Evaluating intraoperative radiation therapy (IORT) and external beam radiation therapy (EBRT) in non-small cell lung cancer (NSCLC). Five years experience

The American Brachytherapy Society consensus statement on intraoperative radiation therapy

PURPOSE

Although radiation therapy has traditionally been delivered with external beam or brachytherapy, intraoperative radiation therapy (IORT) represents an alternative that may shorten the course of therapy, reduce toxicities, and improve patient satisfaction while potentially lowering the cost of care. At this time, there are limited evidence-based guidelines to assist clinicians with patient selection for IORT. As such, the American Brachytherapy Society presents a consensus statement on the use of IORT.

METHODS

Physicians and physicists with expertise in intraoperative radiation created a site-directed guideline for appropriate patient selection and utilization of IORT.

RESULTS

Several IORT techniques exist including radionuclide-based high-dose-rate, low-dose-rate, electron, and low-energy electronic. In breast cancer, IORT as monotherapy should only be used on prospective studies. IORT can be considered in the treatment of sarcomas with close/positive margins or recurrent sarcomas. IORT can be considered in conjunction with external beam radiotherapy for retroperitoneal sarcomas. IORT can be considered for colorectal malignancies with concern for positive margins and in the setting of recurrent gynecologic cancers. For thoracic, head and neck, and central nervous system malignancies, utilization of IORT should be evaluated on a case-by-case basis.

CONCLUSIONS

The present guidelines provide clinicians with a summary of current data regarding IORT by treatment site and guidelines for the appropriate patient selection and safe utilization of the technique. High-dose-rate, low-dose-rate brachytherapy methods are appropriate when IORT is to be delivered as are electron and low-energy based on the clinical scenario.

Combined Modality Treatment of Non-Small-Cell Lung Cancer

Among all nonmetastatic non-small-cell lung cancer (NSCLC) patients, the best survival rates are observed in patients who undergo surgery. Nevertheless, 5-year survival rates vary between 20% and 60% depending on the stage of the disease. Several combined modality treatments have been investigated to improve outcome in localized NSCLC. These include local treatment, systemic before local treatment, concomitant systemic and local treatments, and systemic after local treatment. Preoperative irradiation was shown to be of no benefit on local recurrence rates or overall survival. Even doses of radiation >/=40 grays (Gy) were associated with lower survival rates. Postoperative irradiation did not influence survival in stage III disease and seemed to be deleterious in stages I and II disease. Modern radiotherapy techniques might be of interest in this setting but have been insufficiently tested. The early phase III studies of preoperative chemotherapy versus primary surgery in stage III NSCLC showed a tremendous difference in favor of chemotherapy. A larger study did not confirm these results but suggested that preoperative chemotherapy might have a greater effect in stages I and II of the disease. In locally advanced disease, chemotherapy followed by radiotherapy was shown to increase survival when compared with radiotherapy alone. Studies comparing concurrent chemoradiation with radiotherapy only were in favor of the concomitant schedule, which improved local control. Promising results have been reported with chemoradiation followed by surgery in stage IIIa and even stage IIIb disease. Randomized studies of postoperative chemotherapy demonstrated a 5% improvement in 5-year survival over adjuvant-free treatment. Postoperative chemoradiation showed no advantage over postoperative radiotherapy. Several trials that are ongoing or whose accrual was recently completed should further define the role of perioperative chemotherapy in resectable NSCLC and of trimodality treatments in advanced disease. Targeted agents are being developed in the postoperative setting. New schedules of chemoradiation with higher therapeutic indexes are also being investigated in nonresectable stage III NSCLC.

Intraoperative radiation therapy in the multimodality approach to upper aerodigestive tract cancer

