Comparison of intratracheal pulmonary ventilation and hybrid intratracheal pulmonary ventilation with conventional mechanical ventilation in a rabbit model of acute respiratory distress syndrome by saline lavage

OBJECTIVES

To study changes in PaCO2 and PaO2 during intratracheal pulmonary ventilation (ITPV) and hybrid intratracheal pulmonary ventilation (h-ITPV) compared with conventional mechanical ventilation (CMV) in a rabbit model of respiratory failure, and to define the technique of h-ITPV that combines conventional mechanical ventilation and ITPV.

DESIGN

Prospective, interventional study.

SUBJECTS

Twelve adult New Zealand White rabbits.

INTERVENTIONS

Surfactant deficiency was induced by saline lavage, and rabbits were randomized to either ITPV or h-ITPV. The study consisted of four phases: phase 0, CMV after saline lavage, ventilator rate 30 breaths/min; phase I, ITPV or h-ITPV initiated at the same pressure and rate as in phase 0; phase II, ITPV or 1.0 L/min h-ITPV bias flow, with peak inspiratory pressure (PIP) decreased and ventilator rate increased to achieve the lowest tidal volume while maintaining adequate gas exchange; and phase III, animals returned to CMV.

MEASUREMENTS AND MAIN RESULTS

In phase I, no difference in PaCO2 was observed between ITPV, h-ITPV, or CMV. There was a decrease in PaO2 when switching from CMV to ITPV but not to h-ITPV. In phase II, it was possible to decrease PIP (average of 37% for ITPV and 36% for h-ITPV) and tidal volume (average of 64% for ITPV and 53% for h-ITPV) without compromising gas exchange (p < .05). Oxygenation tended to improve from phase 0 to the end of phase II. In phase III, PaCO2 increased (average of 71% for ITPV and 79% for h-ITPV) and pH decreased (p < .05). Normocapnia was achieved using significantly higher PIP and tidal volume, compared with phase 0 (p < .05).

CONCLUSIONS

ITPV and h-ITPV can effectively ventilate and oxygenate rabbits with surfactant-deficient lungs at tidal volumes and therefore pressures lower than required with CMV. Maximum benefit appears to occur at high ventilator rates. These findings suggest that both modes of ventilation may represent powerful new tools in the management of patients with acute respiratory failure. (Crit Care Med 2000; 28:774-781)

Preliminary report of toxicity following 3D radiation therapy for prostate cancer on 3DOG/RTOG 9406

PURPOSE

A prospective Phase I dose escalation study was conducted to determine the maximally-tolerated radiation dose in men treated with three-dimensional conformal radiation therapy (3D CRT) for localized prostate cancer. This is a preliminary report of toxicity encountered on the 3DOG/RTOG 9406 study.

METHODS AND MATERIALS

Each participating institution was required to implement data exchange with the RTOG 3D quality assurance (QA) center at Washington University in St. Louis. 3D CRT capabilities were strictly defined within the study protocol. Patients were registered according to three stratification groups: Group 1 patients had clinically organ-confined disease (T1,2) with a calculated risk of seminal vesicle invasion of < 15%. Group 2 patients had clinical T1,2 disease with risk of SV invasion > or = 15%. Group 3 (G3) patients had clinical local extension of tumor beyond the prostate capsule (T3). All patients were treated with 3D techniques with minimum doses prescribed to the planning target volume (PTV). The PTV margins were 5-10 mm around the prostate for patients in Group 1 and 5-10 mm around the prostate and SV for Group 2. After 55.8 Gy, the PTV was reduced in Group 2 patients to 5-10 mm around the prostate only. Minimum prescription dose began at 68.4 Gy (level I) and was escalated to 73.8 Gy (level II) and subsequently to 79.2 Gy (level III). This report describes the acute and late toxicity encountered in Group 1 and 2 patients treated to the first two study dose levels. Data from RTOG 7506 and 7706 allowed calculation of the expected probability of observing a > or = grade 3 late effect more than 120 days after the start of treatment. RTOG toxicity scores were used.

RESULTS

Between August 23, 1994 and July 2, 1997, 304 Group 1 and 2 cases were registered; 288 cases were analyzable for toxicity. Acute toxicity was low, with 53-54% of Group 1 patients having either no or grade 1 toxicity at dose levels I and II, respectively. Sixty-two percent of Group 2 patients had either none or grade 1 toxicity at either dose level. Few patients (0-3%) experienced a grade 3 acute bowel or bladder toxicity, and there were no grade 4 or 5 toxicities. Late toxicity was very low in all patient groups. The majority (81-85%) had either no or mild grade 1 late toxicity at dose level I and II, respectively. A single late grade 3 bladder toxicity in a Group 2 patient treated to dose level II was recorded. There were no grade 4 or 5 late effects in any patient. Compared to historical RTOG controls (studies 7506, 7706) at dose level I, no grade 3 or greater late effects were observed in Group 1 and Group 2 patients when 9.1 and 4.8 events were expected (p = 0.003 and p = 0.028), respectively. At dose level II, there were no grade 3 or greater toxicities in Group 1 patients and a single grade 3 toxicity in a Group 2 patient when 12.1 and 13.0 were expected (p = 0.0005 and p = 0.0003), respectively. Multivariate analysis demonstrated that the relative risk of developing acute bladder toxicity was 2.13 if the percentage of the bladder receiving > or = 65 Gy was more than 30% (p = 0.013) and 2.01 if patients received neoadjuvant hormonal therapy (p = 0.018). The relative risk of developing late bladder complications also increased as the percentage of the bladder receiving > or = 65 Gy increased (p = 0.026). Unexpectedly, there was a lower risk of late bladder complications as the mean dose to the bladder and prescription dose level increased. This probably reflects improvement in conformal techniques as the study matured. There was a 2.1 relative risk of developing a late bowel complication if the total rectal volume on the planning CT scan exceeded 100 cc (p = 0.019).

CONCLUSION

Tolerance to high-dose 3D CRT has been better than expected in this dose escalation trial for Stage T1,2 prostate cancer compared to low-dose RTOG historical experience. With strict quality assurance standards and review, 3D CRT can be safely studied in a co

Biologic variables in the outcome of stages I and II neuroblastoma treated with surgery as primary therapy: a children's cancer group study

PURPOSE

To determine prospectively whether surgery alone is sufficient therapy for Evans stages I and II neuroblastoma and to define biologic and clinical features having prognostic potential for this group.

