First Cancer or a Later One? How Diagnostic Sequence Affects Survival in Colorectal Cancer
In this article
The Same Tumor, Different Outcomes: Why Does the Order of Cancer Diagnoses Matter?
Colorectal cancer (CRC) is the third most common cancer worldwide and the second leading cause of cancer-related death. In clinical practice, discussions often focus on a cancer's molecular characteristics, stage, or response to treatment, while a patient's history of other cancers receives less attention. However, an important study published on June 17, 2025, in Journal of the American College of Surgeonsoffers a new perspective: whether colorectal cancer is a patient's first, second, or only cancer may substantially influence survival.
📊 Study Design and Groups
The study retrospectively analyzed 592063 patients diagnosed with colorectal adenocarcinoma between 2000–2020 in the SEER database . Patients were divided into three groups:
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Group A: CRC was the patient's only primary cancer.
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Group B: CRC was the patient's first cancer, but other primary cancers developed afterward.
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Group C: CRC was the patient's second or subsequent primary cancer.
📈 Survival in Numbers: Group B Lived Longest
✅ Mean Survival Over 5 Years:
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Group B (CRC as the first cancer): 50.4 months
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Group A (CRC as the only cancer): 41.8 months
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Group C (CRC as the second cancer): 39.2 months
Although longer survival in Group B may seem surprising, closer examination of the data reveals possible explanations.
🧬 Clinical and Molecular Differences
| Characteristic | Group A | Group B | Group C |
|---|---|---|---|
| Mean age (years) | 65.7 | 67.3 | 72.6 |
| Liver metastases | 17.5% | 7.4% | 12.1% |
| Lung metastases | 6.3% | 2.5% | 4.2% |
| Proportion of T4 tumors | 14.5% | 10.4% | 12.4% |
| Proportion of right-sided colon tumors | 33.1% | 35.3% | 38.6% |
| Elevated CEA | 49.7% | 43.2% | 46.9% |
Although patients in Group A were younger, they had a more aggressive tumor profile . This group had the highest rates of metastases and T4 tumors. Group C had a poorer prognosis, with older patients who often presented with right-sided colon cancer.
Group B was generally diagnosed at an earlier stage, had lower rates of metastases, and had the highest rate of surgery (94.8%).
🧠 Possible Explanations
🧪 Genetic Predisposition and Lynch Syndrome
In explaining this observation, the authors particularly emphasize genetic predispositions such as Lynch syndrome . People with Lynch syndrome undergo more frequent screening because they are at risk of developing multiple cancers over their lifetime. This contributes to
earlier detection of CRC and better survival.
"Cases in which CRC is the first cancer may be associated with hereditary syndromes such as Lynch syndrome. These individuals undergo intensive screening protocols, allowing tumors to be detected at an early stage." — From the article
🛡️ The Immune System and Response to Treatment
Patients in Group B may have a distinct immunological profile. Previous studies show that higher expression of certain immune genes and T cells is associated with better survival in colorectal cancer.
💪 Lifestyle and Psychological Resilience
People who survive their first cancer may change their lifestyle, engage more closely with the healthcare system, and receive an earlier diagnosis of a subsequent cancer. This can be described as "survivor bias."
⚖️ Recommendations for Clinical Practice
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If a patient with CRC has a history of another cancer, this may influence survival positively or negatively and should be considered in diagnosis and treatment planning.
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When CRC is the first primary cancer, Lynch syndrome or other hereditary syndromes should be considered and genetic counseling recommended.
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Surgical planning and systemic treatment strategiesshould be tailored to the patient's previous cancer history.
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Prospective analyses of the molecular profile (MSI, KRAS/BRAF, TIL density, etc.) may clarify the pathophysiological basis of these findings.
✨ Conclusion: More Than a Routine CRC Diagnosis
This study suggests that colorectal cancer is not simply a tumor: its position within a biological journey with a before and an after may influence survival. Clinical decisions may therefore need to consider not only cancer type and stage, but also the sequence of cancer diagnoses as an important parameter.
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