Final report of the general clinical results of the British Institute of Radiology fractionation study of 3F/wk versus 5F/wk in radiotherapy of carcinoma of the laryngo-pharynx

Radiation for Early Glottic Cancer

Multidisciplinary evaluation of early-stage glottic cancer facilitates optimal treatment with either surgery or radiation therapy. Standard of care radiation treatment of early-stage glottic cancer continues to be three-dimensional opposed lateral fields to include the whole larynx. Modern radiation treatment techniques are allowing studies to examine the efficacy and toxicity of altered doses and treatment volumes. Advanced techniques, such as stereotactic body radiation therapy or single-vocal cord irradiation, are not yet considered standard of care for early-stage glottic cancer and should be performed at institutions with clinical trials to ensure adequate expertise and quality assurance.

Measures of Late Effects in Conservative Treatment of Breast Cancer with Standard or Hypofractionated Radiotherapy

Aims and Background

To confirm the equivalence in terms of late effects between two fractionation schedules of radiotherapy in conservative treatment of breast cancer.

Methods

Fifty-eight patients treated at our institution from 1999 to 2002, with a median follow-up of 15 months (range, 7-46 months), were evaluated retrospectively. Twenty-nine patients (group A) were treated with standard fractionation: 5000 cGy/25fx/5 weeks, and 29 patients (group B) were treated with a hypofractionated schedule: 4500 cGy/15fx/5 weeks, three fractions per week. Late effects were evaluated using the LENT-SOMA scoring scale. The cosmetic results were assessed on a five-point scale. Skin elasticity was measured using a dedicated device (Cutometer SEM 575).

Results

There were no differences in breast volume, age at diagnosis and follow-up between groups. The LENT-SOMA toxicity observed in groups A and B, respectively, was as follows: grade 2-3 pain in five patients in each group; grade 2 breast edema in two and three patients; grade 2-3 and grade 2 fibrosis in six and eight patients; grade 2 and grade 2-3 telangiectasia in two and three patients; grade ≥2 and 2 arm edema in two and one patients; no ulceration or atrophy were observed. Two patients in group A and one patient in group B needed treatment for breast and arm edema and arm edema, respectively. Very good, good-acceptable, and poor cosmetic results were observed in seven and two, fifteen and nineteen, and six and eight patients, respectively. Median skin elasticity loss due to treatment was −4.19% in group A and −6.29% in group B. These results are not statistically different.

Conclusions

LENT-SOMA toxicities were minimal and no differences were observed between groups. Few patients in the hypofractionated group had very good cosmetic results, but it is debatable if radiotherapy was the only cause. Skin elasticity was not different between groups. Our results seem to suggest that it is possible to treat patients with both schedules, with similar late toxicity.

Radiation fractionation: the search for isoeffect relationships and mechanisms

PURPOSE

Review the historical basis for the use of fractionated radiation in radiation oncology.

CONCLUSION

The history of dose fractionation in radiation oncology is long and tortuous, and the radiobiologist's understanding of why fractionation worked came decades after radiation oncologists had adopted multi-week daily-dose fractionation as 'standard'. Central to the history is the search for 'isoeffective' formulas that would allow different radiation schedules to be compared. Initially, this meant dealing with different lengths of treatment, leading to the 1944 Strandqvist formulation that dominated thinking for decades. Concerns about the number of fractions, not just the total time, led to the 1967 Ellis NSD formulation that held sway through the 1980s. The development of experimental radiotherapy in 1970s (e.g. Fowler's work at the Gray Laboratory, and Fischer's work at Yale) led to biologically-based approaches that culminated with the Biologically Effective Dose (BED) concept. BED is the current dogma for treatment optimization, but it must be used with caution, as there are multiple formulations, and some parameters have debatable values. There is also a controversy about whether BED is biologically-based or a 'curve-fitting' exercise. These latter issues are beyond the scope of this article, but the history of fractionation models suggests that our current concepts are probably wrong, although when used with caution they are clearly useful.

