Nowadays, there is still no established standardized treatment strategy for elderly EC patients due to their special characteristics. Although considerations which include age, functional status, risk of treatment-related morbidities, life expectancy, and personal preference should be taken into account when making treatment decisions, the prognosis of elderly patients with EC is still poorer than young non-elderly patients [5]. Furthermore, RECIST 1.1 which has been widely used in the clinic to evaluate tumor's response to anticancer therapy still has some limitations. First, its main evaluation criteria are to measure changes in the longest diameter of assessable lesions, while ignoring short diameter and tumor volume; secondly, the one-dimensional measurement based on morphological changes ignores molecular changes and cannot effectively reflect the biological changes in tumors, which may lead to inaccurate prediction of treatment responses; thirdly, the evaluation of efficacy by RECIST 1.1 criteria is usually carried out one or three months after treatment, which may delay the detection of disease progression and recurrence [22]. Hence, it is necessary to explore new biomarkers to predict the ETR of elderly ESCC patients. Tumor volume can be easily gotten from the Varian treatment planning system, and IBs have the advantages of economy, simple detection, and easy to be accepted by the majority of patients. Based on those, we investigated the tumor volume, pre-IBs, and their dynamic changes on ETR in newly diagnosed elderly ESCC patients (≥ 70 years) who underwent radiotherapy. And our present study found that TVCR, pre-NLR, and delta-NLR were significantly associated with ETR in elderly ESCC patients. Furthermore, the developed nomogram based on all independent predictors had a better prediction ability for ETR.
Generally speaking, the bigger tumor volume is, the great tumor burden is. As far as EC is concerned, Boggs et al thought that the greater the tumor volume load, the lower the survival time of patients, and tumor volume is an independent prognostic factor affecting the survival of patients [10]. Chen et al retrospectively analyzed the clinical data of 187 patients after radiotherapy and found that the survival time of patients with higher GTV (> 39.41cm3) which was based on the radiation therapy planning system was significantly lower than that of the comparison group (GTV < 39.41cm3) [11]. Furthermore, Créhange et al have also retrospectively analyzed the tumor volume of 148 patients with EC underwent radiotherapy and found that overall survival (OS) of patients with tumor volume ≥ 100cm3 which was calculated by assimilation as the sum of two pairs of truncated cones was significantly lower than that of patients with tumor volume < 100cm3 (P = 0.041) [12]. The tumor volume in the present study was automatically calculated by the radiotherapy planning system, and neither GTVi nor GTVs was associated with ETR. One reason was that all the ESCC patients were elderly which had dull sensation, late appearance of self-feeling symptoms, and late medical treatment so that most of the tumor volume were larger than non-elderly patients when diagnosed. Another was that esophagus was a hollow organ, the hollow tissue would affect the accuracy of the automatic drawing of tumor tissue. However, it did not mean that tumor volume had no predictive value in elderly ESCC patients. It seemed to be more valuable to quantify tumor volume change during treatment from the aspect of disease regression. Jobbour et al had reported that tumor volume reduction during CRT could predict post-CRT survival in NSCLC [23]. Yang et al also found that volume reduction rate was an outcome predictor for head-and-neck cancer patients treated with radiotherapy [24]. Interestingly, NSCLC patients with pronounced volume regression had worse locoregional tumor control and overall survival in Brinkv et al study [25]. However, elderly ESCC patients who were bigger TVCR (≥ 6.24%) had better ETR in this study which might suggest that TVCR might be a more sensitive indicator than tumor volume. Moreover, there was a significant decrease between GTVi and GTVs which indicated that radiotherapy was an effective treatment for elderly ESCC patients. Currently, radiotherapy physicians still manually delineate and calculate tumor volumes by computer systems and therapeutic planning systems, while many factors such as doctors' clinical knowledge, experience, energy, and status determine that there are some differences in drawing quality between different doctors and different patients [26]. There is no doubt that these also affect target delineation and calculation of tumor volume. It is possible to solve these problems with artificial intelligence (AI) at the age of precision medicine. Lin et al have used AI technology to automatically draw nasopharyngeal tumors on magnetic resonance images, which provided a solution for accurate and efficient delineation of radiotherapy targets [27]. Choi et al have confirmed the plausibility of deep learning-based automatic segmentation for clinical implementations in breast cancer [28]. So, the prospect of precision medicine based on radiotherapy for tumors will be promising with the development of AI.
