We reported a single-institution experience on radiomic differentiation on MPLCs from SPLCs, especially emphasis on their long-term variation. The reported incidence of synchronous lung carcinoma is variably between 0.2–20%[12]. In our study, the incidence of MPLCs was 24.5%, which was slightly higher than the reported incidence. It may be related to the universality of chest computed tomography screening programs. There were no statistical difference between the characteristics of gender and age. Slightly different from the outcome in the past study, female gender and smoke free statue were more frequent in MPLCs[7]. And the MPLCs were more easier to the pathological type of MIA compared with SPLCs (45.9% vs. 32.7%, p<0.05). This result supported the previous view that the proportion of MIA and adenocarcinoma in situ is high in sMPLCs[13]. This also may be due to timely detection of MPLCs at a early stage with regular surveillance for the first primary carcinoma[14]. However, present clinical and traditional methods are unable to understand the different evolution between MPLCs and SPLCs. Thus, studies of novel factors that differ significantly between patients with MPLCs and SPLCs are necessary vehicles for identifying subtleties in two diseases.
Patients with first primary cancer remain at risk of developing a secondary tumor at a distant site through metastasis via the lymphatic or circulatory system[15]. Second primary carcinomas showed specific associations with the first one and their nature course were not the same[16]. The etiology of MPLCs is ambiguous[17]. Our radiomics analysis between MPLCs and SPLCs found of interest that radiomics could identify the difference between two groups with the AUC of 0.840 (95%CI, 0.810–0.867) in the training set and that of 0.670 (95%CI, 0.611–0.724) in the validation set. Nevertheless, this low discrimination efficiency was insufficient to supplied accurate information to better understand the difference between MPLCs and SPLCs. To best of our knowledge, it is the first article focused on the distinction between MPLCs and SPLCs from the point view of radiomics and delta-radiomics.
The crucial challenge regarding MPLCs is what they differed with SPLCs in the course of development, on which both the treatment strategies and prognosis are based[18]. The possible of difference between MPLCs and SPLCs should always be considered during the follow-up surveillance, which determines the subsequent management strategy[19]. It has conclusively been suggested that the overall survival of MPLCs was better than SPLCs with intrapulmonary metastasis[20]. Therefore, a delta-radiomics approach studied the variation of radiomic features during baseline examination and follow-up duration[21]. The AUC of FC-delta of group C was the highest both in the training set (0.998 vs. 0.989 and 0.972) and the validation set (0.853 vs. 0.821 and 0.798). With the extension of follow-up intervals, the difference between MPLCs and SPLCs was more obvious. The literature on survival difference between sMPLCs and SPLCs has quantified and highlighted that the prognosis of sMPLCs was poorer and resembled that of SPLCs of a higher stage[22]. Our results suggested that the nature course of two diseases was inconsistent and the delta-radiomics could better distinct the MPLCs and SPLCs than radiomics. We firstly reported the difference of two diseases in terms of both radiomics and delta-radiomics to help us make decision on individual therapy and predict the prognosis of diseases.
Our present study has several limitations. Currently, there are no definitive guideline for the diagnosis and treatment of MPLCs. In 2003, the American College of Chest Physicians (ACCP) developed a new diagnostic criteria for MPLCs with evaluations of lymphatic and systemic metastasis and the interval between mMPLC was extended to at least 4 years[23]. Antakli et al. revised the criteria of Martini and Melamed by adding DNA ploidy validation for distinction[24]. However, they have not widely applied to clinical practice due to its disadvantages of expensive, time consuming, and low sensitivity. Hence, we adopted the most cited criteria of the 2nd edition of ACCP in our research. Second, the MPLCs can be subdivided into mMPLCs and sMPLCs. Due to the limitation of incidence and sample size, we performed a general analysis of MPLCs which may lead to a biased result. Third, we only enrolled the cohort with pathological types of MIA and IAC to analysis and neglected other pathological types of lung carcinomas. The MPLCs and SPLCs with pathological types of adenocarcinoma in situ, squamous carcinoma[25], and so on should further be studied after collecting enough cases.