Clinical Assessment and Treatment of the Dysfunctional Larynx after Radiation

Objective

To review the pathophysiology of early and late radiation-related tissue changes, methods to differentiate these changes from disease recurrence, and treatment of these changes in the irradiated larynx.

Data Sources

Peer-reviewed publications.

Review Methods

PubMed database search.

Conclusions/Implications for Practice

Early and late radiation-related changes in the larynx manifest variably between individual patients. Severe radiation-related tissue changes in the larynx and recurrent malignancy share many clinical characteristics, and the presence of malignancy must be considered in these patients. Positron emission tomography may help select patients who need operative biopsy to rule out recurrence. In patients with a cancer-free but dysfunctional larynx, both surgical and nonsurgical treatment options, including hyperbaric oxygen, are available for attempted salvage. Further investigation is needed before hyperbaric oxygen can be considered standard-of-care treatment for these patients.

Small cell carcinoma of the bladder: long term outcome with integrated chemoradiation

BACKGROUND

Small cell carcinoma of the bladder (SCCB) is an uncommon tumor with approximately 8% 5-year survival reported in the literature for patients with disease confined to the pelvis. It exhibits biologic behavior similar to that of small cell carcinoma of the lung (SCLC). The authors sought to determine whether etoposide and cisplatin chemotherapy integrated with local irradiation is associated with improved survival in SCCB, as has been shown in SCLC.

METHODS

The authors performed a retrospective analysis of stage, treatment, disease free survival (DFS), and overall survival (OS) among 14 British Columbia Cancer Agency (BCCA) patients treated between 1985 and 1996 for SCCB.

RESULTS

When multiagent chemotherapy was combined with local irradiation, the authors observed a 70% 2-year and 44% 5-year actuarial OS among 10 patients without contraindications to systemic chemotherapy. Actuarial DFS was 70% at 2 and 5 years. The mean survival was 47 months (95% confidence interval, 18.5-76.1 months) and the median survival was 41 months. Nine of these patients had disease confined to the pelvis, and one had metastases to retroperitoneal lymph nodes. Five patients were alive and disease free an average of 82 months following diagnosis. Two patients had died of other causes without evidence of disease at 34 and 48 months following diagnosis. The incidence of second primary transitional cell bladder neoplasms following successful treatment was 60% at 2 years (3 of 5 long term survivors).

CONCLUSIONS

Integrated chemoradiation for patients with limited stage SCCB generates a realistic expectation of long term survival. Prospective trials to confirm these findings are warranted.

Time factors in larynx tumor radiotherapy: lag times and intertumor heterogeneity in clinical datasets from four centers

PURPOSE

To use the time-dependent linear-quadratic model, both in the standard form and in a form modified to incorporate intertumor heterogeneity, in a reanalysis of 4 datasets for larynx tumor control, to provide more representative and direct estimates of the lag period, the time factor (lambda/alpha), and the clonogen population inactivation dose ([lnk]/alpha).

METHODS AND MATERIALS

The data comprised 2,225 patients treated in Edinburgh (UK), Glasgow (UK), Manchester (UK), or Toronto (Canada), with tumor control assessed after at least 2 years. Heterogeneity in each series was taken into account using the coefficient of variation (CV) of the clonogen radiosensitivity (alpha). Maximum likelihood techniques were used to provide best estimates of the parameters, and also direct estimation of the more stable parameter ratios of interest.

RESULTS

The use of different heterogeneity factors for the different series allowed common dose/time parameters to be fitted across all four series in a way not possible using the standard model, enabling the inherent effect of heterogeneity in flattening dose-response curves and in reducing time factors to be separated from the underlying more-representative values. Radiosensitivity CVs were calculated to be 30% (Edinburgh), 36% (Glasgow), 40% (Manchester), and 71% (Toronto). The lag phase was 32 days (95% CL 20-38 days) which was longer than the value of 23 days (11-36 days) deduced using the standard model without the heterogeneity parameter. The time factor was 1.2 (0.8-2.2) Gy/day, again greater than the value of 0.80 (0.54-1.41) Gy/day derived using the standard model. Similar larger time factors and longer lag periods could be reproduced using the standard model either by using a parameterization based on parameter ratios, or by omitting the discordant Toronto data and refitting just the data from the three UK centers.

