Mechanical stability assessment of novel orthodontic mini-implant designs: Part 2

OBJECTIVE

To assess the mechanical stability of a newly revised orthodontic mini-implant design (N2) compared with a design introduced in Part 1 of the study (N1) and the most widely-used commercially-available design (CA). To evaluate the mean buccal bone thickness of maxillary and mandibular posterior teeth using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

From the CBCT scans of 20 patients, six tomographic cross-sections were generated for each tooth. Buccal bone thickness was measured from the most convex point on the bone to the root surface. CA (1.5 mm in diameter and 6 mm in length), N1, and N2 (shorter and narrower than N1) were inserted in simulated bone with cortical and trabecular bone layers. Mechanical stability was compared in vitro through torque and lateral displacement tests.

RESULTS

The bone thickness ranged from 2.26 to 3.88 mm. Maximum insertion torque was decreased significantly in N2 compared to N1. However, force levels for all displacement distances and torque ratio were the highest in N2, followed by N1 and CA (α = .05).

CONCLUSIONS

Both torque and lateral displacement tests highlighted the enhanced stability of N2 compared with CA. Design revisions to N1 effectively mitigated N1's high insertion torque and thus potentially reduced microdamage to the surrounding bone. The N2 design is promising as evidenced by enhanced stability and high mechanical efficiency. Moreover, N2 is not limited to placement in interradicular spaces and has the capacity to be placed in the buccal bone superficial to the root surface with diminished risk of endangering nearby anatomic structures during placement and treatment.

Postoperative extended-volume external-beam radiation therapy in high-risk esophageal cancer patients: a prospective experience

Background and Purpose

Extended-volume external-beam radiation therapy (rt) following esophagectomy is controversial. The present prospective study evaluates the feasibility of extended-volume rt treatment in high-risk esophagectomy patients with a cervical anastomosis receiving postoperative combined chemoradiation therapy.

Patients and Methods

From 2001 to 2006, 15 patients with resected esophageal cancer were prospectively accrued to this pilot study to evaluate the adverse effects of extended-volume rt. Postoperative management was carried out at London Regional Cancer Program. Eligibility criteria were pathology-proven esophageal malignancy (T3–4, N0–1), disease amenable to surgical resection, and esophagectomy with or without resection margin involvement. Patients with distant metastases (M1) and patients treated with previous rt were excluded. All 15 study patients received 4 cycles of 5-fluorouracil–based chemotherapy. External-beam rt was conducted using conformal computed tomography planning, with multi-field arrangement tailored to the pathology findings, with coverage of a clinical target volume encompassing the primary tumour bed and the anastomotic site in the neck. The radiation therapy dose was 50.40 Gy at 1.8 Gy per fraction. The rt was delivered concurrently with the third cycle of chemotherapy. The study outcomes—disease-free survival (dfs) and overall survival (os)—were calculated by the Kaplan–Meier method. Treatment-related toxicities were assessed using the U.S. National Cancer Institute’s Common Toxicity Criteria.

Results

The study accrued 10 men and 5 women of median age 64 years (range: 48–80 years) and TNM stages T3N0 (n = 1), T2N1 (n = 2), T3N1 (n = 11), and T4N1 (n = 1). Histopathology included 5 adenocarcinomas and 10 squamous-cell carcinomas. Resection margins were clear in 10 patients. The median follow-up time was 19 months (range: 3.5–53.4 months). Before radiation therapy commenced, delay in chemotherapy occurred in 20% of patients, and dose reduction was required in 13.3%. During the concurrent chemoradiation therapy phase, 20% of the patients experienced chemotherapy delay, and 6.6% experienced dose reduction. No patient experienced treatment-related acute and chronic esophagitis above grade 2. Disease recurred in 40% of the patients (6/15), and median time to relapse was 24 months. No tumour recurred at the anastomotic site. The median dfs was 23 months, and the median os was 21 months.

Conclusions

Extended-volume external-beam rt encompassing the tumour bed and the anastomotic site is feasible and safe for high-risk T3–4, N0–1 esophageal cancer patients after esophagectomy.

