Survey study on sentinel lymph node biopsy: indications and perceived value among small animal surgical specialists

Abstract

Introduction: Despite the growing adoption of sentinel lymph node biopsy (SLNB) for nodal staging in dogs, standardized guidelines defining its specific indications remain lacking. This survey study aimed to assess the indications for SLNB among small animal surgical specialists and evaluate its perceived value.

Methods: An online survey was distributed through the European College of Veterinary Surgeons (ECVS), comprising five sections: clinical practice type, nodal staging, lymphadenectomy, mapping techniques, and the perceived value of SLNB. Descriptive statistics summarized responses, while cluster analysis explored associations between clinical practice type and SLNB recommendations.

Results: Seventy-four surgeons participated, with 74% practicing in non-academic and 26% in academic institutions. The majority (80%) performed lymphadenectomy with histopathological evaluation for nodal staging, and 53% recommended it for all malignant tumors, irrespective of nodal size. Additionally, 80% preferred SLNB over regional lymphadenectomy, particularly for specific tumor types (mast cell tumors, melanomas, carcinomas) or anatomical locations (oral tumors). Indirect CT lymphography was the most commonly used preoperative mapping technique (59.4%), yet only 23% of respondents combined preoperative and intraoperative mapping techniques. While 63% considered SLNB a reliable diagnostic tool, cluster analysis indicated that the type of clinical practice (academic vs. non-academic) did not influence SLNB recommendations.

Discussion: Despite a low response rate (8.3%), findings suggest that SLNB is widely performed by specialists across different practice settings, particularly for select tumor types. However, with 20% not performing SLNB and 37% uncertain about its reliability, these results highlight the need for standardized guidelines to define clear indications and improve consistency in clinical decision-making.

Keywords: cancer; dog; lymphadenectomy; sentinel lymph node; survey study.

Figure 1

Heatmap representing the distribution of the answers (rows) in each cluster (columns). [Inst = Institution, Inst-AO01 = University teaching hospital, Inst-AO02 = Non-academic referral practice. Ly_en = I recommend lymphadenectomy concurrent with tumor excision if lymph nodes are clinically enlarged, Ly_en-0 = No, Ly_en-1 = Yes, Ly_en-NA = missing answer. Ly_MT = I recommend lymphadenectomy concurrent with tumor excision in case of Malignant Tumors, Ly_MT-0 = No, Ly_MT-1 = Yes, Ly_MT-NA = missing answer. Ly_never = Never I recommend lymphadenectomy concurrent with tumor excision, Ly_never-0: No, Ly_never-1 = Yes, Ly_never-NA = missing answer. Ly_npf = I recommend lymphadenectomy concurrent with tumor excision only if the primary tumor has negative prognostic factors, Ly_npf-0 = No, Ly_npf-1 = Yes, Ly_npf-NA = missing answer. Ly_STT = I recommend lymphadenectomy concurrent with tumor excision only for specific tumor types. Ly_STT-0 = No, Ly_STT-1 = Yes, Ly_STT-NA = missing answer. N_o_Y = How many surgical oncology procedures are performed in your institution every year? N_o_Y-Ao01 = <50, N_o_Y-Ao02 = 50–100, N_o_Y-Ao03 = 100–200, N_o_Y-Ao04 > 200, N_o_Y-NA = missing answer. Se_ep = I recommend resection of the sentinel lymph node(s) if the regional lymph node is clinically enlarged or cytologically positive for metastases. Se_ep- AO01 = No, Se_ep- AO02 = Only for specific tumor type or locations OR “Only if the primary tumor has negative prognostic factors,” Se_ep- AO03 = Yes. Se_ep-NA = missing answer. Se_rr = In which cases do you recommend sentinel lymphadenectomy rather than regional?, Se_rr -AO01 = Never, Se_rr -AO02 = Only for specific tumor types and locations, Se_rr -AO03 = Only if the primary tumor has negative prognostic factors, Se_rr -AO04 = In all cytologically/histologically confirmed malignant tumors, Se_rr -NA = missing answer. Se_scars = Do you suggest sentinel lymphadenectomy also in case of scars from previously excised tumors that did not have lymphadenectomy before? Se_scars- AO01 = No, never, Se_scars- AO02 = Only if previous excision was incomplete (R1 margins), Se_scars- AO03 = Only if the primary tumor has negative prognostic factors, Se_scars- AO04 = Yes, always. Se_scars- NA = missing answer. V_Re_5 = Have your recommendations for sentinel lymphadenectomy changed in the past 5 years? V_Re_5- AO01 = “I used NOT to recommend it and I am still NOT” OR “I used to recommend it, but now I do NOT recommend it anymore,” V_Re_5- AO02 = “I used NOT to recommend it, but now I am,” V_Re_5- AO03 = “I used to recommend it and I am still doing so,” V_Re_5-NA = missing answer. V_Se_Id = Do you believe that sentinel lymphadenectomy (followed by histological examination) is a reliable procedure to identify nodal metastases? V_Se_Id- AO01 = Only for specific tumor types or locations, V_Se_Id- AO02 = Depending on which mapping method is applied, V_Se_Id- AO03 = Yes, V_Se_Id-NA = “I do not have an opinion about it” OR missing answer. V_Se_Im_SA = What is your perceived impact of implementation of sentinel lymphadenectomy in small animal surgical oncology? V_Se_Im_SA-AO01 = “It does not have an impact on treatment choices and outcome of patients” OR “It affects staging” OR “It affects staging and treatment recommendations,” V_Se_Im_SA-AO02 = It affects staging, treatment recommendations and outcome V_Se_Im_SA-NA = missing answer].