CONCLUSION

It was concluded that the heterogeneity model provides a better representation of the time factor for tumor control when data are analyzed comprising different stages of disease treated at different centers. The model allows different amounts of heterogeneity in different series, which tend to flatten dose-responses curves and reduce time factors, to be taken in to account. Also, direct maximum likelihood estimates can be made of the lag period, the time factor (lambda/alpha), and the fractionation sensitivity (beta/alpha), as well as the clonogen population inactivation dose (lnk)/alpha. Values of these parameter ratios are more robust and stable than the individual parameter values. The results of the present analysis using a total of 2,225 patients from four centers indicate that the average lag period may be somewhat longer and the average time factor somewhat greater (and the 95% confidence limits of the time factor exclude previous estimates), than the values deduced previously using simpler models and more diverse multi-center datasets.

A realistic closed-form radiobiological model of clinical tumor-control data incorporating intertumor heterogeneity

PURPOSE

To investigate the role of intertumor heterogeneity in clinical tumor control datasets and the relationship to in vitro measurements of tumor biopsy samples. Specifically, to develop a modified linear-quadratic (LQ) model incorporating such heterogeneity that it is practical to fit to clinical tumor-control datasets.

METHODS AND MATERIALS

We developed a modified version of the linear-quadratic (LQ) model for tumor control, incorporating a (lagged) time factor to allow for tumor cell repopulation. We explicitly took into account the interpatient heterogeneity in clonogen number, radiosensitivity, and repopulation rate. Using this model, we could generate realistic TCP curves using parameter estimates consistent with those reported from in vitro studies, subject to the inclusion of a radiosensitivity (or dose)-modifying factor. We then demonstrated that the model was dominated by the heterogeneity in alpha (tumor radiosensitivity) and derived an approximate simplified model incorporating this heterogeneity. This simplified model is expressible in a compact closed form, which it is practical to fit to clinical datasets. Using two previously analysed datasets, we fit the model using direct maximum-likelihood techniques and obtained parameter estimates that were, again, consistent with the experimental data on the radiosensitivity of primary human tumor cells. This heterogeneity model includes the same number of adjustable parameters as the standard LQ model.

RESULTS

The modified model provides parameter estimates that can easily be reconciled with the in vitro measurements. The simplified (approximate) form of the heterogeneity model is a compact, closed-form probit function that can readily be fitted to clinical series by conventional maximum-likelihood methodology. This heterogeneity model provides a slightly better fit to the datasets than the conventional LQ model, with the same numbers of fitted parameters. The parameter estimates of the clinically important time factors and lag periods are very similar to those obtained from the conventional LQ model, but with slightly narrower confidence intervals, reflecting the better fit to the clinical data.

DISCUSSION

We have demonstrated, as have others, the importance of intertumor heterogeneity in the response of patient populations to radiotherapy. With the possible inclusion of a radiosensitivity-modifying factor (in vitro/in vivo) of around 1.7, the in vivo data can be made consistent with the in vitro SF2 and Tpot data. Fitting two previously analyzed multicenter datasets indicated that previous analyses based on conventional LQ models gave results for clinically important time factors and lags periods that were not significantly biased by the failure to include intertumor heterogeneity, with slightly narrower confidence intervals, reflecting the better fit to the clinical data. The simple closed-form model we have developed allows direct estimation of the heterogeneity in radiosensitivity within clinical series, and should prove useful in the analysis of other clinical series.