PATIENTS AND METHODS

Between June 1989 and August 1995, 374 eligible children (age range, 0 to 18 years) with newly diagnosed stage I (n = 141) and stage II (n = 233) neuroblastoma were registered onto Children's Cancer Group trial 3881. Surgical resection was the only primary therapy except in cases with spinal cord compression, where radiation therapy was allowed. Event-free survival (EFS) and overall survival (OS) were analyzed by life-table methods according to clinical and biologic features.

RESULTS

EFS and OS (mean +/- SE) for all stage I patients were 93% +/- 3.0% and 99% +/- 1.0%, respectively, compared with 81% +/- 4.0% and 98% +/- 2. 0%, respectively, for stage II patients. The significantly higher recurrence rate among stage II patients was managed successfully in 38 of 43 children with either surgery or multimodality treatment. There was one death among stage I patients and six among stage II. For stage II patients tumor MYCN gene amplication, unfavorable histopathology, an age greater than 2 years, and positive lymph nodes predicted a lower OS (P <.05).

CONCLUSION

Children with stages I and II neuroblastoma have 98% survival with surgery alone as primary therapy. Supplemental treatment was necessary in only 10% of stage I patients and 20% of stage II patients. In children with localized neuroblastoma, a subset of patients that are at higher risk for death can be defined as those with stage II disease who have tumor MYCN amplification or who are >/= 2 years of age with either unfavorable histopathology or positive lymph nodes.

Two-point vibrotactile discrimination related to parameters of pulse burst stimulus

Tactile spatial resolution is an important factor in the design of vibrotactile arrays. The two-point discrimination distance is used as a measure of tactile spatial resolution. An experimental study is presented showing the effect of pulse burst stimulus parameters, pulse repetition period and duty cycle on two-point vibrotactile spatial discrimination. An array of piezoceramic vibrators is used to measure two-point spatial discrimination on the index finger. In a group of 14 subjects, the average two-point discrimination distance for a pulse repetition period of 1/25s is 2.1 mm (SD = 1.0), whereas for 1/500 s it is 5.1 mm (SD = 0.9). Differences in discrimination distances are statistically significant according to the ANOVA analysis (p < 0.001). Results show that the two-point discrimination distance is better for longer pulse repetition periods. Therefore the pulse repetition period in an excitatory waveform composed of bursts of pulses is important for tactile resolution. No statistically significant differences in discrimination distances are found between bursts of pulses of 50% duty cycle and those of lower duty cycle. The latter result indicates that, by choosing low-duty cycle waveforms for vibrotactile stimulation, the power can be reduced with no loss in two-point discrimination capacity.

Stage I (T1 N0 M0) squamous cell carcinoma of the laryngeal glottis: therapeutic results and voice preservation

BACKGROUND

The therapeutic outcomes for voice preservation in Stage I (T1 N0 M0) glottic carcinoma, treated with conservation surgery, radiation therapy, and endoscopic resection, are controversial.

METHODS

A retrospective tumor registry retrieval of data on patients treated with curative intent at Washington University Medical Center-Barnes Hospital between January 1971 and December 1990 for the surgical group, January 1971 to December 1985 for the low-dose radiation group, and January 1986 to January 1995 for the high-dose radiation group, was performed.

RESULTS

The 659 patients with Stage I (T1 N0 M0) glottic carcinoma treated with curative intent were subdivided into four groups: (1) 90 patients received low-dose radiation (mean dose 58 Gy, range 55-65 Gy, daily fractionation 1.5-1.8 Gy); (2) 104 patients received high-dose radiation (mean dose 66.5 Gy, range 65-70 Gy, daily fractionation 2-2.25 Gy); (3) 404 patients underwent conservation surgery; and (4) 61 patients had endoscopic resection. T1A (85%) and T1B (15%) disease was equally distributed among the groups. The anterior commissure was involved in 38 patients in the radiation therapy groups and 56 patients in the surgical groups. The overall local control was 89%. The overall local salvage was 84%. The overall unaided laryngeal voice preservation was 90%. The overall 5-year disease specific and actuarial survival rates were 95% and 81%, respectively. Prevalence of 2% regional metastases, 1.2% distant metastases, and 14% second primary malignancies were documented. The cure rate was 69% for regional metastases, 13% for distant metastases, and 44% for second primary malignancies. There were 5 complication deaths (0.1%), and 38 (6%) patients died of intercurrent disease. The use and dose of tobacco products was significantly increased in patients who died of intercurrent disease (p = 0.004) or developed second primary malignancies (p = 0.024). No significant difference was observed among the four therapeutic groups in the 5-year cause-specific survival rate (p, 0.68). Actuarial survival was significantly decreased in the low-dose radiation therapy group as compared with the other three therapeutic groups (p = 0.04). Initial local control was poorer for the endoscopic (77%) and low-dose radiation (78%) groups as compared with the high-dose radiation (89%) and conservation surgery (92%) groups (p = 0.02) but significant differences were not found for ultimate local control following salvage treatment. Unaided laryngeal voice preservation was similar for high-dose radiation (89%), conservation surgery (93%) and endoscopic resection (90%), but significantly poorer for low-dose radiation (80%; p = 0.02). T1B disease (N = 94) had similar local control and voice preservation with conservation surgery (87%) and high-dose radiation (88%) but lower results with low-dose radiation and endoscopic resections (67% unaided laryngeal voice preservation; p = 0.02).

CONCLUSION

(1)The four therapeutic groups achieved similar rates of disease specific survival and ultimate local control. (2) Low-dose radiation was associated with significantly lower overall actuarial survival and unaided laryngeal voice preservation. (3) Endoscopic resection was associated with a significantly lower initial local control rate, but following salvage therapy achieved equivalent results to the other treatment methods. (4) Patients with (T1 N0 M0) glottic carcinoma had similar survival, local control, and unaided laryngeal voice preservation rates with high-dose radiation, conservation surgery, and endoscopic resections, but not with low-dose radiation therapy. (c) 1999 John Wiley & Sons, Inc. Head Neck 21: 707-717, 1999.

Stage I (T1 N0 M0) squamous cell carcinoma of the laryngeal glottis: therapeutic results and voice preservation

BACKGROUND

The therapeutic outcomes for voice preservation in Stage I (T1 N0 M0) glottic carcinoma, treated with conservation surgery, radiation therapy, and endoscopic resection, are controversial.

METHODS

A retrospective tumor registry retrieval of data on patients treated with curative intent at Washington University Medical Center-Barnes Hospital between January 1971 and December 1990 for the surgical group, January 1971 to December 1985 for the low-dose radiation group, and January 1986 to January 1995 for the high-dose radiation group, was performed.

