Comparison of head direction cell firing characteristics across thalamo-parahippocampal circuitry

Head direction (HD) cells, which fire persistently when an animal's head is pointed in a particular direction, are widely thought to underlie an animal's sense of spatial orientation and have been identified in several limbic brain regions. Robust HD cell firing is observed throughout the thalamo-parahippocampal system, although recent studies report that parahippocampal HD cells exhibit distinct firing properties, including conjunctive aspects with other spatial parameters, which suggest they play a specialized role in spatial processing. Few studies, however, have quantified these apparent differences. Here, we performed a comparative assessment of HD cell firing characteristics across the anterior dorsal thalamus (ADN), postsubiculum (PoS), parasubiculum (PaS), medial entorhinal (MEC), and postrhinal (POR) cortices. We report that HD cells with a high degree of directional specificity were observed in all five brain regions, but ADN HD cells display greater sharpness and stability in their preferred directions, and greater anticipation of future headings compared to parahippocampal regions. Additional analysis indicated that POR HD cells were more coarsely modulated by other spatial parameters compared to PoS, PaS, and MEC. Finally, our analyses indicated that the sharpness of HD tuning decreased as a function of laminar position and conjunctive coding within the PoS, PaS, and MEC, with cells in the superficial layers along with conjunctive firing properties showing less robust directional tuning. The results are discussed in relation to theories of functional organization of HD cell tuning in thalamo-parahippocampal circuitry.

Bortezomib therapy for prostate specific antigen (PSA)-only relapse after definitive local therapy

e16053

Background: We conducted a single arm, phase II trial of single-agent bortezomib, a proteasome inhibitor, in patients with prostate cancer with biochemical recurrence (PSA relapse) after definitive local therapy. Eligible patients had previous radical prostatectomy and/or radiation therapy (including brachytherapy), and a rising PSA over 1 ng/mL without bone scan evidence of metastasis. The primary goal of this study was to determine the PSA response to single agent bortezomib. Secondary goal was to identify the time to PSA relapse after bortezomib therapy defined as time from nadir to PSA >1ng/ml. Methods: Treatment was composed of bortezomib 1.3mg/m2 IV on days 1,4,8,11 then 10 days off for the first two cycles. The third cycle was comprised of weekly bortezomib therapy for three out of four weeks. Sixteen patients were enrolled and treated at 4 sites with13 evaluable patients. Results: Median baseline PSA was 12.0 ng/ml. 3 of 13 patients (23%) achieved complete responses and 1 a partial response (PR) for a response rate of 30% (95% CI: 0.09 –0.61). Median time to PSA relapse in these 3 patients was 6.0 months. Linear longitudinal modeling was used to compare the rate of increase in PSA prior to treatment versus during treatment with bortezomib and found that treatment significantly decreased the slope of log PSA during treatment, slowing PSA rise (p = 0.003). The major toxicity associated with bortezomib therapy was peripheral neuropathy (7 pts, grade 3 in 3 pts) requiring dose reductions in 3 cases and discontinuation of therapy in 4 patients. Other toxicities included non-neutropenic infections (shingles in 2 pts), 1 small bowel ileus (grade 3), and 1 case of thrombocytopenia (grade 3). Conclusions: In a small number of patients there was a 30% PSA response rate to single agent bortezomib therapy. Further investigations using bortezomib as a single-agent or in combination are warranted in this patient population.

No significant financial relationships to disclose.

Breast-feeding, weaning and the diarrhoeal syndrome in a Guatemalan Indian village

Prospective studies in Mayan Indian children living in their natural setting were carried out from 1964 through 1974; observations began at birth and extended at least throughout the first three years of life. Adequate growth and survival were characteristic of exclusively breast-fed infants in the first months of life. Despite the high rate of infection, children exhibited a considerable resistance to intestinal protozoa, enterobacteriaceae and enteric viruses. Resistance against colonic invaders is attributed to the bifidus flora, and that against agents acting in the small bowel, to specific antibodies present in colostrum and milk. Diarrhoeal disease was least in this period and increased with weaning to reach maximum peaks at the time of weaning. The protracted weaning consisted of progressive administration of foods of low biological value given under deficient sanitary conditions. The nutrient value of the diet as a function of the child's weight was adequate in protein but in most cases it was markedly deficient in calories. Infectious diseases, particularly diarrhoea, were found associated with pronounced reductions in the already deficient calorie intake. Infection and infectious disease were common particularly during the first 6 to 18 months of life. Weight loss was a frequent finding during and after episodes of disease. The consequence of the malnutrition-infection interaction is a marked stunting of growth, clearly evident from examination of the growth curves of village children. Nutrient intake did not correlate with growth velocity. By contrast, the duration of breast-feeding was strongly associated with growth in the linear segment of the curve, while in the period of faster growth the correlation was inverse. On the other hand, morbidity was inversely correlated with calorie and protein intake and this was more obvious in the second than in the first year of life. The data indicate that infection is one of the leading factors associated with reduced calorie (and protein) intakes during the critical period of onset of malnutrition and mortality in childhood. By preventing infection, particularly diarrhoea, the food intake, nutrition and growth of children could be significantly improved.

