The role of radiotherapy in the conservative treatment of rectal carcinoma--the Lyon experience

Radiotherapy in the treatment of resectable rectal adenocarcinoma

The goal of treatment is to cure whereas maintaining sphincter function and minimizing toxicity. Although the mainstay of the treatment is surgery, radiotherapy (RT) is used in a substantial proportion of patients depending on the location and extent of the tumor. The aim of this article is to discuss the role of RT in patients with resectable rectal adenocarcinoma. This article is a review of the pertinent literature. Results show that patients with T1N0 exophytic, well to moderately differentiated, mobile tumors < or = 3 cm in diameter may be treated with either transanal excision or endocavitary RT. The probability of cure with either approach is approximately 80% to 90% and depends on selection criteria. The advantages of endocavitary RT are that it is an outpatient procedure requiring, at most, local anesthesia and is suitable for elderly, infirm patients. The disadvantage is that few of these treatment units are available. Patients who experience a local-regional recurrence may be surgically salvaged. Patients who undergo transanal excision and have unfavorable pathologic findings including equivocal or close margins, poor differentiation, invasion of the muscularis propria, and/or endothelial-lined space invasion have a high risk of local-regional recurrence after surgery alone. The addition of postoperative RT improves the likelihood of cure from 85% to 90%. Patients presenting with unfavorable tumors that are borderline resectable with a transanal excision may be downstaged with preoperative RT and rendered suitable for a wide local excision. The addition of concomitant chemotherapy probably enhances downstaging and may improve the likelihood of sphincter preservation. Patients with T3 and/or N1 rectal cancers have a relatively high probability of local-regional recurrence after surgery alone. Preoperative RT and postoperative RT combined with adjuvant chemotherapy have been shown to significantly reduce the risk of local-regional recurrence and improve survival. Whether preoperative RT alone or combined with chemotherapy is more efficacious than postoperative chemoradiation remains unclear. Endocavitary RT or transanal excision is suitable for patients with T1N0 cancers. Depending on tumor location and extent, adjuvant RT may improve the probability of local-regional control and survival for patients with locally advanced rectal adenocarcinomas.

Salvage or planned esophagectomy after chemoradiation therapy for locally advanced esophageal cancer--a review

Definitive chemoradiation (without esophagectomy) and neoadjuvant chemoradiation followed by planned esophagectomy are commonly used treatments for locally advanced esophageal cancer. These two treatment strategies have similar survival outcomes, so the value of planned esophagectomy is debated. However, persistence or recurrence of local disease is not uncommon after definitive chemoradiation. Salvage esophagectomy for isolated local failures of definitive chemoradiation is an option for selected patients. In this article we review the debate over definitive chemoradiation versus neoadjuvant chemoradiation and surgery, and then restate the argument in terms of salvage versus planned esophagectomy. Although both forms of esophagectomy are done in the setting of previous chemoradiation, they are different in several ways. Salvage esophagectomy appears to be a more morbid operation than planned esophagectomy. Surgeons supportive of the salvage esophagectomy strategy face the challenge of reducing its postoperative mortality.

The role of preoperative and postoperative radiotherapy in rectal cancer

Radiotherapy has an important role to play when used in addition to surgery in primary and recurrent rectal cancer. In primary resectable rectal cancer, a large number of randomized trials have shown that preoperative radiotherapy can slightly improve survival and can decrease local recurrence rates by more than half. Postoperative radiotherapy may also decrease the risk of local failure although with less efficacy. A preoperative schedule of 5 Gy/day for 5 out of 7 days is a convenient and low-toxic treatment, provided it is not given with 2 beams to large volumes, and it appears to be at least as effective as postoperative radiochemotherapy, generally meaning 6 months of therapy with 5 weeks of radiation. The schedule of 5 Gy/day for 5 days also reduces local recurrences with total mesorectal excision. It is unlikely that preoperative radiochemotherapy will substantially increase the chances of a sphincter-preserving procedure in a low-lying rectal cancer and that the long-term function will be adequate even if this is believed by many. In primary nonresectable or locally recurrent rectal cancer, preoperative radiotherapy may downsize or downstage the tumor so that it can be resected. Scientific support that radiochemotherapy is more efficient than radiotherapy alone in this situation is weak.

