The role of irradiation as a component of combined modality treatment for gastric cancer.

Adjuvant therapy following complete surgical resection of gastric cancers is indicted on the basis of failure patterns and survival results with surgery alone (high incidence of local-regional relapse and distant metastases). To date, however, single modality adjuvant therapy has not had a meaningful impact on outcome (disease control or survival). Most Western chemotherapy trials are negative for both single and multiple drugs. Irradiation alone reduces local-regional relapse but doesn't alter survival. Data from single institution phase II and small phase III trials suggest that combined modality adjuvant therapy (irradiation plus chemotherapy) may have a positive outcome on both disease control and survival. A U.S. intergroup trial is therefore underway to further evaluate disease control and survival benefit trends for combined modality postoperative irradiation plus chemotherapy that were found in a small Mayo Clinic randomized study. For patients with locally advanced disease (locally unresectable or resected but residual disease), combined external irradiation plus chemotherapy or intraoperative irradiation (IORT) produces long-term survival in 10% to 20% of patients in most randomized and nonrandomized trials. Studies using preoperative (neoadjuvant) chemotherapy for locally unresectable disease reveal a possible increase in resection rates but a high incidence of local-regional relapse. It would be of interest to merge together those treatments that have produced apparent improvements in response rates, disease control, or survival for locally advanced disease (add external radiation plus concomitant chemotherapy, IORT, or combinations thereof to preoperative chemotherapy regimes.