RESULTS

The 659 patients with Stage I (T1 N0 M0) glottic carcinoma treated with curative intent were subdivided into four groups: (1) 90 patients received low-dose radiation (mean dose 58 Gy, range 55-65 Gy, daily fractionation 1.5-1.8 Gy); (2) 104 patients received high-dose radiation (mean dose 66.5 Gy, range 65-70 Gy, daily fractionation 2-2.25 Gy); (3) 404 patients underwent conservation surgery; and (4) 61 patients had endoscopic resection. T1A (85%) and T1B (15%) disease was equally distributed among the groups. The anterior commissure was involved in 38 patients in the radiation therapy groups and 56 patients in the surgical groups. The overall local control was 89%. The overall local salvage was 84%. The overall unaided laryngeal voice preservation was 90%. The overall 5-year disease specific and actuarial survival rates were 95% and 81%, respectively. Prevalence of 2% regional metastases, 1.2% distant metastases, and 14% second primary malignancies were documented. The cure rate was 69% for regional metastases, 13% for distant metastases, and 44% for second primary malignancies. There were 5 complication deaths (0.1%), and 38 (6%) patients died of intercurrent disease. The use and dose of tobacco products was significantly increased in patients who died of intercurrent disease (p = 0.004) or developed second primary malignancies (p = 0.024). No significant difference was observed among the four therapeutic groups in the 5-year cause-specific survival rate (p, 0.68). Actuarial survival was significantly decreased in the low-dose radiation therapy group as compared with the other three therapeutic groups (p = 0.04). Initial local control was poorer for the endoscopic (77%) and low-dose radiation (78%) groups as compared with the high-dose radiation (89%) and conservation surgery (92%) groups (p = 0.02) but significant differences were not found for ultimate local control following salvage treatment. Unaided laryngeal voice preservation was similar for high-dose radiation (89%), conservation surgery (93%) and endoscopic resection (90%), but significantly poorer for low-dose radiation (80%; p = 0.02). T1B disease (N = 94) had similar local control and voice preservation with conservation surgery (87%) and high-dose radiation (88%) but lower results with low-dose radiation and endoscopic resections (67% unaided laryngeal voice preservation; p = 0.02).

CONCLUSION

(1)The four therapeutic groups achieved similar rates of disease specific survival and ultimate local control. (2) Low-dose radiation was associated with significantly lower overall actuarial survival and unaided laryngeal voice preservation. (3) Endoscopic resection was associated with a significantly lower initial local control rate, but following salvage therapy achieved equivalent results to the other treatment methods. (4) Patients with (T1 N0 M0) glottic carcinoma had similar survival, local control, and unaided laryngeal voice preservation rates with high-dose radiation, conservation surgery, and endoscopic resections, but not with low-dose radiation therapy. (c) 1999 John Wiley & Sons, Inc. Head Neck 21: 707-717, 1999.

Lack of effect of tumor size on the prognosis of carcinoma of the uterine cervix Stage IB and IIA treated with preoperative irradiation and surgery

PURPOSE

The purpose of this analysis was to evaluate the prognostic significance of cervical tumor size in patients with Stages Ib and IIa carcinoma of the cervix treated with preoperative irradiation and radical or conservative hysterectomy.

METHODS AND MATERIALS

This study is a retrospective analysis of 177 patients. One hundred forty-one patients had Stage Ib and 36 patients had Stage IIa carcinoma of the cervix. All patients were treated with preoperative irradiation and surgery. Radiation therapy consisted of external pelvic irradiation and intracavitary brachytherapy; total doses ranged from 30 to 60 Gy to the pelvic sidewall and 60 to 70 Gy to point A. Surgery consisting of radical hysterectomy and lymph node dissection or a conservative hysterectomy and lymph node dissection was performed 4 to 6 weeks after completion of irradiation.

RESULTS

The 5-year progression-free survivals were 80% for Stage Ib and 63% for Stage IIa (p = 0.03). The 5-year cumulative pelvic failure rates for Stage Ib were 16% for tumors <3 cm and 9% for tumors >3 cm (p = 0.90). The 5-year cumulative pelvic failure rates for Stage IIa were 22% for tumors <3 cm and 22% for tumors >3 cm (p = 0.75). The corresponding cumulative distant metastasis failure rates at 5 years for Stage Ib were 21% for tumors <3 cm and 21% for tumors >3 cm (p = 0.60). For patients with Stage IIa disease, the 5-year cumulative distant metastasis rates were 33% for tumors <3 cm and 36% for tumors >3 cm (p = 0.70). A multivariate analysis was performed to evaluate prognostic factors for the endpoint of progression-free survival. The variables that were analyzed were patient age, tumor histology, tumor size, clinical stage, point A and pelvic lymph node irradiation dose, and cervical tumor status and pelvic lymph node status at the time of hysterectomy. The variables that were found to be of independent significance for progression-free survival by multivariate analysis were pelvic lymph node irradiation dose (p <0.001), pelvic lymph node status at the time of hysterectomy (p = 0.01), and clinical stage (p = 0.02). Cervical tumor size at the time of diagnosis and the presence of tumor cells in the cervix in the hysterectomy specimen was not an independent prognostic factor by multivariate analysis. The overall severe complication rate was 11% for all patients.

CONCLUSIONS

For this population of patients treated with preoperative irradiation and surgery, pelvic lymph node status at the time of hysterectomy and the preoperative irradiation dose to the pelvic lymph nodes are independent predictors of progression-free survival and the development of distant metastasis. The pretreatment cervical tumor size is of less importance for predicting progression-free survival and the development of distant metastasis but clinical stage is an important prognostic variable. These results are in contrast with those of surgery or irradiation alone, in which primary tumor size is a critical prognostic factor for all outcome parameters.

Effects of intraabdominally insufflated carbon dioxide and elevated intraabdominal pressure on postoperative gastrointestinal transit: an experimental study in mice

BACKGROUND/PURPOSE

Postoperative ileus after abdominal operations is thought to be related to the degree of surgical trauma, and it has been shown that the simple act of opening the peritoneum can decrease gastrointestinal motility. Accordingly, some investigators have shown a reduction in the duration of postoperative ileus after laparoscopic procedures. It is not clear, however, if this reduction is secondary to less manipulation of the viscera or to the lack of an abdominal incision. The aim of this study was to determine the effect of intraabdominal insufflation with CO2 on postoperative gastrointestinal transit.

METHODS

Twenty-eight male mice weighing between 25 and 30 g were divided randomly into 4 groups: Control (unoperated), Incision (conventional laparotomy), Cecal (laparotomy plus cecal manipulation), and Insufflation (abdominal insufflation with CO2). Postoperative gastrointestinal motility was assessed by weighing total fecal output over the first 15 postoperative hours.

