Exposure to Agent Orange is associated with increased recurrence after surgical treatment of stage I non-small cell lung cancer

OBJECTIVE

Approximately 3 million Americans served in the armed forces during the Vietnam War. Veterans have a higher incidence rate of lung cancer compared with the general population, which may be related to exposures sustained during service. Agent Orange, one of the tactical herbicides used by the armed forces as a means of destroying crops and clearing vegetation, has been linked to the development of several cancers including non-small cell lung cancer. However, traditional risk models of lung cancer survival and recurrence often do not include such exposures. We aimed to examine the relationship between Agent Orange exposure and overall survival and disease recurrence for surgically treated stage I non-small cell lung cancer.

METHODS

We performed a retrospective cohort study using a uniquely compiled dataset of US Veterans with pathologic I non-small cell lung cancer. We included adult patients who served in the Vietnam War and underwent surgical resection between 2010 and 2016. Our 2 comparison groups included those with identified Agent Orange exposure and those who were unexposed. We used multivariable Cox proportional hazards and Fine and Gray competing risk analyses to examine overall survival and disease recurrence for patients with pathologic stage I disease, respectively.

RESULTS

A total of 3958 Vietnam Veterans with pathologic stage I disease were identified (994 who had Agent Orange exposure and 2964 who were unexposed). Those who had Agent Orange exposure were more likely to be male, to be White, and to live a further distance from their treatment facility (P < .05). Tumor size distribution, grade, and histology were similar between cohorts. Multivariable Cox proportional hazards modeling identified similar overall survival between cohorts (Agent Orange exposure hazard ratio, 0.97; 95% CI, 0.86-1.09). Patients who had Agent Orange exposure had a 19% increased risk of disease recurrence (hazard ratio, 1.19; 95% CI, 1.02-1.40).

CONCLUSIONS

Veterans with known Agent Orange exposure who undergo surgical treatment for stage I non-small cell lung cancer have an approximately 20% increased risk of disease recurrence compared with their nonexposed counterparts. Agent Orange exposure should be taken into consideration when determining treatment and surveillance regimens for Veteran patients.

Lobe-specific lymph node sampling is associated with lower risk of cancer recurrence

Objective

Adequate intraoperative lymph node (LN) assessment is a critical component of early-stage non-small cell lung cancer (NSCLC) resection. The National Comprehensive Cancer Network and the American College of Surgeons Commission on Cancer (CoC) recommend station-based sampling minimums agnostic to tumor location. Other institutions advocate for lobe-specific LN sampling strategies that consider the anatomic likelihood of LN metastases. We examined the relationship between lobe-specific LN assessment and long-term outcomes using a robust, highly curated cohort of stage I NSCLC patients.

Methods

We performed a cohort study using a uniquely compiled dataset from the Veterans Health Administration and manually abstracted data from operative and pathology reports for patients with clinical stage I NSCLC (2006-2016). For simplicity in comparison, we included patients who had right upper lobe (RUL) or left upper lobe (LUL) tumors. Based on modified European Society of Thoracic Surgeons guidelines, lobe-specific sampling was defined for RUL tumors (stations 2, 4, 7, and 10 or 11) and LUL tumors (stations 5 or 6, 7, and 10 or 11). Our primary outcome was the risk of cancer recurrence, as assessed by Fine and Gray competing risks modeling. Secondary outcomes included overall survival (OS) and pathologic upstaging. Analyses were adjusted for relevant patient, disease, and treatment variables.

Results

Our study included 3534 patients with RUL tumors and 2667 patients with LUL tumors. Of these, 277 patients (7.8%) with RUL tumors and 621 patients (23.2%) with LUL tumors met lobe-specific assessment criteria. Comparatively, 34.7% of patients met the criteria for count-based assessment, and 25.8% met the criteria for station-based sampling (ie, any 3 N2 stations and 1 N1 station). Adherence to lobe-specific assessment was associated with lower cumulative incidence of recurrence (adjusted hazard ratio [aHR], 0.83; 95% confidence interval [CI], 0.70-0.98) and a higher likelihood of pathologic upstaging (aHR, 1.49; 95% CI, 1.20-1.86). Lobe-specific assessment was not associated with OS.

Conclusions

Adherence to intraoperative LN sampling guidelines is low. Lobe-specific assessment is associated with superior outcomes in early-stage NSCLC. Quality metrics that assess adherence to intraoperative LN sampling, such as the CoC Operative Standards manual, also should consider lobe-specific criteria.