Start Submission Become a Reviewer

Reading: Comparison of Local Recurrence Patterns of Postoperative Radiotherapy with Surgery Alone for...

Download

A- A+
Alt. Display

Experimental Research

Comparison of Local Recurrence Patterns of Postoperative Radiotherapy with Surgery Alone for Esophageal Carcinoma Patients

Authors:

Zhi-Chen Xu ,

Department of Radiation Oncology, First Hospital of Quanzhou Affiliated to Fujian Medical University, Quanzhou (362000), CN
X close

Bao-An Su

Department of Radiation Oncology, First Hospital of Quanzhou Affiliated to Fujian Medical University, Quanzhou (362000), CN
X close

Abstract

Background: We analyzed local regional recurrence patterns of thoracic esophageal carcinoma after three-field lymph node dissection (3-FLD) with and without postoperative radiotherapy, and assessed the postoperative radiation value for local control.

Methods: The study reviewed 239 local recurrences of esophageal squamous cell carcinoma after 3-FLD from 2010 to 2018 in our hospital, retrospectively, and compared local regional recurrence patterns between surgery followed by radiotherapy (S+RT) and surgery alone (SA).

Results: In 239 thoracic esophageal carcinomas that underwent curative surgery, the lymph node recurrence was the most common type of local recurrence for patients in both groups. The sequence of lymph node recurrence rate in both groups from highest to lowest was mediastinal, cervical, and abdominal. The recurrence rate of superior mediastinal lymph node in patients without radiotherapy was significantly higher than that in patients with radiotherapy (67.72% vs. 47.54%, x2 = 7.615, P = 0.006). The recurrence rate of abdominal lymph node in the upper TEC was significantly lower than that in the middle and lower TEC (x2 = 9.452, P = 0.009). The abdominal lymph node recurrence rate in patients with preoperative abdominal LNM was very significantly higher than that in patients without preoperative abdominal LNM (43.63% vs. 6.66%, P < 0.001).

Conclusions: The dangerous lymph node recurrence regions included superior, middle mediastinum, and neck. Postoperative radiotherapy shows great value for patients in reducing superior mediastinal lymph node recurrence rate. The lower segment of thoracic esophageal carcinoma and preoperative abdominal lymph node metastasis, especially para-aortic lymph node metastasis, may be risk factors for abdominal lymph node recurrence.

How to Cite: Xu Z-C, Su B-A. Comparison of Local Recurrence Patterns of Postoperative Radiotherapy with Surgery Alone for Esophageal Carcinoma Patients. International Journal of Surgery: Oncology. 2021;6(1):33–40. DOI: http://doi.org/10.29337/ijsonco.65
27
Views
4
Downloads
  Published on 17 Jun 2021
 Accepted on 22 Feb 2021            Submitted on 09 Feb 2021

Introduction

At present, the overall 5-year survival rate of esophageal carcinoma is 45.7% [1]. Despite recent advances in minimally invasive oesophagectomy [2], there was no significant improvement in survival. The main treatment failure causes after surgery were local recurrence and distant metastasis. The local recurrence rates after surgery ranged from 42.9% to 57.9% [3, 4, 5, 6, 7]. Although there is no common consensus for postoperative radiotherapy, a growing number of researchers [8, 9, 10, 11] suggest that postoperative radiotherapy, which can reduce local recurrence, was associated with better survival rates for patients with node-positive thoracic esophageal carcinoma (TEC). However, the universally accepted prophylactic radiotherapy target volume for TEC has not yet been established. Initially, the target volume includes the entire mediastinum, bilateral supraclavicular area, and left gastric area. However, patients frequently had side effects, such as gastrointestinal reaction or bone marrow suppression. Latest researchers [12, 13, 14, 15, 16] thought supraclavicular, and station 1–5 and 7 lymph nodes should be included in postoperative radiotherapy. In this way, many patients could avoid many adverse effects.

This study compared the recurrence rate and relapse site in TEC patients after three-field lymph node dissection (3-FLD) between surgery followed by radiotherapy (S+RT) and surgery alone (SA), and may show its possible impact on target delineation for postoperative radiotherapy.

Methods

General information

From January 2010 to December 2018, 980 patients with thoracic esophageal squamous cell carcinoma (ESCC) were treated with three-field lymph node dissection (3-FLD) [17]. 239 patients with ESCC who had local-regional recurrence, including 175 cases in SA group and 64 cases in S+RT group, were identified in our hospital. Patients with palliative surgical treatment or apparent residual tumors were excluded.

