The pattern of lymphatic metastasis of breast cancer and its influence on the delineation of radiation fields.

PURPOSE

The delineation of radiation fields should cover the clinical target volume (CTV) and minimally irradiate the surrounding normal tissues and organs. This study was designed to explore the pattern of lymphatic metastasis of breast cancer and indications for radiotherapy after radical or modified radical mastectomy and to discuss the rational delineation of radiation fields.

METHODS AND MATERIALS

Between September 1980 and December 2003, 78 breast cancer patients receiving extended radical mastectomy in the Margottini model and 61 cases with complete data were analyzed to investigate the internal mammary lymphatic metastatic status. Between March 1988 and December 1988, 46 patients with clinical negative supraclavicular nodes received radical mastectomy plus supraclavicular lymph node dissection. The supraclavicular lymph nodes and axillary lymph nodes were labeled as S and levels I, II, or III, respectively, and examined pathologically. Between January 1996 and April 1999, 412 patients who had radical or modified radical mastectomy underwent the pathologic examination of axillary or levels I, II, or III nodes.

RESULTS

The incidence of internal mammary lymph node metastasis was 24.6%. It was 36.7% for the patients with positive axillary lymph nodes and 12.9% for the patients with negative axillary lymph nodes. All the metastatic internal mammary lymph nodes were located at the first, second, and third intercostal spaces. Skipping metastasis of the supraclavicular and axillary lymph nodes was observed in 3.8% and 8.1% of patients, respectively.

CONCLUSIONS

According to our data, we suggest that the radiation field for internal mammary lymph nodes should exclude the fourth and fifth intercostal spaces, which may help to reduce the radiation damage to heart. It is unnecessary to irradiate the supraclavicular lymph nodes for the patients with negative axillary level III nodes, even with positive level I and level II nodes.