0360.3016193 $6.00 + 00 Copynghf 6 I993 Pergamon Press Ltd. ?? Correspondence RESPONSE TO EDITORIAL BY DRS. LANCIANO AND CORN To the Edifor: Nodal control sustained at > 90% with 40-month median follow-up. Drs. Lanciano and Corn provide an excellent appraisal of the current status of groin irradiation in patients with vulvar carcinoma. We agree with their concerns about the radiation technique used in the recent randomized COG study (3). We have previously demonstrated the po- tential dosimetric pitfalls of radiating the inguino-femoral nodes using I2- to I3-MeV electrons, as done in the COG study (2). Although this energy of electrons adequately treats the superficial groin nodes, the deep femoral nodes, also at risk, are not sufficiently treated. Drs. Lanciano and Corns’ main concern regarding the University of Wisconsin experience is the range and duration of follow-up. The current median follow-up of the radiation group is 40 months with a range of 9-103 months. No further nodal failures have developed (21/23 nodal control), underscoring our contention that the majority of nodal failures occur early. Only I patient has follow-up less than 1 I months; she died of intercurrent disease One of 23 patients has developed bilateral femoral neck fractures at IO months postradiation. Our nodal control appears durable with considerably longer follow-up. We therefore continue to support the use of photons only in the treatment of inguino-femoral nodes as described in this article (I). DANIEL G. PETEREIT, M.D. MINESH P. MEHTA, M.D. DOLORES A. BUCHLER, M.D. TIMOTHY J. KINSELLA, M.D. Department of Human Oncology University of Wisconsin Medical School Madison. WI 53792 Petereit, D. G.: Mehta. M. P.; Buchler, D. A.; Kinsella, T. J. In- guinofemoral radiation of N0.N I vulvar cancer may be equivalent to lymphadenectomy if proper radiation technique is used. Int. J. Radiat. Oncol. Biol. Phys. 27:963-967; 1993. Petereit, D. G.: Mehta, M. P.; Buchler. D. A.; Kinsella, T. J. A retrospective review of nodal treatment for vulvar cancer. Am. J. Clin. Oncol. 16:38-42; 1993. Stehman. F. B.: Bundy, B. N.; Thomas. G.: Varia, M.; Okagaki, T.; Roberts, J.; Bell, J.; Heller, P. B. Groin dissection versus groin ra- diation in carcinoma of the vulva: A Gynecologic Oncology Group study. Int. J. Radiat. Oncol. Biol. Phys. 24:389-396; 1992. RADIOTHERAPY IN THE TREATMENT OF VULVAR CARCINOMA To the Edikvt The role of Radiotherapy in the treatment of vulvar malignancies continues to evolve as data from prospective trials provide deeper insight into the patterns, and sites of failure for this malignancy. Data from the Gynecologic Oncology Group (GOG) has demonstrated the importance of external beam therapy in the treatment of subclinical pelvic disease in those patients found to have pathologically positive inguinal lymph nodes (2). This information is consistent with the expected sensitivity of epithelial tumors to radiotherapy (I). The GOG recently addressed the role of Radiotherapy in the treatment of inguinal disease in vulvar carcinoma. In an article entitled “Groin Dissection Versus Groin Radiation in Carcinoma of the Vulva: A Gynecologic Oncology Group Study” the authors, Dr. Stehman, Dr. Bundy, and Dr. Thomas concluded that groin irradiation is “significantly inferior” to elective dissection in patients presenting with clinical stage NO or N 1 disease (5). We believe that several treatment related factors (specific to the radiation alone arm) may account for the apparent difference in regional nodal control between the two groups. Additionally. specific information ad- dressing the correlation between clinical and pathologic findings may aid in the determination of a minimum effective dose necessary to control inguinal disease. The term groin, as applied to the regional lymphatics in Gynecological malignancies, refers to two distinct nodal chains: a superficial inguinal branch and a subinguinal branch composed of lymphatics on either side of the Great Saphenous vein, and deep nodes (medial to the femoral vein) (3). Review of anatomic relation between these two groups dem- onstrates that they lie at different depths in the A-P plane. This fact has important dosimetric implications when one is determining a specific depth upon which to base treatment calculations. Furthermore, it is un- likely that a single number will provide a uniform dose to the entire region (i.e., both superficial and deep lymphatics). One runs a significant risk of underdosing the deep femoral nodes when 3 cm is chosen as a representative depth for all groin nodes. Additionally, the electron energies used to boost lymph nodes at 3 cm will not correspond to those necessary for nodes lying in a deeper plane. The authors do not specifically address the dose given to the superficial and deep chains in those patients ex- periencing groin failures. Similarly, they do not state which sites were involved when patients failed (i.e., superficial, deep, or both). The importance of body habitus in the determination of prescription depth was not specifically addressed in this paper. We believe that sig- nificant dosimetric errors can be encountered if a fixed depth of 3 cm is chosen as representative for all patients. Obese patients, (perhaps several known to have Quetelet indices > 28) may have a significant amount of subcutaneous inguinal fat. Fixed prescription depths do not allow the Radiation Oncologist the necessary flexibility to account for these dif- ferences when prescribing treatment. This issue is certainly of concern when photon treatment is being given; however, it is ofgreater importance when electrons are being used to boost the treatment field, as the energy of the electron beam will be determined by the target depth. The rapid fall off of electron depth doses, in tissue, may lead to inadequate treatment in obese patients if the electron energy for “boost” therapy is based on a prescription depth of 3 cm. We were concerned that the authors did not address the correlation between their clinical and pathologic findings on inguinal dissection. In Table 1, the authors report that five patients (20%) in the groin dissection arm and seven patients (25.9%) in the RT arm had Clinical Stage Nl disease. The results of the groin dissection demonstrate that five of the surgical patients (20%) had PS N( +) groins. One would suspect that there was some overlap between the CS( +) and the PS( +) patients. Further- more. it would be reasonable to expect that at least as many patients in the RT group would be PS(+) as was seen in the surgery arm. As stated in the paper, the total dose offered to all patients was 50 Gy @ 200 cGy per fx. One would not expect a dose of 50 Gy to be sufficient to control gross disease (1). If the patients who subsequently failed in the groin were known to be the same group as those CS N 1, then it might be reasonable to consider delivering a higher dose of RT to these patients. Finally. the authors state that most patients did not have a CT ex- amination of the pelvis/inguinal region performed. Although the spec- ificity for this study is not high, it should not be considered an unrea- sonable exam to perform in patients presenting with N I disease. A CT scan would not only provide information regarding the nodal status of the patient, but would allow for more accurate measurement of the depth(s) of the superficial and deep chains. The significant degree of morbidity associated with bilateral inguinal node dissection is well es- tablished: therefore, every attempt should be made to develop alternative therapies. Until a prospective randomized study can insure that an ad- equate dose of RT to the inguinal nodes is ineffective in the treatment of early staged vulvar carcinoma. we do not believe that the role of 991