Among the 239 patients, there were 212 male patients and 27 female patients. Ages ranged from 38 to 78 years, with a median age of 57 years old. 43 patients had upper TEC, 176 had middle TEC, and 20 had lower TEC. Patients were staged according to TNM classification (AJCC/UICC, 2009). Patient characteristics are shown in Table 1. In this study, the median time to recurrence was 16.6 months (range10–43 months).

Table 1

Patient and tumor characteristics.


VARIABLE SA S+RT x2 VALUE P VALUE

Age (years)

    >60 years 104 45 2.365 0.124

    ≤60 years 71 19

Sex

    Male 150 58 0.190 0.663

    female 25 8

Localization of the tumors

    Upper thoracic third 34 9 2.852 0.240

    Middle thoracic third 124 52

    Lower thoracic third 17 3

Length of tumor on X-ray

    >5cm 82 28 0.182 0.670

    ≤5cm 93 36

Tumor differentiation

    Low (G3) 43 16 1.202 0.548

    Moderate (G2) 103 41

    High (G1) 29 7

pT category

    T1/T2 45 13 0.744 0.388

    T3/T4 130 51

pN category

    N0 12 52 5.075 0.166

    N1 17 47

    N2 10 31

    N3 25 45

Postoperative chemotherapy

    YES 134 52 0.594 0.441

    NO 41 12

Abbreviations: SA = surgeryalone; S+RT = surgery plus postoperative radiotherapy; G = grad.

Postoperative radiation

Radiotherapy with 18-MV X-rays was started 4 weeks after surgery. For upper and middle TEC, the supraclavicular, and station 1–5 and 7 lymph nodes regions, anastomosis and tumor bed were irradiated. For lower TEC, supraclavicular, station 1–5 and 7 lymph nodes and upper abdominal lymph nodes area, anastomosis and tumor bed were irradiated. The median radiation dose was 50 Gy in 25 fractions at 2 Gy per fraction, 5 days per week.

Diagnostic criteria

Preoperative lymph node metastasis was confirmed pathologically after 3-LND. All patients were followed up every 3–6 months. Local-regional recurrence included lymph node, anastomosis, and tumor bed recurrence.

Supraclavicular lymph node recurrence diagnosis was mainly based on physical examination, Doppler ultrasound, CT, and fine needle aspiration cytology if necessary. Mediastinal lymph node recurrence diagnosis was mainly based on CT or PET-CT. Abdominal lymph node recurrence diagnosis was based mainly on Doppler ultrasound and CT.

As diagnostic criterion, detected nodes were considered recurrence if the short axis was greater than 1cm [18, 19]. Additionally, we also took uptake of contrast medium or FDG into consideration. Anastomotic recurrence was determined pathologically by gastric endoscopy. Tumor bed recurrence was diagnosed by CT or PET-CT.

Terminology of the regional lymph nodes in esophageal cancer

According to a lymph node mapping system for esophageal carcinoma (AJCC-UICC in 2009), the fields of lymph nodes were as follows: 1R (right highest mediastinal nodes); 1L (left highest mediastinal nodes); 2R (right upper paratracheal nodes); 2L (left upper paratracheal nodes); 3P (posterior mediastinal nodes); 4R (right lower paratracheal nodes); 4L (left lower paratracheal nodes); 5 (subaortic nodes); 6 (paraaortic nodes); 7 (subcarinal nodes); 8M (middle paraesophageal lymph nodes); 8L (lower paraesophageal lymph nodes); 9 (pulmonary ligament nodes); 10R (right hilar nodes); and 10L (left hilar nodes). The lymph nodes in the 1, 2, 3, 4, 5 and 6 levels were included in the superior mediastinal lymph node; the lymph nodes in the 7, 8M, and 10 level were included in the middle mediastinal lymph node; the lymph nodes in the 8L and 9 level were included in the inferior mediastinal lymph node.

Statistical analysis

SPSS 19.0 statistical software was used for data analysis. A chi square test was used for enumeration data. A P value less than 0.05 was considered statistically significant.

Results

Recurrence patterns

Among 239 patients, lymph node recurrence was the most common pattern of local regional recurrence in both group. There was no significant difference between S+RT and SA regarding lymph node recurrence (95.31% vs. 90.29%, P = 0.214), anastomosis recurrence (10.94% vs. 19.43%, P = 0.123), and tumor bed recurrence (4.69% vs. 9.71%, P = 0.214) (Table 2).

