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.


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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

  1. 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
  2. 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.