Background: No reports have, to date, focused on the relationship between preoperative determination of the depth of invasion and lymph node metastasis. The present study, under the leadership of the Japanese Gastric Cancer Association, was designed to form a basis for decision making in limited treatment for early gastric cancer (EGC).
Methods: From eight major hospitals in Japan, 2672 gastric cancers whose preoperative depth of invasion was mucosal(M-cancer), and 6209 EGCs, consisting of 3584 mucosal(m-) and 2625 submucosal(sm-) cancers, were collected by questionnaire. All registered patients underwent gastrectomy with D1 or more extensive lymphadenectomy between 1985 and 1998.
Results: The accuracy of preoperative diagnosis of depth of invasion of M-cancers was 80.2% (2144/2672). However, of the total of 2432 M-cancers in which no nodal involvement was observed intraoperatively (N0), histological examination of the resected specimens confirmed that lymph node metastasis was absent in 2353 (96.8%). The frequencies of lymph node metastasis in early gastric, m-, and sm-cancers were 8.9%, 2.5%, and 17.6%, respectively. Node involvement was associated with a higher frequency of undifferentiated than differentiated histology, as well as with greater tumor size. The incidences of lymph node metastasis in m-cancers with a diameter of less than 4 cm, and in sm-cancers with a diameter below 1 cm were 1.3% (37/2837) and 4.9% (4/82), respectively. These metastases rarely extended beyond the first tier.
Conclusion: N0 and M-cancers, m-cancers less than 4 cm in diameter, and sm-cancers no larger than 1 cm in diameter may be appropriate indications for limited surgery.