The optimization of dose delivery for intraoperative high-dose-rate radiation therapy using curved HAM applicators

Intraoperative implantation of a mesh of directional palladium sources (CivaSheet): Dosimetry verification, clinical commissioning, dose specification, and preliminary experience

PURPOSE

To present the clinical commissioning of a novel ¹⁰³Pd directional brachytherapy device (CivaSheet) for intraoperative radiation therapy.

METHODS AND MATERIALS

Clinical commissioning for the CivaSheet consisted of establishing: (1) source strength calibration capabilities, (2) experimental verification of TG-43 dosimetry parameters, (3) treatment planning system validation, and (4) departmental practice for dose specification and source ordering. Experimental verification was performed in water with radiochromic film calibrated with a 37 kVp X-ray beam. Percentage difference ([measurements - calculation]/calculation) and distance to agreement (difference between film-to-source distance and distance that minimized the percentage difference) were calculated. Nomogram values (in U/100 Gy) for all configurations (up to 20 × 20 sources) were calculated for source ordering. Clinical commissioning was used on patients enrolled in an ongoing Institutional Review Board-approved protocol.

RESULTS

A source calibration procedure was established, and the treatment planning system was commissioned within standard clinical uncertainties. Percentage dose differences (distances to agreement) between measured and calculated doses were 8.6% (-0.12 mm), 0.6% (-0.01 mm), -6.4% (0.22 mm), and -10.0% (0.44 mm) at depths of 2.3, 5.1, 8.0, and 11.1 mm, respectively. All differences were within the experimental uncertainties. Nomogram values depended on sheet size and spatial extent. A value of 2.4U/100 Gy per CivaDot was found to satisfy most cases, ranging from 2.3 to 3.3U/100 Gy. Nomogram results depended on elongation of the treatment area with a higher variation observed for smaller treatment areas. Postimplantation dose evaluation was feasible.

CONCLUSIONS

Commissioning and clinical deployment of CivaSheet was feasible using BrachyVision for postoperative dose evaluation. Experimental verification confirmed that the available TG-43 dosimetry parameters are accurate for clinical use.

Recent developments and best practice in brachytherapy treatment planning

Brachytherapy has evolved over many decades, but more recently, there have been significant changes in the way that brachytherapy is used for different treatment sites. This has been due to the development of new, technologically advanced computer planning systems and treatment delivery techniques. Modern, three-dimensional (3D) imaging modalities have been incorporated into treatment planning methods, allowing full 3D dose distributions to be computed. Treatment techniques involving online planning have emerged, allowing dose distributions to be calculated and updated in real time based on the actual clinical situation. In the case of early stage breast cancer treatment, for example, electronic brachytherapy treatment techniques are being used in which the radiation dose is delivered during the same procedure as the surgery. There have also been significant advances in treatment applicator design, which allow the use of modern 3D imaging techniques for planning, and manufacturers have begun to implement new dose calculation algorithms that will correct for applicator shielding and tissue inhomogeneities. This article aims to review the recent developments and best practice in brachytherapy techniques and treatments. It will look at how imaging developments have been incorporated into current brachytherapy treatment and how these developments have played an integral role in the modern brachytherapy era. The planning requirements for different treatments sites are reviewed as well as the future developments of brachytherapy in radiobiology and treatment planning dose calculation.

Intraoperative radiation therapy for locally advanced primary and recurrent colorectal cancer: ten-year institutional experience

BACKGROUND

We evaluated the role of intraoperative radiation therapy (IORT) during radical resection of locally advanced colorectal cancer (CRC).

METHODS

We retrospectively evaluated all patients with CRC treated with IORT at our institution from 2001 to 2010. IORT was delivered using high-dose-rate brachytherapy (median 12.5-Gy). We analyzed factors associated with postoperative morbidity, local control (LC), and overall survival (OS).

RESULTS

One hundred patients were evaluated with 70% received IORT for recurrent tumors. R0 resection rate was 58%. Postoperative Grade ≥3 complications (33%) were independently associated with transfusions ≥3 units packed red blood cells (P = 0.016) and body mass index (BMI) ≥35 (P = 0.0499). Eighty-two patients underwent external beam radiation therapy (EBRT) before IORT. Five-year LC was 94%, for primary and 56%, for recurrent tumors, respectively (P = 0.007). Microscopic positive (R1) margins were not associated with LC (P = 0.316). BMI ≥30 (P = 0.048) and post-discharge complications (P = 0.041) were independent risk factors for worse LC. Median post-IORT OS was 67.7 (95% CI 51.1-84.3) months for all patients.

CONCLUSION

For patients with primary or recurrent locally advanced CRC, treatment with radical surgery and IORT achieved excellent LC outcomes irrespective of microscopic margin status. IORT may be indicated for tumors suspected to have close or positive microscopic margins.

Research opportunities in intraoperative radiation therapy: the next decade 2013-2023

The reality of intraoperative radiation therapy (IORT) practice is consistent with an efficient and highly precise radiation therapy technique to safely boost areas at risk for local recurrence. Long-term clinical experience has shown that IORT-containing multi-modality regimens appear to improve local disease control, if not survival in many diseases. Research with IORT is a multidisciplinary scenario that covers knowledge from radiation beam adapted development to advance molecular biology for bio-predictability of outcome. The technical parameters employed in IORT procedures are important information to be recorded for quality assurance and clinical results analysis. In addition, specific treatment planning systems for IORT procedures are available, to help in the treatment decision-making process. A systematic revision of opportunities for research and innovation in IORT is reported including radiation beam modulation, delivery, dosimetry and planning; infrastructure and treatment factors; experimental and clinical radiobiology; clinical trials, innovation and translational research development.