Pathological response has emerged as a valuable endpoint and surrogate marker for overall survival in lung cancer studies, but much work remains to be done, said William D. Travis, MD, director of thoracic pathology at Memorial Sloan Kettering Cancer Center, New York.
In a keynote address at the 2022 European Lung Cancer Conference, Travis highlighted advances in the use of pathological response in this setting and outlined areas that need refinement. "Pathologic response after preoperative therapy is important because the extent of pathologic response strongly correlates with improved overall survival, and it is reflective of neoadjuvant therapy. The degree of response is associated with the degree of benefit in survival, and it's being used as a surrogate for survival in phase 2 and 3 neoadjuvant clinical trials."
In fact, multiple studies have demonstrated that non–small cell lung cancer patients with 10% or less viable residual tumor after treatment have improved overall survival and disease-free survival, compared with patients who have more residual tumor, he explained.
Recent studies have demonstrated the value of pathological response as an endpoint in the neoadjuvant therapy and molecular targeted therapy setting, he said, citing a study published in the Journal of Clinical Oncology that showed major pathological response rates of 14%-45% and pathological complete response rates up to 29% in patients treated with single-agent checkpoint inhibition.
In the CheckMate 816 trial, both major pathologic response and pathological complete response were significantly higher in patients treated with combination nivolumab and chemotherapy, compared with those treated with chemotherapy alone (37% vs. 8.9% and 24% vs. 2%, respectively).
"This high rate of responses with combined immunotherapy and chemotherapy is quite exciting," he said.
Travis also stressed the importance of consulting the current International Association for the Study of Lung Cancer Recommendations for Pathologic Assessment of Lung Cancer Resection Specimens After Neoadjuvant Therapy.
He highlighted several key points regarding pathological response in lung cancer:
Major pathological response (MPR) is calculated as the estimated size of viable tumor divided by the size of the tumor bed.
Optimal cutoffs for determining MPR is currently 10%, but recent data suggest that in the conventional chemotherapy setting this may vary by tumor histology, with much higher cutoffs of about 65% for adenocarcinoma.
Estimating the amount of viable tumor is "quite complicated and requires quite a number of steps," and one the most important steps is "for the surgeon to the pathologist know that given specimen is from a patient who received neoadjuvant therapy."
Determining the border of the tumor bed can be challenging, therefore "resection specimens after neoadjuvant therapy should be sampled to optimize comprehensive gross and histologic assessment of the lung tumor bed for pathologic response ... as outlined in the guidelines."
The IASLC panel determined that having a single approach for estimating treatment effect would be best, despite the different therapy types and combinations used, but "it is recognized that there may be certain types of features that need to be addressed," such as immune cell infiltrates in pats who received immunotherapy.
The recommendations provide specific guidance for measuring tumor size for staging, including for special circumstances.
As for future direction, Travis said, "one question is how to assess treatment effect in lymph node samples.
"This is done for lymph nodes in breast cancer but not in lung cancer. We need system[s] for lung cancer."
Good "infrastructure for pathology departments" is needed to support clinical trials, he said, noting that the team at Memorial Sloan Kettering Cancer Center includes physician assistants, tissue procurement staff, frozen section techs, research fellows, and research assistants.
Future work should also aim to standardize pathology assessment for clinical trials, improve the current recommendations, make use of new technology like artificial intelligence, optimize banking protocols and special techniques, and identify radiologic-pathological correlations, he said.
He added that "IASLC is promoting the design and implementation of an international database to collect uniformly clinical and pathologic information with the ultimate goal of fostering collaboration and to facilitate the identification of surrogate endpoints of long-term survival."
Travis is a nonpaid pathology consultant for the LCMC3 and LCMC4 trials.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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Cite this: Weighing the Complexity of Pathologic Response in Lung Cancer - Medscape - Apr 11, 2022.