RESULTS

Fecal pellet output over 15 hours in the untreated control group was 1.20 +/- 0.12 g. In mice subjected to peritoneal incision alone, fecal pellet output was significantly decreased to 0.82 +/- 0.11 g (P < .05). However, in mice subjected to abdominal insufflation with CO2, fecal pellet output was not significantly different from untreated controls (1.2 +/- 0.05 g; not significant). Fecal pellet output was markedly reduced by incision combined with cecal manipulation (0.24 +/- 0.02 g, P < .01).

CONCLUSIONS

The current study findings show that abdominal insufflation, in a procedure similar to that used during laparoscopic surgery, had no measurable effect on gastrointestinal transit in awake mice. This suggests that the lack of an abdominal incision can contribute to a reduced postoperative ileus after abdominal surgery.

Clinical dose-volume histogram analysis for pneumonitis after 3D treatment for non-small cell lung cancer (NSCLC)

PURPOSE

To identify a clinically relevant and available parameter upon which to identify non-small cell lung cancer (NSCLC) patients at risk for pneumonitis when treated with three-dimensional (3D) radiation therapy.

METHODS AND MATERIALS

Between January 1991 and October 1995, 99 patients were treated definitively for inoperable NSCLC. Patients were selected for good performance status (96%) and absence of weight loss (82%). All patients had full 3D treatment planning (including total lung dose-volume histograms [DVHs]) prior to treatment delivery. The total lung DVH parameters were compared with the incidence and grade of pneumonitis after treatment.

RESULTS

Univariate analysis revealed the percent of the total lung volume exceeding 20 Gy (V20), the effective volume (Veff) and the total lung volume mean dose, and location of the tumor primary (upper versus lower lobes) to be statistically significant relative to the development of > or = Grade 2 pneumonitis. Multivariate analysis revealed the V20 to be the single independent predictor of pneumonitis.

CONCLUSIONS

The V20 from the total lung DVH is a useful parameter easily obtained from most 3D treatment planning systems. The V20 may be useful in comparing competing treatment plans to evaluate the risk of pneumonitis for our individual patient treatment and may also be a useful parameter upon which to stratify patients or prospective dose escalation trials.

Comparison of intratracheal pulmonary ventilation with hybrid intratracheal pulmonary ventilation in a rabbit model of acute respiratory distress syndrome by saline lavage

We compared different hybrid mode ITPV (h-ITPV) flow rates, and h-ITPV with intratracheal pulmonary ventilation (ITPV) with respect to CO2 clearance and oxygenation. Surfactant deficiency was induced in six adult rabbits with saline lavage. The study consisted of three phases. Phase 0: Stabilization on conventional mechanical ventilation (CMV). Phase I: Bias flow initiated at same pressure and respiratory rate as Phase 0. Flow rates of 25%, 50%, 75% h-ITPV, and ITPV were initiated. Animals were transitioned from CMV to 25% h-ITPV proceeding sequentially to ITPV or vice versa. Phase II: Animals were returned to CMV. Statistical analysis included the two-way analysis of variance (ANOVA) and repeated measures ANOVA with Tuckey's test. No difference in PaCO2 was observed among all h-ITPV flow rates or between h-ITPV and ITPV. After bias flow was introduced (transition from Phase 0 to Phase I), PaCO2 decreased by 37%. PaCO2 increased by 119% during Phase II. Oxygenation improved in all animals, particularly in those transitioned to 25% h-ITPV and proceeding to ITPV. No difference in CO2 clearance between ITPV and h-ITPV was observed. Even at low bias flows, excellent CO2 clearance was achieved. Oxygenation was superior when animals were transitioned from CMV to h-ITPV. Hybrid-ITPV offers some advantages over ITPV and may represent a powerful tool in the management of acute respiratory distress syndrome (ARDS).

Gastric emptying after fundoplication is dependent on changes in gastric volume and compliance

BACKGROUND/PURPOSE

Nissen gastroesophageal fundoplication (GEF) increases gastric emptying (GE); however, the duration and the mechanisms for this improvement in GE remain unclear. The aim of this study was to evaluate the effects of a GEF on GE of a mixed meal, and to determine the correlation between GE and changes in intragastric pressure (IGP) and compliance.

METHODS

Using a radiolabeled mixed meal, GE was measured preoperatively 15 and 30 days after operation in 24 Sprague-Dawley rats divided into SHAM and GEF groups. Results were expressed as percent gastric retention at 90 minutes (GRg90), and time to evacuate 50% of the isotope meal (T1/2). Changes in IGP and compliance were determined at the same time-points using a different set of 20 rats.

RESULTS

Fifteen days after surgery, GR90 and T1/2 in the GEF group were reduced significantly when compared with preoperative values but returned to near preoperative values 30 days postoperation. In contrast, rats from the SHAM group showed no change in GR90 and T1/2 at 15 days and 30 days postoperation. Immediately after GEF, maximal distension of the stomach resulted in pressures 65% higher than those recorded before operation (20.2 v 11.7 mm Hg; P< .05), which persisted on the 15th postoperative day (17.7 v 10.7 mm Hg; P<.05). On the 30th postoperative day, however, there was no difference in the IGP between rats undergoing GEF compared with those undergoing a SHAM operation (11.7 v 12.0 mm Hg; P < .05). Similarly, mean gastric compliance decreased significantly immediately after and 15 days after GEF, but returned to preoperative levels 30 days after the operation.

CONCLUSIONS

In a rat model, GEF produces a transitory increase in GE, which is related to a simultaneous decrease in gastric volume and compliance. However, 30 days after GEF, associated with an elevated IGP, gastric volume increases and GE returns to preoperative levels.

Simultaneous superficial hyperthermia and external radiotherapy: report of thermal dosimetry and tolerance to treatment

BACKGROUND

In vitro and animal studies indicate that a moderate temperature of 41 degrees C maintained for approximately 1 h will provide radiosensitization if radiation (RT) and hyperthermia (HT) are delivered simultaneously, but not with sequential treatment. A minimum tumour temperature of 41 degrees C is a more feasible goal than the goal of >42 degrees C needed for sequential treatment.