Modelling the optimal radiotherapy regime for the control of T2 laryngeal carcinoma using parameters derived from several datasets

PURPOSE

A number of previous studies have used direct maximum-likelihood methods to derive the values of radiobiological parameters of the linear-quadratic model for head and neck tumors from large clinical datasets. Time factors for accelerated repopulation were included, along with a lag period before the start of this repopulation. This study was performed to attempt to utilise these results from clinical datasets to compare treatment regimes in common clinical use in the UK, along with other schedules used historically in a number of clinical series in North America and elsewhere, and to determine if an optimal treatment regime could be derived based on these clinical data.

METHODS

The biologically-based linear-quadratic model, applied to local tumor control and late morbidity, has been used to derive theoretical optimum (maximising tumor control whilst not exceeding tolerance for late reactions) radiotherapy schedules based on daily fractions. The specific case of T2 laryngeal carcinoma was considered as this is treated primarily by radiotherapy in many centers. Parameter values for local control were taken from previous analyses of several large single-center and national datasets. A time factor and a lag period were included in the modelling. Values for the alpha/beta ratio for late morbidity were used in the range 1-4 Gy, which is compatible with the limited range of values reported in the literature for particular complications following radiotherapy for head and neck cancer. Early reactions and their consequential late morbidity were not modelled in this study, but assumed to be within tolerance.

RESULTS

For treatments using daily fractions there was a broad optimum treatment time of between 3-6 weeks. The theoretical optimum depended to some extent on the value of the alpha/beta ratio for late morbidity, but in many cases was at or just beyond the end of the purported lag period of 3-4 weeks, although small values of alpha/beta between 1-2 Gy favour longer treatment times. Similar results were obtained using a range of parameter values derived from four independent clinical datasets.

CONCLUSION

The mathematical modelling of this broad range of once-daily treatments for most of which differences in local control and late morbidity are essentially undetectable (< 5%) has shown how this clinically-recognised phenomenon is interpreted in terms of the combination of dose-response slopes, fractionation sensitivities and time factors for both tumor control and normal tissue morbidity. Although the conclusions are inevitably tempered by a number of caveats concerning confounding factors in different centers; for example, the use of different treatment volumes, the present analysis provides a framework with which to explore the potential value of modifications to conventional treatment schedules, such as the use of multiple fractions per day.

Fractionation in radiotherapy: a view from the clinic

A century of the evolution of the fractionation of radiotherapy has brought clinical oncologists to the testing of protocols in randomized controlled clinical trials. The British Institute of Radiology's pioneering trials, together with more recent studies, are described and future developments suggested.

Tumour recurrence or treatment sequelae following radiotherapy for larynx cancer

Differentiating between recurrent carcinoma and significant sequelae of radiotherapy after treatment of laryngeal carcinoma is an uncommon but difficult clinical problem. Head and neck surgeons can be faced with deciding on the necessity for salvage laryngectomy without prior histological confirmation of recurrence. This paper reviews the literature pertaining to this topic to provide a better overall estimate of the risk of recurrence in these cases. Approximately 50% of patients with severe oedema or necrosis following radiotherapy for larynx cancer will have recurrence. Less than 10% of all larynges removed will be histologically negative when persistent or recurrent tumour is suspected clinically or indicated by biopsy following radiotherapy.

Influence of fraction size on the development of late radiation enteropathy. An experimental study in the rat

