Place and Technics of Radiation Therapy in the Management of Malignant Tumors of the Major Salivary Glands

Abstract
The management of malignant tumors of the major salivary glands is primarily surgical, but the radiotherapist should be consulted in certain clinical situations, as (a) inoperable tumor; (b) postoperative residue: gross tumor too diffuse for attempted complete surgical excision; (c) postoperative prophylaxis: no gross disease left, but only marginal clearance at the planes of excision, or tumor extending along nerve sheaths, or disease traced to the base of the skull; (d) postoperative recurrence of disease either in the local area (parotid or submandibular fossa) or in the skin of the neck. There is abundant literature on the management of tumors, both benign and malignant, of the major salivary glands. Little precise information, however, can be collected on the radiation technics employed in the management of such tumors. In the past decades, interstitial radium implants and teleradium units were commonly used in the institutions in which they were available. By and large, the malignant tumors of the major salivary glands have had the reputation of being quite radioresistant, and radiotherapy was considered of little, if any, use in their management. Clinical Material The clinical material in our series consists of 69 patients treated from January 1948 through December 1963. Recently treated patients have been included because the purpose of this communication is not to analyze long-term survivals, but to correlate technics and dosage with the local control of the disease achieved in varied clinical situations. The material was analyzed in two ways: (a) by clinical situations, that is, primary inoperable, postoperative residue, postoperative prophylaxis, recurrences; and (b) by various histological types, i.e., malignant mixed tumor (mucoepidermoid carcinoma), adenocarcinoma, poorly differentiated carcinoma, squamous-cell carcinoma, cylindroma, lymphosarcoma, and unclassified (questionable) carcinoma metastatic to the parotid glands. Through the years various technics have been employed. Prior to the availability of megavoltage, radium implants alone or combined with external irradiation were the main modality of treatment, as kilovoltage external irradiation alone could not deliver adequate tumor doses. With megavoltage, either a Co60 unit or a CS137 unit with a 22 cm SSD was used. A cross section at the level of the ear lobule (Fig. 1) demonstrates that short distance teletherapy units or wedge pair filters give the best volume distributions for irradiation of the parotid fossa. With the exception of two lymphosarcomas which received tumor doses of 3,000 rads in two and one-half weeks, the tumor doses ranged from 5,500 rads in four weeks to 7,000 rads in six weeks.