[The locoregional recurrence of rectal carcinoma. A computed tomographic analysis and a target volume concept for adjuvant radiotherapy].

BACKGROUND

In the adjuvant postoperative radiotherapy of rectal carcinoma the knowledge of the predominant areas of recurrences is of major importance for the definition of the target volume. We analysed the pattern and locations of tumor recurrences in the CT scans of 155 patients and correlated the findings with the primary tumor location (above and below the peritoneal duplication) and the operating method (abdominoperineal extirpation, anterior resection. Hartmann procedure).

PATIENTS AND METHOD

Hundred and fifty-five patients with the diagnosis of rectal carcinoma recurrences were treated in our institution between 1980 and 1995. To determine the extension of the recurrent tumor within the pelvic levels (presacral levels S1-S5, precoccygeal, pelvic floor level and perineal level) and the tumor infiltration of pelvic organs and muscles we analysed the pretherapeutic CT images. The lymph node recurrences were classified as: pararectal, presacral, iliac internal, iliac external, iliac communis and para-aortal recurrences.

RESULTS

Sixty-one percent of the patients with rectum extirpation and 66% with anterior resection showed a combined local and nodal recurrence. Isolated lymph node recurrences were rare (4% and 5%) (Tables 2 and 3). The local recurrence was mostly situated in the presacral pelvis, predominantly there was an infiltration of the presacral space at the level of S4, S5 and os coccygis regardless of the operating method and the primary tumor location (Figure 1). The anastomosis was involved in the tumor recurrence in 93% of the anteriorly resected patients (Table 3). In 9 out of 96 patients after rectum extirpation the pelvic region caudal of the tip of the coccyx was the origin of the recurrent tumor (Table 2, Figure 2). Primarily all 9 patients had a deep-seated carcinoma (< 6 cm ab ano). Only 2 patients showed an isolated perineal recurrence after rectum extirpation (Table 2. Figure 2). Two thirds of the deep-seated tumors showed a vaginal involvement (Figures 3 and 4). The incidence of iliac internal and presacral nodal recurrence was 47 to 59% (Figures 3 and 4). The incidence of iliac external lymph node recurrences was 7% after rectum extirpation and 2% after anterior resection/Hartmann procedure.

CONCLUSION

Our data demonstrate that 2/3 of the patients with tumor-bed recurrences also show lymph node recurrences predominantly in the iliac internal and presacral groups. This has to be considered in the definition of the boost target volume. The target volume must also include the dorsal wall of the urogenital organs. A ventral extension of target volume up to iliac external lymph nodes is not necessary.