ESTRO 38 Abstract book

S110 ESTRO 38

weeks from CRT completion including clinical assessment with digital rectal examination, rigid proctoscopy and CEA levels in combination with radiological assessment, mainly performed to rule out residual extra-luminal disease. Only patients fulfilling these stringent criteria have been considered for this non-operative approach (Watch & Wait). Patients managed by this approach, did no worse than patients managed by radical surgery and pathological complete response in terms of survival. Late local relapses were all amenable to salvage resection, occurring in approximately 10% of these patients not immediately operated on and in a considerably longer interval when compared to systemic relapses. In a retrospective review, there was no survival compromise in patients with initial suspicion for complete clinical response who undergone delayed surgery for early tumor regrowth. Recently, other Institutions have observed similar results further supporting this treatment strategy in highly selected patients. Assessment of tumor response remains a challenging issue associated with a learning curve that has probably improved over time during our 25-year experience period. Even so, a subset of patients who were initially considered as complete responders presented with residual disease or early tumor regrowth/recurrence within 12 months of follow-up. It is worth mentioning that we have arbitrarily considered this period of 12 months as the minimum to consider a sustained complete clinical response in these patients. The share of patients with complete tumor regression may actually increase with modern CRT drugs and regimens and earlier baseline disease. 20 In fact the addition of chemotherapy cycles during the RT and the “resting” period between RT and surgery with a modest increase in RT dose (50.4Gy to 54Gy) has led to a significant increase in complete clinical response rates to over 50% of patients.

1 University of Turin, Department of Oncology, Turin,Italy

Abstract not received

SP-0210 Are radiation specialists good global cancer citizens? J.Torode 1 1 Union for International Cancer Control (UICC), Geneva, Switzerland

Abstract not received

SP-0211 Putting down the scalpel. The evolution of rectal cancer treatment A. Habr-Gama 1 1 Angelita and Joaquim Gama Institute, Colorectal Surgery, São Paulo, Brazil Abstract text The benefits of neoadjuvant chemoradiation were not restricted to long-term local disease control as confirmed by an update of the German Trial after 11 years of follow- up. Neoadjuvant treatment may lead to variable degrees of tumor regression, reflected by primary tumor reduction in size (downsizing), in depth of penetration and possible perirectal node sterilization (downstaging). In up to 42% of the cases, complete pathological tumor regression has been reported. Such findings challenged the role of standardized radical resection in all patients with rectal cancer irrespective of tumor response to neoadjuvant therapy. One could ask about the oncological benefit in a patient following radical rectal resection where not a single cancer cell is removed. But the solution is not straightforward, as it seems. Assuring complete tumor regression is not an easy task, unless radical resection is performed. However, exposing patients to considerable morbid procedure leading to urinary, sexual and fecal dysfunctions, the requirement for temporary or permanent stomas and the expected procedure-related mortality may not be considered the best alternative. In addition, the degree of tumor regression may be influenced by several different factors that should be taken into account. Studies have not definitively explained the reasons why after similar doses some tumors respond completely while others seem to be absolutely resistant to such therapy. Another factor that seems to influence tumor regression is the time elapsed between completion of treatment and response assessment. This was first suggested by data of patients with anal cancer. Similarly, in rectal cancer, retrospective studies also indicated that longer interval periods were associated with increased rates of complete tumor regression, suggesting that the more you wait, the more you get in terms of tumor regression. In this setting, patients with apparent complete clinical tumor regression would be ideal candidates for alternative treatment strategies including no immediate surgery and rigorous close observation. The main obstacle to this approach is the risk of leaving microscopic residual disease. Indeed, distinguishing transmural fibrosis from microscopic residual disease maybe quite difficult. Clinical assessment alone has been shown quite disappointing sensitivity and specificity rates in previous retrospective studies. However, some of these studies included tumor response assessment performed at 6 weeks from CRT completion, possibly too early and reflecting the detection of residual disease in the setting of ongoing necrosis. Also, studies have detected residual microscopic nodal disease in ypT0 patients. Again, these studies included patients managed by radical surgery after 6 weeks from CRT completion. This is suggested by the observation of absence of residual nodal disease in patients with ypT0 after periods of longer intervals than 6 weeks after CRT completion. It has been our strategy to assess tumor response at least after 8