Patients with colorectal cancer who have certain clinical characteristics may benefit from more frequent chest imaging to help identify and target cancer that has metastasized to the lungs, according to a new study presented at the 2022 Scientific Forum of the American College of Surgeons Clinical Congress. The findings also show the potential to improve long-term outcomes for patients with metastatic colorectal cancer.

Although rates of colorectal cancer have declined among people aged 65 years and older, largely thanks to increased screening efforts, rates among younger adults are rising. Colorectal cancer can metastasize in up to 50% of patients, and 18% of metastasized colorectal cancer spreads to the lungs. Detecting cancerous nodules in the lungs early provides patients with the best outcomes, but there are no evidence-based standards for when and how often to screen patients with colorectal cancer using chest computed tomography (CT) or positron-emission tomography (PET) scans.

“After patients are diagnosed with colorectal cancer, many of them want to better understand what their cancer diagnosis entails in terms of their surveillance and survivorship for the rest of their lives, but we currently lack data and uniform guidelines to support how often these patients should be screened with chest imaging,” said study coauthor Mara Antonoff, MD, FACS, Associate Professor and Program Director of Education in the Department of Thoracic and Cardiovascular Surgery at The University of Texas MD Anderson Cancer Center. “With this study, we sought to develop a strategy that is evidence-based to determine how frequently, at what intervals, and for how long patients at risk of developing lung metastases should undergo imaging of their chest.”

Study Details

To identify which patients with colorectal cancer had the greatest potential to benefit from early chest imaging and at what time intervals, Dr. Antonoff and colleagues investigated evidence-based surveillance guidelines for patients most at risk of developing lung metastases. Using two MD Anderson cancer databases that included both patients with colorectal cancer and patients with thoracic cancer, the study team retrospectively reviewed data from patients with colorectal cancer who did and did not develop lung metastases.

Patients were grouped according to the development of lung metastases and the timing of their diagnoses. The team used statistical methods to investigate which clinical characteristics, such as age or genetic factors, correlated most with the risk of developing lung metastases.

Key Findings

Of the 1,600 patients with colorectal cancer who participated in the study, 14.6% developed pulmonary metastases, with a median time of 15.4 months following colorectal surgery. The team identified the following clinicopathologic characteristics as risk factors for developing lung metastases: increasing age, receipt of neoadjuvant or adjuvant systemic therapy, increasing lymph node ratio, lymphovascular and perineural invasion, and the presence of KRAS genetic mutations.

Further data analysis revealed that patients who required systemic therapy around the time of their colorectal cancer surgery, those who had an elevated lymph node ratio, and those with a KRAS mutation were at risk of developing lung metastases within 3 months of surgery. The study authors concluded that these patients may benefit from more frequent surveillance with chest CT or PET scans.

“A concrete clinical application of this research, following validation, is to build evidence-based guidelines affecting chest surveillance in patients with resected colorectal cancer,” said lead study author Nathaniel Deboever, MD, a general surgery resident at the McGovern Medical School at The University of Texas Health Science Center at Houston. “These guidelines will hopefully allow high-risk patients to undergo radiographic screening in a timely manner, permitting the early diagnosis of pulmonary disease.”

Dr. Deboever also noted that while these risk factors were not necessarily surprising from a clinical perspective, they highlighted the need to adequately screen certain patients with colorectal cancer after surgical treatment. In some cases, removing cancerous lung nodules surgically early on significantly improved patient outcomes.

Next Steps

In future research, the researchers plan to validate findings in a separate group of patients, with the hope of formalizing chest surveillance protocols for widespread clinical adoption. The study authors noted that as colorectal cancer research evolves, sensitive blood tests to detect cancer or advanced radiographic screening methods using artificial intelligence may also play an important role in monitoring patients.

“There are many patients who receive cancer care outside of cancer hospitals, so having algorithms, pathways, and recommended protocols can be very helpful for providers who care for a lot of different diseases with rapidly changing recommendations,” Dr. Antonoff said. “I think this research is really just the tip of the iceberg.”

Disclosure: This study was funded by the Department of Thoracic and Cardiovascular Surgery at MD Anderson Cancer Center, which included financial support from the Mason Family Philanthropic Research Fund. For full disclosures of the study authors, visit facs.org.