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Elevated micropapillary component increased recurrence risk in lung adenocarcinoma
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Micropapillary component greater than 5% predicted increased recurrence risk in certain lung malignancies, according to study results.
Researchers conducted the investigation to evaluate the prognostic significance of a novel classification system in lung adenocarcinoma. The classification put forth by the International Association for the Study of Lung Cancer, the American Thoracic Society and the European Respiratory Society is for patients undergoing resection for lung malignancies ≤2cm.
The other purpose of the study was to assess the predictive ability of histologic subtyping, specifically after limited resection or lobectomy.
Eligible participants received comprehensive histologic subtyping after limited resection or lobectomy for small lung adenocarcinoma at Memorial Sloan-Kettering Cancer Center between 1995 and 2009. The subtyping was performed according to standards set by the new classification in all 734 consecutive patients.
Researchers retrospectively reviewed clinical characteristics and pathologic data for the 258 patients in the resection cohort and the 476 patients in the lobectomy cohort. The researchers calculated cumulative incidence of recurrence risk.
Applying the classification demonstrated that micropapillary component of 5% or greater was associated with increased recurrence risk compared with micropapillary component of less than 5%, but only in the resection group.
In the resection arm, the 5-year cumulative incidence risk for this component was 34.2% (95% CI, 23.5-49.7) for ≥5% and 12.4% (95% CI, 6.9-22.1,) for <5%. In the lobectomy arm, the risk was 19.1% (95% CI, 12-30.5) at 5 years in ≥5% group and 12.9% (95% CI, 7.6-21.9) at 15 years for the < 5% group.
More than half (63.4%) of resected patients with a micropapillary component of ≥5% had relapses that were locoregional. Researchers observed a significant association between micropapillary component of ≥5% and increased local recurrence when the surgical margin was less than 1 cm (5-year cumulative increased risk=32.0%; 95% CI, 18.6-46 for micropapillary component ≥5% vs. 5-year cumulative increased risk=7.6%; 95% CI, 2.3-15.6 for micropapillary component <5%).
When the surgical margin was ≥1 cm, the 5-year cumulative increased for local recurrence was 13% (95% CI, 4.1-22.1) in individuals with micropapillary component of ≥5% compared with 3.4% (95% CI, 0-7.7) for those with a micropapillary component <5%.
“Hopefully our findings will encourage further investigations to determine whether pathologists can recognize and report this feature on frozen sections of lung adenocarcinoma,” the researchers wrote. “Given our findings, patients treated with limited resection whose tumors are determined to have MIP morphologic pattern by use of permanent sections may require completion segmentectomy or lobectomy. Among patients for whom a larger anatomical resection is not feasible, treatment options include adjuvant external-beam radiation therapy and postoperative iodine-125 brachytherapy, which have been shown to decrease local recurrence after wedge resection.”
Disclosure: The study was supported by the International Association for the Study of Lung Cancer, American Association for Thoracic Surgery, National Lung Cancer Partnership/LUNGevity Foundation and other entities.
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