METHODS AND MATERIALS

Forty-four patients with 47 recurrent superficial cancers received simultaneous external beam radiotherapy and superficial hyperthermia on successive IRB approved phase I/II studies. All lesions had failed previous therapy, 35 were previously irradiated (mean dose 52.7 Gy). Hyperthermia was delivered with 915 MHz microwave or 1-3.5 MHz ultrasound using commercially available applicators. The average dimensions of 19 lesions treated with microwave were 4.7 x 3.6 x 1.7 cm and the average dimensions of 28 lesions treated with ultrasound were 8.0 x 6.1 x 2.9 cm. The most common sites were chest wall (15 cases) and head and neck (21 cases). Temperatures were monitored at an average of six intratumoral locations using multisensor probes. The median number of hyperthermia treatments was three and the median radiation dose 30 Gy. Radiation dose per fraction was 4 Gy with hyperthermia and 2 Gy or 4 Gy (depending on protocol) on non-hyperthermia days.

RESULTS

Six different measures of minimum monitored temperature and duration were found to be highly correlated with each other. There was nearly a one-to-one correspondence between minimum tumour time at or above 41 degrees C (Min t41) and minimum tumour Sapareto Dewey equivalent time at 42 degrees C (Min teq42). After four sessions 63% of cases had a per session average Sapareto Dewey equivalent time at 41 degrees C which exceeded 60 min in all monitored tumour locations. The complete and partial response rate in evaluable lesions were respectively 21/41 (51%) and 7/41 (17%) and were best correlated with site (chest wall showing best response). Toxicity consisted of 10/47 (21%) slow healing soft tissue ulcers which healed in all cases but required a median of 7 months. The most important predictors for chronic ulceration were cumulative radiation dose >80 Gy and complete response to treatment.

CONCLUSIONS

Minimum tumour temperatures maintained for durations compatible in vitro with thermal radiosensitization (if RT and HT are delivered simultaneously) are clinically feasible and tolerable for broad but superficial lesions amenable to externally applied ultrasound or microwave hyperthermia. The current in-house protocol is evaluating the impact of more than four hyperthermia sessions on the overall thermal dose distribution and toxicity.

Radiation therapy morbidity in carcinoma of the uterine cervix: dosimetric and clinical correlation

PURPOSE

To quantitate the impact of total doses of irradiation, dose rate, and ratio of doses to bladder or rectum and point A on sequelae in patients treated with irradiation alone for cervical cancer.

METHODS AND MATERIALS

Records were reviewed of 1456 patients (Stages IB-IVA) treated with external-beam irradiation plus two low-dose rate intracavitary insertions to deliver 70 to 90 Gy to point A. Follow-up was obtained in 98% of patients (median, 11 years; minimum, 3 years; maximum, 30 years). The relationships among various dosimetry parameters and Grade 2 or 3 sequelae were analyzed.

RESULTS

In Stage IB, the frequency of patients developing Grade 2 morbidity was 9%, and Grade 3 morbidity, 5%; in Stages IIA, IIB, III, and IVA, Grade 2 morbidity was 10% to 12% and Grade 3 was 10%. The most frequent Grade 2 sequelae were cystitis and proctitis (0.7% to 3%). The most common Grade 3 sequelae were vesicovaginal fistula (0.6% to 2% in patients with Stage I-III tumors), rectovaginal fistula (0.8% to 3%), and intestinal obstruction (0.8% to 4%). In the bladder, doses below 80 Gy correlated with less than 3% incidence of morbidity and 5% with higher doses (p = 0.31). In the rectosigmoid, the incidence of significant morbidity was less than 4% with doses below 75 Gy and increased to 9% with higher doses. For the small intestine, the incidence of morbidity was less than 1% with 50 Gy or less, 2% with 50 to 60 Gy, and 5% with higher doses to the lateral pelvic wall (p = 0.04). When the ratio of dose to the bladder or rectum in relation to point A was 0.8 or less, the incidence of rectal morbidity was 2.5% (8 of 320) vs. 7.3% (80 of 1095) with higher ratios (p < or = 0.01); bladder morbidity was 2.3% (7 of 305) and 5.8% (64 of 1110), respectively (p = 0.02). The incidence of Grade 2 and 3 bladder morbidity was 2.9% (10 of 336) when the dose rate was less than 0.80 Gy/h, in contrast to 6.1% (62 of 1010) with higher dose rates (p = 0.07). Rectal morbidity was 2% to 5% in Stage IB, regardless of dose rate to the rectum; in Stages IIA-B and III, morbidity was 5.2% (28 of 539) with a dose rate of 0.80 Gy or less and 10.7% (37 of 347) with higher dose rates (p < 0.01). Multivariate analysis showed that dose to the rectal point was the only factor influencing rectosigmoid sequelae, and dose to the bladder point affected bladder morbidity.

CONCLUSIONS

Various dosimetric parameters correlate closely with the incidence of significant morbidity in patients treated with definitive irradiation for carcinoma of the uterine cervix. Careful dosimetry and special attention to related factors will reduce morbidity to the lowest possible level without compromising pelvic tumor control.

Overexpression of the Helix-Loop-Helix protein Id2 blocks T cell development at multiple stages

The Id proteins are inhibitors of basic-Helix-Loop-Helix transcription factor function that have been implicated in the control of cell differentiation and proliferation. To study the role of Id proteins in the control of T cell development, we generated transgenic mice that overexpress the Id2 protein in thymocytes. We detect a significant expansion of the early CD4(-)CD8(+)TCR(-) thymocyte stage and a depletion of the thymocytes of the subsequent developmental stages. These data indicate that the overexpression of Id2 leads to a stage-specific developmental block early in thymopoiesis. In addition, progeny mice from five of the six Id2 transgenic founder lines succumb to aggressive T cell hyperproliferation that resembles lymphoma. Thus, overexpression of the Id2 protein has profound effects on T cell development and oncogenesis, consistent with the hypothesis that the bHLH proteins play critical roles in these processes.

Radiation therapy for clinically localized prostate cancer: a multi-institutional pooled analysis

CONTEXT

Prostate-specific antigen (PSA) evaluation leads to the early detection of both prostate cancer and recurrences following primary treatment. Prostate-specific antigen outcome information on patients 5 or more years following treatment is limited and available mainly as single-institution reports.

OBJECTIVES

To assess the likelihood and durability of tumor control using PSA evaluation 5 or more years after radical external beam radiation therapy and to identify pretreatment prognostic factors in men with early prostate cancer treated since 1988, the PSA era.

DESIGN AND SETTING

Retrospective, nonrandomized, multi-institutional pooled analysis of patients treated with external beam radiation therapy alone between 1988 and 1995 at 6 US medical centers. Follow-up lasted up to a maximum of 9 years. Outcome data were analyzed using Cox regression and recursive partitioning techniques.

