Accelerated fractionation in inoperable non-small cell lung cancer. A phase I/II study

Altered Fractionation in Radiotherapy

Differences between late-responding (slowly proliferating) normal tissues and early-responding (rapidly proliferating) normal tissues and tumor cells and the event of tumor cell repopulation occurring during treatment have essentially led to the development of altered fractionation schemes. Altered fractionation regimens mainly refer to schedules utilising two or more (small dose) fractions per day for part of or for the entire treatment course. It must be underlined that a true standard or conventional fractionation regimen does not exist: no schedule is universally recognised as the standard of reference to be compared with. However, continental European and U.S. conventional regimens are the considered control arm with which the new experimental regimens have to be compared. For this reason they are generally recognised as the standards. The basic rationale for hyperfractionated or accelerated regimens respectively lies in the possibility (a) to deliver higher total doses reducing late-responding normal tissue damage, (b) to deliver total doses in a reduced overall treatment time to defeat tumor clonogen repopulation. Multiple fractions per day should not be delivered with interfraction intervals smaller than 6 hours. Clinical results of phase I-II and limited but convincing phase III randomised trials suggest that a therapeutic benefit can be achieved with new altered regimens.

Radiation therapy of the older patient

Radiotherapy has a major role in the multidisciplinary approach to cancer therapy. It is widely used for curative and palliative treatment of cancer involving various sites. Radiotherapy is of particular benefit to older and frail cancer patients as an alternative to surgery and to systemic therapy. The available data on the sensitivity of normal tissues to radiotherapy in elderly patients strongly suggest that older patients with good functional status tolerate radiotherapy as well as younger patients and have comparable tumor response and survival rates. Aggressive radiotherapy should not be withheld from older patients because of chronological age alone.

[Radiotherapy for stage III, inoperable, asymptomatic small cell lung cancer. Final results of a prospective randomized study (240 patients)]

PURPOSE

To report the results of a prospective randomized study concerning the role of radiotherapy in the treatment of stage III, unresectable, asymptomatic non-small cell lung cancer.

MATERIAL AND METHODS

Between 1992 and 1996, 240 patients with stage III, unresectable, asymptomatic non-small cell lung cancer were enrolled in this study, and sequentially randomized to one of the three treatment arms: conventional irradiation, hypofractionated irradiation and control group. In the conventional irradiation arm (79 patients), a dose of 50 Gy in 25 fractions in five weeks was delivered to the primary tumor and the mediastinum. In the hypofractionated irradiation arm (81 patients), there were two courses of irradiation separated by an interval of four weeks. In each series, patients received 20 Gy in five fractions in five days, in the same treatment volume as the conventional irradiation group. In the control group arm, 80 patients initially did not receive radiotherapy and were only observed. Delayed palliative hypofractionated irradiation (20-25 Gy in four to five fractions in four to five days) was given to the primary tumor when major symptoms developed.

RESULTS

The two-year actuarial survival rates for patients in the conventional irradiation, hypofractionated irradiation and control group arms were 18%, 6% and 0%, with a median survival time of 12 months, nine months and six months respectively. The differences between survival rates were statistically significant at the 0.05 level.

CONCLUSION

Although irradiation provides good palliation, the results are disappointing. The comparison of conventional and hypofractionated irradiation shows an advantage for conventional schedules.

Is the chest radiograph a reliable tool in the assessment of tumor response after radiotherapy in nonsmall cell lung carcinoma?

BACKGROUND

The purpose of this study was to evaluate whether the chest radiograph is a reliable tool to assess response to radiotherapy.

MATERIALS AND METHODS

Pre- and post-treatment chest radiographs and computed tomographs (CT) of 63 patients with nonsmall cell lung cancer (NSCLC) treated by radiotherapy were reviewed by four observers with regard to suitability for tumor measurement, and response. Suitability for tumor measurement was expressed as the number of measurable diameters. In addition, the consequences to clinical outcome were studied by survival analysis.

RESULTS

The CT turned out to be more suited for tumor measurement before as well as after radiotherapy, resulting in an increase of the number of measurable cases. The number of measurable cases with CT was 52 (83%) as compared to 28 (44%) with chest radiography. Especially in case of centrally localized tumors, the presence of an atelectasis, or squamous cell carcinoma, CT contributed to a higher rate of measurable cases. The interobserver agreement with regard to response using chest radiograph was good (mean kappa = 0.74). In 25 of 28 cases (89%) measurable with CT as well as with chest radiograph, response was equally classified. When CT was used, the median survival of the responders was 14.2 months as compared to 6.8 months of the nonresponders. When chest radiograph was used, the median survival of these groups was 12.0 and 6.6 months respectively, which was not significantly different when response was assessed by CT.

CONCLUSION

We conclude that CT is more suited for tumor measurement because more measurable lesions can be found and more evaluable lesions on chest radiograph become measurable on CT. The chest radiograph does have a valuable role to play in those lesions that are measurable because of the good interobserver agreement with regard to the response classification, the high overall agreement between CT and chest radiograph in case of measurable cases, and the lack of important differences with regard to survival.

A phase II trial, feasibility of combination of daily cisplatinum and accelerated radiotherapy via concomitant boost in stage III non-small cell lung cancer

PURPOSE

A prospective phase II trial was conducted by the Institute of Oncology, Istanbul University in December 1994 on patients with locally-advanced non-small cell lung cancer to assess acute toxicity and the feasibility of a combination of radiosensitizer and accelerated radiotherapy with concomitant boost.

