PAP smear after radiation therapy for cervical carcinoma

Vaginal PAP smear is frequently used for the follow-up of cervical carcinoma after primary therapy. Irradiation induced atypia can interfere with cytological analysis and thus detection of a local recurrence, or simulate malignant atypia and cause unnecessary suspicion of recurrence. In this retrospective study we evaluated the reliability of cytological analysis and the reported frequency of irradiation induced atypia after radiotherapy. Eighty-nine patients treated for cervical carcinoma at Turku University Central Hospital during the years 1970-88 were included in the study. During the median follow-up of 34 months a total of 697 PAP smears were taken with a median of 7.8 samples per patient. During the follow-up 44 (50%) patients had a recurrent disease, which was local in 17 (39%) cases. Nine out of 12 PAP smears taken 0-60 days before detection of a local recurrence showed class III-V cellular atypia. However, three PAP smears showed class I-II, and were therefore false negative. The rate of false positive samples was only 3%. In 567 PAP smears irradiation induced atypia was indicated as present/not present (+/-) and it was positive in 89 (16%) samples. The detection rate was considerably higher (75%) in class II samples than in rest of the material. Irradiation induced atypia was detected in 28% of the PAP smears taken during the first four months after radiotherapy and the rate decreased thereafter. Cytological analysis of vaginal PAP smear was a reliable indicator of recurrence in most cases and is a valuable tool for the detection of local recurrence of cervical carcinoma after primary radiotherapy.