Results of a retrospective study of patients with stage IA lung adenocarcinoma showed that while part-solid nodules (PSNs) are independently associated with improved cure rates compared with solid nodules, inclusion of nodule type in the clinical T category did not add prognostic value.1
The eighth edition of the American Joint Commission on Cancer (AJCC) TNM staging system for non-small cell lung cancer (NSCLC), including lung adenocarcinoma, was implemented in 2018. It classified tumor nodules of 1 cm or less in size as T1a; more than 1 cm, but less than 2 cm as T1b; and more than 2 cm, but less than 3 cm as T1c. Lung adenocarcinoma tumors classified as T1N0M0 are staged as IA.2
In the current AJCC TNM staging system, only the solid portion of a PSN is taken into account when determining clinical T category (ie, in the case of ground-glass nodules, the ground-glass opacity, is not considered). Nevertheless, there is controversy concerning whether PSNs are independent prognostic factors compared with solid nodules, and whether these types of tumors should be included in a separate clinical T category.
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This study included data for 744 patients with clinical stage IA lung adenocarcinoma who underwent surgical resection between January 2008 and March 2014 at a single tertiary referral center and for whom survival records were available. Of these, 362 and 382 patients were diagnosed with PSNs and solid nodules, respectively.
Patients with PSNs were more likely to be younger than those with solid nodules, with respective median ages of 61 years and 64 years, (P =.009), never smokers (P =.002), and to be diagnosed with earlier clinical T categories (ie, cT1a in 34.3% vs 4.7%, respectively; P <.001).
At a median follow-up of 2463 days for patients with PSNs and 2543 days for those with solid nodules, the 5-year overall survival (OS) rates were 97.6% and 94.4%, respectively. On multivariable analyses, nodule type was not significantly associated with OS (P =.291). Conversely, there was a significant association between clinical T categories and OS (hazard ratio [HR] of cT1b, 2.33; 95% CI, 1.07-5.06; P =.033]; HR of cT1c, 5.74; 95% CI, 2.51-13.12; P <.001).
“There were no interactions between nodule type and the clinical T categories (P >.05),” the study authors wrote.
However, multivariable analyses using a “mixture cure model” also demonstrated that nodule type was associated with long-term survival, with cure rates of 93.6% and 74.1% in patients with PSNs compared with those with solid nodules (adjusted odds ratio [OR], 0.40; 95% CI, 0.19-0.84; P =.016). Other negative predictors of long-term survival included age and male sex.
In their concluding remarks, the study authors noted that “the clinical T categorization system is valid for PSNs and solid nodules. Nevertheless, PSNs are a prognostic factor associated with long-term survival.”
References
- Kim H, Goo JM, Kim YT, et al. Validation of the eighth edition clinical T categorization system for clinical stage IA resected lung adenocarcinomas: Prognostic implications of the ground-glass opacity component [published online December 23, 2019]. J Thorac Oncol. doi: 10.1016/j.jtho.2019.12.110
- National Comprehensive Cancer Network (NCCN) non-small cell lung cancer guidelines. V1.2020. https://www.nccn.org/professionals/physician_gls/pdf/nscl.pdf. Accessed January 13, 2020.
