Simultaneous irradiation of the breast and regional lymph nodes in prone position using helical tomotherapy.

OBJECTIVE: We investigated dosimetric advantages of using helical tomotherapy to simultaneously irradiate the breast and regional lymph nodes for patients positioned prone, and compared tomotherapy plan qualities for the prone position with those previously published for the supine position. METHODS: Tomotherapy plans for 11 patients (5 left breast, 6 right) simulated with the involved breast suspended downward were generated. Each target (ipsilateral breast and supraclavicular, axillary and internal mammary chain nodes) was to receive 45 Gy. RESULTS: For targets, V(40.5)≥99.9% and V(42.8)≥99.5% for all patients, where V(40.5) and V(42.8) denote the relative target volume receiving at least 40.5 and 42.8 Gy, respectively. The targets' maximum dose was, on average, approximately 49.5 Gy. The mean doses to the contralateral lung and heart were lower for right-breast cases (2.8 Gy lung, 2.7 Gy heart) than for left-breast cases (3.8 Gy lung, 8.7 Gy heart). Mean organ doses to the ipsilateral lung (9.3 Gy) and contralateral breast (2.3 Gy) from the prone breast tomotherapy plans were similar to those reported for conventional radiotherapy techniques. For the left breast with regional nodes, tomotherapy plans for prone-positioned patients yielded lower mean doses to the contralateral breast and heart than previously reported data for tomotherapy plans for supine-positioned patients. CONCLUSION: Helical tomotherapy with prone breast positioning can simultaneously cover the breast and regional nodes with acceptable uniformity and can provide reduced mean dose to proximal organs at risk compared with tomotherapy with supine position. The similarity of plan quality to existing data for conventional breast radiotherapy indicates that this planning approach is appropriate, and that the risk of secondary tumour formation should not be significantly greater.

Arbitrary-order Hilbert spectral analysis for time series possessing scaling statistics: comparison study with detrended fluctuation analysis and wavelet leaders.

In this paper we present an extended version of Hilbert-Huang transform, namely arbitrary-order Hilbert spectral analysis, to characterize the scale-invariant properties of a time series directly in an amplitude-frequency space. We first show numerically that due to a nonlinear distortion, traditional methods require high-order harmonic components to represent nonlinear processes, except for the Hilbert-based method. This will lead to an artificial energy flux from the low-frequency (large scale) to the high-frequency (small scale) part. Thus the power law, if it exists, is contaminated. We then compare the Hilbert method with structure functions (SF), detrended fluctuation analysis (DFA), and wavelet leader (WL) by analyzing fractional Brownian motion and synthesized multifractal time series. For the former simulation, we find that all methods provide comparable results. For the latter simulation, we perform simulations with an intermittent parameter µ=0.15. We find that the SF underestimates scaling exponent when q>3. The Hilbert method provides a slight underestimation when q>5. However, both DFA and WL overestimate the scaling exponents when q>5. It seems that Hilbert and DFA methods provide better singularity spectra than SF and WL. We finally apply all methods to a passive scalar (temperature) data obtained from a jet experiment with a Taylor's microscale Reynolds number Re(λ)≃250. Due to the presence of strong ramp-cliff structures, the SF fails to detect the power law behavior. For the traditional method, the ramp-cliff structure causes a serious artificial energy flux from the low-frequency (large scale) to the high-frequency (small scale) part. Thus DFA and WL underestimate the scaling exponents. However, the Hilbert method provides scaling exponents ξ(θ)(q) quite close to the one for longitudinal velocity, indicating a less intermittent passive scalar field than what was believed before.

Neoadjuvant tamoxifen for operable breast cancer: a need for phase III studies?

We conducted a case-control study to analyze the effect of neoadjuvant tamoxifen on steroid receptors and histologic grade and to evaluate the feasibility of phase III studies in operable breast cancer. Between 1987 and 1990, 107 patients without clinical metastases who had had no chemotherapy preoperatively, were treated preoperatively with 20 mg/day of tamoxifen for 3 weeks. Of them, 92 were matched with controls for age at diagnosis, year of diagnosis, presence or absence of lymph node involvement, and preoperative radiotherapy. The percentage of ER1 tumors (P = .03) and the mean and median ER levels (P<.001 for both) were lower in the tamoxifen group than in the control group. In six patients analyzed longitudinally, the mean ER decreased from 52 to 19 fmol/mg protein. The difference in relapse-free survival between the two groups was not significant (mean follow-up 87 months). This study suggests a decrease in ER content in patients treated with neoadjuvant tamoxifen. This change may thus be taken into account when ER determination is performed after tamoxifen therapy is started. Further randomized trials should determine whether patients with operable breast cancer benefit from neoadjuvant tamoxifen treatment.