Table 2

The comparison of local recurrence patterns between two groups.


GROUPS LYMPH NODES RECURRENCE ANASTOMOSIS RECURRENCE TUMOR BED RECURRENCE

SA 158(90.29%) 34 (19.43%) 17 (9.71%)

S+RT 61(95.31%) 7 (10.94%) 3 (4.69%)

statistics x2 = 1.544, P = 0.214 x2 = 2.377, P = 0.123 x2 = 1.544, P = 0.214

Abbreviations: SA = surgeryalone; S+RT = surgery plus postoperative radiotherapy.

Lymph node recurrence

The mediastinal lymph node recurrence was the most common lymph node recurrence in both groups. The difference was not statistically significant between S+RT and SA in the cervical (40.98% vs. 49.37%, P = 0.265), mediastinal (69.93% vs. 72.78%, P = 0.199), and abdominal lymph node recurrence (20.25% vs. 27.87%, P = 0.225) (Table 3). In patients without postoperative radiotherapy, there was no significant difference in the cervical lymph node recurrence among different primary tumor segments (x2 = 1.599, P = 0.449). In patients without postoperative radiotherapy, there was no significant difference in the mediastinal lymph node recurrence among different primary tumor segments (x2 = 4.088, P = 0.130). However, the recurrence rate of abdominal lymph node in the upper TEC was significantly lower than that in the middle and lower TEC (x2 = 9.452, P = 0.009).

Table 3

The comparison of lymph node recurrence between two groups.


GROUPS THE CERVICAL LYMPH NODE RECURRENCE THE MEDIASTINAL LYMPH NODE RECURRENCE THE ABDOMINAL LYMPH NODE RECURRENCE

SA 78 (49.37%) 115 (72.78%) 32 (20.25%)

S+RT 25 (40.98%) 39 (63.93%) 17 (27.87%)

statistics x2 = 1.242, P = 0.265 x2 = 1.652, P = 0.199 x2 = 1.470, P = 0.225

Abbreviations: SA = surgeryalone; S+RT = surgery plus postoperative radiotherapy.

Mediastinal lymph node recurrence

The superior mediastinal lymph node recurrence was the most common mediastinal recurrence both groups. The recurrence rate of superior mediastinal lymph node in patients (SA) was significantly higher than that in patients (S+RT) (67.72% vs. 47, 54%, x2 = 7.615, P = 0.006). Hower, there was no significant difference between two groups of middle and inferior mediastinal lymph node recurrence.

Local recurrence of superior mediastinal lymph nodes occurred mostly in 4R region. There was very significant difference in the recurrence among these regions in patients with postoperative radiotherapy (x2 = 38.812, P < 0.001). It was the same case for patients without postoperative radiotherapy (x2 = 155.416, P < 0.001).

Local recurrence of middle mediastinal lymph nodes occurred mostly in 7 region, and there was significant difference in the recurrence among these regions in patients with postoperative radiotherapy postoperative radiotherapy (x2 = 11.186, P < 0.001). It was the same case for patients without postoperative radiotherapy (x2 = 35.726, P < 0.001). However, the recurrence of inferior mediastinal lymph nodes was rare in both groups (Tables 4 and 5).

Table 4

The distribution of mediastinal lymph node recurrence in the SA group.


GROUP NO.(%) GROUP NO.(%)

SMLNR 107(67.72%) 6 region 4(2.53%)

1R region 20(12.66%) MMLNR 45(28.48%)

2R region 22(13.92%) 7 region 37(23.42%)

4R region 55(34.81%) 8M region 8(5.06%)

1L region 11(6.96%) 10R region 11(6.96%)

2L region 21(13.29%) 10L region 12(7.59%)

4L region 35(22.15%) IMLNR 2(1.27%)

5 region 30(18.99%) 8L region 2(1.27%)

3A region 0(0.00%) 9 region 0(0.00%)

3P region 0(0.00%)

Abbreviations: SMLNR = superior mediastinal lymph node recurrence. MMLNR = middle mediastinal lymph node recurrence. IMLNR = inferior mediastinal lymph node recurrence. SA = surgeryalone.

Note: Superior mediastinal lymph node recurrence: x2 = 155.416, p < 0.001; Middle mediastinal lymph node recurrence: x2 = 35.726, p < 0.001.

Table 5

The distribution of mediastinal lymph node recurrence in the S+RT group.


