Cisplatin as a Radiosensitizer in Clinical Practice: A Pilot Study

Tumoricidal activity of low-energy 160-KV versus 6-MV X-rays against platinum-sensitized F98 glioma cells

The purposes of this study were (i) to investigate the differences in effects between 160-kV low-energy and 6-MV high-energy X-rays, both by computational analysis and in vitro studies; (ii) to determine the effects of each on platinum-sensitized F98 rat glioma and murine B16 melanoma cells; and (iii) to describe the in vitro cytotoxicity and in vivo toxicity of a Pt(II) terpyridine platinum (Typ-Pt) complex. Simulations were performed using the Monte Carlo code Geant4 to determine enhancement in absorption of low- versus high-energy X-rays by Pt and to determine dose enhancement factors (DEFs) for a Pt-sensitized tumor phantom. In vitro studies were carried out using Typ-Pt and again with carboplatin due to the unexpected in vivo toxicity of Typ-Pt. Cell survival was determined using clonogenic assays. In agreement with computations and simulations, in vitro data showed up to one log unit reduction in surviving fractions (SFs) of cells treated with 1-4 µg/ml of Typ-Pt and irradiated with 160-kV versus 6-MV X-rays. DEFs showed radiosensitization in the 50-200 keV range, which fell to approximate unity at higher energies, suggesting marginal interactions at MeV energies. Cells sensitized with 1-5 or 7 µg/ml of carboplatin and then irradiated also showed a significant decrease (P < 0.05) in SFs. However, it was unlikely this was due to increased interactions. Theoretical and in vitro studies presented here demonstrated that the tumoricidal activity of low-energy X-rays was greater than that of high-energy X-rays against Pt-sensitized tumor cells. Determining whether radiosensitization is a function of increased interactions will require additional studies.

Convection enhanced delivery of carboplatin in combination with radiotherapy for the treatment of brain tumors

The purpose of this study was to further evaluate the therapeutic efficacy of convection enhanced delivery (CED) of carboplatin in combination with radiotherapy for treatment of the F98 rat glioma. Tumor cells were implanted stereotactically into the brains of syngeneic Fischer rats, and 13 or 17 d. later carboplatin (20 μg/10 μl) was administered by either CED over 30 min or by Alzet osmotic pumps (0.5 μg/μl/h for 168 h.) beginning at 7 d after tumor implantation. Rats were irradiated with a 15 Gy fractionated dose (5 Gy × 3) of 6 MV photons to the whole brain beginning on the day after drug administration. Other groups of rats received either carboplatin or X-irradiation alone. The tumor carboplatin concentration following CED of 20 μg in 10 μl was 10.4 μg/g, which was equal to that observed following i.v. administration of 100 mg/kg b.w. Rats bearing small tumors, treated with carboplatin and X-irradiation, had a mean survival time (MST) of 83.4 d following CED and 111.8 d following pump delivery with 40% of the latter surviving >180 d (i.e. cured) compared to 55.2 d for CED and 77.2 d. for pump delivery of carboplatin alone and 31.8 d and 24.2 d, respectively, for X-irradiated and untreated controls. There was no microscopic evidence of residual tumor in the brains of all long-term survivors. Not surprisingly, rats with large tumors had much shorter MSTs. Only modest increases in MSTs were observed in animals that received either oral administration or CED of temozolomide plus X-irradiation (23.2 d and 29.3 d) compared to X-irradiation alone. The present survival data, and those previously reported by us, are among the best ever obtained with the F98 glioma model. Initially, they could provide a platform for a Phase I clinical trial to evaluate the safety and potential therapeutic efficacy of CED of carboplatin in patients with recurrent glioblastomas, and ultimately a Phase II trial of carboplatin in combination with radiation therapy.

Radiosurgery of isolated cerebral vessels following administration of paclitaxel in the rat

Object

Progressive obliteration occurs in arteriovenous malformations (AVMs) after radiosurgery; however, the risk of hemorrhage remains until the obliteration process is complete. The authors sought to enhance the radiation effect and reduce the risk of hemorrhage by facilitating faster vessel obliteration. To that end, a combination of a lower radiation dose with the addition of a radiosensitizing agent was compared with the effect of a higher radiation dose alone.

