Treatment of macular degeneration with proton beams

Subfoveal neovascular membranes (SNVMs) are a leading cause of severe visual loss in the elderly in the United States. Previously, the only treatment that could halt progression of this disease was laser photocoagulation, which was, however, accompanied by immediate reduction in visual acuity. A single narrow proton beam was used to irradiate 45 patients to either 8 or 14 Cobalt Gray Equivalent. The alignment technique and dosimetry of these treatments are described. The proton beam direction, range, and modulation were planned with the assistance of an eye-specific planning program. A single anterior beam was used, with patients looking nasally toward a blinking fixation light at an angle of 30 degrees. Patients were aligned using a light field projected through a slit collimator. Patients' positions were monitored during treatment with a short-focal-length camera. Depth dose in a flat phantom was measured with a small-diameter parallel plate ionization chamber. Lateral profiles were measured at several depths with silver halide film. Each treatment session lasted 15 min, of which 1 min consisted of beam delivery. The proton beam stopped in the orbital cavity, delivering no primary proton dose to the brain. Dose to the center of the lens of the involved eye was less than 0.5% of the dose delivered to the macula. Treatments of SNVMs with proton beams require only a short visit to the hospital, little immobilization effort, and a minimal amount of treatment room and beam time. Compared to previous treatment trials using x-ray beams, the dose to nonocular tissues is reduced significantly.

Proton therapy for pediatric cranial tumors: preliminary report on treatment and disease-related morbidities

PURPOSE

Accelerated protons were used in an attempt to limit treatment-related morbidity in children with tumors in or near the developing brain, by reducing the integral dose to adjacent normal tissues.

METHODS AND MATERIALS

Children treated with protons at Loma Linda University Medical Center between August 1991 and December 1994 were analyzed retrospectively. Twenty-eight children, aged 1 to 18 years, were identified as at risk for brain injury from treatment. Medical records, physical examinations, and correspondence with patients, their parents, and referring physicians were analyzed. The investigators tabulated post-treatment changes in pre-treatment signs and symptoms and made judgments as to whether improvement, no change, or worsening related to disease or treatment had supervened. Magnetic resonance images were correlated with clinical findings and radiographic impressions were tabulated.

RESULTS

Follow-up ranged from 7 to 49 months (median 25 months). Four instances of treatment-related morbidity were identified. Forty-one instances of site-specific, disease-related morbidity were identified: 15 improved or resolved and 26 remained unchanged after treatment. Four patients had radiographic evidence of local failure. Three of these patients, including two with high-grade glioma, have died.

CONCLUSION

Early treatment-related morbidity associated with proton therapy is low. Tumor progression remains a problem when treating certain histologies such as high-grade glioma. Escalating the dose delivered to target volumes may benefit children with tumors associated with poor rates of local control. Long-term follow-up, including neurocognitive testing, is in progress to assess integral-dose effects on cognitive, behavioral and developmental outcomes in children with cranial tumors.

Combined proton and photon conformal radiation therapy for locally advanced carcinoma of the prostate: preliminary results of a phase I/II study

PURPOSE

A study was developed to evaluate the use of combined photons and protons for the treatment of locally advanced carcinoma of the prostate. This report is a preliminary assessment of treatment-related morbidity and tumor response.

METHODS AND MATERIALS

One hundred and six patients in stages T2b (B2), T2c (B2), and T3 (C) were treated with 45 Gy photon-beam irradiation to the pelvis and an additional 30 Cobalt Gray Equivalent (CGE) to the prostate with 250-MeV protons, yielding a total prostate dose of 75 CGE in 40 fractions. Median follow-up time was 20.2 months (range: 10-30 months). Toxicity was scored according to the Radiation Therapy Oncology Group (RTOG) grading system; local control was evaluated by serial digital rectal examination (DRE) and prostate specific antigen (PSA) measurements.

RESULTS

Morbidity evaluation was available on 104 patients. The actuarial 2-year rate of Grade 1 or 2 late morbidity was 12% (8% rectal, 4% urinary). No patients demonstrated Grade 3 or 4 late morbidity. Treatment response was evaluated on 100 patients with elevated pretreatment serum PSA levels. The actuarial 2-year rate of PSA normalization was 96%, 97%, and 63% for pretreatment PSAs of > 4-10, > 10-20, and > 20, respectively. The 13 patients with rising PSA demonstrated local recurrence (3 patients), distant metastasis (8 patients), or no evidence of disease except increasing PSA (2 patients).

CONCLUSIONS

The low incidence of side effects, despite the tumor dose of 75 CGE, demonstrates that conformal protons can deliver higher doses of radiation to target tissues without increasing complications to surrounding normal tissues. The initial tumor response, as assessed by the high actuarial rate of normalization with pretreatment PSA < or = 20, and the low rate of recurrences within the treatment field (2.8%), are encouraging.

Growth kinetics of Escherichia coli and expression of a recombinant protein and its isoforms under heat shock conditions

Preinduction culture conditions were found to have significant impact on the expression and post-translational modification of a recombinant human protein in Escherichia coli under heat shock conditions (30 to 42 degrees C shift). Higher preinduction growth rates (micrograms) favored better cell viability, greater cell mass yields, and increased cloned gene expression during induction. Formation of recombinant protein isoforms (those containing N epsilon-modified lysine residues) exhibited an increasing trend with increasing micrograms. The different extents of post-translational modifications were suspected to be linked to the different concentrations of certain heat shock protein chaperones resulting from different micrograms. In view of the extensive involvement of E. coli heat shock proteins in cellular activities-including the synthesis, processing, modification, and degradation of proteins-at elevated temperatures, it is believed that micrograms dictated the cellular resources available for synthesizing the heat shock proteins required for cell survival, which in turn determined the ability of the cells to respond to the heat shock. With a higher micrograms both the synthesis of host proteins (as indicated by cell growth and survival) and the cloned gene expression were enhanced. The results demonstrate that there exists an intermediate micrograms for optimum production of the unmodified foreign protein in a heat shock environment. More importantly, they also illustrate the feasibility of improving the recombinant protein homogeneity in fermentation, thereby facilitating downstream processing.

Effect of preinduction specific growth rate on secretion of granulocyte macrophage colony stimulating factor by Escherichia coli

The effect of preinduction specific growth rate on the rate of synthesis and processing of granulocyte macrophage colony stimulating factor (GMCSF) secreted by Escherichia coli was investigated. A chemostat was used to explore preinduction growth rates ranging from 0.038 to 0.2/h. The maximum yields of both total GMCSF and processed GMCSF were found to occur at a preinduction growth rate of 0.13/h. It was also discovered that if the postinduction feed rate is reduced at a preinduction growth rate near 0.13/h, then the same amount of processed GMCSF is formed, but no unprocessed GMCSF is produced. It was hypothesized that the rate of synthesis of total GMCSF increases with an increased preinduction specific growth rate, but translocation across the cytoplasmic membrane and processing is rate-limiting. Increased degradation of GMCSF during induction at higher preinduction specific growth rates decreased the amount of GMCSF produced.