Papillary serous carcinoma--a less radio-sensitive subtype of endometrial cancer.

OBJECTIVE: To explore factors that determine the response of endometrial cancer to radiation therapy. Such factors may influence treatment outcome and yield predictive information about individual patients and their tumors.
METHODS: A retrospective study of the complete pathologic response (pCR) rates in the hysterectomy specimens of patients, who had undergone pre-operative radiotherapy for > or = Stage II biopsy-proven endometrial carcinoma, was performed. 62 patient records were reviewed with respect to patient characteristics, tumor stage, histological grade and subtype, radiation technique and dose, and presence or absence of pCR in the post-operative hysterectomy specimen.
RESULTS: 24 of 62 specimens exhibited a pCR. The only significant factor with respect to pCR was presence of uterine papillary serous carcinoma (UPSC). None of the seven cases of UPSC displayed a pCR (P = 0.036 Fischer's exact test), despite not differing from the non-UPSC cases in any other tumor, treatment, or patient factors. No factors were found that separated non-UPSC cases with a pCR from those without.
CONCLUSIONS: These data suggest an intrinsic radioresistance within UPSC, which may have implications for future treatment strategies. UPSC has documented genetic aberrations that may account for this, although its true radiosensitivity has yet to be quantitated directly. Future studies should focus on the molecular basis of its response to radiation. The reasons for the heterogeneous response of non-UPSC has yet to be elucidated and should also be investigated.