Non-invasive methods of assessing angiogenesis and their value in predicting response to treatment in colorectal cancer

BACKGROUND

Tumour neoangiogenesis can be assessed non-invasively by measuring angiogenic cytokine concentrations in peripheral circulation and by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). The aim of this study was to assess whether these methods can predict and monitor response to treatment in patients with rectal cancer treated with preoperative chemoradiotherapy.

METHODS

Serum and plasma vascular endothelial growth factor levels were measured in 31 patients with T3/T4 rectal cancers before quantitating tumour permeability (ln Ktrans) by DCE-MRI. Sixteen patients receiving preoperative chemoradiotherapy had serial vascular endothelial growth factor (VEGF) and DCE-MRI measurements. Response to treatment was assessed using World Health Organization criteria.

RESULTS

Serum VEGF and ln Ktrans correlated before treatment (r = 0.48, P = 0.01). Responsive tumours (n = 8) had higher pretreatment permeability values than non-responsive tumours (n = 8) (mean ln Ktrans - 0.46 and - 0.72 respectively; P = 0.03). Compared with pretreatment values, responsive tumours showed a marked reduction in permeability at the end of treatment (mean ln Ktrans - 0.46 and - 0.86 respectively; P = 0.04). Pretreatment serum VEGF levels were not statistically different between the two groups.

CONCLUSION

Rectal tumours with higher permeability at presentation appear to respond better to chemoradiotherapy than those of lower permeability. This may allow preselection of appropriate tumours for these regimens, with patients with low-permeability tumours being considered for alternative therapies.

The prevalence of avascular necrosis in patients treated with chemotherapy for testicular tumours

To study the prevalence of avascular necrosis in patients receiving chemotherapy for testicular cancer we invited 103 consecutive patients treated by chemotherapy to attend for MRI scan of the hips. Four of 47 (9% (CI 2-20%)) patients scanned and 4/103 (3.8% (CI 1-10%)) of patients invited to participate in the study had evidence of avascular necrosis. As not all patients in the study had completed the at risk period this equates to a 3-year actuarial risk of 6.3% (95% confidence limits (CI) 2.4-16.1). These data suggest that avascular necrosis is an uncommon but significant complication of chemotherapy including steroids as anti-emetics.

What is the prevalence of symptomatic or asymptomatic femoral head osteonecrosis in patients previously treated with chemoradiation? A magnetic resonance study of anal cancer patients

It is generally assumed that femoral head osteonecrosis (FHO) is a serious but rare complication of pelvic radiotherapy. A review of the literature carried out by the authors indicates a prevalence of 4/763 (95% confidence interval 0.1%-1.3%). A recent publication has suggested that the prevalence of symptomatic FHO may be much greater than previously assumed as a result of sensitization of bone to radiation by concomitant treatment with chemotherapy. Magnetic resonance imaging (MRI) is currently the most sensitive modality for detecting and confirming symptomatic or asymptomatic FHO of any aetiology. The aim of this study therefore was to assess the prevalence of symptomatic and asymptomatic FHO in patients previously treated for anal cancer by chemoradiation (CRT). The hips of 34 currently disease-free individuals (11 men and 23 women; median age 67 years, range 32-86) were scanned using a coronal T1-weighted sequence. The images were assessed for evidence of FHO. The median time of scanning after the end of CRT was 35 months (range 6-107). No cases (0/34) of symptomatic or asymptomatic FHO were detected in these patients. Given the established sensitivity of MRI in the detection of FHO, it is concluded that changes indicative of osteonecrosis were uncommon after CRT in the current cohort of patients. Recent evidence from the literature suggests, however, that elderly females are at greatest risk of developing FHO after CRT.

The quantitative 19F-imaging of albumin at 1.5 T: a potential in-vivo tool

19F-MR-imaging has been used to quantitate albumin concentration in a phantom at 1.5 T. The experimentally derived relationship between albumin concentration and the T1 relaxation time of a fluorinated marker, tetrafluorosuccinic acid (TFSA) was used to calculate the albumin concentration from a quantitative 19F T1 map acquired using a gradient echo sequence. There was close correlation between calculated and actual BSA concentrations (r = 0.99, SE = 0.15). The potentially interfering effect of paramagnetic species on T1 relaxation times was also investigated. Relaxivity data show that albumin concentration measurements should be performed prior to any contrast agent administration.

Gallbladder localization of (19)F MRS catabolite signals in patients receiving bolus and protracted venous infusional 5-fluorouracil

The hepatobiliary distribution of 5-fluorouracil (5FU) catabolites was investigated in nine patients. Using fluorine 3D-chemical shift imaging, four patients receiving protracted venous infusion of 5FU demonstrated catabolite localized to the gallbladder. No hepatobiliary fluorine signals were detected in three patients whose gallbladders were absent or abnormal. Signals from the gallbladder showed a 2.2-2.4 ppm high-frequency shift from alpha-fluoro-beta-alanine, suggesting the presence of alpha-fluoro-beta-alanine-bile-acid conjugates. 3D-chemical shift imaging of two patients receiving bolus 5FU revealed alpha-fluoro-beta-alanine to be localized to the liver within 1 hr of administration. In one patient examined 4 hr after bolus administration, catabolite signal was detected only in the gallbladder.

Spin-lattice relaxation of laser-polarized xenon in human blood

The nuclear spin polarization of 129Xe can be enhanced by several orders of magnitude by using optical pumping techniques. The increased sensitivity of xenon NMR has allowed imaging of lungs as well as other in vivo applications. The most critical parameter for efficient delivery of laser-polarized xenon to blood and tissues is the spin-lattice relaxation time (T1) of xenon in blood. In this work, the relaxation of laser-polarized xenon in human blood is measured in vitro as a function of blood oxygenation. Interactions with dissolved oxygen and with deoxyhemoglobin are found to contribute to the spin-lattice relaxation time of 129Xe in blood, the latter interaction having greater effect. Consequently, relaxation times of 129Xe in deoxygenated blood are shorter than in oxygenated blood. In samples with oxygenation equivalent to arterial and venous blood, the 129Xe T1s at 37 degrees C and a magnetic field of 1.5 T were 6.4 s +/- 0.5 s and 4.0 s +/- 0.4 s, respectively. The 129Xe spin-lattice relaxation time in blood decreases at lower temperatures, but the ratio of T1 in oxygenated blood to that in deoxygenated blood is the same at 37 degrees C and 25 degrees C. A competing ligand has been used to show that xenon binding to albumin contributes to the 129Xe spin-lattice relaxation in blood plasma. This technique is promising for the study of xenon interactions with macromolecules.

Does 100 mm photofluorography always have a dose advantage over conventional film-screen radiography in barium meals?

It is generally held that 100 mm photofluorography has a significant dose saving advantage over conventional radiography. The dose area product (DAP) data for the two formats were available for study in consecutive patients undergoing barium meal examination. There was no significant difference in DAP readings between the two formats. Conventional radiographs expose a 40% greater area than the 100 mm format, probably accounting for the lower mean DAP value of photofluorography. The mean DAP for whole examinations was 26.1 Gy cm2 for photofluorography, and 30.5 Gy cm2 for conventional radiography. These are both above the third quartile of national reference dose levels. There is little apparent difference in the doses incurred by patients between the two formats in respect of the working practice of the department. Barium meals will therefore continue to be recorded on both formats.