Highlights from

ASCO 2019

American Society of Clinical Oncology annual meeting

Chicago, USA 31 May - 4 June 2019

Sentinel lymph node biopsy shows promise for early oral cancer

Medical writer: Michelle Dalton, ELS

Sentinel lymph node biopsy (SNB)–navigated neck dissection (ND) could replace elective ND without survival disadvantage and reduce postoperative disability of the neck in patients with early-stage oral cancer, according to results from a Japanese study (Abstract 6007).

During his presentation, Yasuhisa Hasegawa, MD, PhD, of Asahi University Hospital, in Japan, said that another recent study identified a survival benefit with prophylactic ND at the time of primary surgery compared with a “wait and see” approach followed by therapeutic ND for nodal relapse in patients with early-stage oral squamous cell carcinoma.

In this trial, the eligibility criteria included histologically confirmed squamous cell carcinoma in the oral cavity that were classified as clinical categories T1 and T2, N0M0 by the Union for International Cancer Control (UICC) TNM classification 7th edition. The clinical depth of invasion of T1 disease was > 4 mm (defined as late T1), and tumours were previously untreated. The primary endpoint was 3-year overall survival (OS), with secondary endpoints including 3-year disease-free survival (DFS), as well as postoperative functional disabilities of the neck and neck complications.

A radioisotope method was used to detect sentinel nodes (SNs), and they were examined with multi-slice frozen section analysis intraoperatively, after hematoxylin and eosin and cytokeratin stain for a final postoperative diagnosis. One-stage or backup neck discussion procedures were used for patients with positive SNs.

Study Results

From November 2011 through January 2016, the researchers identified 275 oral cancers with late T1 or T2N0. There were 137 patients in the ND group and 134 patients in the SNB group who comprised the full analysis set. (Baseline characteristics of the two groups were evenly matched.) In the SNB group, pathologic positive nodal status was 34% (45/134), while in the ND group, the pathologic positive nodal status was 25% (34/137).

Overall, there were 93 patients (34%) who did not undergo neck dissection, 168 patients (62%) who underwent unilateral dissection, and 10 (4%) who underwent bilateral dissection. Postoperatively, 258 patients (95%) did not have any additional therapy (128 patients in the ND group and 130 patients in the SNB group). A total of 10 patients (4%) required radiation/chemoradiation (six patients in the ND group and four patients in the SNB group). The median follow-up was 37 months (interquartile range 36 to 39).

The 3-year OS in SNB group was 88% (95% CI [0.8106, 0.9243]), which was noninferior to the OS in ND group (87%, 95% CI [0.7955, 0.9133]). The 3-year DFS was 79% (95% CI [0.7063, 0.8476]) in SNB group and 81% (95% CI [0.7364, 0.8699]) in the ND group.

“Functionally, the patients who had SNB had better outcomes at 1 and 3 months,” Dr. Hasegawa said.

Discussant Maie A. St. John, MD, PhD, of the David Geffen School of Medicine, University of California, Los Angeles, said there is level 1 evidence from earlier studies that elective treatment offers a survival advantage, but as metastatic disease occurs in only 20% to 30% of patients, “how do you avoid overtreating the remaining 70%?” she asked.

“If no imaging tests are accurate enough to predict the presence of metastatic disease in the neck, SNB should be considered as an alternative to elective ND,” Dr. St. John said. However, there are several reasons why SNB has not “caught on,” she said, including a concern that it may miss 10% to 15% of occult metastatic disease and that head and neck surgeons are comfortable performing elective NDs.

The content and interpretation of these conference highlights are the views and comments of the speakers/authors.