The differentiation of pT1 rectal cancers into ‘low-risk’ and ‘high-risk’ criteria was already recommended ¼ of a century ago, and a large number of studies about local excision exist. The majority of investigations, however, ignored this classification. One possible reason may be that these so-called high-risk criteria (G34/L1/V1) are difficult to determine preoperatively and that patients decline further therapeutic steps after local excision after receiving these results [3, 10, 11].

From large single mono- or multicentre studies, it became clear that a local recurrence rate of >20 %, and thus unfavourable oncological courses, can be expected in patients with pT1 ‘high-risk’ rectal cancers [3–10, 12–26]. If these results are further split into inadequate local excisions (R1) and tumours that were not excised ‘en bloc’ or if the minimal distance of the tumour to the resection margin is smaller than 1 mm, the local recurrence rates rose to 50, 38, and 50 %, respectively [3, 4, 12]. Even if other researchers did not consequently separate their results according to these criteria, they indirectly confirmed the above-mentioned results since the median of recurrence rates from these studies was much higher (Table 6.1) [12–26].

The importance of the invasion level of the tumour into the submucosa (sm), for the development of local recurrences, was proven by other studies. Bach et al. and previously Schäfer et al. have demonstrated that the sm level is important for the risk for local recurrences (e.g. ~20 % for sm3 rectal carcinomas) [4, 26]. If only ‘low-risk’ (G1–2/L0) criteria were considered, similar results of 5 % local recurrences were found, as if the sm level (sm1/G1–2/L0) was additionally included. The reason for this is unclear.

One reason for this may be that the division of the submucosa (sm1–3) can vary from one investigator to the next. Further, with increasing depth of tumour invasion into the submucosa, the risk for lymph vessel invasion increases. In this context it is unclear if determination of one parameter (sm2–3 level or L1) is sufficient or if both are needed for consideration.

Novel factors such as tumour buddings at the tumour front and molecular biological markers (factors for angiogenesis, their receptors, pro- and anti-apoptotic markers, regulatory T cells, etc.) have potential as prognostic markers for the development of local recurrences and lymph node metastases [27–30]. However, it needs to be mentioned that these have only been investigated in single studies with small patient collectives so far.

For pT2 tumours, the option to perform adjuvant radio(chemo)therapy exists as an alternative to local excision alone. Only retrospective heterogeneous results support this concept of adjuvant therapy after local excision, and interpretations should only be considered with caution [33]. The single studies included different adjuvant therapeutic regimens, and even within one study, the patients were treated differently, i.e. with combined radiochemotherapy or with radiation or chemotherapy only. Thus, the results obtained cannot be compared directly (Table 6.2) [33].

The studies also included patients with varying risk factors [33]. Up to 44 % ‘high-grade’ or ‘high-risk’ findings, up to 29 % of cases with R1 resections, and 57 % Rdoubtful or Rclose findings were included. The high rates of inadequate resections of pT2 rectal carcinomas do point to the difficulties associated with the surgical procedure if the tumour could not be excised by full-thickness technique. If, against expectation, a T2 carcinoma is detected in a tumour preoperatively staged as adenoma or cT1 tumour, a high frequency of inadequate resections can be expected if only mucosa or submucosa resection was performed [31, 32].

Patients receiving radiochemotherapy after surgery developed local recurrences in 12 % of the cases. If only irradiation was offered, the local recurrence rate increased to 18 % [33].

In comparison to local excision of pT2 rectal cancers alone, the local recurrence rate was halved using adjuvant radio(chemo)therapy. However, compared to results after primary radical surgery, these recurrence rates are still unacceptably high [32, 33].

After local excision of a pT1 rectal carcinoma with prognostically unfavourable criteria (G3–4/L1/V1 R1/Rdoubtful/Rclose) or a pT2 carcinoma, an immediate radical reoperation can be performed instead of an adjuvant therapy. Investigations have documented that after immediate conventional reoperation, i.e. within 4 weeks after local excision, oncological results comparable to those after primary radical surgery can be obtained [14, 33].

In contrast, after follow-up and later salvage surgery for the recurrence, the developed recurrence is associated with a significant higher risk of positive lymph nodes and systemic metastases [14, 33]. Therefore, if inadequate resections and ‘high-risk’ pT1 or pT2 carcinomas are detected after the local excision, the procedure should be considered as an extended diagnostic procedure, which requires additional therapeutic actions. In this context, adjuvant radiochemotherapy is clearly inferior to immediate radical reoperation [14, 32, 33].