Radiation therapy in early glottic carcinoma: significance of prognostic factors and dose fractionation.

ABSTRACT

A retrospective analysis of 208 cases with early glottic cancers treated by radiation therapy is presented. Early T1 (156 cases) and T2 (52 cases) lesions accounted for only 43 per cent of all glottic tumours that presented at the Tata Memorial Hospital between 1975-80. A markedly predominant male to female ratio of 221 was noted with 66 percent presenting in the fifth and sixth decades of life. Radical Radiation therapy was delivered with two different regimens according to the then prevalent physician preference. Regimen 1 delivered 50 Gy/15 frs. in three weeks and regimen 2 with 60 Gy/24 frs./5 weeks. The actual total survival and disease free survival was 92 per cent and 85 percent for T1 lesions and 82 percent and 67 percent for T2 tumours respectively. Minimal tumour volume involving a unilateral mobile vocal cord had the best prognosis. With extension to more lengths of cord and/or involvement of the anterior commissure or with tethering or fixation of the cord the prognosis was adversely influenced. In T1 lesions, the shorter course with the higher fractionation dosage levels showed improved local controls. However, the results were not statistically significant. This was not so in the T2 lesions probably due to small number of cases. Treatment failure was recorded in 19 per cent cases of which 90 per cent was seen in the first two years after treatment. Persisting laryngeal oedema confirmed a high index of suspicion towards recurrent disease. A radiotherapeutic technique using proper patient positioning and accurate beam direction with total dosage level above 1850 rets and TDF between 101-106 values is the recommended optimal treatment. In conclusion, an understanding of the prognostic features and an appropriate dose fractionation schedule allows optimization to effectively control early glottic tumours and retain function in the majority of patients.