Clinical Data Do Not Support the Hypothesis That Irradiation Promotes Biologically Aggressive Local Recurrences through Stromal Activation

Objective: Recent data in select pre-clinical models suggest that radiation can activate normal stroma to promote tumor metastases and aggressiveness. We hypothesized that if these were occurring clinically, there would be a lower survival after locoregional recurrence (LRR) in patients after post-mastectomy radiation therapy (PMRT) compared to mastectomy (Mx) alone. This study used two independent datasets to compare survival after LRR in women treated with versus without PMRT.Methods: Data from 229 of 1,505 patients who experienced LRR after treatment on sequential non-randomized institutional prospective trials at the MD Anderson Cancer Center (MDA) and 66 of 318 patients enrolled in the British Columbia (BC) PMRT randomized trial who experienced LRR were analyzed. All patients underwent Mx and level I/II axillary dissection. In both data sets analysis was based on treatment received. Patients from MDA received doxorubicin based chemotherapy +/- PMRT, with 45 LRR after PMRT and 184 LRR after Mx alone). Patients treated on the BC trial received CMF chemotherapy +/- PMRT, with LRR in 14/160 after PMRT versus 52/158 after Mx alone. Survival was calculated from time of LRR to death using Kaplan-Meier and log rank statistics.Results:MDA Data: Median follow up of living patients was 192 months. Analyzing data from all patients with LRR regardless of distant metastasis (DM), patients with LRR after PMRT were younger (47 vs. 51 y, p = 0.033) and had shorter time to first LRR (40mo vs. 51 mo, p = 0.018). 5-yr/10-yr OS were 31%/16% without PMRT and 20%/7% after PMRT (p = 0.008). However, PMRT-treated patients had increased risk factors for DM (advanced T and N stage) and more PMRT-treated patients developed DM prior to LRR (58% vs. 36% p = 0.009). Analyzing only patients without DM there was no difference in OS between groups (p = 0.67), and a separate analysis of all patients who developed metastatic disease (N = 385 no PMRT, 233 after PMRT) revealed no difference in 5 or 10-yr OS after DR (15%/4% without PMRT vs. 13%/6% after PMRT, p = 0.5).BC Data: Median follow up of living patients was 235 months. The distributions of age, T stage, N stage, grade, LVI, ER status, excised nodes and nodal ratio were similar between patients with LRR after Mx alone vs. Mx plus PMRT. (all p > 0.05). The mean time to first LRR was 39 mo in patients treated with Mx alone and 57 mo in patients treated with PMRT, p= 0.27). The rate of DM was similar in patients with LRR after Mx with vs without PMRT (93% vs. 96%, p=0.60). Distant relapse free survival after LRR was similar in Mx alone vs. PMRT-treated patients (log rank p=0.75). Overall survival was also similar in the two groups (5-yr/10-yr OS 21%/8% without PMRT vs. 23%/12% with PMRT, log rank p=0.93).Conclusions: Decades of randomized data have demonstrated that PMRT reduces LRR and improves overall survival. In the non-randomized dataset, removing the competing risk of DM which is higher in patients selected for PMRT by studying patients with isolated LRR, we find no difference in survival after LRR in the PMRT setting. Analysis of the randomized PMRT trial dataset confirmed the finding of similar survival among women with LRR irrespective of PMRT use.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4101.

Survival Outcomes in Women with Ipsilateral Breast Tumor Relapse: An Analysis of Cohorts Classified Clinically as 'True Recurrence' Versus 'New Primary'