The use of large fraction sizes in radiotherapy may be associated with an increased risk of complications from late responding normal tissues. However, in the intestine, chronic injury may develop either as primary late effect or secondary to disruption of mucosal integrity as so-called consequential injury. Mucosal damage is relatively less sensitive to changes in fraction size than late reacting, slowly proliferating cells. The relationship between fraction size and chronic radiation enteropathy in a given situation may thus depend on which of the two mechanisms that predominates. Most previous studies of the influence of fraction size on radiation injury are confounded by differences in treatment time. The present study was therefore designed to assess subacute and chronic radiation enteropathy after three different fractionation regimens where fraction size was the only experimental variable. A total of 96 male Sprague-Dawley rats were orchiectomized and a functionally intact loop of small intestine was transposed into the left scrotum. These 'scrotal hernias' containing intestine were subsequently exposed to 50.4 Gy localized fractionated irradiation over 18 days with either 2.8 Gy every 24 h, 4.2 Gy every 36 h, or 5.6 Gy every 48 h. Control animals were sham irradiated. The animals were observed for development of intestinal complications (intestinal obstruction or enterocutaneous fistula formation) up to 6 months after irradiation. Histologic damage was assessed in groups of animals at 2 weeks (subacute injury) and 26 weeks (chronic injury), using a previously validated radiation injury score (RIS). RIS increased significantly with increasing fraction size at both observation times. However, the increase was more pronounced at 26 weeks than at 2 weeks. Increased chronic injury was characterized by increased incidence and severity of mucosal ulceration, serosal thickening, vascular sclerosis and intestinal wall fibrosis. We conclude that increasing fraction size increases both subacute and, even more markedly, chronic injury in the intestine. With the fractionation regimens used here, the chronic radiation enteropathy develops as a combined consequential and primary late effect, but the primary mechanism predominates.

Head and neck cancer

This synthesis of the literature on radiotherapy for head and neck cancer is based on 424 scientific articles, including 3 meta-analyses, 38 randomized studies, 45 prospective studies, and 246 retrospective studies. These studies involve 79174 patients. The literature review shows that radiotherapy, either alone or in combination with surgery, plays an essential role in treating head and neck cancers. When tumors are localized, many tumor patients can be cured by radiotherapy alone and thereby maintain full organ function (1, 2). Current technical advancements in radiotherapy offer the potential for better local tumor control with lower morbidity (3). This, however, will require more sophisticated dose planning resources. To further improve treatment results for advanced tumors, other fractionation schedules, mainly hyperfractionation, should be introduced (5). This mainly increases the demands on staff resources for radiotherapy. The combination of radiotherapy and chemotherapy should be subjected to further controlled studies involving a sufficiently large number of patients (4, 5). Interstitial treatment (in the hands of experienced radiotherapists) yields good results for selected cancers. The method should be more generally accessible in Sweden. Intraoperative radiotherapy should be targeted for further study and development.

Further analysis of radiobiological parameters from the First and Second British Institute of Radiology randomized studies of larynx/pharynx radiotherapy

PURPOSE

This retrospective analysis of 1345 patients treated for cancer of the larynx or pharynx by randomization into two groups in each center in two separate trials of fractionated radiotherapy was carried out in an attempt to extract the radiobiological parameters alpha (dose), beta (fraction size), and gamma (overall time) from the data.

METHODS AND MATERIALS

Details of the trials have been published previously. In the first, 734 patients were randomized to either five or three fractions per week, in centers each using their own overall time, which varied from 3 to 7 weeks in different centers. In the second trial, 611 patients were randomized to "short" (< or = 4 weeks) or "long" (4-7 weeks) overall time. We combine the data from both studies and use the linear-quadratic formula with logistic regression and maximum-likelihood methods to obtain the radiobiological factors, taking into account other variables such as stage or age, when significant.

RESULTS

The parameters calculated for local tumor control showed significant estimates of alpha, very small estimates of beta, and significant values of gamma. The derived estimates of alpha/beta were large, but very variable. The time-dose tradeoff--gamma/alpha was 0.76 Gy/day for larynx and 0.3 Gy/day for pharynx tumors (not significantly different from each other). Late complications gave indeterminate alpha/beta ratios and a time-dose factor not significantly different from zero. Acute normal-tissue effects gave alpha/beta estimates of 8-9 Gy and time factors of 0.8-0.9 Gy/day.

CONCLUSIONS

The results are consistent with other published values with the exception that significant time factors for late complications could not be excluded.

