The historical perspective on anal cancer therapy: what have we learnt, where did we fail?

Squamous-cell cancer of the anus is a rare entity. Fifty years ago, understanding the natural history was limited by the lack of an agreed staging system and a largely irrelevant but complex histological categorisation. Retrospective reports described a small number of patients, generally with small tumours, treated by diverse methods with limited follow-up. The use of therapeutic radiation was limited by observed acute toxicity. Some centres gained substantial experience with interstitial radiation, but knowledge and expertise regarding the natural history and optimal methods of treatment were difficult to accumulate and hand on. Radiotherapy (RT) with or without interstitial radiation as the primary treatment, chemoradiotherapy (CRT) both definitive and preoperative, local excision for residual after CRT and small margin carcinomas and 'prophylactic' groin dissections after radical surgery all had advocates in different centres. The dogma in Europe at the time favoured split-course treatments. Early experiments combining fluoropyrimidines and RT were refined with Nigro et al.'s landmark study in 1974. Subsequent regimens are variations and today CRT with concurrent fluoropyrimidines and mitomycin C is accepted as the standard primary treatment. Early randomised phase III trials proved CRT to be more effective than external beam RT alone, but uncertainty remained over the optimal integration of chemotherapy, the type of chemotherapy, the ideal RT doses and potential late effects. These questions were imperfectly addressed and led to subsequent pragmatic phase III trials testing the impact of induction and consolidation chemotherapy and dose escalation. We describe the historical perspective and examine the opportunities we failed to grasp.