Effect of SARS and COVID-19 outbreaks on urology practice and training.

INTRODUCTION: The objective was to investigate the changes in urology practice during coronavirus disease 2019 (COVID-19) pandemic with a perspective from our experience with severe acute respiratory syndrome (SARS) in 2003. METHODS: Institutional data from all urology centres in the Hong Kong public sector during the COVID-19 pandemic (1 Feb 2020-31 Mar 2020) and a non-COVID-19 control period (1 Feb 2019-31 Mar 2019) were acquired. An online anonymous questionnaire was used to gauge the impact of COVID-19 on resident training. The clinical output of tertiary centres was compared with data from the SARS period. RESULTS: The numbers of operating sessions, clinic attendance, cystoscopy sessions, prostate biopsy, and shockwave lithotripsy sessions were reduced by 40.5%, 28.5%, 49.6%, 44.8%, and 38.5%, respectively, across all the centres reviewed. The mean numbers of operating sessions before and during the COVID-19 pandemic were 85.1±30.3 and 50.6±25.7, respectively (P=0.005). All centres gave priority to cancer-related surgeries. Benign prostatic hyperplasia-related surgery (39.1%) and ureteric stone surgery (25.5%) were the most commonly delayed surgeries. The degree of reduction in urology services was less than that during SARS (47.2%, 55.3%, and 70.5% for operating sessions, cystoscopy, and biopsy, respectively). The mean numbers of operations performed by residents before and during the COVID-19 pandemic were 75.4±48.0 and 34.9±17.2, respectively (P=0.002). CONCLUSION: A comprehensive review of urology practice during the COVID-19 pandemic revealed changes in every aspect of practice.

The accuracy of dose calculations by anisotropic analytical algorithms for stereotactic radiotherapy in nasopharyngeal carcinoma.

Nasopharyngeal tumors are commonly treated with intensity-modulated radiotherapy techniques. For photon dose calculations, problems related to loss of lateral electronic equilibrium exist when small fields are used. The anisotropic analytical algorithm (AAA) implemented in Varian Eclipse was developed to replace the pencil beam convolution (PBC) algorithm for more accurate dose prediction in an inhomogeneous medium. The purpose of this study was to investigate the accuracy of the AAA for predicting interface doses for intensity-modulated stereotactic radiotherapy boost of nasopharyngeal tumors. The central axis depth dose data and dose profiles of phantoms with rectangular air cavities for small fields were measured using a 6 MV beam. In addition, the air-tissue interface doses from six different intensity-modulated stereotactic radiotherapy plans were measured in an anthropomorphic phantom. The nasopharyngeal region of the phantom was especially modified to simulate the air cavities of a typical patient. The measured data were compared to the data calculated by both the AAA and the PBC algorithm. When using single small fields in rectangular air cavity phantoms, both AAA and PBC overestimated the central axis dose at and beyond the first few millimeters of the air-water interface. Although the AAA performs better than the PBC algorithm, its calculated interface dose could still be more than three times that of the measured dose when a 2 × 2 cm(2) field was used. Testing of the algorithms using the anthropomorphic phantom showed that the maximum overestimation by the PBC algorithm was 20.7%, while that by the AAA was 8.3%. When multiple fields were used in a patient geometry, the dose prediction errors of the AAA would be substantially reduced compared with those from a single field. However, overestimation of more than 3% could still be found at some points at the air-tissue interface.

Salvage treatment for persistent and recurrent T1-2 nasopharyngeal carcinoma by stereotactic radiosurgery.

OBJECTIVE: To study the efficacy of stereotactic radiosurgery in salvaging early-stage persistent and recurrent nasopharyngeal carcinoma (NPC) after primary radiotherapy. METHODS: A prospective single-arm study evaluating the response and outcome of patients with rT1-2 NPC treated by stereotactic radiosurgery. Eleven patients with rT1-2 were treated by radiosurgery between March 1998 and March 2000. Four patients were treated for persistent disease occurring within 4 months after primary radiotherapy, six were treated for first recurrence, and one for third recurrence. Six patients had rT1 disease and five had rT2 disease. Most patients had disease not amenable to brachytherapy, surgery, or external re-irradiation. The median target volume was 5.8 cc (range, 3.3-16.9). Radiosurgery was performed with multiple noncoplanar arcs of photon, with a median dose of 12.5 Gy delivered to the 80% isodose line (range, 12-14 Gy). Median follow-up time after radiosurgery was 18 months (range, 9-30). RESULTS: Nine patients had complete regression of tumor as assessed by imaging, nasopharyngoscopy, and biopsy; one patient had partial regression of tumor; whereas one patient had static disease. The overall response rate was 91% (10 of 11) and the complete response rate was 82% (9 of 11). Two patients with complete response subsequently had local relapse develop, with one recurrence outside the treated volume 8 months after radiosurgery, and the other within the treated volume 6 months after radiosurgery. One patient with a partial response had neck node recurrence develop. Temporal lobe necrosis occurred in one patient but probably represents sequelae of primary radiation after reviewing the dosimetry. Ten patients are still alive, whereas one patient with local relapse had distant metastases develop and died. The estimated 1-year local control rate after radiosurgery was 82%. CONCLUSIONS: Our preliminary results indicate that stereotactic radiosurgery is an effective treatment modality for persistent and recurrent T1-T2 NPC, and early control rate seems to be comparable to other salvage treatments. More clinical experiences and longer follow-up are still needed to validate our results and to address fully the role of radiosurgery in salvaging local failures of NPC.

