Intraoperative high dose rate brachytherapy in recurrent or metastatic colorectal carcinoma

Population pharmacokinetics of humanized monoclonal antibody HuCC49deltaCH2 and murine antibody CC49 in colorectal cancer patients

To predict the optimal time for surgery after antibody administration, the population pharmacokinetics of (125)I-HuCC49deltaCH2 and (125)I-CC49 were characterized in 55 patients with colorectal cancers. A 2-compartment linear model was used to fit the pharmacokinetic data. Model stability and performance were assessed using a visual predictive check procedure. Different clinical trial designs were evaluated by simulation in combination with Bayesian estimation method to predict the optimal time for surgery. The results showed that HuCC49deltaCH2 had 65% faster clearance from blood circulation and 24% shorter mean residence time than CC49. Population pharmacokinetic analysis identified body weight as the only covariate to explain between-subject variability in clearance, intercompartmental flow rate, and volume of distribution. Model predictions indicated a wide interval for the optimal time of surgery, suggesting that it would be beneficial to individualize the time of surgery for each patient by measurement of antibody disposition. Clinical trial designs with at least 3 measurements of antibody disposition were found to be better than an empirical direct observation method for the optimal prediction of surgery time.

Quantifying IOHDR brachytherapy underdosage resulting from an incomplete scatter environment

PURPOSE

Most brachytherapy planning systems are based on a dose calculation algorithm that assumes an infinite scatter environment surrounding the target volume and applicator. Dosimetric errors from this assumption are negligible. However, in intraoperative high-dose-rate brachytherapy (IOHDR) where treatment catheters are typically laid either directly on a tumor bed or within applicators that may have little or no scatter material above them, the lack of scatter from one side of the applicator can result in underdosage during treatment. This study was carried out to investigate the magnitude of this underdosage.

METHODS

IOHDR treatment geometries were simulated using a solid water phantom beneath an applicator with varying amounts of bolus material on the top and sides of the applicator to account for missing tissue. Treatment plans were developed for 3 different treatment surface areas (4 x 4, 7 x 7, 12 x 12 cm(2)), each with prescription points located at 3 distances (0.5 cm, 1.0 cm, and 1.5 cm) from the source dwell positions. Ionization measurements were made with a liquid-filled ionization chamber linear array with a dedicated electrometer and data acquisition system.

RESULTS

Measurements showed that the magnitude of the underdosage varies from about 8% to 13% of the prescription dose as the prescription depth is increased from 0.5 cm to 1.5 cm. This treatment error was found to be independent of the irradiated area and strongly dependent on the prescription distance. Furthermore, for a given prescription depth, measurements in planes parallel to an applicator at distances up to 4.0 cm from the applicator plane showed that the dose delivery error is equal in magnitude throughout the target volume.

CONCLUSION

This study demonstrates the magnitude of underdosage in IOHDR treatments delivered in a geometry that may not result in a full scatter environment around the applicator. This implies that the target volume and, specifically, the prescription depth (tumor bed) may get a dose significantly less than prescribed. It might be clinically relevant to correct for this inaccuracy.

High-dose-rate intraoperative radiotherapy for close or positive margins in patients with locally advanced or recurrent rectal cancer

PURPOSE

A high-dose-rate intraoperative radiotherapy (HDR-IORT) technique for rectum cancer was developed and the technique, local failure, and survival were analyzed.

METHODS AND MATERIALS

After the exclusion of metastatic patients, 37 patients were treated with external beam RT, surgery, and HDR-IORT between 1997 and 2000. Primary locally advanced rectum cancer was found in 18 patients and recurrent disease in 19. HDR-IORT was only administered if the resection margins were < or =2 mm. The flexible intraoperative template is a 5-mm-thick pad with 1-cm-spaced parallel catheters. Clips were placed during surgery to define the target area. A dose of 10 Gy was prescribed at a 1 cm depth from the template surface and calculated using standard plans. After treatment, the dose at the clips was calculated using the reconstructed template geometry and the actual treatment dwell times. The median follow-up of surviving patients was 3 years. No patients were lost to follow-up.