The influence of radiotherapy treatment time on the control of laryngeal cancer: a direct analysis of data from two British Institute of Radiology trials to calculate the lag period and the time factor

This study analyses node-negative laryngeal tumour control data from two clinical trials conducted by the British Institute of Radiology in order to determine the time factors and the presence or absence of a lag period before the time factor takes effect. A direct maximum likelihood approach is used to fit a double-logarithmic model including a repopulation term which commences after an initial lag period, Tk. The analysis yields a time factor of 0.8 Gy per day (95% confidence interval 0.5-1.1 Gy per day) as the extra dose required to counteract the reduction in tumour control probability (TCP) with extension of the treatment time. The latter reduction amounted to between 5 and 12% TCP per week, depending on the stage and time period. With this dataset, where few patients were treated for short times, no statistically significant lag phase can be demonstrated. However, the best estimate of Tk is 21 days (95% confidence interval 0-27 days), which is consistent with estimates from other studies on other datasets. If a lag phase exists, this study would indicate that the duration is less than 27 days. Other studies have used retrospective data and are subject to a number of potential biases. The present study, using data from multicentre prospective randomized clinical trials, is free from some of these sources of bias. The fact that very similar estimates of the radiobiological parameters are obtained lends credence to these other studies and suggests that the potential biases may be small in practice.

Dose, fractionation and overall treatment time in radiation therapy--the effects on local control for cancer of the larynx

The effect of total tumor dose, split course treatment and overall treatment time on local control was analysed in a retrospective series of 997 patients with carcinoma of the larynx, treated with megavoltage radiotherapy only. Primary tumors were classified by site (glottis and supraglottis) and T-stage. Continuous course (CC, n = 594) treatment was given primarily to small tumors. Split course radiation (SC, n = 403) was generally given to patients with larger field sizes. Total doses of irradiation ranged from 50 to 79 Gy, with a mean of 64 Gy in CC and 66 Gy in SC. Most of the treatments were given with fraction sizes between 2.0 and 2.1 Gy (91%). Overall treatment times ranged between 25 and 60 days in the CC group (mean, 45 days) and between 45 and 120 in the SC group (mean, 76 days). A local recurrence was observed in 256 patients. T-stage was the only tumor characteristic strongly related to local failure. Corrected for T-stage, no difference in local relapse rate was observed between glottic and supraglottic tumors, or between node-negative (n = 886) and node-positive patients (n = 111). After correction for T-stage the local failure rate of SC-treated tumors was 2.1 (95% confidence limits: 1.4-3.1) times higher than of CC-treated tumors. However, this effect could not be explained as an effect of the overall treatment time (OTT) itself, as no effect of OTT was found within the SC and the CC group, even though the variation in OTT's was considerable in the SC group. A higher tumor dose was associated with a lower local failure rate in the CC group (p = 0.005), but not in the SC group (p = 0.56).

Influence of dose-rate and dose per fraction on clinical outcome of breast cancer treated by external beam irradiation plus iridium-192 implants: analysis of 289 cases

PURPOSE

To study the influence of Iridium 192 implant dose-rate and dose per fraction of external irradiation on clinical outcome, the results in 289 patients with early breast cancer were analyzed retrospectively.

METHODS AND MATERIALS

From 1980 to 1990, 118 T1 and 171 T2 lesions of breast were treated definitively by radiotherapy, following conservative surgery. External irradiation dose of 45 Gy was delivered either with 2.5 Gy or 1.8 Gy per fraction to the entire target volume, plus boost to the primary tumor. Boost dose of 15 to 30 Gy was given to the primary tumor either with iridium-192 implants or electrons. The implant dose-rate varied between 20 cGy/hr to 160 cGy/hr.

RESULTS

The minimum follow-up was of 12 months and maximum of 11 years (median: 56 months). Out of 273 tumors boosted with implants, the 270 patients were divided into five groups according to dose-rate as, groups 1 (20-29 cGy/hr, n = 17), group 2 (30-49 cGy/hr, n = 144), group 3 (50-69 cGy/hr, n = 69), group 4 (70-99 cGy/hr, n = 27) and group 5 (100-160 cGy/hr, n = 13). The local failure rate was significantly increased in the group of patients treated with implant dose-rate < 30 cGy/hr (p < 0.05). While the incidence of late normal tissue complications and poor cosmetic outcome was significantly higher in the group of patients treated with implant dose-rate > 100 cGy/hr (p < 0.05).