GROUP NO.(%) GROUP NO.(%)

SMLNR 29(47.54%) 6 region 3(4.92%)

1R region 5(8.20%) MMLNR 18(29.51%)

2R region 7(11.48%) 7 region 13(21.31%)

4R region 15(24.59%) 8M region 3(4.92%)

1L region 1(1.64%) 10R region 4(6.56%)

2L region 2(3.28%) 10L region 5(8.20%)

4L region 7(11.48%) IMLNR 2(3.28%)

5 region 7(11.48%) 8L region 2(3.28%)

3A region 2(3.28%) 9 region 0(0.00%)

3P region 0(0.00%)

Abbreviations: SMLNR = superior mediastinal lymph node recurrence. MMLNR = middle mediastinal lymph node recurrence. IMLNR = inferior mediastinal lymph node recurrence. S+RT = surgery plus postoperative radiotherapy.

Note: Superior mediastinal lymph node recurrence: x2 = 38.812, p < 0.001; Middle mediastinal lymph node recurrence: x2 = 11.186, P = 0.011.

The local control efficacy of postoperative radiotherapy for patients with preoperative subcarinal or abdominal lymph node metastases

In patients without postoperative radiotherapy, the subcarinal lymph node recurrence rate in patients with preoperative subcarinal LNM was significantly higher than that in patients without preoperative subcarinal LNM (34.28% vs. 17.85%, P = 0.033). There was no significant difference in the subcarinal lymph node recurrence between SA and S+RT in patients with preoperative subcarinal LNM (x2 = 0.005, P = 0.943) (Table 6).

Table 6

The local control efficacy of postoperative radiotherapy for patients with preoperative subcarinal lymph node metastases.


SURGERY ALONE GROUP SURGERY + RADIATION GROUP


PSNM SUBCARINAL NODES PSNM SUBCARINAL NODES


RECURRENT NORMAL RECURRENT NORMAL

Positive 12 23 Positive 6 11

Negative 25 115 Negative 7 40

Statistics: x2 = 4.533, P = 0.033 Statistics: x2 = 2.073, P = 0.150

Abbreviations: PSNM = Preoperative subcarinal nodal metastasis.

Note: Comparison of subcarinal recurrence between two groups in patients with preoperative subcarinal nodal metastasis: x2 = 0.005, P = 0.943.

In patients without postoperative radiotherapy, the abdominal lymph node recurrence rate in patients with preoperative abdominal LNM was very significantly higher than that in patients without preoperative abdominal LNM (43.63% vs. 6.66%, P < 0.001), and it was the same case for patients with postoperative radiotherapy (52.38% vs. 13.95%, P = 0.001). There was no significant difference in the abdominal lymph node recurrence between SA and S+RT in patients with abdominal subcarinal LNM (x2 = 0.468, P = 0.494) (Table 7).

Table 7

The local control efficacy of postoperative radiotherapy for patients with preoperative abdominal lymph node metastases.


SURGERY ALONE GROUP SURGERY + RADIATION GROUP


PANM ABDOMINAL NODES PANM ABDOMINAL NODES


RECURRENT NORMAL RECURRENT NORMAL

Positive 24 31 Positive 11 10

Negative 8 112 Negative 6 37

Statistics: x2 = 34.498, p < 0.001 Statistics: x2 = 10.681, P = 0.001

Abbreviations: PANM=Preoperative abdominal nodal metastasis.

Note: Comparison of abdominal recurrence between two groups in patients with preoperative abdominal nodal metastasis: x2 = 0.468, P = 0.494.

