Insights from SEER database: Secondary lung cancer (LC) following head and neck-cancer (HNC) treatment.
Authors: Guevara Rodriguez Nehemias Antonio , Perez Rosario Esmirna M. , Chapiolkina Volha , Sanchez Orbe Jorge Octavio , Budhathoki Pravash , Pokharel Nisheem , Florez Narjust , Olazapasti Coral 
Published: September 2024

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Background:
HNC accounts for 4% of all cancers in the USA, with exceptionally high morbidity in oncology. HNC is associated with secondary primary malignancies and LC, which are predominant in the population, with an increase of 54% in incidence after HNC. Moreover, incidence and prevalence are multifactorial, sharing risk factors and radiation therapy—nevertheless, LC mortality and morbidity increase when present after HNC.
Methods:
SEER database was used. Patients ≥18 with primary site codes in oral cavity, including oropharynx, hypopharynx, nasopharynx, and larynx, included. LC patients identified using SEER staging (2000-2020) post 12-month HNC diagnosis. Statistical analysis performed via Stata. Kaplan Meir methods for survival estimates, log-rank tests for comparison. Primary endpoint: LC incidence post HNC and survival. Secondary:demographics race, ethnicity, etc).
Results:
A total of 1339 patients were diagnosed with LC; out of these, 1183 were diagnosed after HNC treatment. Patient's ages ranged from 26-90 years-old, with a mean of 68 years old. The majority of patients were males, 900 of the total population. 1146 of the patients were nonHispanic, with only 37 Hispanics. The most common stage of LC diagnosis was stage 4 (43%), followed by stage 1 (27%), stage 3 (22%) and stage 2 (9.4%). Squamous was the most common histology (44%), followed by a lesser incidence of adenocarcinoma (24%), small cell (11%), and other nonspecified histology (21%). Treatment was provided with chemotherapy (CTX) in 39% of patients and radiation (RTx) in 42%. Stage 1 LC was more commonly treated with RTx (33%), while stage 2 was treated with both CTX (45%) and RTx (52%). Similar trends were seen in stage 3, with the same proportion of CTX and RTx (56%), and for stage 4, CTX (45%) and RTx (37%). In the sample, the patient's primary diagnosis of HNC was made at a mean age of 63 years old. The most common site of HNC origin was the larynx(41%), followed by the oral cavity (28%) and the tongue (18%). In patients with stage 1 LC, the 3-year survival was 44.3% (38.1–50.3), and the 5 year survival was 30.7% (24.9–36.73). For stage 2, the 3 year survival was 26.5% (17.9–35.9) and the 5 year survival was 15.1% (7.8–24.7). For stage 3, the 3 year survival was 15.9 % (11.2–21.2) and the 5 year survival was 8.8% (5.3–13.5). For stage 4, the 3 year survival was 13.7% (10.5-17.4%) and the 5 year survival was 9.8% (6.8–13.5) (P<0.001).
Conclusions:
Our retrospective study showed that 88.4% of LC cases emerge post HNC cancer treatment. Predominantly affecting older males (67.3%) and nonHispanic individuals (85.6%). The survival rate of LC after HNC varies broadly depending on the stage of diagnosis. Moreover, most of the patients diagnosed with LC after HNC were diagnosed at an advanced stage carry on a grim prognosis (5 year survival rate of 9.8%). Therefore, early detection remains paramount, given the high prevalence of advanced stage diagnoses (stage 4: 43%).