Effect of obesity on overall survival following permanent prostate brachytherapy

15576

Background: To evaluate the impact of obesity on cause-specific (CSS), biochemical progression-free (bPFS) and overall survival (OS) following prostate brachytherapy. Methods: From April 1995 through March 2003, 1,093 consecutive patients underwent brachytherapy for clinical T1b-T3a (2002 AJCC) prostate cancer. The median follow up was 5.6 years. All patients were implanted at least 3 years prior to analysis. Evaluated body mass index (BMI) subgroups were < 25 (n=258), 25.0 to 29.9 (n=547), 30.0 to 34.9 (n=214) and = 35 (n=74) kg/m2, respectively. Four-hundred and thirty (39.9%) and 589 (53.9%) of the patients received androgen deprivation therapy or supplemental external beam radiation therapy, respectively. Multiple clinical, treatment and dosimetric parameters were evaluated as predictors of CSS, bPFS and OS. Results: The 11 year CSS, bPFS and OS for the entire cohort were 97.5%, 95.6% and 77.6% respectively. BMI did not impact CSS or bPFS for any of the BMI cohorts. However, OS was statistically lower in patients with a BMI < 25 kg/m2 (p = 0.014). A Cox linear regression analysis demonstrated that Gleason score was the best predictor of CSS while percent-positive biopsies, risk group,V100 and hypertension predicted for bPFS. Patient age and tobacco use were the strongest predictors of OS. One-hundred and twenty-eight patients have died with 108 (84.4%) of the deaths the result of cardiovascular/pulmonary disease (73) and second malignancies (35). To date, 12 patients have died of metastatic prostate cancer. Conclusions: Following brachytherapy, obesity did not impact CSS, bPFS or OS. Cardiovascular or pulmonary disease and second malignancies substantially outweighed prostate cancer as competing causes of death.

No significant financial relationships to disclose.

The impact of primary Gleason pattern on survival following brachytherapy for Gleason score 7 prostate cancer

15588

Background: A recent radical prostatectomy series reported lower rates of biochemical control and cause-specific survival in Gleason score 7 patients with primary Gleason pattern 4. In this study, we evaluated the impact of Gleason 4+3 versus 3+4 on cause-specific, biochemical progression-free and overall survival in patients managed with permanent prostate brachytherapy. Methods: From April 1995 to June 2003, 530 prostate cancer patients underwent brachytherapy for clinical stage T1b-T3c (2002 AJCC) prostate cancer with Gleason score 3+4 (n=300) or Gleason score 4+3 (n=230) histology. All patients underwent brachytherapy more than three years prior to analysis. The mean and median follow-up was 6.0 and 5.7 years, respectively (range 3.2–11.2 years). Of the evaluated cohort, 412 (77.7%) received supplemental XRT and 177 (33.4%) received androgen deprivation therapy. No statistical differences were discerned between the use of XRT, however, Gleason 4+3 patients were more likely (37.4% versus 30.3%, p=0.002) to receive ADT. Multiple clinical, treatment and dosimetric parameters were evaluated as predictors of cause-specific, biochemical progression-free and overall survival. Results: At 10 years, primary Gleason 3+4 versus 4+3 did not predict for cause-specific survival (96.7% versus 93.3%, p=0.506), biochemical progression-free (97.0 versus 92.9%, p=0.085) or overall survival (77.0% versus 78.0%, p=0.9333). Cox linear regression analysis demonstrated no significant predictors for cause-specific survival while pre-treatment PSA, prostate volume and clinical stage predicted for biochemical progression-free survival. Patient age, tobacco use and diabetes were the strongest predictor for overall survival. To date, 57 patients have died (25 with Gleason 4+3 and 32 with Gleason 3+4). Of the deaths, 76% were due to cardiovascular events or second malignancies. To date, 4 patients (2 in each cohort) have died of metastatic prostate cancer. Conclusions: Following brachytherapy, the primary Gleason pattern did not impact cause-specific, biochemical progression-free or overall survival in Gleason score 7 prostate cancer. Cardiovascular disease and second malignancies were responsible for 9 times more deaths than prostate cancer.

No significant financial relationships to disclose.

Androgen deprivation therapy does not impact cause-specific or overall survival in high-risk prostate cancer treated with brachytherapy and supplemental external beam