Modeling volume effects of experimental brachytherapy in the rat rectum: uncovering the limitations of a radiobiologic concept

PURPOSE

To analyze the significance of volume effects in experimental brachytherapy, based on modeling normal tissue complication probability.

METHODS AND MATERIALS

Experimental brachytherapy in the rat rectum was based on an eight-step 2.5-mm step size source configuration for 192Ir, afterloaded into an unshielded polystyrene applicator. Volume effects were studied using a half-circumferential lead-shielded applicator and a shorter (two-step) source configuration. The main end point was rectal stenosis.

RESULTS

Rectal stenosis was always caused by a radiation ulcer. With the shielded configuration, single-dose ED50 (50% incidence of rectal stenosis) increased from 23 Gy to 36.5 Gy. Single-dose ED50 for the short configuration was 77.9 Gy. The data showed a reasonable fit to a three-parameter version of the biophysical model described by Jackson et al. (1995). This model assumes that organs consist of a large number of radiobiologically independent subunits and that radiation causes a complication if the fraction of the organ damaged is greater than its functional reserve. The fraction of the organ damaged is calculated summing over fractions of the organ damaged at each dose level. The calculated mean functional reserve (nu50) of the rat rectum, assuming a cumulative functional reserve distribution in the group of experimental rats, was 0.53.

CONCLUSIONS

The volume effect observed within small brachytherapy volumes agreed well with clinical experience of large tolerance doses in contact X-ray therapy. However, the nu50 value was comparable to the high functional reserve value reported for liver. Experimental volume effects probably reflect repair processes originating in the areas adjacent to small radiation fields of brachytherapy more than the radiobiologic characteristics of the cells in the irradiated volume.

Role of radiation therapy in the treatment of resectable rectal adenocarcinoma

The purpose of this study is to review the role of radiation therapy in the treatment of resectable rectal adenocarcinoma. Selection criteria, treatment techniques, and results are discussed.

Chemoradiotherapy for rectal cancer--is there an optimal combination?

PURPOSE

Chemoradiotherapy is increasingly used in the primary management of rectal cancer. A critical review of present knowledge of whether an optimal combination exists was made for each of the major clinical situations.

RESULTS

As preoperative therapy to reduce local recurrence rates in primarily resectable rectal cancers, radiotherapy has almost exclusively been used as single modality, and combined chemoradiotherapy should remain experimental until further evidence is available. This can only be achieved in randomised trials. Postoperatively, a combination of chemotherapy and radiotherapy appears to be more efficient in reducing local failure rates and improving survival than either modality alone, but the literature-based evidence is partly conflicting. As a reference treatment, a combination of continuous infusion 5-fluorouracil (5-FU) and radiotherapy can be advocated based upon one trial. In primarily irresectable cancer, there is some support that chemoradiotherapy may be more efficient than radiotherapy alone in causing tumour regression allowing radical surgery, but the literature is again conflicting. A great number of phase II studies have been performed in these cancers and in those considered to be locally advanced, revealing promising activity and claims of superiority to radiotherapy alone or other schedules. The studies are, however, inconclusive with respect to antitumour activity, and patient selection may be of greater relevance for the results. Chemoradiation has also increasingly been used to facilitate a sphincter-preserving procedure in low-lying cancers. Again, literature is inconclusive as to whether an optimal combination exists, whether it is superior to radiotherapy alone, or if it actually facilitates sphincter preservation at all. Long-term functional outcome is poorly known. Again, 5-FU has been most extensively used, but many other drugs are presently being tested in various combinations.

CONCLUSIONS

An optimal combination of chemoradiotherapy for rectal cancer does not exist. Actually, a critical review of the literature shows that the support for superiority of chemoradiation over radiation alone is weak, or lacking. There is a great need of both more conclusive study designs and a more rational exploration of drug-radiation interactions prior to clinical testing.