Apart from tumor volume, some studies also found that inflammatory response is closely associated with tumor prognosis [19, 29]. The inflammatory response can participate in and promote the malignant transformation, migration, and diffusion of tumor cells by up-regulating cytokines, producing inflammatory mediators, inhibiting apoptosis, promoting angiogenesis, and inducing DNA mutation [14,30−31]. Lymphocytes, neutrophils, platelets, and monocytes have always been considered to play an important role in immune balance and inflammatory response. Lymphocytes are considered to be tumor suppressor cells, which can induce tumor cell death and inhibit tumor progression [32]. An abnormal increase of neutrophils may lead to tumor proliferation, increased potential of local invasion and metastasis, tumor vascularization, and help tumor cells escape immune surveillance [33]. Platelets can cooperatively activate tumor cells and are essential for early metastasis of cancer [34]. Monocytes may be involved in tumor growth and promote tumor progression and metastasis [35]. Furthermore, the complex IBs which include NLR, PLR, and LMR can reflect the dynamic relationship between anti-tumor and promoting tumor. Our present study found there was a significant increase in pre-NLR during radiotherapy, as well as in pre-PLR, and a significant decrease in pre-LMR. This association between changes of IBs and radiotherapy at different time points could at least be partly explained. Besides immunity gradually decreases with age, larger tumor volume (P < 0.0001), concurrent chemotherapy (P < 0.0001), and stage III disease (P = 0.05) would lead to a lower count of lymphocytes [36].
The predictive value of NLR in EC has been confirmed in many studies. Yoo et al have conducted a retrospective study on 138 locally advanced EC patients who received concurrent CRT, and found that high pre-NLR group the progression-free survival (PFS) time and OS time were significantly shorter in the high pre-NLR group (NLR ≥ 2.0) were significantly associated with decreased PFS and OS (all P < 0.05) [15]. Zhou et al have also analyzed 517 locally advanced EC patients who received CRT and pointed out that pre-NLR > 5 was an independent predictor of PFS and overall OS (all P < 0.001). Similar to these results, pre-NLR was an independent predictor for ETR in elder ESCC patients who underwent radiotherapy in this study [16]. Additionally, delta-NLR was also significant associated with ETR, and elderly ESCC patients who were with low delta-NLR (<-1.728) would get better ETR which might suggest that delta-IBs were also predictors for them. Choil et al have found that changes in NLR after neoadjuvant treatment showed a statistically significant correlation with advanced breast cancer patients' survival [37]. Templeton et al reported that early decline of NLR was associated with favorable outcomes, whereas an increase was associated with worse outcomes for metastatic renal cell carcinoma with targeted therapy [38]. Whether pre-NLR or delta-NLR, these studies did not specifically analyze the elderly patients. This was the first significant study that analyzed the predictive value of pre-NLR and delta-NLR in elderly ESCC patients. In therapy, delta-NLR should be better reflect the sensitivity of the tumor to treatment. However, pre-NLR had a better predictive value than delta-NLR in this study which might be that pre-NLR was better able to reflect the state of the body's original response.
Recently, many scholars have studied the prognostic value of PLR and LMR in cancer patients, but their role in ESCC is still controversial. Xie et al found that PLR had the predictive ability for ESCC patients with different stages, which was an independent predictor for stage I ~ II, but not for stage III ~ IV [17]. While Jun et al thought that there was no significant correlation between PLR and postoperative survival time by analyzing the clinical data of patients with ESCC [39]. Another study also reported that a low LMR (< 4) was a significant and independent predictor of poor survival in non-elderly EC patients who received curative thoracoscopic esophagectomy [18]. But our present study found that PLR and LMR were not significant with ETR in multivariate analyses for elderly ESCC patients. The reason might be that radiotherapy might result in part of necrosis and death of cancer cells as well as the surrounding tissues, which in turn cause an inflammatory response similar to the wound healing response. Interestingly, there was a correlation between delta-NLR and delta-LMR, as well as delta-PLR, while only delta-NLR was significantly associated with ETR in this study.
We have confirmed that the IBs and TVCR were significant with early tumor response in ESCC patients who underwent radiotherapy or CRT by different retrospective studies [40–41]. However, we did not analyze the tumor volume and IBs on ETR in elderly ESCC patients. To our knowledge and limited literature searches, this was the first report that describes the prognostic significance of ETR combined with tumor volume, IBs, and their dynamic changes in elderly ESCC patients who underwent radiotherapy. But several limitations would be addressed here. First, this was a retrospective, single-center, and small population study that was entire of elderly ESCC patients, which might limit the universality of the results. Second, oncology does not have a specific age threshold for elderly patients with cancer. And we defined the elderly as the patient whose age ≥ 70 years. Last, there is no consensus on the exact cut-off value for IBs, and various methods including ROC and median values have been used to determine the optimal segregation points. Consequently, larger, multicenter, and prospectively designed clinical trials are required to confirm these initial results.