15578

Background: To determine cause-specific (CSS), biochemical progression-free (bPFS) and overall survival (OS) in high risk prostate cancer patients undergoing brachytherapy with or without supplemental therapies. Methods: From April 1995 through July 2002, 204 patients with high risk prostate cancer (Gleason score = 8 and/or PSA > 20 ng/mL and/or clinical stage = T2c) underwent brachytherapy with or without supplemental therapies. Of the 204 patients, 193 (94.6%) received supplemental XRT and 119 (58.3%) received ADT (ADT = 6 months n=40 and ADT > 6 months n = 79). Median follow-up was 7.0 years. All patients were implanted at least 4 years prior to analysis. BPFS was defined by a PSA = 0.40 ng/mL after nadir. Multiple clinical, treatment and dosimetric parameters were evaluated for the impact on survival. Results: The ten-year CSS, bPFS and OS were 88.9%, 86.6% and 68.6%, respectively. A statistically significant difference in bPFS was discerned between hormone naïve, ADT = 6 months and ADT > 6 month cohorts (79.7% vs. 95.0% vs. 89.9%, p= 0.032). ADT did not impact CSS (94.0% vs. 87.1%, p=0.983 ) or OS (65.2% vs. 70.3%, p = 0.713). For bPFS patients, the median post-treatment PSA was < 0.04 ng/mL. A Cox linear regression analysis demonstrated that Gleason score was the best predictor of CSS while percent positive biopsies and duration of ADT best predicted for bPFS. OS was best predicted by Gleason score and diabetes. Thirty-eight patients have died with 26 of the deaths due to cardiovascular/pulmonary disease or second malignancy. Eleven patients have died of metastatic prostate cancer. Conclusions: Androgen deprivation therapy improved 10-year bPFS without statistical impact on CSS or OS. Death as a result of cardiovascular/pulmonary disease and second malignancies were more than twice as common as prostate cancer deaths. Strategies to improve cardiovascular health should positively impact overall survival.

No significant financial relationships to disclose.

Prostate cancer distribution in patients diagnosed by transperineal template-guided saturation biopsy: Implications for brachytherapy treatment planning

15533

Background: Prostate cancer remains undetected in approximately one-third of patients following standard transrectal ultrasound-guided biopsy. In this study, we evaluated prostate cancer incidence, anatomic distribution, Gleason score profile and tumor burden in patients diagnosed by transperineal template-guided saturation biopsy (TTSB). Methods: One hundred and seventeen patients underwent TTSB. TTSB was performed under general anesthesia. All but one patient had undergone at least one prior negative TRUS biopsy. Criteria for inclusion included an elevated PSA and/or the diagnosis of ASAP or high-grade PIN on prior biopsy. The prostate gland was divided into 24 regional biopsy locations with 1–3 biopsies per region. The median number of biopsy cores was 50. Multiple clinical parameters were evaluated as predictors for prostate cancer diagnosis. Results: The mean patient age was 64.8 years with a mean PSA of 9.1 ng/mL and a prostate volume of 78.6 cm3. On average, patients had undergone 2.1 prior negative TRUS biopsies with a mean of 22.4 core biopsies. Prostate cancer was diagnosed in 49 patients (41.9%) with a Gleason score distribution of 6–9. Patients with a prostate volume of = 60 cm3 had a higher rate of cancer diagnosis compared to patients with larger glands (66% vs. 30%). Although no anatomic region of the prostate gland was spared of cancer, there was a preponderance of anterior-based malignancies. In patients with prostate cancer, an average of 9.9 cores were involved. In multivariate analysis, pre-saturation biopsy diagnosis and prostate volume were the best predictors for prostate cancer diagnosis. Conclusions: Transperineal template-guided saturation biopsy diagnosed prostate cancer in 41.9% of previously biopsied patients. Considerable anatomic variability in prostate cancer distribution was documented. Based on this and other reports, cancer eradication will be dependent on treatment of the entire prostate gland.

No significant financial relationships to disclose.

Prediction of PSA spikes by isotope and patient age following permanent prostate brachytherapy

15535

Background: To evaluate prostate specific antigen (PSA) spikes (bounces) following permanent prostate brachytherapy in low-risk patients randomized to Pd-103 or I-125. Methods: The study population consisted of 164 prostate cancer patients who were part of a prospective randomized trial comparing Pd-103 with I-125 for low-risk disease. Sixty-one patients (37.2%) received short course cytoreductive androgen deprivation therapy (ADT). No patient received supplemental XRT. The median follow-up was 5.4 years. All patients were implanted at least 3 years prior to analysis. On average, 10.1 post-treatment PSA’s were obtained per patient. Biochemical disease-free survival was defined as a PSA = 0.40 ng/mL after nadir. A PSA spike was defined as a rise of = 0.2 ng/mL followed by a durable decline to pre- spike levels. Multiple clinical, treatment and dosimetric parameters were evaluated as predictors for a PSA spike. Results: Forty- four patients (26.9%) developed a PSA spike including 45.7% (21/46) of the hormone naïve I-125 patients and 14.0% (8/57) of the hormone naïve Pd-103 patients. In hormone naïve patients, the mean time between implant and spike was 22.6 months and 18.7 months for I-125 and Pd-103 patients, respectively. In patients receiving neoadjuvant ADT, the incidence of spikes was comparable between isotopes (28.1% for I- 125 and 20.7% for Pd-103). The incidence of spikes was substantially different in patients < 65 vs = 65 years of age (16.3% vs. 38.5%). In multivariate Cox regression analysis, patient age at implant (p < 0.001) and isotope (p = 0.002) were significant predictors for spike. Conclusions: In low-risk prostate cancer patients, PSA spikes are most common in patients implanted with I-125 and/or younger than 65 years of age. Differences in isotope-related spikes are most pronounced in hormone naïve patients.

No significant financial relationships to disclose.