PATIENTS

A total of 1765 men with stage T1b, T1c, and T2 tumors treated between 1988 and 1995 with external beam radiation. The majority (58%) of patients were older than 70 years and 24.2% had initial PSA values of 20 ng/mL or higher. A minimum of 2 years of subsequent follow-up was required for participation.

MAIN OUTCOME MEASURE

Actuarial estimates of freedom from biochemical failure.

RESULTS

The 5-year estimates of overall survival, disease-specific survival, and the freedom from biochemical failure are 85.0% (95% confidence interval [CI], 82.5%-87.6%), 95.1% (95% CI, 94.0%-96.2%), and 65.8% (95% CI, 62.8%-68.0%), respectively. The PSA failure-free rates 5 and 7 years after treatment for patients presenting with a PSA of less than 10 ng/mL were 77.8% (95% CI, 74.5%-81.3%), and 72.9% (95% CI, 67.9%-78.2%). Recursive partitioning analysis of initial PSA level, palpation stage, and the Gleason score groupings yielded 4 separate prognostic groups: group 1, included patients with a PSA level of less than 9.2 ng/mL; group 2, PSA level of at least 9.2 but less than 19.7 ng/mL; group 3, PSA level at least 19.7 ng/mL and a Gleason score of 2 to 6; and group 4, PSA level of at least 19.7 ng/mL and a Gleason score of 7 to 10. The estimated rates of survival free of biochemical failure at 5 years are 81 % for group 1, 69% for group 2, 47% for group 3, and 29% for group 4. Of the 302 patients followed up beyond 5 years who were free of biochemical disease, 5.0% relapsed from the fifth to the eighth year.

CONCLUSIONS

Estimated PSA control rates in this pooled analysis are similar to those of single institutions. These rates indicate the probability of success for subsets of patients with tumors of several prognostic category groupings. These results represent a multi-institutional benchmark for evidence-based counseling of prostate cancer patients about radiation treatment.

Bone metastasis: review and critical analysis of random allocation trials of local field treatment

PURPOSE

Compare and contrast reports of random allocation clinical trials of local field radiation therapy of metastases to bone to determine the techniques producing the best results (frequency, magnitude, and duration of benefit), and relate these to the goals of complete relief of pain and prevention of disability for the remaining life of the patient.

METHODS AND MATERIALS

Review all published reports of random allocation clinical trials, and perform a systematic analysis of the processes and outcomes of the several trial reports.

RESULTS

All trials were performed on selected populations of patients with symptomatic metastases and most studies included widely diverse groups with regard to: (a) site of primary tumor, (b) location, extent, size, and nature of metastases, (c) duration of survival after treatment All trial reports lack sufficient detail for full and complete analysis. Much collected information is not now available for reanalysis and many important data sets were apparently never collected. Several of the variations in patient and tumor characteristics were found to be much more important than treatment dose in the outcome results. Treatment planning and delivery techniques were unsophisticated and probably resulted in a systematic delivery of less than the assigned dose to some metastases. In general the use and benefit of retreatment was greater in those patients who initially received lower doses but the basis and dose of retreatment was not documented. Follow-up of patients was varied with a large proportion of surviving patients lost to follow-up in several studies. The greatest difference in the reports is the method of calculation of results. The applicability of Kaplan-Meier actuarial analysis, censoring the lost and dead patients, as used in studies with loss to follow-up of a large number of patients is questionable. The censoring involved is "informative" (the processes of loss relate to the outcome) and not acceptable since it results in artificial elevation of the frequency of response. Overall, higher dose fractionated treatment regimens produced a better frequency, magnitude, and duration of response than lower dose single-fraction regimens. Relapse after initial response was frequent. The "median duration of relief" was much shorter than the "median duration of survival" post-treatment. Thus the "net pain relief" is far less than the goal of pain relief for the total duration of life after treatment.

CONCLUSIONS

The pain relief obtained in all studies is poor and our care practices need to be improved. Many patients never achieved complete relief and for most who did, the duration of relief was much less than their period of survival after treatment. Higher dose, fractionated treatments produced a greater frequency, magnitude, and duration of response with an improved "net pain relief." Additional trials with selection of comparable cases, good definition of extent of disease, exemplary treatment, and complete follow-up are required.

Antireflux surgery in children under 3 months of age

PURPOSE

The aim of this study was to analyze the indications and results of fundoplication in 110 infants under 3 months of age.

METHODS

A retrospective review was conducted on the charts of all infants operated on for gastroesophageal reflux disease (GERD) at the UCLA Medical Center from January 1980 to December 1997. There were 59 boys and 51 girls. Recurrent emesis was the indication for operation in 62 of 110 infants, and respiratory symptoms in 85 of 110, with 54 of 110 having both. Neurological impairment was present in 32%. Prematurity was present in 21%; 35% had associated anomalies. Overall, 81 of 110 infants (73.6%) had one or more associated major malformations or disorders. Reflux was confirmed by upper gastrointestinal series findings in 63 of 78, esophageal pH monitoring in 60 of 62, and endoscopy in five of seven.

RESULTS

Mean age at operation was 1.8+/-0.1 months and mean weight was 3,686+/-90.2 g. A Nissen fundoplication was performed on 104 children, and six underwent a Thal procedure. Thirty-one had a gastric emptying procedure for delayed gastric emptying. Complications occurred in 7 infants. Emesis was controlled in 57 of 62 patients, aspiration in 38 of 48, and apneic spells in 54 of 57. Follow-up greater than 6 months was available for 73 patients. There were nine late deaths, all related to severe associated malformations. Seven patients required a redo fundoplication for recurrent reflux.

CONCLUSIONS

Nissen fundoplication can be performed safely in symptomatic infants under 3 months of age with low mortality and morbidity rates and with resolution of the presenting symptoms in 79% of infants.

Factors affecting long-term outcome of irradiation in carcinoma of the vagina

OBJECTIVE

This report evaluates prognostic and technical factors affecting outcome of patients with primary carcinoma of the vagina treated with definitive radiation therapy.

METHODS AND MATERIALS

A retrospective analysis was performed on records of 212 patients with histologically confirmed carcinoma of the vagina treated with irradiation.

