Does irradiation for initial primary lung cancer affect the risk of metachronous second primary lung cancer?

Risk-based screening for second primary extrapulmonary malignancies in stage I lung cancer patients: A study based on SEER database

OBJECTIVES

We conducted this study to identify the risk for second primary malignancy (SPM), especially for second primary extrapulmonary malignancy (SPEM), in resected stage I lung cancer patients.

MATERIALS AND METHODS

Resected stage I lung cancer patients were retrospectively enrolled from the SEER database (2008-2017). Standardized incidence ratio (SIR) was used to evaluate the relative risk of SPM of patients as compared to general population. Competing risk model was utilized to identify the risk factors for SPEM of increased risk (rSPEM). A simplified nomogram based on the factors was developed to stratify patients at different risks of rSPEM.

RESULTS

A total of 14,495 patients were enrolled, and 1779 (12.27%) patients developed SPM during follow-up, of which 896 (50.37%) were SPEM. Enrolled patients had higher risk of SPM than general population (SIR: 1.92, 95% CI: 1.83 - 2.01). The yearly morbidity of SPM was about 3% - 4% over time. The three most frequent SPEM were prostate cancer, breast cancer, and urinary bladder cancer. The competing-risk multivariable analysis showed that increasing age, male, and white race were independent risk factors for rSPEM. The simplified nomogram showed favorable performance in stratifying patients at different risks of rSPEM (P < 0.001).

CONCLUSION

The risk of SPM in stage I lung cancer patients was high. Risk factors for rSPEM were identified and the corresponding simplified nomogram based on the risk factors could discriminate patients at different risks well. The nomogram might help physicians to make more appropriate screening strategy for the SPEM.

Postoperative radiotherapy might be a risk factor for second primary lung cancer: A population-based study

BACKGROUND

Surgery is the main curative therapeutic strategy for patients with initial primary lung cancer (IPLC). Most international guidelines recommend regular follow-ups after discharge to monitor patients for tumor recurrence and metastasis. As the overall survival (OS) in patients with lung cancer improves, their risk of secondary primary lung cancer (SPLC) increases. Previous studies on such patients lack separate assessment of different survival outcomes and evaluation of high-risk factors for SPLC. Therefore, we aimed to determine the correlation between high-risk factors and causes of death in patients with SPLC, based on the Surveillance, Epidemiology, and End Results (SEER) database.

METHODS

We screened the SEER database for patients with IPLC and SPLC from 2004 to 2015 and included only patients who underwent surgery since the IPLC and in whom the cancer was pathologically verified of an International Classification of Diseases grade of 0-3 and to be non-small-cell lung cancer. The standardized incidence ratio (SIR) was calculated between variables and SPLC. Multivariable Cox proportional-hazards regression analyses were conducted to calculate the correlation of different variables with overall survival (OS) and cancer-specific survival (CSS). A competing-risk model was conducted for SPLC. The effect of baseline bias on survival outcomes by performing propensity score matching analysis in a 1: 6 ratio (SPLC: IPLC).

RESULTS

For patients aged 0-49 years, the overall SIR was higher in older patients, reaching a maximum of 27.74 in those aged 40-49 years, and at 11.63 in patients aged 50-59 years. The overall SIR was higher for patients who were more recently diagnosed with IPLC and increased with time after diagnosis. Male sex, SPLC (hazard ratio, 1.6173; 95% confidence interval, 1.5505-1.6869; P < 0.001), cancer grade III or IV, lower lobe of the lung, advanced stage and postoperative radiotherapy (PORT) were independently detrimental to OS. In terms of CSS, PORT was a high-risk factor.

CONCLUSIONS

Postoperative radiotherapy is a risk factor for second primary lung cancer and detrimental to overall and cancer-specific survival in patients who had initial primary lung cancer. These data support the need for life-long follow-up of patients who undergo treatment for IPLC to screen for SPLC.