Percutaneous interstitial brachytherapy for adrenal metastasis: technical report

Locally targeted delivery of a micron-size radiation therapy source using temperature-sensitive hydrogel

PURPOSE

To propose a novel radiation therapy (RT) delivery modality: locally targeted delivery of micron-size RT sources by using temperature-sensitive hydrogel (RT-GEL) as an injectable vehicle.

METHODS AND MATERIALS

Hydrogel is a water-like liquid at room temperature but gels at body temperature. Two US Food and Drug Administration-approved polymers were synthesized. Indium-111 (In-111) was used as the radioactive RT-GEL source. The release characteristics of In-111 from polymerized RT-GEL were evaluated. The injectability and efficacy of RT-GEL delivery to human breast tumor were tested using animal models with control datasets of RT-saline injection. As proof-of-concept studies, a total of 6 nude mice were tested by injecting 4 million tumor cells into their upper backs after a week of acclimatization. Three mice were injected with RT-GEL and 3 with RT-saline. Single-photon emission computed tomography (SPECT) and CT scans were performed on each mouse at 0, 24, and 48 h after injection. The efficacy of RT-GEL was determined by comparison with that of the control datasets by measuring kidney In-111 accumulation (mean nCi/cc), representing the distant diffusion of In-111.

RESULTS

RT-GEL was successfully injected into the tumor by using a 30-gauge needle. No difficulties due to polymerization of hydrogel during injection and intratumoral pressure were observed during RT-GEL injection. No back flow occurred for either RT-GEL or RT-saline. The residual tumor activities of In-111 were 49% at 24 h (44% at 48 h, respectively) for RT-GEL and 29% (22%, respectively) for RT-saline. Fused SPECT-CT images of RT-saline showed considerable kidney accumulation of In-111 (2886%, 261%, and 262% of RT-GEL at 0, 24, and 48 h, respectively).

CONCLUSIONS

RT-GEL was successfully injected and showed much higher residual tumor activity: 170% (200%, respectively), than that of RT-saline at 24 h (48 h, respectively) after injection with a minimal accumulation of In-111 to the kidneys. Preliminary data of RT-GEL as a delivery modality of a radiation source to a local tumor are promising.

Radiation therapy for advanced and metastatic melanoma

Radiation therapy (RT) is an important modality in cancer treatment. However, the general perception is that melanoma is radio-resistant. High quality clinical trials are helping to establish the place of RT in select scenarios of advanced disease at primary, regional, and distant sites. New RT techniques need to be integrated with effective new systemic therapies within a multidisciplinary environment to ensure optimum patient outcomes. It is important that radiation oncologists embrace this opportunity.

Novel eradicative high-dose rate brachytherapy for internal mammary lymph node metastasis from breast cancer

AIM: To develop a method of delivering an eradicative high radiotherapeutic dose safely preserving the surrounding skin in the treatment of internal mammary lymph node metastasis (IMLNM) of breast cancer.

METHODS: We report a 38-year-old female patient with a solo IMLNM showing no response to 60 Gy in 2.5 Gy fractions of external beam radiotherapy. To eradicate this tumor, a boost brachytherapy plan was created after percutaneous insertion of an applicator needle into the IMLNM lesion avoiding the pleura and vessels under ultrasound monitoring. According to the dose distribution, the required thickness of a spacer between the skin and the tumor was determined, and hyaluronic gel was injected up to this thickness under ultrasound monitoring. We evaluated skin doses, target doses and clinical outcome.

RESULTS: All procedures were performed easily. Sixteen Gy (34.7 Gy equivalent in 2 Gy fractions calculated by the linear quadratic model at α/β = 10: EQD_{2, α/β = 10}, cumulative total was 101.9 Gy EQD10) to 100% of the target volume was irradiated with cumulative maximum skin dose of 70 Gy EQD_{2, α/β = 3} which was 98.7 Gy EQD_{2, α/β = 3} without spacer. No procedure related- or late complications and no local recurrence at the treated site were observed for three years until expiration.

CONCLUSION: We consider that this procedure will provide an eradicative high-dose irradiation to IMLNM of breast cancer, preserving skin from overdose complications.