CONSERVATIVE TREATMENT OF RECTAL ADENOCARCINOMA

Endocavitary radiotherapy and transrectal excision are highly effective treatments for properly selected patients with favorable early-stage rectal adenocarcinoma. The likelihood of local control and survival after treatment with either modality is similar, and differences among various series probably reflect selection. The parameter most predictive of local control and survival in the authors' series was tumor configuration. As has been previously observed, "selection is the silent partner of success." Suitable candidates for endocavitary radiotherapy or wide local excision are patients whose tumors are 3 cm or less in diameter, well-to-moderately differentiated, exophytic, mobile, limited to the submucosa on transrectal ultrasound, and within 10 cm of the anal verge. The advantages of endocavitary irradiation are (1) it is an outpatient procedure, (2) it does not require anesthesia, and (3) it is less expensive than transrectal excision. The advantages of transrectal excision are (1) it may be performed during one brief hospitalization (as opposed to four outpatient visits), and (2) a small subset of patients will have pathologic findings predicting an increased risk of regional lymph node involvement, revealing the need to treat the nodes with external-beam radiotherapy. A disadvantage of wide local excision is that some patients who would be suitable for a local procedure alone must be subjected to a course of external-beam radiotherapy when they are found to have equivocal or positive margins. Patients who are treated with transrectal excision and external-beam radiotherapy have less favorable lesions and are not comparable with patients who are treated with endocavitary radiotherapy or wide local excision alone. They are best compared with patients who have undergone major surgery consisting of abdominoperineal resection or low anterior resection. Because the risk of positive nodes is significantly increased with adverse pathologic findings such as poor differentiation, invasion of the muscularis propria, and endothelial-lined space invasion, a subset of these patients treated with wide local excision would have positive nodes. This subset of patients is not comparable with patients with stage pT1N0 and pT2N0 tumors treated with major surgery. The latter group of patients undergo complete surgical staging, whereas the pathologic staging for patients who undergo wide local excision and radiotherapy is limited to the extent of the primary tumor. With this caveat in mind, wide local excision and radiotherapy seem to result in locoregional control and survival rates similar to the rates obtained with major surgery for patients with pT1 and pT2 cancers (Table 5). Patients who should receive postoperative irradiation have tumors that exhibit one or more of the following characteristics: size greater than 3 cm in diameter, poorly differentiated, invasion of the muscularis propria, endothelial-lined space invasion, fragmented resection, equivocal or positive margins, or perineural invasion. Patients with gross residual disease are not suitable candidates for radiotherapy and require further surgery. The authors' policy is to treat these patients with chemoradiation followed by resection. Patients thought to have transmural invasion before treatment are probably best treated with preoperative chemoradiation combined with major surgery, although a subset of patients can be downstaged and rendered suitable for a wide local excision.

Preoperative (neoadjuvant) chemoradiotherapy in oesophageal cancer

BACKGROUND

Oesophageal cancer carries a poor prognosis. The 5-year survival rate following resection ranges from 10 to 35 per cent. Recent evidence suggests that the addition of non-surgical treatments to surgery may improve resection rates, reduce the risk of recurrence and improve survival. This review examines the role of preoperative chemoradiotherapy (CRT) in oesophageal cancer.

METHODS

A Medline-based literature review (1980-2000) was performed using the key words 'neoadjuvant or preoperative' and 'chemoradiotherapy or radiochemotherapy'. Additional literature was obtained from original papers and published meeting abstracts.

RESULTS

Forty-six non-randomized and six randomized trials of preoperative CRT were found. Resection rates, pathological complete response (pCR), treatment-related mortality rates and relapse patterns are documented. Improved 5-year survival rates approaching 60 per cent may be achieved following pCR. Three of the six randomized trials show a benefit in either overall survival or disease-free survival compared with surgery alone. Treatment-related toxicity can be significant.

CONCLUSION

Preoperative CRT may improve survival. Emerging evidence suggests that CRT alone can achieve similar survival rates to surgery alone. New imaging modalities may help to select which patients require surgery. Larger randomized trials of preoperative CRT or chemotherapy are needed to define optimal regimens and produce higher pCR rates with acceptable toxicity.