Bladder cancer. The selection of patients for treatment by full‐dose irradiation

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Abstract
Cure of muscle-invading bladder carcinoma in 20% to 39% of patients using full-dose external beam irradiation has been reported by many institutions in the last 10 years. Local failure occurs in 50% of patients so treated, however, and successful selection criteria for bladder-sparing radiotherapy are necessary. Prognostic factors which have been identified to be associated with a relatively successful outcome using full-dose irradiation include (1) the clinical stages T2 and T3, (2) the absence of ureteral obstruction on initial intravenous pyelogram, (3) a visibly "complete" transurethral resection having been achieved, and (4) complete response of the local tumor to radiation. In addition, local tumor control appears to be related to total dose administered. Analysis of the results of precystectomy radiation therapy, where papillary tumor histology and small tumor size yielded improved survival, suggests that these characteristics also may prove to be beneficial in patients selected for full-dose irradiation. The four-field box technique has become accepted as the best method to treat patients using beams from linear accelerators or betatrons. The bladder and pelvic lymph nodes should be treated to 50.4 Gy in 1.8 Gy fractions, 5 days/week. A cone-down boost to the tumor volume only then is given for a total dose of 64.8 Gy to 68.4 Gy in 7.5 weeks. The posterior rectosigmoid should receive less than 60 Gy, and the anus and femoral head and neck should be limited to 45 to 50 Gy to avoid toxicity. Innovative approaches to treatment of muscle-invading bladder cancer now are being explored and include the use of intravesical misonidazole combined with fractionated external beam irradiation, and systemic cisplatin administration in combination with radiation. Techniques which have yielded good results in superficial bladder cancer include open interstitial implantation, intraoperative single-dose electron beam irradiation, and trans-Foley radium applications. Further prospective evaluations of clinical and histologic tumor characteristics, treatment techniques and doses reviewed here will be necessary before definitive selection criteria for treatment with full-dose irradiation are established.

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