RESULTS

Overall, 12 patients (32%) had local recurrence, 5 (14%) of which were in the HDR-IORT field. The 3-year local failure rate for primary tumors and recurrent tumors was 19% and 52%, respectively (p = 0.0042). The 3-year local failure rate was 37% for negative margins and 26% for positive margins (p = 0.51). A high mean dose at the clip (17.3 Gy) was found. The overall survival was significantly different for primary vs. recurrent tumors, stage, and grade.

CONCLUSION

Because of the HDR technique, a high dose at the clips was found, with good local control. More out-of-field than in-field failures were seen. The local failure rate was significantly different for primary vs. recurrent disease.

CT-fluoroscopy guided interstitial brachytherapy with image-based treatment planning for unresectable locally recurrent rectal carcinoma

PURPOSE

The aim of the study is to develop high-dose-rate (HDR) conformal interstitial brachytherapy by means of combined CT-fluoroscopy guidance with CT-based treatment planning for locally recurrent rectal carcinoma.

METHODS AND MATERIALS

Brachytherapy needle insertion was guided with a helical CT scanner providing continuous fluoroscopy reconstruction. A video monitor placed adjacent to the CT gantry simultaneously allowed the operator to see the process of needle insertion. Final CT images were transferred by an online system to the treatment-planning computer, which reconstructed the implant needles and organ contours. The doses in planning target volume were normalized and geometrically optimized. The patients received a brachytherapy dose at 5 Gy twice daily with a hypofractionated accelerated schedule at a total dose of 30-50 Gy with or without external radiation therapy. Eighteen patients were treated with this procedure.

RESULTS

Ten to thirty-six needles (average, 17.3) were successfully placed to the planning target volume in each patient. The average time for CT fluoroscopy was 357 seconds for each procedure. No accident was seen at needle insertion, but 2 patients developed incomplete peroneal nerve palsy after needle removal, but gradually recovered. CT-based treatment planning was faster and more accurate than projection reconstruction with conventional radiograms. Analysis of the dose volume histogram showed conformal dose distribution to the target, while avoiding normal structures.

CONCLUSION

CT fluoroscopy guidance ensures safety and increases the accuracy of needle placement in brachytherapy. Conformal high-dose-rate (HDR) interstitial brachytherapy with CT-based treatment planning is a method worth considering for locally recurrent rectal cancer.

A real-time image-guided intraoperative high-dose-rate brachytherapy system

PURPOSE

To develop a real-time, image-guided intraoperative high-dose-rate brachytherapy system.

METHODS AND MATERIALS

The surface applicator, a catheter array on a 1-mm-thick soft and semitransparent silicone rubber sheet, was directly sutured on the surgical bed. A three-dimensional video camera was then used to instantly capture images of the catheters and the surgical surface. Tracing the catheters on the images allowed us to automatically determine the dwell source positions. Dwell times in the dwell positions were optimized to minimize the dose variation and deviation from the treatment prescription. A dose-texture plot was created to quantify the dose distribution.

RESULTS

Treatment planning time was reduced from hours to a few minutes. Phantom tests have shown that the new source localization is accurate with sigma<1.5 mm. All hot spots and cold spots had been eliminated after the dwell-time optimization.

CONCLUSIONS

This real-time, image-guided planning system can provide optimal image-guided intraoperative high-dose-rate brachytherapy with geometric and dosimetric improvements and a short planning time.

High-dose-rate intraoperative brachytherapy for recurrent colorectal cancer

PURPOSE

Management of locally recurrent colorectal adenocarcinoma represents a significant challenge. Many of these tumors adhere to or invade into vital pelvic structures rendering surgery or external beam radiotherapy (EBRT) as palliative treatment. Therefore, a treatment approach was developed to evaluate the role of high-dose-rate intraoperative brachytherapy (HDR-IORT) and surgery as a component of therapy in the management of locally recurrent colorectal cancer. This is an update of our preliminary report with longer follow-up and larger patient numbers.

METHODS AND MATERIALS

Between January 1992 and September 1998, 74 patients with locally recurrent rectal cancer were treated with surgery and HDR-IORT. Additional EBRT was given to 29 patients, and 33 patients received 5-fluorouracil based chemotherapy. All patients underwent complete gross resection, and 21 of 74 had positive microscopic margin. The dose of HDR-IORT ranged from 10 to 18 Gy.