Methods

Using a method described by Mulvany and Halpern, isometric myography measurements were made on isolated rat middle cerebral artery specimens. The vessels were treated with 200 Gy, 80 Gy, 50 Gy, 25 Gy, 20 Gy, or 15 Gy by using Gamma Knife surgery. Taxol (paclitaxel 3 mg/kg/body weight) was administered intravenously to the animals. Survival times posttreatment were 24 hours, 6 weeks, 12 weeks, 12 months, or 18 months. After dissection, the middle cerebral arteries were mounted on a small-vessel myograph, and contraction and relaxation studies were performed.

In a second series of experiments these results were validated in human fibroblast culture. When the cultures were 75 to 80% colonized, the samples were treated in vitro with 60Co gamma radiation in similar doses with or without paclitaxel.

Conclusions

Constriction responses were generally decreased in the paclitaxel-treated vessels. Differences were significant at 6 weeks (p < 0.05) and at 1 year (p < 0.05). After 1 year, in the paclitaxel-treated groups vascular reactivity was completely abolished in vessels receiving 50 Gy. In comparison, it took 6 months longer (18 months) for this reaction to be abolished in vessels without paclitaxel treatment.

In tissue cultures Giemsa staining and immunohistochemical reactions for p53, Ki-67, CD-34, and SMA antigens revealed marked fibroblast hypertrophy in all of the paclitaxel-treated groups. Paclitaxel-treated vessels demonstrated decreased reactivity at significantly earlier stages than vessels that had not been treated. It would appear that paclitaxel causes acceleration in the time course of the late biological effect of gamma radiation. This beneficial effect could be used in Gamma Knife surgery in patients with AVMs, thus reducing the risk of posttreatment hemorrhage.

Ten years of preoperative chemoradiation for extraperitoneal T3 rectal cancer: acute toxicity, tumor response, and sphincter preservation in three consecutive studies

PURPOSE

To compare acute toxicity, tumor response, and sphincter preservation in three schedules of concurrent chemoradiation in resectable transmural and/or node-positive extraperitoneal rectal cancer.

PATIENTS AND METHODS

Between 1990 and 1999, 163 consecutive patients were treated according to the following combined modalities: FUMIR: between 1990 and 1995, 83 patients were treated with bolus i.v. mitomycin C (MMC), 10 mg/m(2) day 1, plus 24-h continuous infusion i.v. 5-fluorouracil (5-FU) 1,000 mg/m(2) days 1-4, and concurrent external beam radiotherapy (37.8 Gy). PLAFUR-4: between 1995 and 1998, 40 patients were treated with cisplatin (c-DDP) 60 mg/m(2) given as slow infusion (1-4 h) on days 1 and 29, plus 24-h continuous infusion i.v. 5-FU 1,000 mg/m(2), days 1-4 and 29-32 with concurrent external-beam radiotherapy (50.4 Gy). PLAFUR-5: between 1998 and 1999, 40 patients were treated with c-DDP 60 mg/m(2) given as slow infusion (during 1-4 h) on days 1 and 29, plus 24-h continuous infusion i.v. 5-FU 1,000 mg/m(2), days 1-5 and 29-33 with concurrent external-beam radiotherapy (50.4 Gy).