CONCLUSION

The present analysis indicate that the implant dose-rate should be maintained between 30-70 cGy/hr to maximize local control and reduce the late normal tissue injury. Also the increase in dose per fraction of external irradiation while not influencing local control rate was crucial for incidence of late complications and cosmetic outcome.

Sensitivity of human squamous cell carcinoma of the larynx to fractionated radiotherapy

Data obtained for the response of tumours from two multicentre clinical trials of the British Institute of Radiology have been combined and studied. Both trials involved patients with laryngopharyngeal carcinoma. There were 734 patients in the first trial, recruited between 1965 and 1975, and 611 patients in the second trial, recruited between 1975 and 1985. Observed survival and tumour-free rates for all patients are calculated. T-class and the nodal status of the patient at the start of the treatment were important factors in the determination of both observed survival and tumour-free rates. Overall treatment time was an important factor in determining the recurrence of tumour. The longer the overall treatment time the greater was the chance of tumour recurrence. The linear-quadratic (LQ) model was used in the analysis of the tumour recurrence data for a large group of patients with laryngeal tumours without nodal involvement. A small alpha/beta ratio of 0.94 Gy was obtained for T3 tumours while that of T2 tumours was negative, -10.5 Gy. The value for T1 tumours was higher at 23 Gy. However, use of the LQ model with a time component increased the alpha/beta ratios to 26.0 +/- 27.20 Gy, 18.0 +/- 12.33 Gy and 13.38 +/- 5.40 Gy for T1, T2 and T3 tumours, respectively. The time component, the gamma/alpha ratios, for these tumours were 0.15 +/- 0.27 Gy/day, 0.81 +/- 0.18 Gy/day and 0.76 +/- 0.15 Gy/day, respectively.

Loss of local control with prolongation in radiotherapy

Twelve published clinical results of radical radiotherapy of head and neck cancer have been reviewed, seven of them with fresh multivariate analyses, to determine the magnitude of time factors relating local control to overall time. In all but two of the data sets a significant loss of local control was observed with prolongation. The median rate of loss was 14% in only 1 week, the range 3 to 25%. This corresponds to a median loss of 26% in 2 weeks (5-42%). These results are comparable with other, less detailed information. Whether these significant losses are due to proliferation of tumor cells or to other causes such as physician selection, it is clear that modest prolongation is associated with a lower chance of local control.

The 1991 Elis Berven Lecture. Radiotherapy in the nineties. Increase in cure, decrease in morbidity

Advance in radiotherapy can be achieved by obtaining a greater tumour control and by reducing the morbidity of treatment, both early and late. The factors influencing both means of benefiting the cancer patient are considered.

Predictive role of TDF values in late rectal recto-sigmoid complications in irradiation treatment of cervix cancer

Radiation-induced late rectal and recto-sigmoid complications for different doses per fraction were analyzed retrospectively in 203 cases of Stage IIIB carcinoma of the uterine cervix. The patients were treated with a combination of external irradiation and a single intracavitary insertion during January 1979 to December 1983. The external irradiation was randomised to deliver by four different fractionation regimens having dose per fraction of 2 Gy, 3 Gy, 4 Gy and 5.4 Gy. The doses for various fractionations were matched with the daily regimen using the time-dose factors (TDF) model. A single intracavitary insertion delivered a dose of 22 to 24 Gy to point A using Fletcher-Suit applicator. All patients had a minimum follow-up of 30 months. Thirty nine cases of late radiation induced rectal and recto-sigmoid complications were observed. The complication rate of 8.2% for daily treatment regimen delivering 2 Gy per fraction was increased to 33.3% for once weekly treatment regimen delivering 5.4 Gy per fraction (p = 0.041). Despite similar Time-Dose Factors (TDF) values in four different treatment regimens, the complication rate increased significantly in the once weekly regimen. The analysis suggest that the Time-Dose Factors (TDF) values do not predict correctly the late normal tissue reactions for different dose fractionation schedules.

