Continuous infusion of carboplatin during conventional radiotherapy treatment in advanced squamous carcinoma of the cervix uteri IIB-IIIB (UICC). A phase I/II and pharmacokinetic study

Abstract

Objective: A prospective, single-arm phase-I/II trial performed to assess the efficacy and toxicity of the concomitant use continuous infusion of low-dose carboplatin and pelvic conventional radiotherapy in patients with locally advanced squamous cell carcinoma of the cervix.

Materials and methods: Between January and July 1994, a total of 12 patients consecutively diagnosed to have squamous cell carcinoma of the cervix uteri stages IIB-IIIB UICC-TNM (five patients, IIB; and seven patients, IIIB) entered the study. All patients were evaluated by a gynecologist and a radiation oncologist and were submitted to standard pretreatment staging procedures. Radiation was delivered with 10-MeV photon beams with the shrinking-field technique. The patients received 2 Gy radiotherapy daily, 5 fractions per week, up to a planned total of 60 Gy in 6 weeks to the primary tumor and 46 Gy in 4 weeks to the whole pelvis. Irradiation was performed using four fixed orthogonal fields. One intracavitary insertion, 8 Gy to point A (dose rate, 1.1 Gy/h), was performed immediately after external pelvic irradiation. Carboplatin (12 mg/m2/day) was also administered in a continuous infusion, starting 1 day before the first fraction of radiotherapy. The platinum in plasma and urine, as well as the platinum concentration in the cytosols of lymphocytes and tumor, was measured weekly.

Results: A complete response was seen in nine (75%) of the 12 patients. Of the nine patients who achieved a complete remission, only one had subsequent failure in the pelvis. The total pelvic failure rate was 33.3% (four of 12 patients). With a median follow-up time of 20 months, the actuarial survival rate at 24 months was 64.8%. All patients completed the treatment without major protocol violations. Grade-2 leukopenia (in nine patients) and grade-1 nausea and vomiting (in five) were the most common acute toxicities. There was one grade-3 hematologic toxicity. Grade-3 late complications were observed in 16.6% of cases (two of 12 patients). On days 28 and 42 of the treatment, the mean total platinum plasma concentrations were 491 micrograms/L (SD = 129) and 672 micrograms/L (SD = 160), and the ultrafilterable fraction was 8-10%. At the same time points, the concentration in lymphocytes was constant at 21 picograms (pg) platinum/lymphocyte. The levels of platinum concentration measured on days 14 and 28 in the cytosols of tumor cells were 0.3 microgram/g (SD = 0.1) and 0.93 microgram/g (SD = 0.2).

Conclusion: The combination of continuous infusion of carboplatin and radiotherapy at the aforementioned doses in patients with locally advanced cervical carcinoma resulted in a relatively low frequency of significant acute and late complications. Platinum in normal tissue (picograms per lymphocyte) was stable from week 1 of treatment, whereas the platinum steady state in plasma and in tumor cells was not reached in 6 weeks and was below that required in vitro to produce radiopotentiation. Further studies to determine the optimal dose of carboplatin and irradiation are needed prior to the initiation of phase-III studies.