Discussion

At present, the setting of postoperative radiation target volume in many centers is mostly based on the location of lymph nodes found during the operation. However, it is unclear whether the rucurrence in the site of preoperative lymph node metastasis would occur after dissection. Fujita et al. [20] reported that in patients with upper TEC, metastasis before operation was commonly found in the cervicothoracic and periesophageal nodes, and recurrence mostly occurred in the cervical nodes. In patients with middle TEC, metastasis before operation was commonly found in the cervicothoracic nodes of the right side, whereas recurrence mostly occurred in that of the left side. In patients with lower TEC, metastasis before operation was commonly found in the periesophageal nodes and upper abdominal nodes, whereas recurrence mostly occurred in the celiac nodes. Therefore, postoperative radiation, whose target volume is based on lymphatic spread regularity, may result in missing the target area. And, the comparison of the recurrence rate in each site for patients with esophageal carcinoma between surgery followed by radiotherapy (S+RT) and surgery alone (SA) is very important to assess the value of postoperative radiation for local control. In this study, The lymph node recurrence was the most common local regional recurrence in patients with and without postoperative radiotherapy. The common recurrent regions were cervical, superior, and middle mediastinal in both groups. This result is consistent with some recent studies [13, 14, 15, 16]. A possible reason for this result was the technical difficulty of lymph node dissection in the lower cervical, superior, and middle mediastinal regions. This is due to complex anatomy with abundant nerves, lymphatic vessels, and adjoining large blood vessels and critical organs in these regions. A few residual cancer cells are sometimes found in connective tissues, particularly in advanced ESCC, which may lead to relapse after surgery. Furthermore in our study, cervical and mediastinal recurrence was not significantly affected by TEC vertical location for patients without radiotherapy. Therefore, regardless of the location of tumor, irradiate supraclavicular and station 1–5 and 7 lymph nodes regions may decrease the risk of local recurrence and become an effective regimen for patients with high risk factors [10, 11].

Lu et al. [21] reported that after surgery, supraclavicular lymph node metastasis in patients in the lower and middle lower thirds were 1/43 and 1/18. So, it seems unnecessary that the bilateral supraclavicular area should be irradiated in the lower and middle lower thirds. Contrarily, Cai et al. [16] reported that the supraclavicular and station 1–5 and 7 lymph nodes had high recurrent rates for esophageal carcinomas in all locations, and the supraclavicular area should be incorporated within the postoperative irradiation target volume. In our study, cervical recurrence rate in patients with and without postoperative radiotherapy was 40.98% and 49.37%,respectively. Therefore, we thought the supraclavicular area should be included in the postoperative radiotherapy target volume. In this study, the superior mediastinal lymph node recurrence rate in SA group was significantly higher than that in S+RT group (67.72% vs. 47.54%, x2 = 7.615, P = 0.006). Possible explanations include that it was technically difficult to dissect all lymph nodes in these areas and that the areas of these lymph nodes (station 1–5 lymph nodes) were incorporated within the postoperative irradiation target volume. The residual cancer cells then were killed by the postoperative radiotherapy with a sufficient dose. Therefore, we suggest the superior mediastinal area must be included in the postoperative radiotherapy target volume for all TEC segments.

Locoregional recurrence of the middle mediastinal lymph nodes was frequent in the 7 region. In patients without postoperative radiotherapy, the subcarinal lymph node recurrence occurred more frequently in those with preoperative subcarinal LNM. This suggested the presence of preoperative subcarinal LNM may be significantly associated with subcarinal recurrence. However, there was not a significant decrease in the recurrent rate of subcarinal lymph node in patients with preoperative subcarinal LNM after postoperative radiotherapy (x2 = 0.005, P = 0.943). We thought the small sample sizes of recurrences with postoperative radiotherapy might influence this result.

Lower TEC mostly metastasizes downward to abdominal para-aortic lymph nodes [22, 23]. In this study, the recurrent rate of abdominal lymph node in the upper TEC was significantly lower than that in the middle thoracic and lower TEC. Furthermore, the abdominal recurrence was significantly associated with the presence of preoperative abdominal LNM. This may be attributed to the technically difficulty in removing all lymph nodes in this area when some are adjacent to the abdominal aorta. These small numbers of residual cancer cells may result in recurrence [24]. In this study, postoperative radiotherapy did not significantly decrease the recurrent proportion of abdominal lymph nodes in patients with preoperative abdominal LNM. One possible explanation includes that the abdominal area was irradiated only in lower TEC and not in upper and middle TEC. Therefore, we suggest abdominal areas, including para-aortic lymph node areas, should be irradiated in patients with preoperative abdominal LNM, especially para-aortic LNM.

Anastomotic radiotherapy is still in dispute considering it may cause anastomotic stricture. In our study, the recurrence rate of anastomosis in patients without radiotherapy was higher than that in patients with radiotherapy (19.43% vs. 10.94%). Therefore, postoperative radiotherapy may reduce anastomotic recurrence if the target volume includes anastomosis.

There were some limitations to our study. First, because this study was a retrospective analysis of local recurrent cases with TEC, a clear conclusion cannot be exactly drawn. Second, we did not test gene expressions by immunohistochemical in every patient. Therefore, the existence of radiotherapy resistance in certain patients may also affect the results. A large sample prospective study with postoperative radiotherapy followed by 3-LND in patients with high risk factors is necessary to assess the postoperative radiation value for local control.

