In 1889, MPCs were first identified by Bill Ross, and this phenomenon has gained increasing attention over the past decades[2]. MPCs account for approximately 8.0% of all cancer cases in the United States, as demonstrated by recent studies[3]. Specifically, approximately 4.5% of colorectal cancer patients have MPCs[4]. Lung cancer and colon cancer are considered two of the most common malignant tumors. However, the simultaneous occurrence of these two types of cancer is extremely rare[5]. In data collected from China since 2015, synchronous colon and lung cancers were detected in only 1.2% of 5,405 patients[6]. In addition, the occurrence rate of colon cancer among lung cancer patients was 0.54%[7]. Despite their rarity, lung-colon tumors are among the most prevalent synchronous tumors with comorbidities[6, 8, 9]. Therefore, a comprehensive understanding of the characteristics of MPCs is important.
The exact cause of MPC remains unclear[10], and its pathogenesis is multifactorial[11]. Identified risk factors for MPCs include dietary habits, smoking[8], and genetic mutations (such as Lynch syndrome)[12, 13]. To date, only 15 cases involving both pulmonary and colonic MPC, including this case, have been documented in previous literature (Table 1). Among these cases, primary lung cancer was identified initially in 7 patients[10, 14–18], and the simultaneous diagnosis of lung cancer and colon cancer was identified in 10 of these cases within 6 months[10, 14, 15, 17, 19–22]. The average age of the reported cases was 64.9 years, with 11 of 15 subjects being male. Adenocarcinoma was the most common histological cancer type of the lungs and colon. For many patients, the first presentation of the disease included abdominal pain, abnormal defecation, cough and chest pain.
Accurate assessment of the clinical stage of each primary tumor is important for predicting patient prognosis and determining the optimal treatment strategy. The primary diagnostic methods for detecting multiple primary colorectal cancers include colonoscopy and computed tomography. However, these methods often face challenges in regard to precisely locating tumors[23]. Furthermore, this may lead to inaccurate information about the lesion location or even missed information, especially in cases with obstructive lesions. In these scenarios, intraoperative colonoscopy serves as a remedial or a supplementary tool, significantly contributing to the accurate diagnosis of synchronous multiple primary colorectal cancer or colon polyps.
In cases where observed colorectal cancer affects the proximal colon, intraoperative colonoscopy plays a dual role. It not only pinpoints the location of colon lesions and defines the scope of operation but also enables one-stage anastomosis following intraoperative colon irrigation. In addition, bleeding issues can be addressed by checking the integrity of the anastomosis. Furthermore, some scholars have noted that combining intraoperative colonoscopy with laparoscopic colorectal surgery is a safe and feasible approach that may even facilitate postoperative recovery[24]. Moreover, this combination will not increase the operational time, intraoperative blood loss or postoperative complications. Consequently, intraoperative colonoscopy is of great value for patients unable to undergo whole-course colonoscopy due to obstructive lesions.
Patients with a single malignant tumor face a higher risk of developing synchronous cancer[25]. As a screening method, PET-CT has also proven to be an important tool not only to detect malignant metastases in cancer patients but also for the screening of multiple primary tumors[26]. Studies have highlighted the significance of PET-CT examinations in detecting gastrointestinal metastases or primary cancers in lung cancer patients[27]. In addition, PET-CT detection for colon cancer patients can assess the presence of tumor metastases or concurrent primary lung tumors. Although PET-CT has certain limitations for cancer screening[26, 28], previous data revealed that PET-CT had a remarkable sensitivity (90%) and specificity (66%) in detecting primary colon tumors[29]. It is an effective tool for identifying synchronous colon cancer in individuals with obstructive colon cancer.
Currently, the management of synchronous MPCs remains a formidable challenge, with an obvious absence of canonical treatment guidelines. Accurate clinical staging is essential to determine the optimal treatment strategy and predict patient prognosis. Multidisciplinary consultation based on molecular targets and immunohistochemistry may provide an effective approach to develop highly individualized treatment plans. Lorena Brandariz et al[12]. reported that only colorectal cancers with well-defined genetic profiles can be extensively resected. Stefano Cecchini et al[30]. have proposed partial colectomy as a selective treatment option for MPCs. The prognosis of patients with synchronous primary colon cancers aligns with that of colon cancer alone. However, cases with synchronous lung cancer are associated with a higher risk of adverse outcomes and mortality[19]. Therefore, tumors with negative prognosis and higher risk should be treated first when the patients are in a poor general condition and cannot undergo simultaneous radical excision. In addition, the specific design of colectomy surgery should be guided by whether the colon cancer is obstructive, with radical resection options aimed at improving prognosis being the ideal procedure.
According to the NCCN guidelines, the frontline treatment regimen for colorectal cancer involves the combination of 5-fluorouracil (5-FU), leucovorin, oxaliplatin and irinotecan (CPT-11). For small cell lung cancer, the recommended chemotherapy regimen includes cisplatin or carboplatin combined with etoposide. In the case of synchronous colon and lung cancers, there is no well-established postoperative chemotherapy regimen due to limited case reports. Moreover, the potential of combining low-toxicity immunotargeted therapy with radiotherapy is being explored. This therapeutic strategy aims to minimize the toxic side effects of the drugs while maintaining therapeutic effectiveness, showing promise for individualized treatment of patients with MPCs[10].
In conclusion, with the increasing incidence of MPCs, clinical efforts should extend beyond diagnosing a single cancer while neglecting the possibility of others. Instead, a systematic approach with a comprehensive diagnosis is imperative. For colorectal tumors, a preoperative whole-course colonoscopy should be emphasized, complemented by intraoperative colonoscopy when applicable. Although the occurrence of combined lung and colon cancers may still be infrequent and individuals with MPCs are often excluded from clinical testing, especially when dealing with patients suffering syndromic colorectal and lung cancers, a thorough assessment should be made based on clinical requirements to develop personalized treatment plans. In the future, it will be important to perform both genetic and epidemiological research to clarify the recessive link between these two cancers.