Proton radiotherapy for recurrent or metastatic sarcoma with palliative quad shot

FLASH proton reirradiation, with or without hypofractionation, mitigates chronic toxicity in the normal murine intestine, skin, and bone

Background and purpose

The normal tissue sparing afforded by FLASH radiotherapy (RT) is being intensely investigated for potential clinical translation. Here, we studied the effects of FLASH proton RT (F-PRT) in the reirradiation setting, with or without hypofractionation. Chronic toxicities in three murine models of normal tissue toxicity including the intestine, skin, and bone were investigated.

Materials and methods

In studies of the intestine, single-dose irradiation was performed with 12 Gy of Standard proton RT (S-PRT), followed by a second dose of 12 Gy of F-PRT or S-PRT. Additionally, a hypofractionation scheme was applied in the reirradiation setting (3 x 6.4 Gy of F-PRT or S-PRT, given every 48 hrs). In studies of skin/bone of the murine leg, 15 Gy of S-PRT was followed by hypofractionated reirradiation with F-PRT or S-PRT (3 x 11 Gy).

Results

Compared to reirradiation with S-PRT, F-PRT reduced intestinal fibrosis and collagen deposition in the reirradiation setting and significantly increased survival rate, demonstrating its protective effects on intestinal tissues. In previously irradiated leg tissues, reirradiation with hypofractionated F-PRT created transient dermatitis that fully resolved in contrast to reirradiation with hypofractionated S-PRT. Lymphedema was also alleviated after a second course of radiation with F-PRT, along with significant reductions in the accumulation of fibrous connective tissue in the skin compared to mice reirradiated with S-PRT. The delivery of a second course of fractionated S-PRT induced tibial fractures in 83.3% of the mice, whereas only 20% of mice reirradiated with F-PRT presented with fractures.

Conclusion

These studies provide the first evidence of the sparing effects of F-PRT, in the setting of hypofractionated reirradiation. The results support FLASH as highly relevant to the reirradiation regimen where it exhibits significant potential to minimize chronic complications for patients undergoing RT.

Comparative In Silico Analysis of Ultra-Hypofractionated Intensity-Modulated Photon Radiotherapy (IMRT) Versus Intensity-Modulated Proton Therapy (IMPT) in the Pre-Operative Treatment of Retroperitoneal Sarcoma

BACKGROUND

While pre-operative radiation did not improve abdominal recurrence-free survival for retroperitoneal sarcoma (RPS) in the randomized STRASS trial, it did reduce rates of local recurrence. However, the risk of toxicity was substantial and the time to surgery was prolonged. A combination of hypofractionation and proton therapy may reduce delays from the initiation of radiation to surgery and limit the dose to surrounding organs at risk (OARs). We conducted a dosimetric comparison of the pre-operative ultra-hypofractionated intensity-modulated photon (IMRT) and proton radiotherapy (IMPT).

METHODS

Pre-operative IMRT and IMPT plans were generated on 10 RPS patients. The prescription was 25 Gy radiobiological equivalents (GyEs) (radiobiological effective dose of 1.1) to the clinical target volume and 30 GyEs to the margin at risk, all in five fractions. Comparisons were made using student T-tests.

RESULTS

The following endpoints were significantly lower with IMPT than with IMRT: mean doses to liver, bone, and all genitourinary and gastrointestinal OARs; bowel, kidney, and bone V5-V20; stomach V15; liver V5; maximum doses to stomach, spinal canal, and body; and whole-body integral dose.

CONCLUSIONS

IMPT maintained target coverage while significantly reducing the dose to adjacent OARs and integral dose compared to IMRT. A prospective trial treating RPS with pre-operative ultra-hypofractionated IMPT at our institution is currently being pursued.

Development of HSP90 inhibitors-SN38 conjugates for cancer treatment

Presently, chemotherapy remains to be one of the most important therapeutic approaches for malignant tumors. Ligands based drug conjugates are showing considerable promise as potential therapeutic agents delivery systems for cancer. Here, a series of HSP90 inhibitors-SN38 conjugates were developed through cleavable linkers for tumor-specific delivery of SN38 and reducing its side effects. In vitro assays showed that these conjugates exhibited acceptable stability in PBS and plasma, appreciable HSP90 binding affinity, and potent cytotoxic abilities. Cellular uptake behaviors also indicated that these conjugates could selectively target cancer cells in a time-dependent manner via HSP90. Among them, compound 10b with a glycine linkage exhibits appreciable in vitro and in vivo pharmacokinetic profiles, and excellent in vivo antitumor activity in Capan-1 xenograft models, demonstrating the selective targeting and accumulation of the active payload at tumor sites. Above all, these results suggest that compound 10b has the potential as a potent anticancer drug, meriting further evaluation in the future.

Diagnosis of pulmonary leiomyosarcoma extending into the main bronchus using repeated transbronchial cryobiopsy

The diagnosis of pulmonary leiomyosarcoma using bronchoscopy is difficult, and surgical resection is often performed for definitive diagnosis and curative therapy. We report a case of pulmonary leiomyosarcoma, successfully diagnosed using repeated transbronchial cryobiopsy (TBCB). A 69-year-old-woman was found to have an oval mass in the left hilar region extending into the left main bronchus on computed tomography (CT). All transbronchial biopsy specimens were necrotic, but repeated TBCB removed the necrotic tissue from the tumour and finally led to the diagnosis of pulmonary leiomyosarcoma. Proton therapy was administered, which caused shrinkage of the tumour. Thus, TBCB is useful for definitive diagnosis of leiomyosarcoma without surgical biopsy. Repeated TBCB can reduce tumour volume, eliminate atelectasis, and reduce the extent of radiotherapy exposure.

Rapid and Durable Symptom Palliation With Quad Shot Radiation Therapy to Nonosseous Metastatic/Recurrent Cancer in Elderly or Frail Patients in a Rural Community Clinic

More than half of patients with cancer receiving radiation therapy (RT) are treated in a palliative setting. Elderly or frail patients with metastatic/recurrent cancer require palliative RT that can provide a rapid cancer-related symptom response with low toxicity and short overall treatment time. Cyclical hypofractionated RT (quad shot: 14-14.8 Gy/4 fractions, twice-daily treatments with 6-hour intervals on 2 consecutive days monthly to a total of 42-44.4 Gy) can be a practical palliative RT regimen for patients with poor performance status. In this report, we present palliative symptom response and objective tumor response after quad shot for elderly or frail patients with nonosseous metastatic/recurrent cancers in various sites with varying histology.