In conclusion, the main pattern of local esophageal squamous cell carcinoma recurrence after radical 3-FLD may be lymph node metastasis. The dangerous regions of lymph node recurrence included superior, middle mediastinum and neck. Postoperative radiotherapy shows great value in reducing superior mediastinal lymph node recurrence, and the fields of these lymph nodes should be delineated in the postoperative irradiation target volume. The lower segment of thoracic esophageal carcinoma and preoperative abdominal lymph node metastasis, especially para-aortic lymph node metastasis, may be risk factors for abdominal lymph node recurrence. Anastomosis should also be included in the target area.

Ethics and Consent

No animal or human was involved in this study.

Informed consent was obtained from all individual participants included in the study.

Competing Interests

The authors have no competing interests to declare.

Author contributions

ZX had the idea for the article and performed the literature search and data analysis, and ZX and BS drafted and/or critically revised the work.

References

  1. Oppedijk V, van der Gaast A, van Lanschot JJB, et al. Treatment pattern and overall survival in esophageal cancer during a 13-year period: A nationwide cohort study of 6,354 Korean patients. Clin Oncol. 2014; 32(5): 385–91. DOI: https://doi.org/10.1371/journal.pone.0231456 

  2. Siaw-Acheampong K, Kamarajah SK, Gujjuri R, Bundred JR, Singh P, Griffiths EA. Minimally invasive techniques for transthoracic oesophagectomy for oesophageal cancer: systematic review and network meta-analysis. BJS Open. 2020; 4(5): 787–803. DOI: https://doi.org/10.1002/bjs5.50330 

  3. Wang Y, Zhang L, Ye D, Xia W, Jiang J, Wang X, Zhang M, Wang F. A retrospective study of pattern of recurrence after radical surgery for thoracic esophageal carcinoma with or without postoperative radiotherapy. Oncol Lett. 2018; 15(3): 4033–4039. DOI: https://doi.org/10.3892/ol.2018.7807 

  4. Lin G, Haibo Liu, Jian Li. Pattern of recurrence and prognostic factors in patients with pT1-3 N0 esophageal squamous cell carcinoma after surgery: analysis of a single center experience. Cardiothorac Surg. 2019; 14(1): 58. DOI: https://doi.org/10.1186/s13019-019-0883-1 

  5. Ni W, Yang J, Deng W, et al. Patterns of recurrence after surgery and efficacy of salvage therapy after recurrence in patients with thoracic esophageal squamous cell carcinoma. BMC Cancer. 2020; 20(1): 144. DOI: https://doi.org/10.1186/s12885-020-6622-0 

  6. Hamai Y, Hihara J, Emi M, Furukawa T, Ibuki Y, Yamakita I, Kurokawa T, Okada M. Treatment Outcomes and Prognostic Factors After Recurrence of Esophageal Squamous Cell carcinoma. World J Surg. 2018; 42(7): 2190–2198. DOI: https://doi.org/10.1007/s00268-017-4430-8 

  7. Nobel TB, Livschitz J, Xing XX, et al. Surveillance Implications of Recurrence Patterns in Early Node-Negative Esophageal Adenocarcinoma. Ann Thorac Surg. 2019; 108(6): 1640–1647. DOI: https://doi.org/10.1016/j.athoracsur.2019.05.066 

  8. Luo H, Cui YY, Zhang JG, et al. Meta-analysis of survival benefit with postoperative chemoradiotherapy in patients of lymph node positive esophageal carcinoma. Clin Transl Oncol. 2018; 20(7): 889–898. DOI: https://doi.org/10.1007/s12094-017-1803-2 

  9. Kang J, Chang JY, Sun X, et al. Role of Postoperative Concurrent Chemoradiotherapy for Esophageal Carcinoma: A meta-analysis of 2165 Patients. Cancer. 2018; 9(3): 584–593. DOI: https://doi.org/10.7150/jca.20940 

  10. Hsu P-K, Huang C-S, Wang B-Y, Wu Y-C, Hsu W-H. Survival benefits of postoperative chemoradiation for lymph node-positive esophageal squamous cell carcinoma. Ann Thorac Surg. 2014; 97(5): 1734–41. DOI: https://doi.org/10.1016/j.athoracsur.2013.12.041 