RESULTS

Grade > or = 3 acute toxicity occurred in 14%, 5%, and 17% of patients treated in the FUMIR, PLAFUR-4, and PLAFUR-5 studies, respectively (p = 0.201). In the FUMIR, PLAFUR-4, and PLAFUR-5 studies, clinical response rate was 77%, 70%, and 83%, respectively. Tumor downstaging occurred in 57%, 68%, and 58% of patients, respectively. Pathologic complete response was recorded in 9% (FUMIR), 23% (PLAFUR-4), and 20% (PLAFUR-5) of patients. Sphincter-preserving surgery was feasible in 44% (FUMIR), 40% (PLAFUR-4), and 61% (PLAFUR-5) of patients having a distance between the anal-rectal ring and the lower pole of the tumor of 0-30 mm, and in 95%, 100%, and 100%, respectively, in those having a distance of 31-50 mm. Comparing FUMIR vs. PLAFUR, the clinical response rate was similar in the two series: a partial response was observed in 62/81 (77%) patients with FUMIR treatment, and in 61/80 (76%) patients with PLAFUR treatment. Tumor downstaging was observed in 46/81 (57%) patients and in 50/80 (68%) patients, respectively. The pathologic complete response rate was statistically higher in the PLAFUR series: 7/81 (9%) patients with FUMIR treatment and 17/80 (21%) patients with PLAFUR treatment (p = 0.04). Major downstaging (pT0+ pTmic+ pT1) in the FUMIR group was reported in 12/81 (15%) patients versus 31/80 (39%) patients in the PLAFUR group (p = 0.0006). The anal sphincter was preserved in 63/81 (78%) patients with FUMIR treatment and in 69/80 (86%) patients with PLAFUR treatment. The perioperative morbidity was statistically lower with PLAFUR: a perioperative morbidity was experienced by 20/81 (25%) patients with FUMIR treatment and by 9/80 (11%) patients with PLAFUR treatment (p = 0.042).

CONCLUSION

In our experience, higher radiation dose (50.4 Gy vs. 37.8 Gy), a second course of concurrent 5-FU, and the use of c-DDP instead of MMC improved the pathologic response rate without increasing acute toxicity and perioperative morbidity. The use of 5-FU 5-day infusion (PLAFUR-5) resulted in higher toxicity with a similar response rate compared to 4-day infusion (PLAFUR-4).

Preoperative chemoradiation with cisplatin and 5-fluorouracil for extraperitoneal T3 rectal cancer: acute toxicity, tumor response, sphincter preservation

PURPOSE

To evaluate the impact of preoperative external radiation therapy intensified by systemic chemotherapy including bolus cisplatin (c-DDP) and 4-day infusional 5-fluorouracil (PLAFUR-4) on tumor response and sphincter preservation in patients with extraperitoneal T3 rectal cancer with acceptable toxicity, and to compare the results to our previous experience with bolus mitomycin c (MMC) and 4-day infusion 5-FU (FUMIR).

METHODS AND MATERIALS

Between October 1995 and March 1998, 40 consecutive patients with resectable extraperitoneal adenocarcinoma of the rectum were treated with preoperative chemoradiation: slow infusion i.v. c-DDP, 60 mg/m2, day 1 and 29 plus 24-h continuous infusion i.v. 5-fluorouracil (5-FU) 1000 mg/m2, days 1-4 and 29-32, and concurrent external beam radiotherapy (45 Gy whole pelvis followed by 5.4 Gy boost). All but 3 patients had T3 disease. Surgery was performed 6-8 weeks after the end of chemoradiation.

RESULTS

No patient had Grade 4 acute toxicity. Grade 3 hematological toxicity was observed only in 2 (5%) patients. No patient had major gastrointestinal, skin, or urological acute toxicity. All patients had radical surgery. There was no perioperative mortality; perioperative morbidity rate was 12%. Overall, 23% (9 of 40) of patients had a complete pathological response and 10% (4 of 40) of patients had rare isolated residual cancer cells (Tmic). Comparing the stage at the diagnostic workup with the pathological stage, tumor downstaging was observed in 27 (68%) patients; nodal status downstaging was detected in 24 (60%) patients. Thirty-four (85%) patients had a sphincter-saving surgical procedure. In 4 of 10 (40%) patients who were definitive candidates for an abdominoperineal resection (APR), the sphincter was preserved, as it was in 13 of 13 (100%) probable candidates. Lengthening of the distance between the anorectal ring and the lower pole of the tumor > or =20 mm was observed in 9 (23%) patients. None of the patients had soilage after the sphincter-saving procedure. In our previous experience with FUMIR the complete pathological response was 9%, the sphincter-saving surgical procedure was performed in 66% cases, and the Grade 3+ toxicity was observed in 13% of patients.

CONCLUSIONS

The addition of c-DDP to 5-FU (PLAFUR-4) in a neoadjuvant radiochemotherapy schedule improved the pathological response rate in comparison with our previous experience. Toxicity was low indeed, thus we commenced another study adding one more day of 5-FU infusion (PLAFUR-5) to further improve our results.