Characteristics of additional primary malignancies in Korean patients with non-small cell lung cancer

Long-term cancer survival results in increasing numbers of multiple primary malignancies in one person, which represents growing clinical challenge in patients with lung cancer. This study was intended to assess the incidence rate, temporal relationship, and characteristics of additional primary malignancies (APM) in Korean patients with non-small cell lung cancer (NSCLC).

We reviewed all 632 NSCLCs (313 adenocarcinomas, 276 squamous cell carcinomas, and 43 other NSCLCs) patients who underwent curative resection of NSCLC at the Dong-A University Medical Center from January 1991 to December 2009. We used the hospital information system and medical record to collect data about these patients and their tumors. In the data base, the following parameters were recorded: patient's demographics (age, gender and smoking habit), time interval between the diagnosis of the NSCLC and APM, NSCLC characteristics (date of diagnosis, histology, TNM staging, operative details, and survival) and characteristics of APM (site of tumor, date of diagnosis, histology, TNM staging, operative details, and survival).

Eighty-one (12.8%) of the 632 patients with NSCLC had APMs. Thirty-three patients (40.8%) had APM in their history [occurring earlier than six months or more before NSCLC diagnosis; prior (P) group], 18 patients (22.2%) were diagnosed with an APM synchronously [diagnosed within six months before or after NSCLC; synchronous (S) group], and the remaining 30 patients (37.0%) were diagnosed with an APM during the follow-up period [occurring six months or more after NSCLC diagnosis; metachronous (M) group]. The second primary malignancy occurred most often two to five years in both P group (39.4%) and M group (36.7%). The most frequent APM was stomach cancer (25.0%), followed by colorectal cancer (19.0%), and thyroid cancer (10.7%). Interestingly, we found difference in the incidence of APM between different NSCLC histotypes. In the adenocarcinoma group, colorectal cancer was the most frequently discovered [12 of 46 events (26.1%)], followed by thyroid cancer [9 of 46 events (19.6%)]. In the squamous cell carcinoma group, stomach cancer occurred most frequently [12 of 36 events (33.3%)].

APMs are commonly seen in patients with NSCLC, either preceding or following its occurrence. Therefore, it is important to recognize the characteristic of NSCLC patients with APM in order to detect the second primary malignancy as early as possible and to achieve a possible cure of disease.