Contemporary Incidence Of Synchronous Multiple Primary Lung Cancers In The Era Of Lung Cancer Screening
Nika Samadzadeh Tabrizi, Ben Gallant, Erin Harris, Brian N. Arnold, Thomas Fabian.
Albany Medical College, Albany, NY, USA.
Background: Not only does the reported incidence of synchronous multiple primary lung cancer (SMPLC) vary widely in the literature, 0.2 - 8%, but so does the reported 5-year survival, 10 - 76%. This discrepancy is partially attributed to inconsistent identification of SMPLCs which has hindered our understanding of these patients. Utilizing strict inclusion criteria, we sought to identify the contemporary incidence and survival of patients with SMPLC. Methods: From January 2018 to September 2019, 227 consecutive patients who underwent lung cancer resection at a single academic institution were retrospectively reviewed. Using the modified Martini criteria, patients with SMPLC were included. Three patients were excluded from survival analysis due to failure to undergo R0 resection for all tumors. Results: During the 21-month period, 297 lung cancers were resected with curative intent. 47 (21%) patients had 113 tumors that were pathologically confirmed SMPLC. Overall and cancer-specific survival (Figure 1) was 42/44 (96%) and 42/43 (98%), 42/44 (96%) and 42/43 (98%), 38/43 (88%) and 38/41 (93%) at 1-, 2-, and 3-years respectively. In those with two SMPLC, tumors were ipsilateral in 20 (43%) and bilateral in 14 (30%). 13 (28%) had multiple tumors which was associated with a significantly lower overall (p = 0.043) and cancer-specific (p= 0.002) survival. Tumor histology was different in 38 (81%) patients. Most tumors were composed of only adenocarcinomas in 28 (60%) or adenocarcinoma(s) mixed with another histologic type in 12 (25%). Adenocarcinomas had a significantly lower overall survival (p = 0.005), but cancer-specific survival was not significantly different (p = 0.08). Demographics and pathologic staging also did not significantly impact survival. Conclusions: The incidence of SMPLC is much higher than historical data would predict. Our 3-year overall survival is also considerably higher than what has been reported, 88% and 63% respectively. This study is highly exclusive and likely reflects the true outcomes for patients with SMPLC. Survivorship in these patients suggests that SMPLCs behave like primary lung cancers - which can be treated with sublobar resection - not metastatic disease. Awareness of SMPLC by thoracic surgeons is critical in accurately staging, managing, and optimizing outcomes in this patient population. Legend: Figure 1. Kaplan-Meier survival curve depicting overall and cancer-specific survival (N = 44). Shaded areas indicate 95% confidence intervals. 
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