Figure 2

Partition tree. The variable that is represented first (at the top) (V_Se_lm_SA) is the one that discriminates clusters the most, followed by two variables (Ly_en and Ly_MT) (on the same level), which discriminate clusters asymmetrically with respect to the first and further separations. Finally, the procedure allocates the subjects into terminal nodes, which should correspond to the original classification of the clusters. The subjects were separated into 4 terminal nodes (bottom), which give the subject classifications provided by the partition tree procedure. As it is an approximate procedure, not all subjects were correctly classified according to the cluster they belong to, and classification errors are also reported. For example, in terminal node 1, there are no classification errors (all 15 subjects actually belong to cluster 1). In terminal node 2 (left) there are three classification errors: 30 subjects actually belong to cluster 2 and 1 to cluster 3. [V_Se_Im_SA = What is your perceived impact of implementation of sentinel lymphadenectomy in small animal surgical oncology? V_Se_Im_SA-AO01 = “It does not have an impact on treatment choices and outcome of patients” OR “It affects staging” OR “It affects staging and treatment recommendations,” V_Se_Im_SA-AO02 = It affects staging, treatment recommendations and outcome V_Se_Im_SA-NA = missing answer. Ly_en = I recommend lymphadenectomy concurrent with tumor excision if lymph nodes are clinically enlarged, Ly_en-0 = No, Ly_en-1 = Yes, Ly_en-NA = missing answer. Ly_MT = I recommend lymphadenectomy concurrent with tumor excision in case of Malignant Tumors, Ly_MT-0 = No, Ly_MT-1 = Yes. Ly_STT = I recommend lymphadenectomy concurrent with tumor excision only for specific tumor types. Ly_STT-0 = No, Ly_STT-1 = Yes. Se_rr = In which cases do you recommend sentinel lymphadenectomy rather than regional? Se_rr -AO01 = Never, Se_rr -AO02 = Only for specific tumor types and locations, Se_rr -AO03 = Only if the primary tumor has negative prognostic factors, Se_rr -AO04 = In all cytologically/histologically confirmed malignant tumors, Se_rr -NA = missing answer].