Normal tissue reactions in the British Institute of Radiology Study of 3 fractions per week versus 5 fractions per week in the treatment of carcinoma of the laryngo-pharynx by radiotherapy

The radiobiological data obtained from a multicentre clinical trial of the British Institute of Radiology, which compared the treatment of carcinoma of the laryngo-pharynx by 3 fractions per week (3F/wk) with 5 fractions per week (5F/wk) radiotherapy, have been studied. The trial involved an intake of 734 patients between 1966 and 1975. The number of fractions, overall treatment time and total doses used by different treatment centres ranges from 9 to 40 fractions, 18 to 70 days and 3880 to 7800 cGy, respectively. An 11-13% reduction in the total radiation dose was applied for treatments with 3F/wk as compared with 5F/wk in centres treating over 6 weeks and 3 weeks, respectively. All patients were followed for 10 years from the start of treatment. Different types of early and late normal-tissue reactions were investigated, ranging from a low percentage incidence of perichondritis to 95% for slight early reactions. Greater than 80% of the late normal-tissue reactions seen were observed within the first year after the start of treatment, and 96% were observed within the first 5 years. There was no statistically significant difference in the normal-tissue event-free rates between the 3F/wk and 5F/wk treatment groups. This finding did not differ when different major treatment centres were studied separately. For a number of end-points, alpha/beta ratios and N- and T-exponents of a modified nominal standard dose (NSD) formula have been calculated.

The predictive value of histological classification into degrees of differentiation of squamous cell carcinoma of the larynx and hypopharynx compared with the survival of patients

In the course of running two clinical trials between 1966 and 1985, data became available for 1315 patients, 713 in the first trial and 602 patients in the second trial, which has allowed comparison between histological findings in laryngeal and hypopharyngeal carcinoma, the observed survival and the tumour-free rates for these patients who were followed for up to 10 years. Extensive histopathology reviews have revealed over 98% agreement on tumour cell type between the initial report and that of the reviewer. Highly significant differences have been found for squamous cell carcinoma between the observed survival and the tumour-free rates for patients with well-differentiated and with anaplastic lesions. There was a statistically significant greater proportion of patients with well-differentiated tumours at larynx sites and in stage 1 when compared with patients with anaplastic tumours, but even when this was taken into account, multivariate analyses showed that tumour grading still made an independent significant contribution to the prediction of prognosis. For squamous cell carcinoma only very simple and rapidly assessed histopathological features need to be identified to classify tumours into the two grades employed in this study. The analyses have confirmed the prognostic significance of tumour grading in squamous cell carcinoma in the larynx and hypopharynx.

Economic evaluation of trends in cancer therapy. Marginal or average costs?

Evaluating the use of resources as well as outcomes in cancer therapy is increasingly becoming recognized by both clinicians and others as a legitimate and indeed even desirable activity. While this trend is to be welcomed if it facilitates the efficient use of resources for cancer care, there are dangers in applying estimates of unit costs, in particular average costs to the evaluation of trends in practice in cancer therapies. This article examines the use of appropriate measures of average and marginal cost in the economic evaluation of developments in cancer therapy, taking illustrations from radiotherapy and chemotherapy.

Recruitment, follow-up and analysis times in clinical trials of cancer treatment: a case study

A study has been made of the way in which the number of events available for analysis in a clinical trial was dependent on the recruitment period, the maximum follow-up time on individual patients and the length of time between the start of the trial and its analysis. The events considered were deaths, local recurrences and late radiation effects on normal tissue in patients treated for cancer of the laryngo-pharynx by two different fractionation regimes. The relationship is demonstrated between the number of events and the 95% confidence intervals that can be placed on differences between results in the two arms of the trial. It was found, in this particular trial, that no significant improvement in precision was gained by following up patients beyond 5 years or carrying out the analysis later than 2 years after the end of recruitment. The results are discussed in the context of the initial design of clinical trials, particularly those in which the aim is to test therapeutic equivalence.