Histologic Classification Could Aid Prognosis in Lung Adenocarcinoma

New classification guidelines for histologic subtypes of stage I lung adenocarcinoma offer prognostic value, according to a new study. Solid-predominant subtype was associated with an increased risk of early recurrence and post-recurrence survival.

“The new International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society (IASLC/ATS/ERS) classification characterizes lung adenocarcinoma as a heterogeneous mixture of histologic subtypes, with the predominant histologic subtype able to stratify recurrence-free survival,” wrote study authors led by Prasad S. Adusumilli, MD, of Memorial Sloan Kettering Cancer Center in New York. The new study was designed to assess the prognostic utility of this classification.

The classification guidelines group tumors into adenocarcinoma in situ, minimally invasive adenocarcinoma, and invasive adenocarcinoma, which is then subdivided into lepidic-predominant, acinar-predominant, papillary-predominant, micropapillary-predominant, solid-predominant, colloid-predominant, and invasive mucinous carcinoma. Using those categories, tumors were given an architectural grade of low, medium, or high.

The study included a total of 1,120 patients with resected stage I lung adenocarcinoma. During a median follow-up of 60 months, 188 patients (17%) experienced recurrence; at the end of the study period, 308 of the patients had died and 103 of the patients with recurrence died as a result of lung cancer. Results were published in the Journal of Clinical Oncology.

Patients with solid-predominant tumors had the highest risk of recurrence. Those patients had a recurrence risk of 75% within 2 years compared with 51% in nonsolid tumors (P = .007). They also had more extrathoracic recurrences (77% vs 37%; P < .001) and more multisite recurrences (47% vs 26%; P = .011).

Among those patients who experienced recurrence, the 2-year post-recurrence survival rate was 45%, with a median of 26.1 months. On multivariate analysis among patients who recurred, solid-predominant histologic pattern yielded a worse post-recurrence survival, with a hazard ratio (HR) of 1.76 (P = .016). Age older than 65 years was also a significant predictor, with an HR of 1.63 (P = .01), as was sublobar resection, with an HR of 1.6 (P = .01).

The authors concluded that the IASLC/ATS/ERS classification system “can be readily implemented in the treatment of patients with early-stage lung adenocarcinoma,” and that the finding that solid-predominant tumors are associated with poorer outcomes “underlines the need to investigate adjuvant therapeutic strategies for these patients.”