Poster - Thur Eve - 72: Conversion of helical tomotherapy plans into clinically favourable step-and-shoot IMRT plans deliverable on a c-arm linac

The treatment planning software SharePlan is designed to convert dose distributions generated by the TomoTherapy planning station into step-and-shoot IMRT plans deliverable on a c-arm linear accelerator. Five anal canal patients who were planned for TomoTherapy treatments were exported into a SharePlan system and plans were generated for delivery on an Elekta Synergy unit. A total of 80 plans were generated for those five patients, with either seven, nine, eleven or twenty-one gantry angles and different priorities between focusing on matching either the target doses or healthy tissue sparing of the TomoTherapy plan. The plans generated by SharePlan, while often not matching target coverage at prescription, matched well the TomoTherapy coverage at 95% and 105% of the prescription dose. Organ at risk dose, when heavily emphazied in the SharePlan calculations matched or bettered the TomoTherapy dose due to the placement of the beams and the sharper sup-inf fall off of the dose distribution on a linac. For one of the patients, it was possible to produce a better DVH with SharePlan than the original TomoTherapy plan for those reasons. The TomoTherapy plans boasted significantly shorter delivery times than the plans generated with SharePlan.

An experimental feasibility study on the use of scattering foil free beams for modulated electron radiotherapy

The potential benefit of using scattering foil free beams for delivery of modulated electron radiotherapy is investigated in this work. Removal of the scattering foil from the beamline showed a measured bremsstrahlung tail dose reduction just beyond R(p) by a factor of 12.2, 6.9, 7.4, 7.4 and 8.3 for 6, 9, 12, 16 and 20 MeV beams respectively for 2 × 2 cm(2) fields defined on-axis when compared to the clinical beamline. Monte Carlo simulations were matched to measured data through careful tuning of source parameters and the modification of certain accelerator components beyond the manufacturer's specifications. An accelerator model based on the clinical beamline and one with the scattering foil removed were imported into a Monte Carlo-based treatment planning system (McGill Monte Carlo Treatment Planning). A treatment planning study was conducted on a test phantom consisting of a PTV and two distal organs at risk (OAR) by comparing a plan using the clinical beamline to a plan using a scattering foil free beamline. A DVH comparison revealed that for quasi-identical target coverage, the volume of each OAR receiving a given dose was reduced, thus reducing the dose deposited in healthy tissue.

Changes in serial magnetic resonance spectroscopy predict outcome in high-grade glioma during and after postoperative radiotherapy

AIM

To determine any correlation between magnetic resonance spectroscopy (MRS) pattern of high-grade glioma before, during, and after radiotherapy (RT) with overall survival (OS) and progression-free survival (PFS).

PATIENTS AND METHODS

Twenty-six patients prospectively underwent surgery and RT to 60 Gy. MRS was performed before RT, at week 4 of RT, and 2 months post-RT. Normalized and relative metabolite ratios were evaluated. Patients were grouped according to similar evolving MRS patterns and analyzed for differences in OS and PFS.

RESULTS

Significant decreases in tumor choline/N-acetyl-aspartate and normalized choline were observed from baseline to post-RT. After a median follow-up of 22.9 months, patients with >40% decrease in normalized choline from week 4 during RT to 2 months post-RT had a significantly worse median OS (9.1 months vs. not reached, p<0.00001) and PFS (5.8 vs. 19.8 months, p=0.0018).

CONCLUSION

The change in normalized choline at 2 months post-RT was highly prognostic for PFS and OS. This may allow more individualized response-based treatment.

Abstract P1-10-02: A Novel Attempt To Improve Long-Term Patient Follow-Up in a Low Resource Urban Setting

The lack of either a nationalized health care structure or widespread health insurance in most developing nations is at the root of many of our health care challenges. Amongst them is the loss to follow-up of a majority of patients treated at tertiary care centers. As a consequence, outcomes data from such countries are notoriously non representative. While there have been numerous published reports of treatment outcomes of cancers from India, the reported numbers as a proportion of originally treated patients are probably less than half. We have attempted a simple solution to this problem, made possible primarily by the revolution of low cost mobile cell phones and almost universal access.

Methods.

St. John's Medical College Hospital is a tertiary care centre located in Bangalore, India. We established a patient support group called Aadhara (“Support” in Sanskrit). Aadhara has employed two women with training in counseling and clinical research. Both were provided with cell phones. At the time of initial breast cancer diagnosis, patients are enrolled in a long term follow-up study. Cell phone numbers, address and other contact details of patients and/or next of kin are obtained. The patients and their family are informed about the psycho-social support available at Aadhara that include counseling, psycho-education, talks on psycho-social aspects of the disease, nutrition, news letters, meeting long-term survivors and community breast cancer awareness programs. They are provided phone numbers and email ids to get in touch with the counselors as needed. The patients or their family are contacted by the counselors on a monthly basis. However the patients are free to get in touch with the counselors by just making a “missed call” to the cell phone numbers.

Results

Aadhara has been operational for close to two years. During this period we have enrolled 121 patients into our longitudinal observational study. There have been 11 deaths in our cohort. The most gratifying outcome has been the loss of only 2 patients to follow-up. This represents a greater than 95% follow-up. The costs of this entire program have been made available by a philanthropic organization and are approximately USD 2000 per month. Represented as per patient cost, this is less than USD 20/patient per month and could probably be halved as the enrollments grow. Discussion

The rapid and deep penetration of mobile phone services in India present opportunities for obtaining better metrics of the consequences of medical treatment. This model has the advantage of scalability and diminishing per patient costs as the numbers grow. It is also portable to other clinical conditions where long-term outcomes are needed to guide health care interventions. This is “proof-of-concept” that improved outcome measures can be obtained in low resource settings at costs that are a fraction of the cost of treatment.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-10-02.

Prenatal cocaine exposure increases anxiety, impairs cognitive function and increases dendritic spine density in adult rats: influence of sex

Cocaine exposure during pregnancy can impact brain development and have long-term behavioral consequences. The present study examined the lasting consequences of prenatal cocaine (PN-COC) exposure on the performance of cognitive tasks and dendritic spine density in adult male and female rats. From gestational day 8 to 20, dams were treated daily with 30 mg/kg (ip) of cocaine HCl or saline. At 62 days of age, offspring were tested consecutively for anxiety, locomotion, visual memory and spatial memory. PN-COC exposure significantly increased anxiety in both sexes. Object recognition (OR) and placement (OP) tasks were used to assess cognitive function. Behavioral tests consisted of an exploration trial (T1) and a recognition trial (T2) that were separated by an inter-trial delay of varying lengths. Male PN-COC subjects displayed significantly less time investigating new objects or object locations during T2 in both OR and OP tasks. By contrast, female PN-COC subjects exhibited impairments only in OR and only at the longest inter-trial delay interval. In addition, gestational cocaine increased dendritic spine density in the prefrontal cortex and nucleus accumbens in both genders, but only females had increased spine density in the CA1 region of the hippocampus. These data reveal that in-utero exposure to cocaine results in enduring alterations in anxiety, cognitive function and spine density in adulthood. Moreover, cognitive deficits were more profound in males than in females.