  11. Liu T, Liu W, Zhang H, Ren C, Chen J, Dang J. The role of postoperative radiotherapy for radically resected esophageal squamous cell carcinoma: a systemic review and meta-analysis. Thorac Dis. 2018; 10(7): 4403–4412. DOI: https://doi.org/10.21037/jtd.2018.06.65 

  12. Zhu Y, Li M, Kong L, Yu J. Postoperative radiation in esophageal squamous cell carcinoma and target volume delineation. Onco Targets Ther. 2016 Jul 11; 9: 4187–96. DOI: https://doi.org/10.2147/OTT.S104221 

  13. Zhang X, Yang X, Ni J, et al. Recommendation for the definition of postoperative radiotherapy target volume based on a pooled analysis of patterns of failure after radical surgery among patients with thoracic esophageal squamous cell carcinoma. Radiat Oncol. 2018; 13(1): 255. DOI: https://doi.org/10.1186/s13014-018-1199-3 

  14. Wang X, Luo Y, Li M, Yan H, Sun M, Fan T. Recurrence pattern of squamous cell carcinoma in the midthoracic esophagus: implications for the clinical target volume design of postoperative radiotherapy. Onco Targets Ther. 2016; 9: 6021–6027. DOI: https://doi.org/10.2147/OTT.S116348 

  15. Liu J, Cai X, Liu Q, Li H, Cheng Y, Fu X. Characteristics of the local recurrence pattern after curative resection and values in target region delineation in postoperative radiotherapy for lower thoracic esophageal squamous cell cancer. Thorac Cancer. 2017; 8(6): 630–633. DOI: https://doi.org/10.1111/1759-7714.12499 

  16. Cai W-J, Xin P-L. Pattern of relapse in surgical treated patients with thoracic esophageal squamous cell carcinoma and its possible impact on target delineation for postoperative radiotherapy. Radiother Oncol. 2010; 96: 104–107. DOI: https://doi.org/10.1016/j.radonc.2010.04.029 

  17. Wang J, Yang Y, Shaik MS, et al. Three-Field versus Two-Field Lymphadenectomy for Esophageal Squamous Cell Carcinoma: A Meta-analysis. Surg Res. 2020 Nov; 255: 195–204. DOI: https://doi.org/10.1016/j.jss.2020.05.057 

  18. Wu HR, Liu CQ, Guo MF, et al. Analysis on CT in diagnosis of lymph node metastasis of thoracic esophageal cancer with minimum diameter greater than 1 cm. Zhonghua Wai Ke Za Zhi. 2019; 7(8): 601–606. (in chinese). DOI: https://doi.org/10.3760/cma.j.issn.0529-5815.2019.08.008 

  19. Li J, Chen S, Zhu G, et al. Comparative study of computed tomography (CT) and pathological diagnosis toward mediastinal lymph node metastasis in esophageal carcinoma. Rev Assoc Med Bras. 2018, 64(2): 170–174. DOI: https://doi.org/10.1590/1806-9282.64.02.170 

  20. Fujita H, Kakegawa T, Yamana H, et al. Lymph node metastasis and recurrence in patients with a carcinoma of the thoracic esophagus who underwent three-field dissection. World J Surg, 1994; 18: 266–272. DOI: https://doi.org/10.1007/BF00294412 

  21. Lu JC, Tao H, Zhang YQ, et al. Extent of prophylactic postoperative radiotherapy after radical surgery of thoracic esophageal squamous cell carcinoma. Dis Esophagus, 2008; 21: 502–507. DOI: https://doi.org/10.1111/j.1442-2050.2007.00797.x 

  22. Hagens ERC, van Berge Henegouwen MI, van Sandick JW, et al. Distribution of lymph node metastases in esophageal carcinoma [TIGER study]: study protocol of a multinational observational study. BMC Cancer. 2019; 19(1): 662. DOI: https://doi.org/10.1186/s12885-019-5761-7 

  23. Tachimori Y. Pattern of lymph node metastases of squamous cell esophageal cancer based on the anatomical lymphatic drainage system: efficacy of lymph node dissection according to tumor location. Thorac Dis. 2017; 9(8): 724–730. DOI: https://doi.org/10.21037/jtd.2017.06.19 

  24. Chen J, Cai W, Lin Y, et al. Patterns and rates of abdominal lymphatic metastasis following esophageal carcinoma. PLoS One. 2017; 12(10): e0185424. DOI: https://doi.org/10.1371/journal.pone.0185424