400, bar =25mum).
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Once urinary symptoms were alleviated, bladder biopsy was performed and confirmed the bladder lymphocyte-dominant inflammation and interstitial tissue hyperplasia ( Figure 3 ).