Complete Response to Pembrolizumab in an Elderly Patient With Lung Squamous Cell Carcinoma

The patient was an 84-year-old man with ECOG performance status 1. He reported smoking two packets of cigarettes daily for 20 years; smoking cessation timing was not specified. The report does not provide a detailed comorbidity profile, medication list, family history, or geriatric assessment. [1]

Several weeks of bloody sputum prompted a visit to a general physician. A chest radiograph showed an abnormal opacity in the left middle lung field, leading to hospital referral. Subsequent imaging localized the primary tumor to the left upper lobe. Bronchoscopy demonstrated obstruction of the left upper-lobe airway. [1]

Chest radiography and contrast-enhanced CT demonstrated a left upper-lobe tumor invading the pulmonary artery. The authors reported no distant metastases and assigned clinical stage cT4N2M0, stage IIIB. The publication does not describe every component of the staging workup or give baseline tumor dimensions. [1]

Transbronchial biopsy showed sheets of atypical polygonal/spindle cells with intercellular bridging. Diffuse p40 positivity and negative TTF-1 staining supported squamous cell carcinoma. PD-L1 staining involved at least 80% of tumor cells: the abstract and Figure 2 use ≥80%, whereas the case narrative describes more than 80%. No PD-L1 assay clone or genomic driver-testing results are specified. [1]

Baseline serum cytokeratin 19 fragment was elevated at 5.7 ng/mL, and the neutrophil-to-lymphocyte ratio was 2.35. Exploratory tissue staining showed abundant CD163-positive tumor-associated macrophages, CD15/MPO-positive tumor-associated neutrophils, and cells characterized by the authors as CD3/CD25-positive regulatory T cells. CD4-, CD8-, and CD56-positive cells were sparse. These descriptive findings were not validated predictive tests within this case. [1]

The authors considered radiotherapy hazardous because pulmonary artery invasion raised concern about vascular perforation and sudden death; the patient chose not to receive it. Pembrolizumab monotherapy was therefore started as first-line treatment, with administrations at three-week intervals in the setting of high tumor PD-L1 expression. The dose, infusion details, start date, and exact total number of administrations are not specified. No preceding systemic anticancer therapy is described. [1]

Pembrolizumab continued for two years despite the earlier complete response, then stopped at the patient's request. Discontinuation was not attributed to disease progression or toxicity. The authors reported no side effects during treatment, without providing a formal adverse-event grading table or detailed toxicity monitoring results. [1]

The authors described a complete response at the end of the fifth pembrolizumab cycle, illustrated by CT and bronchoscopic findings. Tumor markers normalized and remained normal during the reported course. This was a reported clinical/imaging response; the article does not document a surgical pathological complete response or specify a formal RECIST assessment. [1]

Following two years of pembrolizumab, the patient remained without reported tumor recurrence for approximately one and a half years after stopping therapy. No additional anticancer treatment during that interval was described. The publication does not specify a surveillance schedule, subsequent biopsy results, or outcomes after that observation period. Complete response and the reported recurrence-free interval should not be equated with cure. [1]

This case documents that an individual in his eighties with PD-L1-high lung squamous cell carcinoma experienced a deep response to pembrolizumab, with response persisting after treatment ended. Its educational significance lies in the combination of advanced age, locally advanced disease, treatment selection constrained by vascular invasion, and a documented treatment-free interval. It does not quantify the likelihood of comparable benefit in other patients or establish a preferred treatment for all stage IIIB disease. [1]

The tumor's high PD-L1 expression was the biomarker used by the treating team to support pembrolizumab selection. The authors proposed that PD-1 blockade might counter an immunosuppressive tumor environment despite sparse CD4-, CD8-, and CD56-positive cells. That explanation remains a hypothesis: the descriptive staining does not demonstrate the causal mechanism of this patient's response. [1]

The decision to stop after two years provides an observation about this patient's course, rather than a comparison of stopping versus continuing treatment. Persistence of response for approximately 18 months without therapy cannot establish the safest stopping point, a surveillance regimen, or the effectiveness of retreatment; no recurrence or rechallenge was reported in this case. [1]

Key takeaways:
- The reported diagnosis was stage IIIB (cT4N2M0) lung squamous cell carcinoma, with tumor PD-L1 expression of at least 80%.
- Complete tumor disappearance was documented by CT and bronchoscopy after five cycles of first-line pembrolizumab.
- Two years of treatment were followed by approximately 18 months of treatment-free observation without reported recurrence.
- A complete response in one patient does not prove cure, predict another patient's response, or define optimal treatment duration.

This is a single published case without a comparator, so it cannot establish response rates, comparative efficacy, or general safety in elderly patients. Detailed comorbidity and frailty data, genomic testing results, pembrolizumab dose, exact calendar dates, baseline tumor measurements, formal response criteria, and surveillance frequency are not provided. The statement that no side effects occurred lacks detailed grading and does not establish absence of all toxicity. Mechanistic interpretation is exploratory. Observation after treatment discontinuation was limited to approximately 18 months; no later outcome is established. The report does not explicitly state patient consent for publication. [1]

The only preferences described are that the patient chose not to undergo radiotherapy and requested pembrolizumab discontinuation after two years. The article provides no direct patient quotation, formal quality-of-life assessment, or explanation of the discontinuation request. [1]