Background:Ipsilateral breast tumor relapse (IBTR) can occur in ∼5-20% of women after breast conserving therapy. Two entities of IBTR have been described: "True Recurrence" (TR), suggested to be cases of regrowth of pre-malignant or malignant cells not completely eradicated by surgery or radiation therapy; and "New Primary" (NP), distinct in histology and located away from the index tumor. Whether these two entities have different prognoses is unclear. This study examined a method of IBTR classification using chart review with pre-defined decision rules to assess histology and tumor location and compared survival between two groups classified as either TR or NP.Methods:Between 1989-1999, 6020 women with newly diagnosed invasive breast cancer, pT1-T2, 0-3 positive nodes, M0, treated with breast conserving surgery with clear margins were referred to the BC Cancer Agency. Of these, 289 cases had pathologically-confirmed IBTR, defined as the first recurrence occurring in the ipsilateral breast. Retrospective chart review was performed to abstract clinical data related to the index tumor and the IBTR. A set of decision rules established a priori (figure 1) was applied to classify these cases as either TR or NP.Time to recurrence, distant-relapse free survival (DRFS), and overall survival (OS) were compared between the two cohorts using Kaplan-Meier and log-rank statistics.Results:Of 289 subjects, 131(45%) were classified as TR, 128 (44%) as NP, and 30 (10%) unclassified due to insufficient information. The distributions of age at diagnosis, age at recurrence, index tumor histology, T size, nodal status, grade, lymphovascular invasion, and estrogen receptor status were similar in the two cohorts, (all p >0.05). The mean time to recurrence was shorter in TR compared to NP patients (4.7 years vs. 6.3 years, p=0.001). Surgical treatment of IBTR differed in the two groups, with 76% mastectomy and 21% local excision only in the TR cohort, compared to 81% mastectomy and 16% local excision only in the NP cohort (p<0.001). Systemic therapy at the time of IBTR also differed in the two groups, with hormone therapy alone used more frequently in the TR compared to the NP cohort (42% vs. 38%, p<0.001); and a smaller proportion of the NP cohort receiving both chemotherapy and hormone therapy compared to the TR cohort (8% vs. 15%, p<0.001). In the TR and NP cohorts, 10-year DRFS were 57% vs. 61%, p=0.59; and 10-year OS were 45% vs. 53%, p=0.67.Conclusions:The median time to recurrence is significantly longer in patients with IBTR classified as 'new primary' compared to 'true recurrence'. Non-statistically significant trends for more favorable DRFS and OS were observed for patients with NP compared to TR tumors. The hypothesis that NP and TR tumors are distinct entities with different survival prognoses requires confirmation with pathology review and molecular analyses.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4116.

Phase III randomized anastrozole exercise (RAE) trial: First planned interim analysis

e20674

Background: Adjuvant anastrozole (aA) is associated with arthralgias/myalgias (A/M), bone density loss, and hot flushes. Analgesics offer limited relief of musculoskeletal (MSK) symptoms and are associated with side effects of their own. The benefit of exercise on bone health, muscle strength, hot flushes, and quality of life (QOL) has been demonstrated; the objective of this trial is to determine if an exercise program improves anastrozole related A/M. Methods: This is a phase III, randomized trial of standard of care (observation) vs 48 weeks (wks) of exercise for women with BC on aA. Subjects in the control group receive literature about AIs (information on bone health, management of SEs of AIs). Subjects in the intervention group participate in a semi-supervised, individualized, and graduated 3x/wk exercise program (aerobic, resistance training, stretching) for 24 wks. From wks 25–48 independent exercise is recommended 3x/wk. The 10 endpoint is change in MSK symptoms as measured by 12 wk SF-36v2 bodily pain scores, NCI CTG toxicity, and visual analogue scale. 20 endpoints are QOL, hot flushes, bone density, and body mass. Physical activity and compliance with aA was monitored in both arms. The 1st interim analysis was planned after 10 patients were enrolled to evaluate accrual, compliance, and rate of discontinuation. Results: Accrual commenced December, 2007. Fourteen of a planned 72 patients have been enrolled (baseline data available for 13); 7 pts in the control arm (A) and 6 in the exercise arm (B). Median age was 59 (A) and 58 (B). Nine pts had baseline and 12 wk data available [5 (A), 4 (B)]. There were no withdrawals and compliance with scheduled exercise was 100%. Of the NCI CTG A/M deemed probably/definitely related to aA, there is no change in the number reported at baseline vs wk 12 in Arm A. In Arm B, 2 of 4 pts report a decrease in the number of A/M at wk 12. Mean norm-based wk 12 SF-36v2 bodily pain domain scores worsened by 4.1 in Arm A; an improvement of 1.9 in mean scores was observed in Arm B. Conclusions: Interim results show that a structured exercise program is well tolerated and compliance is high among women with aA related MSK symptoms. Early results point to a positive impact of exercise on MSK symptoms in women with early BC. Updated data will be presented.

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