The cure rate of operable lung cancer and locally advanced head and neck cancer remains suboptimal, with a limited rate of local control despite improvements in the surgical removal of primary tumors and in methods for mediastinal lymph node dissection, in particular. The efficacy of adjuvant therapy, such as EBRT, has improved, and the immediate efficacy of new chemotherapeutic drugs is increasingly significant, although local recurrences remain frequent. Locoregional failure is not uncommon in upper aerodigestive tract cancers. Factors limiting radiocurability for locally advanced (stage III) lung cancer include mediastinal intolerance of irradiation (high risk of mediastinal fibrosis, which increases exponentially when levels of much more than 50 Gy are administered to the whole mediastinum) and the very high radiosensitivity of the healthy lung, which can develop fibrosis with relatively small or moderate doses starting at 18 to 20 Gy, and even more frequently when larger volumes are irradiated. Head and neck neoplasms are less difficult sites in which to administer doses of up to 70 Gy of external beam radiotherapy initially, but, like locoregionally recurrent lung cancers, they are not easily reirradiated with tumoricidal doses of EBRT. For these reasons, IORT seems to be a good option for increasing local control, because areas of [figure: see text] residual microscopic disease may be irradiated using IOERT approaches without affecting critical organs to the same extent. In addition, careful patient selection is paramount. Combined modality treatment regimens incorporating IORT may benefit patients with locally advanced disease. The ability of IORT to sterilize microscopic residual disease can enhance the "completeness" of resection and thus, theoretically, improve local control. Although distant disease dissemination remains by far the overriding issue, as newer effective agents emerge, local failure will continue to be a problem. Preliminary studies have demonstrated that IORT can be administered to patients who have locally advanced NSCLC and head and neck cancer, in the context of aggressive combined modality therapy, and is generally well tolerated. Long-term efficacy and benefit can only be determined in the setting of carefully designed clinical trials. (See the article by Thomas and Merrick elsewhere in this issue for further discussion of this topic.) Several relatively small, single-institution pilot studies exploring the utility and benefit of IORT for locally advanced upper aerodigestive tract cancers have been conducted. Clear conclusions have been difficult to determine because of the mixing of disease stages, varying degrees and completeness of surgical resection, varying radiation doses, different schemas, and other factors. Yet, given the major morbidity and mortality associated with locally recurrent lung cancer, methods of improving local control need to be pursued and refined. Encouraging preliminary data suggest that IOERT can be safely administered and may benefit local control. Based on several centers' expertise in the combined modality treatment of locally advanced lung cancer and familiarity with IORT, the UCSF Thoracic Oncology Program has proposed a multicenter phase 2 study incorporating IORT in a combined multimodality treatment schema for patients who have completely resected locally advanced stage IIIA and IIIB NSCLC (nonpleural effusion, non-N3) (Fig. 1). It is hoped that this study will commence in the upcoming year.

Potential of mobile intraoperative radiotherapy technology

Mobile IORT units have the potential to change the way patients who have cancer are treated. The integration of IORT into cancer treatment programs, made possible by the new technologies of mobile linear accelerators that can be used in unshielded operating rooms, makes IORT significantly less time-consuming, less costly, and less risky to administer. It is now practical for IORT to be used in early-stage disease, in addition to advanced disease, and in sites for which patient transportation in the middle of surgery is considered too risky. Preliminary results of trials for early-stage breast and rectal cancer indicate benefits of IORT. Pediatric patients and patients who have lung cancer, previously underserved by IORT therapies, can be offered potential gains when patient transport issues do not limit IORT. Furthermore, because many of these mobile systems require no shielding, it is now practical for mobile units to be shared between hospitals, making this new mobile technology much more widely available.

The short and long term effects of intraoperative electron beam radiotherapy (IORT) on thoracic organs after pneumonectomy an experimental study in the canine model

PURPOSE

The tolerance of mediastinal structures and thoracic organs to intraoperative radiotherapy (IORT) was investigated in the canine model.

METHODS AND MATERIALS

Twenty-two adult beagles divided into three groups were subjected to a left pneumonectomy and IORT (10 MeV electrons) at doses of 20 Gy (n = 9), 25 Gy (n = 4), or 30 Gy (n = 9). Intraoperative electron beam radiotherapy was delivered through a 5 cm circular lucite cone encompassing a mediastinal field including the bronchial stump, aorta, esophagus, heart, phrenic nerve, contralateral hilar structures, and lung. Clinical monitoring was performed with regular chest X-ray, ECG, bronchoscopy, esofagoscopy, and fluoroscopy. From the different treatment dose groups, dogs were electively sacrificed at 1.5, 6, 12, and 72 months with complete autopsies.

RESULTS

There was no bronchial stump dehiscence or acute morbidity. Four dogs developed radiation induced esophagitis (18%), one in the 20 Gy IORT group (11%) and three in the 30 Gy IORT group (33%). There were six IORT related mortalities (27.5%), one esophagoaortic fistula (4.5%) and five bronchovascular fistulas (23%): two in the 20 Gy IORT group (22%), two in the 25 Gy IORT group (50%) and two in the 30 Gy IORT group (22%). Histopathological findings in uncomplicated follow-up showed marked myointimal fibrosis in the muscular arteries, submucosal fibrosis of the esophagus, and interstitial fibrosis of bronchial and lung tissue, especially in the higher dose group.

CONCLUSION

The mediastinal vascular, bronchial and esophageal structures are relatively sensitive to doses > 20Gy IORT. The IORT related morbidity found in this study may be lower when the current clinically used IORT doses of 10-15 Gy are applied. Further clinical application of IORT in the future treatment strategies for resectable nonsmall cell lung cancer may be worthwhile to investigate.