Clinical T category may suffice for lung cancer prognosis

By Marilynn Larkin

NEW YORK (Reuters Health) - 2/10/2019

The clinical T category in the eighth edition of the tumor-node-metastasis (TNM) staging for lung cancer is a "powerful" prognostic factor, such that consolidation-to-tumor ratio (CTR) and tumor disappearance ratio (TDR) may no longer be needed, researchers say.

"In the era of the 7th edition TNM staging system of lung cancer, multiple previous studies reported that CTR and TDR had independent prognostic values, and thus these two items should be considered for patients' prognosis prediction," Dr. Chang Min Park of Seoul National University College of Medicine told Reuters Health by email.

"However, in the 8th edition...the T coding system drastically changed, and categorizes lung cancers based on the tumor's solid parts instead of total tumor size; (therefore), CTR and TDR are already reflected in the T-category," he said. The study results support that "T-category would suffice and we do not have to consider CTR or TDR additionally."

As reported online September 17 in Lung Cancer, Dr. Park and colleagues retrospectively analyzed CT images for 691 patients (median age 63, 41% men) with resected lung adenocarcinomas (clinical T1N0M0). Images were matched with patient survival.

"We found that CTR or TDR were not independent prognostic factors after adjusting for the T-category," Dr. Park said. "Instead, patients' age (adjusted hazard ratio 1.026) and clinical T-category (aHR for cT1b: 3.475; aHR for cT1c: 9.938) of the 8th edition staging system were independent prognostic factors."

A subgroup analysis for two part-solid nodule groups (cT1mi/cT1a to cT1c and cT1mi/cT1a to cT1b, respectively), yielded similar results

Summing up, the author state, "Preoperative prognostication based on clinical T category would be sufficient without further stratification according to CTR or TDR."

Dr. Park noted, "This study is one of our series investigating the prognostic factors in the 8th edition of TNM staging of lung cancers. We already (investigated) the prognostic impact of different tumor size measurement methods, different CT window settings, 2-dimensional measurement vs. volume measurement, and so on."

In addition to lung cancer, he noted, "we have recently studied whether or not chest CT examinations should be performed for metastasis work-ups or post-treatment surveillance of breast cancers and colon cancers."

Dr. Abbas E. Abbas, chief of thoracic surgery at Fox Chase Cancer Center in Philadelphia told Reuters Health by email, "Undoubtedly, the most important contribution to staging cancer was the introduction of the TNM staging system by Pierre Denoix in 1943."

"With the widespread use of CT scans, there has also been a rapid rise in detection of lepidic adenocarcinomas, which usually appear as partly solid ground glass densities," he said. "It is proposed that the solid component of these nodules represents the invasive part of the tumor. Therefore, in an attempt to predict the degree of invasiveness of these nodules, different CT scan characteristics have been used, (including) CTR and TDR."

"Based on this study," he said, "we can conclude that the clinical T category remains the gold standard for preoperative prognostication in early stage lung cancer."


Lung Cancer 2019.

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