RESULTS

Tumor stage was the most significant prognostic factor; actuarial 10-year disease-free survival was 94% for Stage 0 (20 patients), 80% for Stage I (59 patients), 55% for Stage IIA (63 patients), 35% for Stage IIB (34 patients), 38% for Stage III (20 patients), and 0% for Stage IV (15 patients). All in situ lesions except one were controlled with intracavitary therapy. Of the patients with Stage I disease, 86% showed no evidence of vaginal or pelvic recurrence; most of them received interstitial or intracavitary therapy or both, and the addition of external-beam irradiation did not significantly increase survival or tumor control. In Stage IIA (paravaginal extension) and IIB (parametrial involvement) 66% and 56% of the tumors, respectively, were controlled with a combination of brachytherapy and external-beam irradiation; 13 of 20 (65%) Stage III tumors were controlled in the pelvis. Four patients with Stage IV disease (27%) had no recurrence in the pelvis. The total incidence of distant metastases was 13% in Stage I, 30% in Stage IIA, 52% in Stage IIB, 50% in Stage III, and 47% in Stage IV. The dose of irradiation delivered to the primary tumor or the parametrial extension was of relative importance in achieving successful results. In patients with Stage I disease, brachytherapy alone achieved the same local tumor control (80-100%) as in patients receiving external pelvic irradiation (78-100%) as well. In Stage II and III there was a trend toward better tumor control (57-80%) with combined external irradiation and brachytherapy than with the latter alone (33-50%) (p = 0.42). The incidence of grade 2-3 complications (12%) correlated with the stage of the tumor and type of treatment given.

CONCLUSION

Radiation therapy is an effective treatment for patients with vaginal carcinoma, particularly Stage I. More effective irradiation techniques, including optimization of dose distribution combining external irradiation and interstitial brachytherapy in tumors beyond Stage I, are necessary to enhance locoregional tumor control. The high incidence of distant metastases emphasizes the need for earlier diagnosis and effective systemic cytotoxic agents to improve survival in these patients.

Management of stage II (T2N0M0) glottic carcinoma by radiotherapy and conservation surgery

BACKGROUND

The best therapeutic approach for the treatment of stage II (T2N0M0) glottic carcinoma is controversial.

METHODS

A retrospective tumor registry data retrieval of patients with stage II glottic carcinoma treated with curative intent at Washington University Medical Center-Barnes Hospital between January 1971 and December 1989 (surgery) and December 1995 (radiotherapy) was performed.

RESULTS

Among 134 patients with stage II glottic carcinomas treated with curative intent and function preservation, there were 47 patients treated with low dose radiotherapy (median dose, 58.5 Gy at 1.5-1.8 Gy daily fractions), 16 patients with high dose radiotherapy (67.5-70 Gy) at higher daily fractionation doses (2-2.25 Gy), and 71 patients underwent conservation surgery. The overall local control rate was 85%. The overall salvage rate was 68%. The 5-year actuarial and disease specific survivals were 81.5% and 92%, respectively. Unaided phonation was achieved in 84.4% of the patients. An incidence of 10.4% regional metastases, 2.2% distant metastases, and 6% second primary tumors was documented. There were no statistical differences in local control, voice preservation, and 5-year actuarial and disease specific cure rates between conservation surgery and high dose radiation (p = .89). Low dose radiation had statistically lower local controls, 5-year survival, and voice preservation (p = .014). In advanced T2B disease, treating the ipsilateral neck nodes reduced regional metastases (p = .02).

CONCLUSIONS

High dose and daily fractionation (70 Gy at 2 Gy daily fraction doses) radiation achieved results equivalent to those of conservation surgery in 5-year local control, survival, and voice preservation. In advanced T2B disease, treatment of the ipsilateral neck nodes by radiotherapy or functional neck dissection reduced regional metastases.

Symptoms as an index of biologic behavior in head and neck cancer

The TNM staging system for head and neck cancer is based on the morphologic description of the tumor and disregards the clinical condition of the patient. Cancer symptoms were evaluated as a biologic index of disease to improve survival estimates. The medical records of 1010 patients receiving initial cancer treatment between 1980 and 1991 were retrospectively reviewed. The mean survival duration was 62 months for the entire population. By use of SAS statistical software (SAS Institute, Cary, NC), 48 symptom variables were screened by univariate analysis, and 23 of these variables were selected for entry into a Cox proportional hazards model on the basis of survival duration. Dysphagia, otalgia, neck lump, and weight loss were identified as independent predictors of survival duration (P < 0.01). A composite symptom-severity staging system was created on the basis of the 4 symptoms. Mean survival duration (95% CI) by symptom-severity stage was as follows: none, 74 months (70 to 79 months); mild, 56 months (51 to 61 months); moderate, 40 months (33 to 47 months); and severe, 31 months (22 to 41 months) (chi 2 = 30.8, P = 0.0001). Survival duration by TNM stage was as follows: I, 89 months (82 to 95 months); II, 71 months (65 to 78 months); III, 53 months (47 to 59 months); and IV, 42 months (37 to 47 months) (chi 2 = 56.2, P = 0.0001). When symptom-severity stage was entered in a proportional-hazards model along with TNM stage, comorbidity, age, and alcohol use, all 5 variables were independently predictive of survival duration (risk ratio: symptom severity 1.28, TNM 1.33, comorbidity 1.80, age 1.47, alcohol use 1.09). Appropriately defined symptom variables contain important prognostic information, which is independent of the TNM system. Therefore symptoms provide an index of biologic behavior in head and neck cancer.

Clinical-severity staging system for oral cavity cancer: five-year survival rates

The objective of this research is to improve the classification and survival estimates for patients with oral cavity cancer by combining cancer symptom severity and comorbidity with the current TNM staging system. The study design is a retrospective medical record review that uses explicit coding criteria. The medical records of 277 patients receiving initial treatment at the Washington University Medical Center between 1980 and 1989 were reviewed. Multivariate analysis identified patient factors that significantly affected 5-year survival. These patient factors, symptom severity and comorbidity, were combined with TNM to create a composite clinical-severity staging system. The overall 5-year survival rate was 46% (128/277). Survival rates by TNM stage were as follows: stage I, 72% (36/50); II, 54% (45/84); III, 37% (24/65); and IV, 29% (23/78) (chi2 = 25.27, P = 0.001). When patients were grouped according to the clinical-severity staging system, survival rates were as follows: stage I, 77% (33/43); II, 56% (45/80); III, 42% (43/103); and IV, 14% (7/51) (chi2 = 40.62, P = 0.001). Survival estimates can be improved by adding carefully studied and suitably defined patient variables to the TNM system. The current TNM staging system for oral cavity cancer is based solely on the morphologic description of the tumor and disregards the clinical condition of the patient. Patient factors, such as cancer symptom severity and comorbidity, have a significant impact on survival. Continued exclusion of patient factors leads to imprecision in prognostic estimates and hinders interpretation of clinical studies.

