The contribution of second primary cancers to the mortality of patients with a gastric first primary cancer

Risk and prediction of multiple primary malignancies after early gastric cancer

BACKGROUND

Patients with early gastric cancer have increased risk of developing multiple primary malignancies (MPM) due to improved survival rates. The purpose of this study was to evaluate the clinicopathological features of MPM and to generate a useful tool for predicting the development of MPM after early gastric cancer.

METHODS

We selected 1025 early gastric cancer patients with complete medical records for a retrospective analysis. The Cox proportional risk regression model was used to analyze the independent risk factors for the development of MPM in early gastric cancer. RStudio software was used to compare the OS of early gastric cancer patients with and without MPM, and a nomogram was established to predict the probability of MPM 1-, 2-, 3-year after early gastric cancer. The predictive effectiveness of the nomogram was evaluated by the C-index and calibration curve. Decision curve analysis (DCA) measured the applicability of the nomogram to clinical practice.

RESULTS

Of the 1025 patients with early gastric cancer, 66 patients (6.4%) had 69 primary cancers other than early gastric cancer. They had a median follow-up of 41 months, and their cumulative incidence of MPM was 4.9%, 5.4% and 5.9% after 1-, 2-, and 3- year, respectively. Oesophageal cancer was the most frequently detected MPM, followed by lung and colorectal cancers. Male (p=0.038), age ≥65 years (p=0.003), smoking history (p=0.036), and lymph node metastasis (p=0.013) were independent risk factors for MPM in patients with early gastric cancer. Patients with early gastric cancer with MPM had a worse OS prognosis than patients with early gastric cancer without MPM (p<0.001). The internally validated nomogram predicted the probability of developing MPM after early gastric cancer (C index= 0.697). The calibration chart showed that the predicted probability of MPM in early gastric cancer was similar to the observed result, and the DCA showed strong clinical practicability.

CONCLUSION

After the diagnosis and treatment of early gastric cancer, we should be alert to the possibility of MPM and perform regular and careful monitoring.

The effect of a gastric second primary cancer on the survival of patients with a previous cancer history

Second primary cancers (SPCs) are an increasing concern among cancer survivors. In Northern Portugal, gastric cancer incidence is high, and alone corresponds to one in 10 SPCs diagnosed. Therefore, this study aims to estimate the contribution of gastric SPCs to the mortality of patients with a previous cancer. A population-based cohort of nongastric first primary cancer (FPC) patients from the North Region Cancer Registry of Portugal, diagnosed between 2000 and 2006, was followed for a gastric SPC until the end of 2012, and for death by any cause until the end of 2017. Patients with a gastric SPC (85 synchronous and 215 metachronous, diagnosed within one and >1 year after the FPC, respectively) were matched (1:3, by sex, five-year age group, year and site of FPC diagnosis) to those who did not develop a gastric SPC and were alive when the corresponding SPC was diagnosed. Significantly higher hazards for mortality [hazard ratio (95% confidence interval)] were observed among patients diagnosed with a synchronous [3.74 (2.69-5.21) in males and 3.36 (2.02-5.58) in females] or metachronous [6.93 (5.41-8.87) in males and 5.93 (4.04-8.72) in females] gastric SPC. The differences in the 10-year cumulative mortality between gastric SPC patients and those with no SPC were approximately 30% for synchronous and over 40% for metachronous gastric SPCs, corresponding to a 1.5- to 2-fold higher relative risk, respectively. In conclusion, cancer patients with a gastric SPC have a nearly two-fold higher risk of death over 10 years than those with a corresponding FPC only.