Pre-existing subclones determine radioresistance in rectal cancer organoids

More than half of all patients with cancer receive radiation therapy, but resistance is commonly observed. Currently, it is unknown whether resistance to radiation therapy is acquired or inherently present. Here, we employed organoids derived from rectal cancer and single-cell whole-genome sequencing to investigate the long-term evolution of subclones in response to radiation. Comparing single-cell whole-genome karyotypes between in-vitro-unirradiated and -irradiated organoids revealed three patterns of subclonal evolution: (1) subclonal persistence, (2) subclonal extinction, and (3) subclonal expansion. Organoids in which subclonal shifts occurred (i.e., expansion or extinction) became more resistant to radiation. Although radioresistant subclones did not share recurrent copy-number alterations that could explain their radioresistance, resistance was associated with reduced chromosomal instability, an association that was also observed in 529 human cancer cell lines. These data suggest that resistance to radiation is inherently present and associated with reduced chromosomal instability.

Colorectal liver metastases that survive radioembolization display features of aggressive tumor behavior

BACKGROUND

Radiation lobectomy is a therapeutic approach that involves targeted radiation delivery to induce future liver remnant hypertrophy and tumor control. In patients with colorectal liver metastases, only 30-40% have complete tumor regression. The importance of tumor biology in treatment response remains elusive.

METHODS

Patients with colorectal liver metastases who received radiation lobectomy were selected from surgical pathology files. Using a machine learning scoring protocol, pathological response was correlated to tumor absorbed dose and expression of markers of radioresistance Ki-67 (proliferation), CAIX (hypoxia), Olfm4 (cancer stem cells) and CD45 (leukocytes).

RESULTS

No linear association was found between tumor dose and response (ρ < 0.1, P = 0.73 (90Y), P = 0.92 (166Ho)). Response did correlate with proliferation (ρ = 0.56, P = 0.012), and non-responsive lesions had large pools (>15%) of Olfm4 positive cancer stem cells (Fisher's exact test, P = 0.0037). Responding lesions (regression grade ≤2) were highly hypoxic compared to moderate and non-responding lesions (P = 0.011). Non-responsive lesions had more tumor-infiltrating leukocytes (3240 cells/mm2 versus 650 cells/mm2), although this difference was not significant (P = 0.08).

CONCLUSION

The aggressive phenotype of a subset of surviving cancer cells emphasizes the importance of prompt resection after radiation lobectomy.

Robot-assisted thoracoscopic esophagectomy for a giant upper esophageal leiomyoma

This is the first report of a thoracoscopic esophagectomy for a giant leiomyoma of the upper esophagus aided by a robotic system. A 37-year-old man presented with progressive dysphagia and nocturnal aspiration. Endoscopic ultrasound and CT scan of the chest revealed an upper esophageal tumor of 9 x 4 cm arising from the muscularis mucosae. A fine needle aspiration showed clustering of mesenchymal cells, confirming the diagnosis of a stromal cell tumor. A mesenchymal malignancy was suspected because the tumor was located in the upper esophagus and was arising from the muscularis mucosae, both uncommon for a leiomyoma. Moreover, tumor size, an indicator of potential malignancy if >3 cm, was 9 cm. Therefore, an esophagectomy was performed thoracoscopically with the formation of a gastric conduit via laparotomy and a hand-sewn end-to-side cervical anastomosis. The thoracoscopic phase was performed with support of the da Vincitrade mark robotic system, which allowed for an excellent 3-dimensional view and a precise dissection of the esophagus along the vital mediastinal structures. The duration of the thoracoscopic part was 115 min and that of the total procedure was 270 min. Blood loss during the thoracoscopic phase was 50 mL; total blood loss was 200 mL. The patient was ventilated for 1 day; his total intensive care stay was 2 days. He left the hospital in good condition on the 11th postoperative day. Histopathological examination combined with immunohistochemistry revealed a leiomyoma of 9.0 x 5.0 x 2.5 cm. After 3 years of follow-up, the patient is in good health.