Gastric emptying procedures decrease the risk of postoperative recurrent reflux in children with delayed gastric emptying

PURPOSE

Although several centers often perform gastric emptying procedures (GEP) together with fundoplication for gastroesophageal reflux (GER) and delayed gastric emptying (DGE), the benefit of GEP is controversial. The present study addresses the question of whether adding a GEP in children with preoperatively diagnosed GER and DGE affects the recurrence rate of GER after Nissen fundoplication (NF).

METHODS

A retrospective chart review was performed on all children under the age of 16 years, operated on for GER from 1980 to 1997, who had a preoperative diagnosis of DGE, and at least 6 months of follow-up. Gastric retention of more than 50% of a radiolabeled meal at 90 minutes was considered DGE. Recurrent reflux was defined as reappearance of GER symptoms, confirmed by postoperative esophagram or 24 hours of pH monitoring.

RESULTS

Of the 183 patients with DGE, 92 were available for long-term follow-up. Of these, 20 had no gastric emptying procedure performed (no-GEP group) and 72 had a GEP performed together with an NF (GEP group). Groups were comparable as to age at operation, mean follow-up time, male to female ratio and prevalence of associated anomalies. A higher prevalence of neurological impairment (NI) was present in the GEP group (48.6% v20.0%). Mean preoperative gastric retention was significantly higher in the GEP group (69.9 +/- 1.3%) than in the no-GEP group (61.4 +/- 2.2%). No complications resulted from the GEP. Recurrent reflux rate was 18.1% in the GEP group (13 of 72) versus 35.0% (7 of 20) in the no-GEP group. Actuarial analysis disclosed a marginally significant difference in the rate of recurrent reflux between the groups (P = .057) and estimation of the relative risk showed a 1.94 increase of recurrent reflux risk in the no-GEP (0.89<RR<4.20).

CONCLUSIONS

Children with DGE, who did not have GEP, had twice the frequency of recurrent reflux as those who had a GER Preoperative screening for DGE, as well as operative correction of DGE at the time of fundoplication, is therefore recommended.

Carcinoma of the tonsillar fossa: prognostic factors and long-term therapy outcome

PURPOSE

To identify prognostic parameters and evaluate the therapeutic outcomes for patients with carcinoma of the tonsillar fossa treated with three treatment modalities.

METHODS AND MATERIALS

The results of therapy are reported in 384 patients with histologically proven epidermoid carcinoma of the tonsillar fossa; 154 were treated with irradiation alone (55-70 Gy), 144 with preoperative radiation therapy (20-40 Gy), and 86 with postoperative irradiation (50-60 Gy). The operation in all but four patients in the last two groups consisted of an en bloc radical tonsillectomy with ipsilateral lymph node dissection.

RESULTS

Treatment modality and total irradiation doses had no impact on survival. Actuarial 10-year disease-free survival rates were 65% for patients with T1 tumors, 60% for T2, 60% for T3, and 30% for T4 disease. Patients with no cervical lymphadenopathy or with a small metastatic lymph node (N1) had better disease-free survival (60% and 70%, respectively) at 5 years than those with large or fixed lymph nodes (30%). Primary tumor recurrence (local, marginal) rates in the T1, T2, and T3 groups were 20-25% in patients treated with irradiation and surgery and 31% for those treated with irradiation alone (difference not statistically significant). In patients with T4 disease treated with surgery and postoperative irradiation, the local failure rate was 32% compared with 86% with low-dose preoperative irradiation and 47% with irradiation alone (p = 0.03). The overall recurrence rates in the neck were 10% for N0 patients, 25% for N1 and N2, and 35-40% for patients with N3 cervical lymph nodes, without significant differences among the various treatment groups. The incidence of contralateral neck recurrences was 8% with the various treatment modalities. On multivariate analysis the only significant factors for local tumor control and disease-free survival were T and N stage (p = 0.04-0.001). Fatal complications were noted in 7 of 144 (5%) patients treated with preoperative irradiation and surgery, 2 of 86 (2%) of those receiving postoperative irradiation, and 2 of 154 (1.3%) patients treated with radiation therapy alone. Other moderate or severe nonfatal sequelae were noted in 30% of the patients treated with preoperative irradiation and surgery, in 53% treated with postoperative irradiation, and in 19% receiving radiation therapy alone.

CONCLUSION

Primary tumor and neck node stage are the only significant prognostic factors influencing locoregional tumor control and disease-free survival. Treatment modality had no significant impact on outcome. Radiation therapy remains the treatment of choice for patients with stage T1-T2 carcinoma of the tonsillar fossa. In patients with T3-T4 tumors and good general condition, combination surgery and postoperative irradiation offers better tumor control than single-modality and preoperative irradiation procedures, but with greater morbidity.

Quantitative dosimetric verification of an IMRT planning and delivery system

BACKGROUND AND PURPOSE

The accuracy of dose calculation and delivery of a commercial serial tomotherapy treatment planning and delivery system (Peacock. NOMOS Corporation) was experimentally determined.

MATERIALS AND METHODS

External beam fluence distributions were optimized and delivered to test treatment plan target volumes, including three with cylindrical targets with diameters ranging from 2.0 to 6.2 cm and lengths of 0.9 through 4.8 cm, one using three cylindrical targets and two using C-shaped targets surrounding a critical structure, each with different dose distribution optimization criteria. Computer overlays of film-measured and calculated planar dose distributions were used to assess the dose calculation and delivery spatial accuracy. A 0.125 cm3 ionization chamber was used to conduct absolute point dosimetry verification. Thermoluminescent dosimetry chips, a small-volume ionization chamber and radiochromic film were used as independent checks of the ion chamber measurements.

RESULTS

Spatial localization accuracy was found to be better than +/-2.0 mm in the transverse axes (with one exception of 3.0 mm) and +/-1.5 mm in the longitudinal axis. Dosimetric verification using single slice delivery versions of the plans showed that the relative dose distribution was accurate to +/-2% within and outside the target volumes (in high dose and low dose gradient regions) with a mean and standard deviation for all points of -0.05% and 1.1%, respectively. The absolute dose per monitor unit was found to vary by +/-3.5% of the mean value due to the lack of consideration for leakage radiation and the limited scattered radiation integration in the dose calculation algorithm. To deliver the prescribed dose, adjustment of the monitor units by the measured ratio would be required.

CONCLUSIONS

The treatment planning and delivery system offered suitably accurate spatial registration and dose delivery of serial tomotherapy generated dose distributions. The quantitative dose comparisons were made as far as possible from abutment regions and examination of the dosimetry of these regions will also be important. Because of the variability in the dose per monitor unit and the complex nature of the calculation and delivery of serial tomotherapy, patient-specific quality assurance procedures will include a measurement of the delivered target dose.