Stereotactic radiosurgery as a salvage treatment for locally persistent and recurrent nasopharyngeal carcinoma.

BACKGROUND: The purpose of this work was to study the efficacy of stereotactic radiosurgery as a salvage treatment in patients with locally persistent and recurrent nasopharyngeal carcinoma (NPC). METHODS: Between March 1996 and August 1997, 10 patients with locally persistent or recurrent NPC were treated by linac-based stereotactic radiosurgery. Four patients had radiosurgery for persistent disease after a first course of radiotherapy, 3 had radiosurgery as a boost after reirradiation for local recurrence, and 3 had radiosurgery for disease that recurred after reirradiation. The tumor volume ranged from 1.3 to 23.7 cc (median: 5.2). Treatment was prescribed at 80% isodose line and ranged from 12 to 18 Gy (median: 13.4), with a mean tumor surface dose ranged from 10-21 Gy (median: 14). The median clinical follow-up was 10.5 months (range 8-27), and the median imaging follow-up was 9.5 months (range 6-26). RESULTS: One patient had complete regression of tumor after radiosurgery, five had reduction in tumor size, three had no change, and one had progression of tumor. The overall response rate to radiosurgery was 60% (6/10), with 10% (1/10) developing in-field progression. Excluding patients receiving radiosurgery as a boost treatment after reirradiation, the response rate was 57% (4/7) and none developed in-field progression. Only one patient developed a new cranial neuropathy in the absence of disease progression. CONCLUSION: In selected patients with locally persistent or recurrent NPC, stereotactic radiosurgery can be considered as a salvage treatment with good short-term local control. The complications appear to be minimal except for treating recurrence in the cavernous sinus. Early results are encouraging although more experience and longer follow-up are still needed to better define the role of radiosurgery in the management of persistent and recurrent NPC.

A new tool for dose conformity evaluation of radiosurgery treatment plans.

PURPOSE: A novel method for dose conformity evaluation of treatment plans produced by the stereotactic radiosurgery treatment planning system is postulated. METHODS AND MATERIALS: By consolidating the information contained in the integral dose-volume histogram and the treatment volume ratio, a plot of treatment volume ratio versus percentage dose may be considered as a useful tool for plan evaluation. To validate the suggested argument, two simple experiments simulating the conformal and nonconformal cases were conducted on the geometric phantom that is commercially available from Radionics. An actual patient treatment plan is also included to explore the effectiveness of the proposed parameters. It is an attempt to establish the baseline of a conformal plan. RESULTS: A plot showed the ability to give the user an idea whether the size of the collimator was adequate to cover the delineated lesion when the user-defined criteria had been in place. Two parameters, namely take-off dose (TOD) and take-off volume (TOV) were defined. The former was defined as the maximum dose level found on the surface of the target volume. The TOD is also the maximum possible dose to be received by the adjacent normal tissue. The latter was defined as the percentage of the target volume that received the TOD. Another parameter, irradiated percentage volume (IPV), was defined here as the percentage of the target volume receiving at least the prescribed dose. When the prescribed dose is also the TOD, the IPV becomes the TOV. They were proved to be effective in evaluating the dose conformity. Another term known as equivalent fall-off distance (EFOD) was defined as the equivalent radial distance calculated between two isodose lines. In fact, the dose fall-off rate can also act as a measuring index for plan comparison, because a fast dose fall-off rate is often a requirement for radiosurgery in order to minimize the risk of radiation damage to the surrounding structures. The two phantom studies showed consistent results with the theoretical predictions. The ability of the plot was further explored in the patient treatment plan studies. It was demonstrated that the plot had a remarkable ability to check whether the hot spot is in the vicinity of the lesion. A baseline of a conformal plan was also established; for example, a plan is said to be conformal if its IPV has attained a value of not less than 95% and its associated TVR is not greater than 2. CONCLUSION: The proposed method has demonstrated the effectiveness in dose conformity evaluation. It supplements the integral dose-volume histogram to provide a complete information of a treatment plan in terms of dose uniformity and conformity.

Pantothenic acid deficiency as the pathogenesis of acne vulgaris.

For years, the pathogenesis of acne vulgaris has been known to be strongly influenced by hormonal factors. However, the exact role of and the interrelationship among the various hormones in question have not been well elucidated. Here, I wish to suggest a radically different theory for its pathogenesis and relate its basic pathology to a deficiency in pantothenic acid, a vitamin hitherto not known to cause any deficiency syndrome in humans. Hence, the effect of hormonal factors in this disease entity becomes secondary to that of the availability of pantothenic acid. A complete cure of this condition is effected by a very liberal replacement therapy with the vitamin.

Pantothenic acid as a weight-reducing agent: fasting without hunger, weakness and ketosis.

With the conventional method of fasting or aggressive dieting to reduce excess body fat, hunger, weakness, ketogenesis and ketosis are the sequential events that follow. It is not fully understood why, under conditions of negative calorie balance where complete energy release from storage fat is critical, ketosis should arise with a concomitant wastage of energy. Here, I wish to propose a theory that relates the formation of ketone bodies under such conditions to a deficiency in dietary pantothenic acid. Supplementation of this vitamin would facilitate complete catabolism of fatty acids and thus the formation of ketone bodies could be circumvented. As a result, a sufficient amount of energy would be released from storage fat to relieve dieters of the sensation of hunger and weakness which otherwise would be difficult to endure. Hence, using this method for weight reduction together with a careful observation of calorie intake, I have great success in treating overweight-to-obese patients to lose weight.