Insights in para-aortic radiation therapy for endometrial carcinoma

Abstract

It was believed in past decades that if patients with gynecologic malignancies had metastatic disease in the periaortic (PA) nodes, cure was all but impossible, and it was indicative of concomitant systemic spread. Or if one did treat the PA nodes, the required radiation dose would produce an unacceptable risk of severe complications. These perceptions began to abate somewhat with observations gleaned from various small studies demonstrating that selected subsets of patients with metastatic disease in the PA nodes could benefit, in terms of survival and local control, if extended field irradiation therapy was given (2, 12, 13). On the presumption that carcinoma of the uterine cervix spreads in a reasonably predictable manner, first to the pelvic nodes and then to the PA nodes, it was hypothesized that effective treatment could be directed prophylactically to the PA nodes. This hypothesis was proposed by Rotman et al. in 1979 and later confirmed by the prospective randomized trial of the RTOG in 1990 (14, 15). Although such information regarding cervical cancer was forthcoming, considerably less information was available regarding endometrial cancer. The incidence of PA nodes in the endometrial carcinoma was first studied in a relatively systematic way by the Gynecologic Oncology Group. Their Pilot Study One was envisioned by Boronow and Morrow, with subsequent collaboration from DiSaia and Creasman (7) early in the 1970s (7). This project was prompted, in part, by the impressive report from Oxford, England who reported their experience with pelvic lymph node metastasis in Stage I cancer of the endometrium (11). It was of great interest that in their series, one-third of the patients achieved cure when postoperative external beam treatment was directed to the pelvis only, and when metastatic pelvic nodes had been resected. The GOG Pilot Study suggested the predictive role that pelvic node dissection could provide (3). If pelvic nodes were negative, only 2% of patients were found to have aortic node metastasis; conversely, if pelvic node metastasis were found, about two-thirds of the patients had positive PA nodes. This surgical pathologic data meshed impressively with the Oxford clinical experience (i.e., one-third with positive pelvic nodes were salvaged with pelvic RT, but two-thirds were not-and the GOG study suggested that these two-thirds likely had aortic spread).