RESULTS

With a median follow-up of 22 months, the 5-year local control, distant metastasis disease-free, disease-free, and overall survival rates were 39%, 39%, 23%, and 23%, respectively. The only predictor of improved local control was a negative margin of resection with a 5-year local control rate of 43%, compared to 26% in those with positive margin (p = 0.02). For overall survival, a negative microscopic margin (p = 0.04) and the use of IORT + EBRT (p = 0.04) were significant predictors of improved survival. The incidence of peripheral neuropathy was 16%.

CONCLUSION

The results with HDR-IORT in this group of patients are encouraging. Further improvements in local and distant control are still needed.

Results and complications of surgery combined with intra-operative radiation therapy for the treatment of locally advanced or recurrent cancers in the pelvis

Intra-operative radiation therapy (IORT) can benefit patients with pelvic tumors by delivering a high dose of radiation with precise delineation of tumor bed and maximal protection of surrounding normal tissues. The IORT experience has been particularly promising for locally advanced primary or recurrent rectal cancers in which a gross total resection is achieved. However, its potential benefit must be weighed against added toxicity. The main dose-limiting toxicity of pelvic IORT is peripheral neuropathy and ureteral stenosis. We will review the techniques for optimal IORT delivery, the results of the major studies investigating IORT treatment of rectal cancer, and the pelvic complications associated with combining surgery and IORT. A team of surgeons and radiation oncologists providing close multidisciplinary coordination is essential to integrate IORT with combined modality regimens in a safe and effective manner.

Three different intraoperative radiation modalities (electron beam, high-dose-rate brachytherapy, and iodine-125 brachytherapy) in the adjuvant treatment of patients with recurrent colorectal adenocarcinoma

BACKGROUND

Intraoperative electron beam radiation therapy (IOERT) has been used in the treatment of patients with recurrent colorectal adenocarcinoma for the last 2 decades. Other intraoperative radiation modalities, such as intraoperative high-dose-rate brachytherapy (IOHDR) and intraoperative iodine-125 (125I) brachytherapy, present theoretic advantages for selected patients with recurrent colorectal adenocarcinoma. The experience of a single-institution series in which these three intraoperative radiation modalities were used in a nonrandomized manner is discussed in this report.

METHODS

Between September 1989 and January 1997, 80 patients with colorectal adenocarcinoma recurrent in the pelvis or in the paraaortic lymph nodes were treated with IOERT (28 patients), IOHDR (23 patients), or 125I brachytherapy (29 patients).

RESULTS

The overall 5-year local control rate was 26% (median = 12 months; 95% confidence interval [95%CI], 6-17). Tumors in paraaortic sites had significantly better local control than those in the pelvis (P = 0.03). The 5-year overall survival rate was 4% (median = 20 months; 95% CI, 17-23). Patients with microscopic residual disease (P = 0.02) and those treated with postoperative external beam irradiation (EBRT) (P = 0.0007) had statistically significant longer survival. Forty-one percent of the treated patients experienced complications: These were severe (Radiation Therapy Oncology Group Grade 4-5) in 19% of patients.

CONCLUSIONS

Intraoperative radiation can locally control recurrent colorectal adenocarcinoma in a select group of patients. Patients with localized relapses, microscopic residual tumor, and no distant metastases and those receiving additional EBRT are most likely to benefit from intraoperative irradiation. The authors now routinely recommend EBRT to all patients for whom it is suitable (including those who have had prior EBRT) and consider the combination of the intraoperative modalities whenever feasible.

Radioimmunoguided-intraoperative radiation therapy in colorectal carcinoma: a new technique to precisely define the clinical target volume

PURPOSE

The clinical target volume (CTV) to be irradiated by intraoperative radiation therapy (IORT) after resection is generally based on the surgeon's estimation of close margins. We have developed a new technique, radioimmunoguided-intraoperative radiation therapy (RIG-IORT), that uses an intraoperative hand-held gamma-detecting probe to define areas of residual microscopic disease containing radiolabeled monoclonal antibodies to tumor associated antigen, to more precisely delineate the CTV for IORT.

