Rapid involution and mobility of carcinoma of the cervix.

PURPOSE

To quantitatively describe the involution and mobility of carcinoma of the cervix while under treatment with chemoradiotherapy (both with external beam radiation [EBRT] and high-dose-rate [HDR] intracavitary therapy). These data have implications for conformal or intensity modulated radiation therapy boost to the cervix.

METHODS AND MATERIALS

Seventeen patients underwent HDR brachytherapy boost to the cervix and were evaluated by repeat clinical examinations. In most cases, 5 weekly HDR brachytherapy insertions were performed after approximately 2 to 3 weeks of the initiation of EBRT. Sequential clinical tumor sizes were recorded in the chart for each patient under treatment. Linear regression analyses were performed to analyze tumor size as a function of total dose of external beam plus brachytherapy and number of elapsed days during the treatment course. In addition, the mobility of the cervix was documented by placement of a uterine sleeve for HDR brachytherapy before the initiation of therapy, and changes in sleeve position were identified on portal films relative to the midline of the pubic symphysis, in three dimensions. The anatomic position of the cervix was also identified at the time of simulation for HDR brachytherapy.

RESULTS

Seventeen patients were identified and selected to receive HDR brachytherapy at our institution. Sixteen of the 17 patients received concurrent chemotherapy. The median dose at which tumor was no longer clinically evident was 61.5 Gy (95% confidence interval [CI]: 50.7-72.3 Gy) by linear regression analysis. This indicates that the median dose to achieve a 50% reduction in tumor size is approximately 30.8 Gy. Similarly, the median number of elapsed days for a complete response was 42 days (95% CI: 34-50 elapsed days). This indicates that it takes 21 days to achieve a 50% clinical complete response for patients undergoing concurrent cisplatin-based chemoradiotherapy and HDR brachytherapy. In addition, the mobility of the cervix during EBRT was noted by serial measurements of the location of a metallic ring in the uterine sleeve, as seen on port films. The median and maximum ranges for change in the position of the cervix in the lateral (x), superior/inferior (y), and anterior/posterior (z) planes were 10, 8, and 16 mm and 24, 36, and 23 mm, respectively. Also, 85 brachytherapy procedures were performed, and the positions of the cervix on 170 orthogonal films were evaluated. The median and maximum ranges for the position of the cervix at the time of HDR brachytherapy in the lateral (x), superior/inferior (y), and anterior/posterior (z) planes were 5, 12, and 10 mm and 11, 25, and 32 mm, respectively.

CONCLUSIONS

Carcinoma of the cervix involutes rapidly with EBRT, concurrent cisplatin-based chemotherapy, and HDR brachytherapy. The time for 50% tumor regression was calculated to be 21 days and occurs after 30.8 Gy. In addition, uterine sleeve placement allowed us to document the median and maximum ranges of cervical mobility during the treatment course of EBRT to be 8-16 mm and 23-36 mm, and at the time of HDR brachytherapy to be 5-12 mm and 11-32 mm, respectively. These data indicate that the cervix gross tumor volume changes rapidly in a systematic fashion during chemoradiotherapy and, together with the mobility of the cervix, urge caution in nonbrachytherapy boost planning.