MATERIALS AND METHODS

Patients were irradiated using 'large' fields (primary tumour and locoregional lymph nodes) with 1.8 Gy per fraction, five fractions a week. Reduced 'boost' fields (primary and involved nodes only) were also irradiated twice-weekly 1.8 Gy per fraction in ten fractions concomitantly 6 h after the administration of large field. Total radiation dose was 63 Gy in 5 weeks (45 Gy 'large' fields and 18 Gy 'boost'). The maximum allowed dose to the spinal cord was 3750 cGy. Cisplatinum, 6 mg/m2 was given daily just before 'large' field irradiation.

RESULTS

As of January 1997, 15 patients were evaluated (median follow-up of 12.5 months with a range of 5.5-23 months). The overall acute toxicity rate was 38% and Grade 3 acute toxicity was 8%. Grade 4 or greater acute toxicities were not observed. The overall rate of cisplatinum-induced nausea and vomiting was 80% (severe in 60%), but all were easily treated with antiemetics. Complete response rate (clinical and radiological) was 40% and an overall response rate was 73%. Median survival was 16 months and progression-free survival was 5.5 months (range of 2.5-21 months).

CONCLUSIONS

Toxicity was well tolerated and no treatment-related death occurred with this combined treatment regimen. Although it appears that better local control rates can be achieved, additional phase II/III studies are needed.

Lack of influence of sequence of top-up doses on repair kinetics in rat spinal cord

BACKGROUND AND PURPOSE

The rat spinal cord model was used to determine whether repair kinetics changed during a course of fractionated radiotherapy if twice daily doses were given either at the initial or final period of a concomitant boost irradiation schedule.

MATERIALS AND METHODS

The rat cervical spinal cord was irradiated from C2-T2 in 870 animals with top-up doses of three daily fractions of 9 Gy representing 75% of the biologic dose at the ED50 level for white matter necrosis. To simulate concomitant boost protocols, these top-up doses were given either preceding (initial top-up) or following (final top-up) a b.i.d. schedule of 1 Gy/F delivered at 0, 1, 2, 4, 8 or 24 h interfraction intervals. The end point was forelimb paralysis secondary to white matter necrosis.

RESULTS

For interfraction intervals of 0, 1, 2, 4, 8 and 24 h, the initial top-up schedules yielded ED50 values of 18.2, 19.2, 23.7, 21.3, 27.2 and 29.7 Gy, respectively; the corresponding ED50s from the final top-up schedules were 17.5, 19.0, 20.7, 21.2, 26.9 and 30.3 Gy, respectively. A 10% reduction in the ED50 value from pooled data was observed when the interfraction interval was reduced from 24 (ED50 = 30.3 Gy) to 8 h (ED50 = 27.1 Gy). Fitting the incomplete repair (IR) version of the LQ model with mono-exponential repair kinetics gave alpha/beta values of 1.4 and 1.5 Gy, and similar repair half-times of 4.3 and 5.0 h for the initial and final top-up experiments, respectively. The IR model with bi-exponential repair kinetics did not provide a better fit to the data.

CONCLUSIONS

We conclude that the sequence of top-up doses has no apparent influence on radiation sensitivity or repair kinetics in the rat spinal cord. The clinical implication is that the interfraction interval but not the timing of the boost is a critical determinant of spinal cord tolerance in concomitant boost protocols.

A palliative accelerated irradiation regimen (PAIR) for advanced non-small-cell lung cancer (NSCLC)

In order to avoid overtreatment in advanced NSCLC we developed a palliative accelerated irradiation regimen (PAIR) applying a total dose of 32 Gy in 10 days with two daily fractions of 2 Gy. This paper reports on a 1-year pilot study carried out in preparation of a randomised trial. Data for the 34 patients receiving PAIR were compared to 179 conventionally irradiated historical controls selected from a pre-existing database according to identical inclusion criteria. Statistical analysis showed that PAIR patients had a significantly longer survival than controls (P = 0.0029). Median survival was 11.8 and 5.8 months, respectively, while 1-year survival was 45.6% vs. 21.2%. Compared to the subgroup of controls who had received the full planned dose of 60 Gy (n = 104) PAIR patients showed no significant difference in survival. In order to adjust for possible imbalances we used a comprehensive blinded prognostic rating design creating one score value per patient out of several known prognostic factors. After adjustment for the resulting prognostic score by means of the Cox proportional hazards model PAIR patients still showed significantly longer survival. We conclude that in advanced NSCLC survival after a palliative short-term regimen appears to be at least equivalent to that following conventional high-dose irradiation.

A mathematical model of intraluminal and intracavitary brachytherapy

The adaptation of the linear-quadratic model to allow for the effect of tumour regression and clonogen repopulation between initial teletherapy and subsequent brachytherapy has been extended to include the geometrical conditions encountered in intraluminal and intracavitary brachytherapy. For a radiation line source placed at the centre of a lumen or cavity, regression of any endoluminal tumour towards its mural origin will not result in any change in the minimum brachytherapy-tumour dose with time. In contrast, regression of transmural tumour will cause a potentially advantageous increase in the minimum brachytherapy-tumour dose with time. The latter effect will be opposed by tumour clonogen repopulation. The log(e) cell kill due to brachytherapy has been calculated for tumours of diameters 2, 4 and 6 cm at completion of teletherapy. The centres of the tumours were assumed to be at distances of 0, 1 and 2 cm from the radiation source. Tumour linear regression rates (lambda) ranging from 0.025 to 0.25 per week and tumour clonogen doubling times (Tp) of 2.5, 5 and 15 days were used in the calculations. The results demonstrate the critical importance of the distance of the tumour centre from the line source as well as the influence of tumour diameter, lambda and Tp. In some instances, both maximum and minimum values of log(e) cell kill occur. Calculations of tumour cure probabilities reveal that these variations in log(e) cell kill predicted by the model can produce highly significant differences in tumour control rates. Where the relevant parameters can be assessed directly or estimated from previous experience, the model provides a basis for the design of future intraluminal or intracavitary brachytherapy protocols.