IASLC Recommendations: Pathologic Evaluation of Lung Cancer Resection Specimens Following Neoadjuvant Therapy

Detailed recommendations from the International Association for the Study of Lung Cancer (IASLC) on the processing and evaluation of lung cancer resection specimens from patients treated with neoadjuvant therapy were published in the Journal of Thoracic Oncology.

Recognition of the need for guidelines on the pathologic processing and assessment of lung cancer specimens resected following exposure to neoadjuvant therapy, as well of the absence of precise definitions of major pathologic response (MPR) and complete pathologic response (CPR) in this setting, were major drivers for the creation of these recommendations, which were based on the opinions of an IASLC expert panel comprised mainly of pathologists, but also involved multidisciplinary input from surgeons, radiologists, and medical oncologists.

Another force motivating these recommendations was an increasing awareness of the trend for evaluating nonchemotherapy-based approaches, such as molecularly targeted therapy and immunotherapy, in clinical trials of patients with early-stage lung cancer.

In this context, the study authors noted that “neoadjuvant treatment with surrogate measures of efficacy such as treatment response have the potential to accelerate curative therapies for the general lung cancer patient population.”

Some of the key elements of these recommendations are as follows:

• In the resection specimen, the term “tumor bed” applies to the location of the pretreated tumor and includes viable tumor, necrotic areas, and stroma
• Good communication between the surgical and pathologic teams is essential to identify any issues that may affect pathologic staging
• Pathologic review of the pretreatment computed tomography (CT) scan may facilitate identification and/or orientation of the tumor
• A review of gross and histologic specimens from the tumor bed periphery may facilitate identification of the tumor bed edge
• Determination of pathologic response needs to include a review of all hematoxylin & eosin (H&E) slides of tumor, including 100% of viable tumor, necrosis, and stroma comprising the tumor bed (ie, the sum of the percentages of each of these components should equal 100%)
• MPR is currently defined is an “estimated size of viable tumor divided by the size of the tumor bed” of 10% or less
• CPR is defined as “lack of any viable tumor cells on review of H&E slides after complete evaluation of a resected lung cancer specimen including all sampled regional lymph nodes”
• The same approach should be used in the evaluation of resection specimens previously exposed to chemotherapy, targeted therapy, immunotherapy, radiation, and chemoradiation in the neoadjuvant setting
• Histologic assessment of lymph nodes is performed according to the approach described for the primary tumor
• Measurement of viable, invasive tumor size for T factor staging is preferably made by using a ruler; if that is not possible, the product of tumor bed size and percentage viable invasive tumor should be used to estimate viable, invasive tumor size.

Although these recommendations were primarily designed to facilitate the pathologic analysis of resection specimens collected within the context of clinical trials of neoadjuvant therapy in patients with lung cancer, the IASLC expert panel encouraged the more general implementation of these rules as best clinical practices in patients with lung cancer that has been treated with neoadjuvant therapy.

In addition, the study authors stated that the IASLC intends to promote 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.”

Disclosure: Some of the authors disclosed financial relationships with pharmaceutical and medical device companies. For a full list of disclosures, please refer to the original study.

Reference

Travis WD, Dacic S, Wistuba I, et al. IASLC multidisciplinary recommendations for pathologic assessment of lung cancer resection specimens following neoadjuvant therapy [published online January 28, 2020]. J Thorac Oncol. doi: 10.1016/j.jtho.2020.01.005