METHODS AND MATERIALS

Patients were injected i.v. with 2 mCi 125I- radiolabeled CC49 antibody approximately 3 weeks before surgery. They then underwent radioimmunoguided surgery (RIGS) with maximal resection of tumor. A hand-held gamma-detecting probe (Neoprobe 1000) was used intraoperatively to detect and resect areas of high radioactivity, representing tumor. Areas with persistently high probe counts after resection were the areas of occult residual disease, and represented the CTV to be irradiated. The IORT was given with either 6-9 MeV electron beam from a dedicated linear accelerator, or with high-dose-rate brachytherapy from a remote afterloader. If all RIGS-positive tissue had been resected, or if widely disseminated disease remained, the patient was not considered for IORT.

RESULT

This technique was used in 31 patients with colorectal adenocarcinoma recurrent into the pelvis (n = 23) or paraortic nodes (n = 8). The CTV for IORT was delineated by increased RIGS count in 13 of 19 patients (68%) with microscopic residual, and in 11 of 12 patients (92%) with gross residual. In the other 7 patients, the tumor area did not accumulate the radiolabeled antibody; therefore, these tumor beds were irradiated based on the surgeon's estimation of close margins. Hence, overall, the RIG-IORT technique was used to define the tumor bed for IORT in 24 of 31 patients (77%). This technical report focuses on the development of the RIG-IORT technique and does not address the outcome results of the treated patients.

CONCLUSION

A new technique, RIG-IORT, which uses radiolabeled monoclonal antibodies to precisely determine the CTV for IORT, is described. Whether the use of this technique will lead to improved tumor control will only be known upon the outcome analysis of RIG-IORT-treated patients compared with those obtained using traditional IORT techniques.

125Iodine brachytherapy for colorectal adenocarcinoma recurrent in the pelvis and paraortics

PURPOSE

To evaluate the results of 125I brachytherapy in colorectal cancers recurrent in the pelvis and paraortics.

METHODS AND MATERIALS

From September 1989 to January 1997, 29 patients with colorectal adenocarcinoma recurrent in the pelvis or the paraortic nodes were treated intraoperatively with permanent 125iodine seed implantation at the James Cancer Center of The Ohio State University (OSU). All patients had undergone prior surgery; 72% had prior EBRT. The implanted residual tumor volume was microscopic in 38% and gross in 62%. The implanted area (median 25 cc) received a median minimal peripheral dose of 140 Gy to total decay. An omental pedicle was used to minimize irradiation of the bowel. Five patients received additional postimplant EBRT (20-50 Gy; median 30 Gy).

RESULTS

The 1-, 2-, and 4-year actuarial local-regional control rates were 38%, 17%, and 17%, respectively, with a median time to local failure of 11 months (95% CI 10-12 months). The first manifestation of disease progression in 52 % of the patients was local-regional. In addition, 22 patients (75%) developed distant metastases. The 1-, 2-, and 4-year actuarial overall survival rates were 70%, 35%, and 21%, (median = 18 months; 95% CI: 14-22 months). Overall survival was better for patients smaller volume implants (p = 0.007), with a lower total activity implanted (p = 0.0003), with a smaller number of implanted sites (p = 0.004), and with microscopic residual disease (p = 0.01). Patients receiving additional EBRT also had a better prognosis (p = 0.005). Local tumor progression was the cause of death in 34% of the patients who have died at the time of this report and 56% died of distant metastases. Of the patients, 13 (45%) experienced 15 toxic events, including 3 patients (10%) with enteric fistula. Neuropathy was not observed.

CONCLUSIONS

125I brachytherapy can be successfully used for salvage in patients with recurrent colorectal cancer. Patients with isolated, microscopic, or minimal gross residual disease requiring small-volume implants and those receiving additional EBRT have a better prognosis. Postimplant EBRT is now routinely added, even for previously irradiated patients, in an attempt to improve local control. Compared to IOERT and IOHDR, 125I brachytherapy is not associated with clinical neuropathy, probably due to the continuous low dose rate irradiation delivered by the 125I seeds.